B4

Question 1

What is photosynthesis?

Answer 1

• a chemical reaction which takes place in plants where glucose is made using energy from the sun

Question 2

Where in the plant does it take place?

Answer 2

• in chlorophyll (a chemical found in chloroplasts)

Question 3

What type of reaction is photosynthesis?

Answer 3

• endothermic

Question 4

Write the word equation for photosynthesis

Answer 4

• carbon dioxide + water → glucose + oxygen

Question 5

Write the chemical symbols for the reactants of photosynthesis

Answer 5

• CO2 = carbon dioxide and H2O = water

Question 6

Write the chemical symbols for the products of photosynthesis

Answer 6

• C6 H12 O6 = glucose and O2 = oxygen

Question 7

What are the uses of the glucose which the plant makes in photosynthesis

Answer 7

• for respiration
• stored as fats or oils
• to make cell walls
• to make amino acids
• to store as insoluble starch granules

Question 8

What are the 4 main limiting factors affecting the rate of photosynthesis?

Answer 8

• the light intensity
• the concentration of CO2
• the temperature
• the amount of chlorophyll a plant has

Question 9

What is a limiting factor?

Answer 9

• is something which can stop photosynthesis happening any faster

Question 10

Explain the graph when light intensity is the limiting factor

Answer 10

• at first, as you increase the light intensity , the rate of photosynthesis increases . Light is the limiting factor
• at a certain point, the graph goes flat and no matter how bright the light is, photosynthesis will not go any faster
• this is because light intensity is no longer the limiting factor. The concentration of CO2 or the temperature is now the limiting factor

Question 11

Explain the graph when CO2 concentration is the limiting factor

Answer 11

• at first, as you increase the CO2 concentration, the rate of photosynthesis increases. CO2 concentration is the limiting factor
• at a certain point, the graph goes flat and no matter how much CO2 there is, photosynthesis will not go any faster
• this is because concentration of CO2 is no longer the limiting factor. The light intensity or the temperature is now the limiting factor

Question 12

Explain the graph when temperature is the limiting factor

Answer 12

• at first, as you increase the temperature, the rate of photosynthesis increases. Temperature is the limiting factor
• the enzymes needed for photosynthesis work best at the temperature shown by the peak of the graph
• after this point, the rate of photosynthesis will slow down as the temperature is too high and the enzymes will start to denature

Question 13

What is respiration?

Answer 13

• a chemical reaction which releases energy from glucose in all cells

Question 14

What type of reaction is respiration?

Answer 14

• exothermic

Question 15

Where does respiration take place?

Answer 15

• in the mitochondria of cells

Question 16

Give 3 ways the organisms use the energy transferred by respiration

Answer 16

• to build large molecules from smaller ones
• to move
• to keep warm

Question 17

What is metabolism?

Answer 17

• the total of all the reactions taking place in a cell or body

Question 18

What controls the rate of chemical reactions in the body?

Answer 18

• enzymes

Question 19

Give examples of 5 large molecules which are made in the body (say what each is made from)

Answer 19

• starch = made from glucose
• glycogen = made from glucose
• cellulose = made from glucose
• lipids (fats) = made from glycerol and 3 fatty acids
• proteins = made from amino acids

Question 20

Give 2 examples of reactions in the body where large molecules are broken down into smaller ones

Answer 20

• respiration = the breakdown of glucose

- excess protein = broken down to make urea

Question 21

What are the 3 type of respiration?

Answer 21

• aerobic respiration
• anaerobic respiration in muscle cells
• anaerobic respiration in plant and yeast cells

Question 22

When does anaerobic respiration take place in muscle cells?

Answer 22

• when not enough oxygen is available

Question 23

What is the word equation for anaerobic respiration in muscle cells?

Answer 23

• glucose → lactic acid

Question 24

Compare the amount of energy released by this type of respiration with aerobic respiration

Answer 24

• much less energy is released in anaerobic respiration

Question 25

Write the word equation for anaerobic respiration in plants and yeast cells

Answer 25

- glucose → ethanol + carbon dioxide

Question 26

What is another name for anaerobic respiration in yeast cells?

Answer 26

- fermentation

Question 27

How do we use this type of respiration in the food and drink industry (2 ways)

Answer 27

- baking bread = the carbon dioxide bubbles make bread rise | - making beer/wine = the fermentation makes ethanol which is the alcohol in the drinks

Question 28

Compare aerobic , anaerobic in muscle cells(mc) and anaerobic in plants & yeast respiration(p&y)

Answer 28

ALL THREE: - use glucose - release energy - happen in mitochondria AEROBIC AND ANAEROBIC IN P&Y RESPIRATION BOTH: - produce CO2 ANAEROBIC IN MC AND ANAEROBIC IN P&Y RESPIRATION BOTH: - no oxygen - small amount of energy however aerobic respiration also: - produces water - needs oxygen whereas anaerobic in mc respiration also: - produces lactic acid also anaerobic in p&y respiration: - produces ethanol

Question 29

Explain how we respond to exercise (1 way)

Answer 29

- When we exercise we need more energy so muscles can contract more - We need to do more respiration so our breathing rate increase and we take deeper breaths to get more oxygen into our body - Our heart rate increase to pump more oxygenated blood to our muscle cells

Question 30

Explain how we respond to exercise (2 way)

Answer 30

- unfortunately, we cannot always get enough oxygen to our muscles - this means our muscles respire anaerobically - this releases less energy than aerobic respiration - another problem is that lactic acid builds up in muscles, which can cause muscle fatigue - this stops muscles from contracting efficiently - after you stop exercising you have an oxygen debt

Question 31

What is the definition of oxygen debt?

Answer 31

- oxygen debt is the amount of extra oxygen the body needs after exercise to react with the build up of lactic acid and remove it from the cells

Question 32

Describe the process by which lactic acid gets fully broken down

Answer 32

- the lactic acid reacts with oxygen and forms carbon dioxide and water

Question 33

Use ideas about oxygen debt to explain why we continue to breathe heavily, even after stopping exercise

Answer 33

- we need to get more oxygen into the blood

Question 34

How is the blood involved in removing lactic acid which has built up in the muscles?

Answer 34

- the blood transports the lactic acid to the liver, where it is converted back to glucose