Paper 2 Bio

Question 1

How does a change from optimum pH affect an enzyme?

Answer 1

It interferes with the bonds holding the enzyme together, changing the shape of the active site which denatures the enzyme.

Question 2

What is turgor pressure?

Answer 2

Turgor pressure is the pressure of water pushing the membrane against the cell wall of a plant cell.

Question 3

When is a plant said to be turgid?

Answer 3

When it is well watered, the cells in a plant will draw in water by osmosis and becomes plump and swollen.

Question 4

Why are turgid cells important in a plant?

Answer 4

As a means of support

Question 5

A balanced diet should include appropriate proportions of which 6 essential nutrients?

Answer 5

Carbohydrates, proteins, lipids, vitamins, minerals, and water.

Question 6

What is the importance of dietary fibre?

Answer 6

To aid the movement of food through the gut

Question 7

Energy requirements vary with what three things?

Answer 7

Activity level, age, and pregnancy

Question 8

Describe how you would carry out an experiment to find out the energy value of a potato crisp. (4)

Answer 8

1. weigh crisp / mass of crisp;
2. burn crisp / eq;
3. burnt completely / eq;
4. heat water /
   hold (burning crisp) under tube /
   hold (burning crisp) under water /
   calorimeter / eq;
5. volume of water / mass of water;
6. measure temperature before and after /
   temperature rise / temperature increase /
   change in temperature / eq;

Question 9

Suggest why oxygen gas is passed into the calorimeter (1)

Answer 9

helps combustion / helps burning / eq;

Question 10

Describe the role of the phloem

Answer 10

• transports sucrose and amino acids (sugars) from the leaves, where they are made, to other parts of the plant.
• this movement of food substances around the plant is called translocation

Question 11

The net exchange of gases (carbon dioxide and oxygen) depends on…

Answer 11

light intensity

Question 12

respiration happens during the…

Answer 12

day AND night (a plants always gotta have its energy yo)

Question 13

photosynthesis happens during the…

Answer 13

day (ie. when there’s light available)

Question 14

Why, in daylight, do plants release oxygen, and take in carbon dioxide?

Answer 14

Light intensity is HIGH, so plants make more oxygen in photosynthesis that they use in respiration, therefore releasing the excess oxygen. They also use up more CO2 than they produce, so take in CO2.

Question 15

Why, at night time, do plants take in oxygen and release carbon dioxide?

Answer 15

Light intensity is LOW, so plants only respire (like us!!) as there’s not enough light for photosynthesis.

Question 16

Describe some advantages of cloning.

Answer 16

• Useful characteristics are always passed on
• Farmers do not have to wait until breeding season to produce new animals so the process is faster
• Infertile animals can be cloned
• Animals that can produce medicines in their milk can be cloned
• Animals that have organs suitable for organ transplantation (i.e. pigs) can be developed by genetic engineering and cloned so that there is not such a long waiting list to recieve organ donations.

Question 17

Describe some disavantages of cloning.

Answer 17

• Cloned animals are often not as healthy as normal ones, embryos formed by cloning from adult cells do not delevop normally
• It is difficult, time consuming and expensive
• As it is a new science it may have unforseen consequences.

Question 18

What is meant by a transgenic organism?

Answer 18

• Organisms that contain genes from other species

- i.e. bacteria that contain the gene for human insulin are transgenic

Question 19

what is the function of platelets?

Answer 19

• When you get cut platelets clump together to form a seal over the wound
• In a clot, platelets are held together by a mesh of a protein called fibrin
• This is known as a blood clot. Blood clots stop you loosing too much blood and prevent the entry of microorganisms

Question 20

Describe how a vaccination protects from future infections

Answer 20

• When a dead or inactive version of a microorganism enters the blood the lymphocytes produce antibodies.
• These antibodies bind to the specific antigen molecules on the microorganism, marking it for destruction
• The phagocytes then engulf the microorganism and digest it using enzymes, effectively destroying it
• Some of the lymphocytes remain in the blood and act as memory cells
• This means you will have a much faster production of antibodies if you are infected with the same microorganism again, preventing infection.

Question 21

What is the iris reflex?

Answer 21

• When the diameter of the pupil changes in reaction to a change of light intensity
• The circular and radial muscles that make up the iris relax and contract in order to change the diameter of the pupil.

Question 22

Explain how the iris changes in bright or dim light.

The iris is made up of circular and radial muscles

Answer 22

BRIGHT LIGHT:
- Very bright light can damage the retina so the pupil has to be made smaller in bright light.
- The radial muscles relax and the circular muscles contract
- This makes the diameter of the pupil much smaller, limiting how much light can enter.
DIM LIGHT:
- You need as much light as possible entering the eye so that you can see
- The radial muscles contract ad the circular muscles relaz

Question 23

Describe the reflex that takes place in the eye when focusing on near or distant objects.

Answer 23

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