ASAL BIOLOGY EXAM PREP

1 Cell structure

1 Cell structure

Getting exam ready Understanding the question

TI AL

Command words

To help you prepare for your exams, this book guides you through a framework of exam skills that will help you to show what you know about Biology in the Cambridge exam context; from the various elements of understanding the question, to writing a good response, to developing the kind of behaviours and habits that will support you along the way.

In this chapter you will check that you know the key concepts of cell structure and practice how you show this knowledge in an exam.

Answering questions and testing your knowledge is very important for your memory. Every time you recall information and write an answer, your knowledge and understanding gets stronger. Once you have consolidated your memory, you can better concentrate on what in particular the exam question is asking you to do.

EN

Alongside recalling your knowledge on cell structure, in this chapter you will also practice understanding command words. The relevant part of the Cambridge Exam Skills Framework is as follows:

Exam questions are very specific and are looking for certain things, so you need to be ready for the approach that they take so that you can really show what you know.

Extract from the Cambridge Exam Skills Framework

Exam skills questions: Questions that practice showing what you know about cell structure in an exam

3

Self Assessment questions: Questions that help you monitor your own progress

&

know the structure of animal, plant and bacterial cells, and of viruses

•

understand the use of light microscopes and electron microscopes to study cells be able to sketch and measure cell structures

•

know the variety of cell structures and their functions

D

R

•

AF

•

T

In this chapter, you will:

2

C

You will also find recall questions through this chapter on something you have already covered. This is because your memory is best increased by a technique called interleaving. This is when you return to a previously studied topic within a certain timeframe to make sure that you remember it properly.

LEARNING OBJECTIVES

Understanding the exam question

Sub-skill

Interpreting command words

Objectives

• •

FI D

2

O

Knowledge recall questions: Questions that increase your memory of what you know about cell structure

N

For that reason, there are three kinds of question in this chapter.

1

Exam skill

•

Identify specific command words in the exam question.

Understand the meaning of specific command words and what they are instructing you to do.

Distinguish between different command words.

In this chapter you are going to increase your understanding of what exam questions are asking you to do. An important part of understanding exam questions is to know what command words are and what they mean.

EXAM SKILLS OBJECTIVES In this chapter, you will: •

show that you understand the ‘outline’ command word and answer an outline question

•

show that you understand the 'state' command word and answer a 'state' question.

•

show that you understand the 'calculate' command word and answer a 'calculate' question.

•

show that you understand the 'suggest' command word and answer a 'suggest' question.

Command words are particular words that tell you how to answer a specific exam question or complete an assessment task. Knowing how to identify command words, and recognise what they mean, will help you to interpret what the examiner is looking for and give you clear guidance on how to answer the question to best show your knowledge.

3

1 Cell structure

1 Cell structure

Getting exam ready Understanding the question

TI AL

Command words

To help you prepare for your exams, this book guides you through a framework of exam skills that will help you to show what you know about Biology in the Cambridge exam context; from the various elements of understanding the question, to writing a good response, to developing the kind of behaviours and habits that will support you along the way.

In this chapter you will check that you know the key concepts of cell structure and practice how you show this knowledge in an exam.

Answering questions and testing your knowledge is very important for your memory. Every time you recall information and write an answer, your knowledge and understanding gets stronger. Once you have consolidated your memory, you can better concentrate on what in particular the exam question is asking you to do.

EN

Alongside recalling your knowledge on cell structure, in this chapter you will also practice understanding command words. The relevant part of the Cambridge Exam Skills Framework is as follows:

Exam questions are very specific and are looking for certain things, so you need to be ready for the approach that they take so that you can really show what you know.

Extract from the Cambridge Exam Skills Framework

Exam skills questions: Questions that practice showing what you know about cell structure in an exam

3

Self Assessment questions: Questions that help you monitor your own progress

&

know the structure of animal, plant and bacterial cells, and of viruses

•

understand the use of light microscopes and electron microscopes to study cells be able to sketch and measure cell structures

•

know the variety of cell structures and their functions

D

R

•

AF

•

T

In this chapter, you will:

2

C

You will also find recall questions through this chapter on something you have already covered. This is because your memory is best increased by a technique called interleaving. This is when you return to a previously studied topic within a certain timeframe to make sure that you remember it properly.

LEARNING OBJECTIVES

Understanding the exam question

Sub-skill

Interpreting command words

Objectives

• •

FI D

2

O

Knowledge recall questions: Questions that increase your memory of what you know about cell structure

N

For that reason, there are three kinds of question in this chapter.

1

Exam skill

•

Identify specific command words in the exam question.

Understand the meaning of specific command words and what they are instructing you to do.

Distinguish between different command words.

In this chapter you are going to increase your understanding of what exam questions are asking you to do. An important part of understanding exam questions is to know what command words are and what they mean.

EXAM SKILLS OBJECTIVES In this chapter, you will: •

show that you understand the ‘outline’ command word and answer an outline question

•

show that you understand the 'state' command word and answer a 'state' question.

•

show that you understand the 'calculate' command word and answer a 'calculate' question.

•

show that you understand the 'suggest' command word and answer a 'suggest' question.

Command words are particular words that tell you how to answer a specific exam question or complete an assessment task. Knowing how to identify command words, and recognise what they mean, will help you to interpret what the examiner is looking for and give you clear guidance on how to answer the question to best show your knowledge.

3

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.0 Exam skills

1.1 The structure of animal, plant and bacterial cells, and of viruses

Some of the questions in this chapter contain the command words outline, state, calculate and suggest. Here is a definition list for each of those command words.

Read these carefully. set out the main points

State

express in clear terms

1

Calculate

work out from given facts, figures or information

Suggest

apply knowledge and understanding to situations where there are a range of valid responses to make proposals/put forward considerations

ribosomes

mitochondria chloroplasts

Outline the features of a hobby or activity that you enjoy.

FI D

Table 1.1: XXXXXXXX

a

State why you enjoy the hobby or activity you outlined.

N O

Calculate how much time you have spent on your hobby in the past year.

C

A friend may not share your enthusiasm for your hobby, but might be looking to take up a different one from a range of options. You could help them decide what to pursue by suggesting some alternatives, based on their interests.

Suggest an idea for a new hobby to your friend.

b

Copy and complete Table 1.1. If a feature can be present in the cell, write a tick in the box. If it cannot be present, write a cross.

You should write either a tick or a cross in each box.

Viruses are not usually considered to be living organisms and are not made of cells. Outline the key features of the structure of a virus.

[5] [2] [Total: 7]

DEFINE THESE TERMS Write your own definition for the following key term: •

organelle

•

nucleus

•

partially permeable

D

R

AF

T

You will practice answering more questions that use these command words in the rest of this chapter.

&

4

Eukaryotic cell

EN

nucleus

If you needed to work out how much time you had spent on this hobby, you would calculate it from the information available.

3

Prokaryotic cell

cell surface membrane

If you were to describe to a friend exactly why you enjoy that same hobby or activity, you might state your reasons. These would need to be clear and specific.

2

Table 1.1 lists some features of prokaryotic and eukaryotic cells.

Feature

Begin by practising responding to the command word, outline. You can do this by making a list of bulleted notes. Each bullet will be a main point.

1

TI AL

Outline

This question relies on your recall of facts and concepts. You could answer part b either in words, or by using a labelled diagram. Note that the command word for b is ‘outline’.

4

5

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.0 Exam skills

1.1 The structure of animal, plant and bacterial cells, and of viruses

Some of the questions in this chapter contain the command words outline, state, calculate and suggest. Here is a definition list for each of those command words.

Read these carefully. set out the main points

State

express in clear terms

1

Calculate

work out from given facts, figures or information

Suggest

apply knowledge and understanding to situations where there are a range of valid responses to make proposals/put forward considerations

ribosomes

mitochondria chloroplasts

Outline the features of a hobby or activity that you enjoy.

FI D

Table 1.1: XXXXXXXX

a

State why you enjoy the hobby or activity you outlined.

N O

Calculate how much time you have spent on your hobby in the past year.

C

A friend may not share your enthusiasm for your hobby, but might be looking to take up a different one from a range of options. You could help them decide what to pursue by suggesting some alternatives, based on their interests.

Suggest an idea for a new hobby to your friend.

b

Copy and complete Table 1.1. If a feature can be present in the cell, write a tick in the box. If it cannot be present, write a cross.

You should write either a tick or a cross in each box.

Viruses are not usually considered to be living organisms and are not made of cells. Outline the key features of the structure of a virus.

[5] [2] [Total: 7]

DEFINE THESE TERMS Write your own definition for the following key term: •

organelle

•

nucleus

•

partially permeable

D

R

AF

T

You will practice answering more questions that use these command words in the rest of this chapter.

&

4

Eukaryotic cell

EN

nucleus

If you needed to work out how much time you had spent on this hobby, you would calculate it from the information available.

3

Prokaryotic cell

cell surface membrane

If you were to describe to a friend exactly why you enjoy that same hobby or activity, you might state your reasons. These would need to be clear and specific.

2

Table 1.1 lists some features of prokaryotic and eukaryotic cells.

Feature

Begin by practising responding to the command word, outline. You can do this by making a list of bulleted notes. Each bullet will be a main point.

1

TI AL

Outline

This question relies on your recall of facts and concepts. You could answer part b either in words, or by using a labelled diagram. Note that the command word for b is ‘outline’.

4

5

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.2 Using light microscopes and electron microscopes to study cells

Sketch and label an animal cell, plant cell, bacterial cell and virus particle.

Copy and complete Table 1.2. In the ‘type of microscope’ column, choose from optical microscope, transmission electron microscope or scanning electron microscope.

Micrograph

TI AL

1

QUICK RECALL 1: SUBJECT KNOWLEDGE

REFLECTION

Feeling anxious can make it harder to think clearly. What can you do to help yourself to feel less anxious? Some examples might be: taking deep slow breaths or writing down anything that is worrying you. Write down three things that make you feel less anxious. These things can be part of your ‘mental health toolbox’.

Type of microscope used to Reason for your decision produce the micrograph

Figure 1.1

EN

Figure 1.2 Figure 1.3 Table 1.2: XXXXX

1.3 Sketching and measuring cell structures Measure the total width of the four palisade cells A, B, C and D in graticule units.

C

Figure 1.3: Drawing of plant cells.

Figure 1.4 shows a micrograph of parts of two cells from the small intestine of a mammal. The structures along the surfaces of the two cells are microvilli.

State the type of microscope that was used to obtain this micrograph.

Give a reason for your answer.

[2]

D

R

AF

a

T

2

Figure 1.2: Micrograph of a cell from the pancreas

&

Figure 1.1: Micrograph of plant cells with starch grains.

O

N

FI D

1

Figure 1.5: XXXXXX

Figure 1.4: XXXXX

6

7

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.2 Using light microscopes and electron microscopes to study cells

Sketch and label an animal cell, plant cell, bacterial cell and virus particle.

Copy and complete Table 1.2. In the ‘type of microscope’ column, choose from optical microscope, transmission electron microscope or scanning electron microscope.

Micrograph

TI AL

1

QUICK RECALL 1: SUBJECT KNOWLEDGE

REFLECTION

Feeling anxious can make it harder to think clearly. What can you do to help yourself to feel less anxious? Some examples might be: taking deep slow breaths or writing down anything that is worrying you. Write down three things that make you feel less anxious. These things can be part of your ‘mental health toolbox’.

Type of microscope used to Reason for your decision produce the micrograph

Figure 1.1

EN

Figure 1.2 Figure 1.3 Table 1.2: XXXXX

1.3 Sketching and measuring cell structures Measure the total width of the four palisade cells A, B, C and D in graticule units.

C

Figure 1.3: Drawing of plant cells.

Figure 1.4 shows a micrograph of parts of two cells from the small intestine of a mammal. The structures along the surfaces of the two cells are microvilli.

State the type of microscope that was used to obtain this micrograph.

Give a reason for your answer.

[2]

D

R

AF

a

T

2

Figure 1.2: Micrograph of a cell from the pancreas

&

Figure 1.1: Micrograph of plant cells with starch grains.

O

N

FI D

1

Figure 1.5: XXXXXX

Figure 1.4: XXXXX

6

7

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.4 Cell structures and their functions

2

Working with your classmates is a great way to help you learn and remember things.

Try this group activity.

Figure 1.6 shows a micrograph of parts of two cells from the small intestine of a mammal. The structures along the surfaces of the two cells are microvilli. a b

State the type of microscope that was used to obtain this micrograph.

Give a reason for your answer.

The magnification of the micrograph is x12 500. i Calculate the length of the microvillus between points X and Y. Show your working.

[2]

TI AL

This next question contains the command word 'calculate'. Remember that this means to work out from given information.

PRACTICAL ACTIVITY 1

Work in groups of ten. Each group should make one copy of the following table on stiff card.

[3]

START

EN

Chloroplast Nucleus

D

Ribosomes

T

Write your own definition for the following key term:

QUICK RECALL 2: SUBJECT KNOWLEDGE

•

standard form

•

graticule

•

mitochondrion

These are found on rough endoplasmic reticulum (RER)

Write your own definition for the following key term: •

semi-permeable

•

chlorophyll

•

feature

This structure contains cellulose as a strengthening material Makes ribosomes

Nucleolus

Site of ATP synthesis in aerobic respiration

Mitochondrion

Makes lysosomes

Golgi apparatus

Has a ‘9 + 2’ arrangement of microtubules

Cilium

Mainly contains digestive enzymes

Lysosome

END

Table 1.3: XXXX Cut up the card so that each piece of card has one term and one description (one row of the table). There are therefore ten cards.

Shuffle the cards and take one each. The student with the START card reads out the description and the student who has the correct matching term reads out THE correct term from their card. They then read out the description on their card. This continues until it reaches the END card. Your teacher will help if you get stuck.

The cards can be reshuffled and the activity repeated to see if you can do it faster the second time.

AF

Figure 1.6 : XXXXXXX

Chromosomes are found in this structure in eukaryotic cells

Cell wall

FI N O C &

DEFINE THESE TERMS

Photosynthesis occurs in this organelle

DEFINE THESE TERMS

D

R

If an organelle is 25 nm, what microscopes can you use to observe it?

8

9

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1.4 Cell structures and their functions

2

Working with your classmates is a great way to help you learn and remember things.

Try this group activity.

Figure 1.6 shows a micrograph of parts of two cells from the small intestine of a mammal. The structures along the surfaces of the two cells are microvilli. a b

State the type of microscope that was used to obtain this micrograph.

Give a reason for your answer.

The magnification of the micrograph is x12 500. i Calculate the length of the microvillus between points X and Y. Show your working.

[2]

TI AL

This next question contains the command word 'calculate'. Remember that this means to work out from given information.

PRACTICAL ACTIVITY 1

Work in groups of ten. Each group should make one copy of the following table on stiff card.

[3]

START

EN

Chloroplast Nucleus

D

Ribosomes

T

Write your own definition for the following key term:

QUICK RECALL 2: SUBJECT KNOWLEDGE

•

standard form

•

graticule

•

mitochondrion

These are found on rough endoplasmic reticulum (RER)

Write your own definition for the following key term: •

semi-permeable

•

chlorophyll

•

feature

This structure contains cellulose as a strengthening material Makes ribosomes

Nucleolus

Site of ATP synthesis in aerobic respiration

Mitochondrion

Makes lysosomes

Golgi apparatus

Has a ‘9 + 2’ arrangement of microtubules

Cilium

Mainly contains digestive enzymes

Lysosome

END

Table 1.3: XXXX Cut up the card so that each piece of card has one term and one description (one row of the table). There are therefore ten cards.

Shuffle the cards and take one each. The student with the START card reads out the description and the student who has the correct matching term reads out THE correct term from their card. They then read out the description on their card. This continues until it reaches the END card. Your teacher will help if you get stuck.

The cards can be reshuffled and the activity repeated to see if you can do it faster the second time.

AF

Figure 1.6 : XXXXXXX

Chromosomes are found in this structure in eukaryotic cells

Cell wall

FI N O C &

DEFINE THESE TERMS

Photosynthesis occurs in this organelle

DEFINE THESE TERMS

D

R

If an organelle is 25 nm, what microscopes can you use to observe it?

8

9

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1

CONTINUED c

The diagram shows a method for separating the different components of cells. This technique is called ultracentrifugation.

Give the letter of the component or components in which you would expect to find: i ii

[1]

phospholipids.

[1]

If this process were carried out using plant cells, which other cell organelles might you expect to find in the pellet containing mitochondria? Explain your answer.

[2] [Total: 10]

EN

d

DNA

TI AL

CONTINUED

SELF-ASSESSMENT

D

The command word ‘Suggest’ means to apply knowledge and understanding to situations where there are a range of valid responses in order to make proposals / put forward considerations. Look at your answers to questions a and b.

Have you fulfilled the command term?

•

Are your answers clear?

Figure 1.9 shows the same eyepiece graticule, using the same objective lens, but this time with a stage micrometer on the microscope stage.

Use the two images to calculate the length of the villus that can be seen beneath the eyepiece graticule. Show each step in your working.

[2]

R

contained a buffer

iii had the same water potential as the cells.

10

Figure 1.8 shows a light micrograph of some villi in the small intestine, seen using an eyepiece graticule.

Suggest why the solution in which the broken-up cells were suspended: ii

Suggest why ribosomes do not collect in the pellet until the final stage of the centrifugation.

D

b

1

AF

Figure 1.7 : XXXXX a

If there is anything you need to do to improve these answers, do this now.

T

&

C

O

N

FI

•

[2]

[1] Figure 1.8: Light micrograph of villi seen using an eyepiece graticule.

Figure 1.9: Stage micrometer seen using an eyepiece graticule.

11

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

1

CONTINUED c

The diagram shows a method for separating the different components of cells. This technique is called ultracentrifugation.

Give the letter of the component or components in which you would expect to find: i ii

[1]

phospholipids.

[1]

If this process were carried out using plant cells, which other cell organelles might you expect to find in the pellet containing mitochondria? Explain your answer.

[2] [Total: 10]

EN

d

DNA

TI AL

CONTINUED

SELF-ASSESSMENT

D

The command word ‘Suggest’ means to apply knowledge and understanding to situations where there are a range of valid responses in order to make proposals / put forward considerations. Look at your answers to questions a and b.

Have you fulfilled the command term?

•

Are your answers clear?

Figure 1.9 shows the same eyepiece graticule, using the same objective lens, but this time with a stage micrometer on the microscope stage.

Use the two images to calculate the length of the villus that can be seen beneath the eyepiece graticule. Show each step in your working.

[2]

R

contained a buffer

iii had the same water potential as the cells.

10

Figure 1.8 shows a light micrograph of some villi in the small intestine, seen using an eyepiece graticule.

Suggest why the solution in which the broken-up cells were suspended: ii

Suggest why ribosomes do not collect in the pellet until the final stage of the centrifugation.

D

b

1

AF

Figure 1.7 : XXXXX a

If there is anything you need to do to improve these answers, do this now.

T

&

C

O

N

FI

•

[2]

[1] Figure 1.8: Light micrograph of villi seen using an eyepiece graticule.

Figure 1.9: Stage micrometer seen using an eyepiece graticule.

11

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

SELF-EVALUATION CHECKLIST

How does this connect with what you already know?

Why do you think it is important to know?

Let’s revisit the learning objectives and exam skills objectives for this chapter.

Decide how confident you are with each statement.

TI AL

REFLECTION

QUICK RECALL 4: SUBJECT KNOWLEDGE

Needs more work

Almost there

Confident to move on

know the structure of animal, plant and bacterial cells, and of viruses

The diagram is a drawing of a cell from the body of a mammal.

understand the use of light microscopes and electron microscopes to study cells

EN

be able to sketch and measure cell structures

know the variety of cell structures and their functions

D

show that you understand the ‘outline’ command word and answer an 'outline' question

FI

show that you understand the 'state' command word and answer a 'state' question.

Figure 1.10: XXXXXXX

AF

List the letters of the structures in the drawing which are made up of, or are surrounded by, phospholipid membranes.

QUICK RECALL 5: EXAM SKILLS

R

b

State the type of microscope that would be used to allow this amount of detail to be seen in the cell.

D

a

What does the command term ‘outline’ mean to you?

12

T

&

C

O

N

show that you understand the 'calculate' command word and answer a 'calculate' question. show that you understand the 'suggest' command word and answer a 'suggest' question.

What will you do to work on the topics that you are not yet ready to move on from?

Once you are confident to move on, complete the table below.

Now I

Show it

know the structure of animal, plant and bacterial cells, and of viruses

Describe at least one difference between each type of cell and particle.s

understand the use of light microscopes and electron microscopes to study cells

Name four organelles you would see with one type of microscope only.

am able to sketch and measure cell structures

Draw a typical animal cell.

know the variety of cell structures and their functions

List three cell structures and their functions.

show that you understand the ‘outline’ command word and answer an 'outline' question

Explain the command word ‘outline’ to another person.

show that you understand the 'state' command word and answer a 'state' question.

Explain the command word ‘state ’ to another person.

show that you understand the 'calculate' command word and answer a 'calculate' question.

Explain the command word ‘calculate’ to another person.

show that you understand the 'suggest' command word and answer a 'suggest' question.

Explain the command word ‘suggest’ to another person.

13

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

1 Cell structure

SELF-EVALUATION CHECKLIST

How does this connect with what you already know?

Why do you think it is important to know?

Let’s revisit the learning objectives and exam skills objectives for this chapter.

Decide how confident you are with each statement.

TI AL

REFLECTION

QUICK RECALL 4: SUBJECT KNOWLEDGE

Needs more work

Almost there

Confident to move on

know the structure of animal, plant and bacterial cells, and of viruses

The diagram is a drawing of a cell from the body of a mammal.

understand the use of light microscopes and electron microscopes to study cells

EN

be able to sketch and measure cell structures

know the variety of cell structures and their functions

D

show that you understand the ‘outline’ command word and answer an 'outline' question

FI

show that you understand the 'state' command word and answer a 'state' question.

Figure 1.10: XXXXXXX

AF

List the letters of the structures in the drawing which are made up of, or are surrounded by, phospholipid membranes.

QUICK RECALL 5: EXAM SKILLS

R

b

State the type of microscope that would be used to allow this amount of detail to be seen in the cell.

D

a

What does the command term ‘outline’ mean to you?

12

T

&

C

O

N

show that you understand the 'calculate' command word and answer a 'calculate' question. show that you understand the 'suggest' command word and answer a 'suggest' question.

What will you do to work on the topics that you are not yet ready to move on from?

Once you are confident to move on, complete the table below.

Now I

Show it

know the structure of animal, plant and bacterial cells, and of viruses

Describe at least one difference between each type of cell and particle.s

understand the use of light microscopes and electron microscopes to study cells

Name four organelles you would see with one type of microscope only.

am able to sketch and measure cell structures

Draw a typical animal cell.

know the variety of cell structures and their functions

List three cell structures and their functions.

show that you understand the ‘outline’ command word and answer an 'outline' question

Explain the command word ‘outline’ to another person.

show that you understand the 'state' command word and answer a 'state' question.

Explain the command word ‘state ’ to another person.

show that you understand the 'calculate' command word and answer a 'calculate' question.

Explain the command word ‘calculate’ to another person.

show that you understand the 'suggest' command word and answer a 'suggest' question.

Explain the command word ‘suggest’ to another person.

13

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2 Biological molecules

Getting exam ready Providing a response to an exam question

TI AL

Mark allocation

To help you prepare for your exams, this book guides you through a framework of exam skills that will help you to show what you know about Biology in the Cambridge exam context; from the various elements of understanding the question, to writing a good response, to developing the kind of behaviours and habits that will support you along the way.

In this chapter you will check that you know the key concepts of biological molecules and practice how you show this knowledge in an exam.

Answering questions and testing your knowledge is very important for your memory. Every time you recall information and write an answer, your knowledge and understanding gets stronger. Once you have consolidated your memory, you can better concentrate on what in particular the exam question is asking you to do.

EN

Alongside recalling your knowledge on biological molecules, in this chapter you will also practice understanding mark allocation and its relation to answer requirements.

The relevant part of the Cambridge Exam Skills Framework is as follows: Extract from the Cambridge Exam Skills Framework

For that reason, there are three kinds of question in this chapter.

3

Self assessment questions: Questions that help you monitor your own progress

N

Exam skills questions: Questions that practice showing what you know about biological molecules in an exam

O

2

Sub-skill

Mark allocation awareness

Objectives

• • •

Identify the total number of marks allocated to an exam question.

Understand how the marks break down across the question and the paper as a whole.

Understand what this means for the depth of response you need to give.

In this chapter you are going to increase your understanding of how marks are allocated and what you need to do in response.

EXAM SKILLS OBJECTIVES In this chapter, you will: •

Understand mark allocation and relate it to answer requirements

In this chapter, you will: understand how large biological molecules are made from smaller molecules

•

know the structure and function of carbohydrates, lipids and proteins

•

know the biochemical tests to identify carbohydrates, lipids and proteins

•

know some key properties of water than make life possible

D

R

AF

•

T

&

C

You will also find questions about cell structure. This is because your memory is best increased by a technique called interleaving. This is when you return to a previously studied topic within a certain timeframe to make sure that you remember it properly.

LEARNING OBJECTIVES

Providing a response to an exam question

FI

Knowledge recall questions: Questions that increase your memory of what you know about biological molecules

1

Exam skill

D

Exam questions are very specific and are looking for certain things, so you need to be ready for the approach that they take so that you can really show what you know.

14

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CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2 Biological molecules

Getting exam ready Providing a response to an exam question

TI AL

Mark allocation

To help you prepare for your exams, this book guides you through a framework of exam skills that will help you to show what you know about Biology in the Cambridge exam context; from the various elements of understanding the question, to writing a good response, to developing the kind of behaviours and habits that will support you along the way.

In this chapter you will check that you know the key concepts of biological molecules and practice how you show this knowledge in an exam.

Answering questions and testing your knowledge is very important for your memory. Every time you recall information and write an answer, your knowledge and understanding gets stronger. Once you have consolidated your memory, you can better concentrate on what in particular the exam question is asking you to do.

EN

Alongside recalling your knowledge on biological molecules, in this chapter you will also practice understanding mark allocation and its relation to answer requirements.

The relevant part of the Cambridge Exam Skills Framework is as follows: Extract from the Cambridge Exam Skills Framework

For that reason, there are three kinds of question in this chapter.

3

Self assessment questions: Questions that help you monitor your own progress

N

Exam skills questions: Questions that practice showing what you know about biological molecules in an exam

O

2

Sub-skill

Mark allocation awareness

Objectives

• • •

Identify the total number of marks allocated to an exam question.

Understand how the marks break down across the question and the paper as a whole.

Understand what this means for the depth of response you need to give.

In this chapter you are going to increase your understanding of how marks are allocated and what you need to do in response.

EXAM SKILLS OBJECTIVES In this chapter, you will: •

Understand mark allocation and relate it to answer requirements

In this chapter, you will: understand how large biological molecules are made from smaller molecules

•

know the structure and function of carbohydrates, lipids and proteins

•

know the biochemical tests to identify carbohydrates, lipids and proteins

•

know some key properties of water than make life possible

D

R

AF

•

T

&

C

You will also find questions about cell structure. This is because your memory is best increased by a technique called interleaving. This is when you return to a previously studied topic within a certain timeframe to make sure that you remember it properly.

LEARNING OBJECTIVES

Providing a response to an exam question

FI

Knowledge recall questions: Questions that increase your memory of what you know about biological molecules

1

Exam skill

D

Exam questions are very specific and are looking for certain things, so you need to be ready for the approach that they take so that you can really show what you know.

14

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CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.0 Exam Skills

2.1 How large biological molecules are made from smaller molecules

Exam questions are allocated a number of marks. You can use the number of marks to help guide you to the required answer length or number of points to make. For example, this question clearly asks you to write three characteristics and is allocated three marks. It is likely that one mark will be awarded for each characteristic. You only need to state the characteristic name – expanding on it with more detail will not gain any additional marks and will instead use up your time.

the test that you would use to distinguish between the two disaccharides

•

the results of the test for each disaccharide.

TI AL

Figure 2.x shows a diagram of the enzyme RNase.

FI

Like lactose, sucrose is a disaccharide. If you were given a solution of lactose and a solution of sucrose, state briefly how you could distinguish between them.

N

[2]

Using information in the diagram, is the alpha or beta form of glucose used to make lactose? Explain your answer.

[2]

C

[2]

&

Draw diagrams to show the structures of separate molecules of glucose and galactose.

O

What do you think your answers would need to contain for the following questions?

T

QUICK RECALL 1: EXAM SKILLS

D

R

AF

Outline the key features of your revision plan.

16

2

D

•

2

Describe the processes of hydrolysis and condensation.

[3]

The following question does not state the number of points you need to make.

However, 2 marks are allocated, so it is likely that you will need to make at least two distinct points to get both marks, such as:

1

1

EN

State three characteristics of monosaccharides.

You will notice in the below question that parts a and b carry different numbers of marks. Why do you think this is?

DEFINE THESE TERMS

Figure 2.1: XXXXXX a b

State the level of protein structure shown in Figure 2.x.

[1] Addition of a substance called ß-mercaptoethanol causes the reduction of disulphide bonds.

Explain the effect this would have on RNase activity.

[4] [Total: 5]

Write your own definition for the following key term: •

peptide bond

•

glycosidic bond

•

monomer

QUICK RECALL 2: SUBJECT KNOWLEDGE Summarise the differences between an animal cell, plant cell, bacterial cell and virus particle.

QUICK RECALL 3: EXAM SKILLS How many points do you think you would need to make to answer the following question?

Name the products of digestion

[2]

17

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.0 Exam Skills

2.1 How large biological molecules are made from smaller molecules

Exam questions are allocated a number of marks. You can use the number of marks to help guide you to the required answer length or number of points to make. For example, this question clearly asks you to write three characteristics and is allocated three marks. It is likely that one mark will be awarded for each characteristic. You only need to state the characteristic name – expanding on it with more detail will not gain any additional marks and will instead use up your time.

the test that you would use to distinguish between the two disaccharides

•

the results of the test for each disaccharide.

TI AL

Figure 2.x shows a diagram of the enzyme RNase.

FI

Like lactose, sucrose is a disaccharide. If you were given a solution of lactose and a solution of sucrose, state briefly how you could distinguish between them.

N

[2]

Using information in the diagram, is the alpha or beta form of glucose used to make lactose? Explain your answer.

[2]

C

[2]

&

Draw diagrams to show the structures of separate molecules of glucose and galactose.

O

What do you think your answers would need to contain for the following questions?

T

QUICK RECALL 1: EXAM SKILLS

D

R

AF

Outline the key features of your revision plan.

16

2

D

•

2

Describe the processes of hydrolysis and condensation.

[3]

The following question does not state the number of points you need to make.

However, 2 marks are allocated, so it is likely that you will need to make at least two distinct points to get both marks, such as:

1

1

EN

State three characteristics of monosaccharides.

You will notice in the below question that parts a and b carry different numbers of marks. Why do you think this is?

DEFINE THESE TERMS

Figure 2.1: XXXXXX a b

State the level of protein structure shown in Figure 2.x.

[1] Addition of a substance called ß-mercaptoethanol causes the reduction of disulphide bonds.

Explain the effect this would have on RNase activity.

[4] [Total: 5]

Write your own definition for the following key term: •

peptide bond

•

glycosidic bond

•

monomer

QUICK RECALL 2: SUBJECT KNOWLEDGE Summarise the differences between an animal cell, plant cell, bacterial cell and virus particle.

QUICK RECALL 3: EXAM SKILLS How many points do you think you would need to make to answer the following question?

Name the products of digestion

[2]

17

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.2 The structure and function of carbohydrates, lipids and proteins

When is staining used for cell samples viewed under microscopes?

TI AL

Complete the table.

QUICK RECALL 5: SUBJECT KNOWLEDGE

Polysaccharide

Name of monomer

Bonds joining monomers

Description

Function

Amylose

α-glucose

α(1,4)

long helical compact

cellular storage of glucose (energy) does not affect osmotic potential found in plants

Name three types of bonds that can be found in large biological molecules.

2.3 Biochemical tests to identify carbohydrates, lipids and proteins

EN

1

QUICK RECALL 4: SUBJECT KNOWLEDGE

Amylopectin Glycogen

Describe is a command word that asks you to give the characteristics and main features of a topic. In the following question this carries more marks because it involves higher order thinking skills.

Figure 2.2: XXXXXX

e

D

f

osmotic potential

•

ester linkage

•

triglyceride

FI 2 a b

O

•

N

Write your own definition for the following key term:

Why do you need to use excess Benedict’s reagent to find the concentration of a sugar solution?

Outline how you could use the Benedict’s test to estimate the concentration of a solution of a reducing sugar.

Describe how you could test a sample of sesame seeds for the presence of lipids.

[2] [2] [3]

Figure 2.3 shows the general structure of a triglyceride.

T

[2]

b

[1] [1]

AF

c d

Suggest two functions that lactose could have.

What is the name given to the reaction between two monosaccharides that results in the formation of lactose?

Identify the bond labelled X in the diagram.

Draw diagrams to show the structures of separate molecules of glucose and galactose.

Using the information in the diagram, is the alpha or beta form of glucose used to make lactose? Explain your answer.

Like lactose, sucrose is a disaccharide. If you were given a solution of lactose and a solution of sucrose, state briefly how you could distinguish between them.

[2]

Figure 2.3: XXXXXX

[2]

R

a b

1 a

DEFINE THESE TERMS

C

Figure 2.2 shows a disaccharide called lactose. The carbon atoms are numbered.

You are not expected to have seen this structure before. Lactose is a reducing sugar found in milk. It is made from a reaction between the two monosaccharides glucose and galactose.

&

2

D

Cellulose

3

Complete the diagram to show the products of hydrolysis of this triglyceride. [2]

[2]

[Total: 10]

Did you find some of these questions more difficult than others?

If so, why do you think this was?

18

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CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.2 The structure and function of carbohydrates, lipids and proteins

When is staining used for cell samples viewed under microscopes?

TI AL

Complete the table.

QUICK RECALL 5: SUBJECT KNOWLEDGE

Polysaccharide

Name of monomer

Bonds joining monomers

Description

Function

Amylose

α-glucose

α(1,4)

long helical compact

cellular storage of glucose (energy) does not affect osmotic potential found in plants

Name three types of bonds that can be found in large biological molecules.

2.3 Biochemical tests to identify carbohydrates, lipids and proteins

EN

1

QUICK RECALL 4: SUBJECT KNOWLEDGE

Amylopectin Glycogen

Describe is a command word that asks you to give the characteristics and main features of a topic. In the following question this carries more marks because it involves higher order thinking skills.

Figure 2.2: XXXXXX

e

D

f

osmotic potential

•

ester linkage

•

triglyceride

FI 2 a b

O

•

N

Write your own definition for the following key term:

Why do you need to use excess Benedict’s reagent to find the concentration of a sugar solution?

Outline how you could use the Benedict’s test to estimate the concentration of a solution of a reducing sugar.

Describe how you could test a sample of sesame seeds for the presence of lipids.

[2] [2] [3]

Figure 2.3 shows the general structure of a triglyceride.

T

[2]

b

[1] [1]

AF

c d

Suggest two functions that lactose could have.

What is the name given to the reaction between two monosaccharides that results in the formation of lactose?

Identify the bond labelled X in the diagram.

Draw diagrams to show the structures of separate molecules of glucose and galactose.

Using the information in the diagram, is the alpha or beta form of glucose used to make lactose? Explain your answer.

Like lactose, sucrose is a disaccharide. If you were given a solution of lactose and a solution of sucrose, state briefly how you could distinguish between them.

[2]

Figure 2.3: XXXXXX

[2]

R

a b

1 a

DEFINE THESE TERMS

C

Figure 2.2 shows a disaccharide called lactose. The carbon atoms are numbered.

You are not expected to have seen this structure before. Lactose is a reducing sugar found in milk. It is made from a reaction between the two monosaccharides glucose and galactose.

&

2

D

Cellulose

3

Complete the diagram to show the products of hydrolysis of this triglyceride. [2]

[2]

[Total: 10]

Did you find some of these questions more difficult than others?

If so, why do you think this was?

18

19

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.4 Key properties of water that make life possible

Look at your diagram for question 2b.

•

Is the diagram clear and neatly drawn?

•

Have you correctly identified single and double bonds? Check against the coursebook if you need to.

•

Have you included all products?

State the property of water that allows each of the following (a, b and c) to take place. Explain the importance of a, b and c:

1

a b c

QUICK RECALL 6: SUBJECT KNOWLEDGE 2

TI AL

SELF-ASSESSMENT

the cooling of skin during sweating the transport of glucose and ions in a mammal much smaller temperature fluctuations in lakes and oceans than in terrestrial (land-based) habitats.

EN

Plan an essay on the biological importance of water.

Start by planning it to include the following: water as a solvent water as a transport medium high specific heat capacity high latent heat of vaporisation density and freezing properties high surface tension and cohesion hydrogen bonding between water molecules water as a reagent.

b

Remember that one small division on the micrometer is 0.01 mm.

Use your answer to a to calculate how many micrometers (µm) are represented by one small division on the eyepiece graticule.

Write your own definition for the following key term: • • •

reagent

suspension emulsion

AF

QUICK RECALL 7: SUBJECT KNOWLEDGE

• •

C

How many small divisions on the micrometer equal 80 small divisions on the eyepiece graticule?

T

a

&

Figure 2.4: Stage micrometer seen using an eyepiece graticule.

For each of these properties you need to:

O

DEFINE THESE TERMS

N

FI

D

• • • • • • • •

Try to give examples of both plants and animals.

REFLECTION How did you find the essay planning task? Did you know what to do, or were there any areas you were unsure about? Identify these, and then consider how you could practise them or who you could ask for support. Being confident about planning essays will help you in the exam by providing a structure and making sure that you include everything you want to say.

Copy and complete the table to summarise some differences between collagen and haemoglobin.

2 3 4 5

20

R

1

Haemoglobin

D

Collagen

explain how water achieves it (hydrogen bonding is very important) give biological examples.

QUICK RECALL 8: SUBJECT KNOWLEDGE

DEFINE THESE TERMS Write your own definition for the following key term:

What tests would you use to identify the presence of the following?

•

heat capacity

•

proteins

•

solvent

•

carbohydrates

•

vaporisation

•

fats

•

characteristics

21

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

2 Biological molecules

2.4 Key properties of water that make life possible

Look at your diagram for question 2b.

•

Is the diagram clear and neatly drawn?

•

Have you correctly identified single and double bonds? Check against the coursebook if you need to.

•

Have you included all products?

State the property of water that allows each of the following (a, b and c) to take place. Explain the importance of a, b and c:

1

a b c

QUICK RECALL 6: SUBJECT KNOWLEDGE 2

TI AL

SELF-ASSESSMENT

the cooling of skin during sweating the transport of glucose and ions in a mammal much smaller temperature fluctuations in lakes and oceans than in terrestrial (land-based) habitats.

EN

Plan an essay on the biological importance of water.

Start by planning it to include the following: water as a solvent water as a transport medium high specific heat capacity high latent heat of vaporisation density and freezing properties high surface tension and cohesion hydrogen bonding between water molecules water as a reagent.

b

Remember that one small division on the micrometer is 0.01 mm.

Use your answer to a to calculate how many micrometers (µm) are represented by one small division on the eyepiece graticule.

Write your own definition for the following key term: • • •

reagent

suspension emulsion

AF

QUICK RECALL 7: SUBJECT KNOWLEDGE

• •

C

How many small divisions on the micrometer equal 80 small divisions on the eyepiece graticule?

T

a

&

Figure 2.4: Stage micrometer seen using an eyepiece graticule.

For each of these properties you need to:

O

DEFINE THESE TERMS

N

FI

D

• • • • • • • •

Try to give examples of both plants and animals.

REFLECTION How did you find the essay planning task? Did you know what to do, or were there any areas you were unsure about? Identify these, and then consider how you could practise them or who you could ask for support. Being confident about planning essays will help you in the exam by providing a structure and making sure that you include everything you want to say.

Copy and complete the table to summarise some differences between collagen and haemoglobin.

2 3 4 5

20

R

1

Haemoglobin

D

Collagen

explain how water achieves it (hydrogen bonding is very important) give biological examples.

QUICK RECALL 8: SUBJECT KNOWLEDGE

DEFINE THESE TERMS Write your own definition for the following key term:

What tests would you use to identify the presence of the following?

•

heat capacity

•

proteins

•

solvent

•

carbohydrates

•

vaporisation

•

fats

•

characteristics

21

CAMBRIDGE INTERNATIONAL AS & A LEVEL BIOLOGY: REVISION GUIDE

QUICK RECALL 9: SUBJECT KNOWLEDGE List: three organelles each lacking a boundary membrane

b

three organelles each surrounded by a single membrane

c

three organelles each surrounded by two membranes (an envelope).

FI D EN TI AL

a

SELF-EVALUATION CHECKLIST

Let’s revisit the learning objectives and exam skills objectives for this chapter.

Decide how confident you are with each statement.

Needs more work

Almost there

Confident to move on

understand how large biological molecules are made from smaller molecules know the structure and function of carbohydrates, lipids and proteins

N

know the biochemical tests to identify carbohydrates, lipids and proteins

O

know some key properties of water than make life possible

C

understand mark allocation and relate it to answer requirements

What will you do to work on the topics that you are not yet ready to move on from?

&

Once you are confident to move on, complete the table below.

T

Now I

Describe how a polysaccharide is formed.

know the structure and function of carbohydrates, lipids and proteins

Describe the structure of a lipid and give one function.

R

AF

understand how large biological molecules are made from smaller molecules

know the biochemical tests to identify carbohydrates, lipids and proteins

Describe the test for protein.

know some key properties of water than make life possible

State one property of water and explain how it makes life possible

understand mark allocation and relate it to answer requirements

Look at two of the exam-style questions in this unit and say how many points you would be likely to need to write in your answer to be awarded the full marks.

D 22

Show it