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9-1 OCR Gateway Combined Science ATopic B1-B3

B1: Homework 1

1. This question is about DNA. Rosalind Franklin was a British scientist. Her work was important in helping James Watson and Francis Crick work out the structure of DNA. She used X-rays to discover that DNA has a helix shape.

(a) Why is DNA important for all living things? (2)

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(b) The structure of DNA is sometimes described as a double helix. Describe what is meant by a double helix. You can use a diagram to help you answer. (2)

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2. This question is about DNA. Erwin Chargaff was an Austrian scientist. His work was important in helping James Watson and Francis Crick work out the structure of DNA. Chargaff discovered that, in any piece of DNA, the number of A bases is always the same as the number of T bases. Also the number of C bases is always the same as the number of G bases.

(a) In one piece of DNA, 27% of the bases are A. Use Chargaff’s discovery to work out the percentages of each of the other bases. (2)

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Mark Grade


3. Scientists have discovered a new cell. They need to decide if the new cell is an animal, plant or bacterial cell. Look at the diagram.

Use the diagram to decide whether the cell is animal, plant or bacterial.

The cell is ______________________________________________________________________________________

Give reasons for your answer. (2)

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4. The diagram shows a cell from a pelargonium leaf.

Describe the function of the vacuole. (2)

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Amylase is an enzyme. Look at the graph.One line shows the effect of temperature on amylase from humans. The other line shows a different amylase from bacteria found in hot water springs.


Compare and explain the shape of the graphs for both types of amylase.

The quality of your written communication will be assessed in your answer to this question.(6 marks)

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Carl is an athlete. He competes in the 200m sprint.

(a) Sprinting needs energy. Respiration is a process that releases energy. Describe this process and suggest how it helps movement during the sprint. (2)

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(b) During the spring Carl’s breathing rate and pulse rate increase. Write down two reasons why. (2)

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(c) Look at the table of data. It shows the maximum oxygen consumption for males of different fitness levels. The males are aged between 13 and 29 years old.

(i) Carl is 25 years old. He has a maximum oxygen consumption of 44cm3 per kg per minute. Carl wants to improve his fitness level to excellent. Look at the table. Calculate Carl’s maximum oxygen consumption as a percentage of the lowest excellent value. (1)

Answer: _______________________________________%

(ii) Carl was tested to obtain his maximum oxygen consumption after further training. He trained for one week doing gentle jogging. His maximum oxygen consumption at the end of the week was 45cm3 per kg per minute. The second week, he trained by sprinting and jogging. His maximum oxygen consumption at the end of this week was 48cm3 per kg per minute. Make a conclusion about Carl’s fitness level and the training he used. (2)

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1. Aaron wants to grow some tomato plants.

a) What are the three factors which he could change to make the plants grow faster? (3)

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b) Aaron decides to grow his tomatoes in a glasshouse. Explain why he did this. (1)

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2. A scientist investigated glucose production in swede plants. He looks at five processes, A to E, that are involved in sugar production. He finds out how energy is lost in each process.

Which process, A,B,C,D, or E produces oxygen gas? (1)

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3. Carbon dioxide and water are needed for photosynthesis. (a) Finish the balanced symbol equation for photosynthesis. (1)

6CO2 + 6H2O __________________________ + ____________________________________

(b) In 1649, scientists though that plants grew by only taking in solid material from the soil. A scientist called van Helmont did an experiment to test this idea. He grew a tree in a large pot of soil. He measured the mass of the soil and the tree before the experiment. He measured them again, five years later.

Please turn over


Explain how van Helmont’s experiment proved the scientists wrong. (2)

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4. Green plants contain chlorophyll. The molecular formula of chlorophyll is C55H72O5N4Mg. Plants get the magnesium (Mg) they need in form of compounds, such as magnesium sulphate, through their roots.

(a) How do plants get the carbon (C) they need to make chlorophyll? (1)

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(b) How do plants get the hydrogen (H) they need to make chlorophyll? (1)

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(c) How do plants get the oxygen (O) they need to make chlorophyll? (1)

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B2: Homework 1

Question 1Carol investigates the effect of water loss on plant cells. Look at the diagram of the apparatus she uses.

Carol records the mass of four different potato chips. She puts potato chip A into water. She puts chips B, C and D into different concentrations of sugar solution. She leaves them for 24 hours. Carol records the new mass of each chip. The table shows some of her results.

Mark Grade


(i) Calculate the missing results. Write your answers in the table. (2)(ii) Potato chip D lost mass. Explain why. Use ideas about osmosis. (2)

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Question 2Cathy is investigating osmosis. She measures the mass of four pieces of potato. She leaves each piece in a different sugar solution for 24 hours. She then measures the mass of each piece again.

The table shows her results.

(a) In which solution does the potato increase in mass the most?

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In which solution does the potato decrease in mass the most? (1)


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(b) Explain why some pieces of potato increase in mass. Use ideas about osmosis in your answer. (2)

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(c) Cathy puts another piece of potato in pure water for 24 hours. She uses a microscope to look at some of the cells from the potato.

(i) What would the cells look like? Choose A, B or C. (1)

(ii) What word describes the cells she sees? Put a ring around the answer. (1)

Crenated flaccid plasmolysed turgid wilted

Total: /9

B2: Homework 2

Question 1The picture shows Dolly the sheep.

Dolly grew from an embryo implanted into a surrogate mother sheep. (a) As the embryo grew, its cells divided. Write down the name of this type of cell division. (1)

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Mark Grade


(b) Just before cells divide, DNA replication occurs. Describe how DNA replication occurs. You may use labelled diagrams to help you answer. (3)

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Question 2Look at the picture of bull sperm cells. Bull sperm cells contain a different number of chromosomes to the number in body cells. Bull skin cells contain 60 chromosomes.

What is the haploid number of chromosomes for a bull? (1)

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Question 3Amy and Sarah are identical twins. Their development began when an egg cell and sperm cell joined to form a zygote. The zygote developed into an embryo made of many cells. After about a week the embryo split into the two twin embryos. The two embryos grew to become Amy and Sarah.


(a) Put one tick in each row of the table to show which cells are haploid and which are diploid. (2)

(b) What type of cell division happens to the zygote to form the embryo? (1)

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Total: /8

B2: Homework 3

Look at the diagram of a human heart.

Mark Grade


(a) Write the letter A to E next to the correct name for each part of the heart. (2)

(b) Blood contains cells. One type of cell is a red blood cell. (i) Red blood cells are adapted for their job by being very small. Explain why this helps them do their job.

(1)

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(ii) Haemoglobin is found in red blood cells. Haemoglobin is a protein made in the cytoplasm. Red blood cells start off life with a nucleus. The gene for haemoglobin is only found in the nucleus. Explain how it is possible that haemoglobin can be made in the cytoplasm. (2)

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(iii) Haemoglobin is important in transporting oxygen. Describe how haemoglobin transports oxygen from the lungs to the body cells. (2)

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(c) Blood also contains white blood cells. White blood cells and red blood cells are made in the bone marrow. Why can cells in the bone marrow produce both red and white blood cells? (2)

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Total:

B3: Homework 1

Question 1

(a)

Mark Grade


(b)

(c)


Total: /9

B3: Homework 2

Mark Grade


Question 1

Question 2Hormones are also used to control the menstrual cycle.

The process of ovulation is shown by the diagram below.

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28


(a) Between days 2 and 12 the follicle is developing. Which hormone is realised to cause

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(b) The developing follicle secretes oestrogen.

Oestrogen peaking stimulates the release of another hormone at about day 14.

Which hormone?

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(c) The corpeus luteum secretes progesterone.

What are the roles of progesterone?

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Question 3

The table shows the effectiveness of the combined pill and male condom as contraceptives.

The theoretical effectiveness is how well the birth control works when used correctly.

The actual effectiveness is how well the birth control works in ‘typical use’, taking into account human error and other factors.

Birth control method

Theoretical effectiveness

Actual effectiveness

combined pill 99% 92%male condom 98% 85%


Which is the better method of birth control and why?

You should consider the effectiveness and method of action.

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Total /11

B3: Homework 3

Question 1

This question is about diabetes

People who have diabetes lack a hormone or the hormone doesn’t work properly.

(a) What does this hormone normally control in the body?

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(b) Look at the picture of the diabetic food pyramid.

It is a guide to the amounts of different types of food that people with diabetes should eat.

There are two forms of diabetes known as Type 1 and Type 2.

Mark Grade


The diabetic food pyramid is used as a guide for people with diabetes.

Explain why using this food guide can help with the control of diabetes and explain the important of this to people with Type 1 diabetes.

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[6]

[Total: 7]

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