TOPIC 4 - BIOENERGETICS

Question 1

What is photosynthesis?

Answer 1

It uses energy to change carbon dioxide and water into glucose and oxygen.
It takes place in chloroplasts in green plant cells - they contain pigment like chlorophyll to absorb light.
Energy is transferred to the chloroplasts from the environment by light.
Photosynthesis is endothermic - this means energy is transferred from the environment in the process.

Question 2

What is the word equation for photosynthesis?

Answer 2

Carbon dioxide + water —> glucose + oxygen

Question 3

What do plants use glucose for?

Answer 3

Respiration
Making cellulose
Stored as oils or fats
Stored as starch

Question 4

What are some limiting factors that effect photosynthesis?

Answer 4

Light
Carbon dioxide oxygen concentration
Temperature
Chlorophyll

Question 5

How does light affect the rate of photosynthesis?

Answer 5

Light provides energy needed for photosynthesis.
As the light levels is raised, the rate of photosynthesis increases steadily, but only to a certain point.
Beyond that, it won’t make a difference because it will ow be temperature or carbon dioxide that are the limiting factors of photosynthesis.

Question 6

How does carbon dioxide affect the rate of photosynthesis?

Answer 6

The a,lung of carbon dioxide will only increase the rate of photosynthesis up to a point. After this, the graph flattens out. This means that carbon dioxide is no longer the limiting factor.

Question 7

How does temperature affect the rate of photosynthesis?

Answer 7

If the temperature is low, the enzymes will work more slowly. But, if the temperature is too high, the enzymes become denatured. This happens at about 45 degrees celsius.

Question 8

What is the practical to show the rate of photosynthesis?

Answer 8

Canadian pondweed can be used to measure the effect of light intensity on the rate of photosynthesis. The rate at which pondweed produces oxygen corresponds to the rate at which it is photosynthesising. The faster the rate of oxygen production, the faster the rate of photosynthesis.

• a source of white light is placed at a specific distance from the pondweed.
• the pondweed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen releases will collect in the capillary tube.
• at the end of the experiment, the syringe is used to draw the gas bubble in the tube up a long side a ruler and the length of the gas bubble is measured. This is proportional to the volume of carbon dioxide produced.
• any variables that could affect the results should be controlled eg temperature and time
• the experiment should be related twice with the light source at the same distance and the mean volume of oxygen produces is calculated.
• then the whole experiment is repeated with the light source at different distances from the pondweed.

Question 9

What is the inverse square law?

Answer 9

The inverse square law links to light intensity and distance.
As the distance of a light source away from a plant increases, the light intensity decreases. This means that distance and light intensity are inversely proportional.

Light intensity (proportional to) 1/distance squared.

Question 10

How can you artificially create ideal conditions for farming?

Answer 10

The most common way to artificially create the ideal environment for plants is to grow them in a greenhouse.
They help to trap the suns heat, and make sure the temperature doesn’t become limiting.
Farmers may supply artificial light after the sun goes down.
Farmers can also increased the level of carbon dioxide in the greenhouse eg by using a paraffin heater. As the paraffin burns, it makes carbon dioxide as a by-product.
Keeping plants in greenhouses keeps them away from pests, farmers may also ass fertilisers to the soil to provide the required minerals.

Question 11

What is respiration?

Answer 11

Respiration is the process of transferring energy from glucose which goes on in every cell.

Respiration is exothermic - it transfers energy to the environment.

Question 12

What does respiration transfer energy for?

Answer 12

To build up larger molecules from smaller ones (like proteins from amino acids).
In animals it is used to allow the muscles to contract
I’m mammals and birds it is used to keep the body temperature steady.

Question 13

What is metabolism?

Answer 13

Metabolism is all (the sum of total) the chemical relations in an organism.

Question 14

What reactions are examples of larger molecules being broken into smaller ones?

Answer 14

Glucose is broken down for respiration.

Excess protein is broke. Down in a reaction to produce urea.

Question 15

What reactions are example of larger molecules being made from smaller ones?

Answer 15

Lots of small glucose molecules join together to form starch, glycogen and cellulose.
Lipid molecules are each made from one molecule of glycerol and three fatty acids.
Glucose is combined with nitrate one to make amino acids, which are then made into proteins.

Question 16

What is aerobic respiration?

Answer 16

Respiration using oxygen.
It is the most efficient way to transfer energy from glucose.
It goes on all the time in plants and animals.
Most of the reactions for aerobic respiration happen in the mitochondria.

Question 17

What is the word equation for aerobic respiration?

Answer 17

Glucose + oxygen —> carbon dioxide + water

Question 18

What is anaerobic respiration?

Answer 18

Happens if there is not enough oxygen.
When you do vigorous exercise and your body can’t supply enough oxygen to your muscles, they start doing a aerobic respiration as well as aerobic respiration.
It does not transfer as much energy as aerobic respiration. This is because the glucose isn’t fully oxidised (because it doesn’t combine with oxygen).

Question 19

What is the word equation for anaerobic respiration?

Answer 19

Glucose —> lactic acid

Question 20

Explain anaerobic respiration in plants.

Answer 20

Plants and yeast cells can relies without oxygen as well. They produce ethanol and carbon dioxide instead of lactic acid.
Anaerobic respiration in yeast cells is called fermentation.
In the food and drinks industry, fermentation by yeast is of great value because it is used to make bread and alcoholic drinks eg beer and wine.
In bread-making, it is the carbon dioxide from fermentation that makes the bread rise.
In beer and wine making, it is the fermentation process that produces alcohol.

Question 21

What is the word equation for anaerobic respiration in plants?

Answer 21

Glucose —> ethanol + carbon dioxide.

Question 22

Why do you respires more when you exercise?

Answer 22

Muscles need more energy from respiration to contract. They need more energy when you exercise because they contract more frequently. Therefore, more respiration.
Your breathing rate and breath volume increase to get more oxygen into the blood, and your heart rate increases to get this oxygenated blood around the body faster. This removes CO2 more quickly as well.

Question 23

When will a person respire anaerobically?

Answer 23

During vigorous exercise like sprinting. This is because your body can’t supply oxygen to your muscles quickly enough, so they start respiring anaerobically. This is not the best way to transfer energy from se lactic acid builds up in the muscles, which gets painful.

Question 24

What is oxygen debt?

Answer 24

After repairing anaerobically, when you stop exercising you will have an oxygen debt.
This is the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells. Oxygen reacts with lactic acid to form carbon dioxide and water. This means that you need to keep breathing heavily when you stop to get more oxygen to the blood, to be transported to the cells.

Also, the blood that enters your muscles transports the lactic acid to the liver. In the liver, the lactic acid is converted back into glucose.