photosynthesis and respiration

Question 1

What is photosynthesis?

Answer 1

Photosynthesis is the process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce glucose (a sugar) and oxygen.

Question 2

Describe the process of photosynthesis

Answer 2

Chloroplasts are the part of the plant cell that contains chlorophyll. Light energy is transferred to chloroplasts. There, carbon dioxide and water forms glucose. Oxygen is released as a byproduct.

Question 3

Why is photosynthesis an endothermic reaction?

Answer 3

It is endothermic because it takes in energy from the environment as sunlight. This energy is used to break more bonds between carbon dioxide and water, than the amount of bonds made when forming glucose.

Question 4

What is the equation for photosynthesis?

Answer 4

Carbon dioxide + Water → Glucose + Oxygen (using light and chlorophyll).

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 5

Name 4 adaptations of plants for photosynthesis

Answer 5

-Leaves are thin so have a large surface area for gas diffusion
-They contain chlorophyll in chloroplasts to absorb light
-They have veins that brings water in the xylem to the cells of the leaves and remove the products of photosynthesis in the phloem.
-They have guard cells that open and close the stomata to regulate gas exchange

Question 6

Which factors limit the rate of photosynthesis?

Answer 6

• Light
  -Temperature
  -Carbon dioxide concentrations
  -Chlorophyll levels in the leaf

Question 7

How do plants use glucose?

Answer 7

Glucose is used during a plants respiration as glucose is broken down using oxygen to provide cells with energy. Carbon dioxide and water is produced as waste. Respiration is the reverse of photosynthesis.

Question 8

Explain what cellulose does/is in a plant

Answer 8

Celluose is a large storage molecule that strengthens the walls of the plant due to where it sits.

Question 9

Explain what starch does/is in a plant

Answer 9

Plants turn glucose to starch for better storage, it is insoluble in water and so won’t move in and out of cells so can stay put for a long time.

Question 10

How do plants use nitrates?

Answer 10

Plants combine nitrates with sugars to make amino acids, these are then built up into proteins to be used in the plant cells in many ways, including as enzymes. Some plants with few nitrates in the soil are carnivores and get their nitrates from insects.

Question 11

How do plants use lipids?

Answer 11

Glucose can be converted to fats and oils, for storage of food into seeds or to strengthen the cell wall.

Question 12

How does a greenhouse affect the rate of photosynthesis?

Answer 12

The glass/plastic contained environment means we can control the environment inside. Also it keeps more heat inside, speeding up the rate of photosynthesis.

Question 13

What is the Xylem?

Answer 13

Transports water and minerals from the roots to the rest of the plant. The process is called transpiration.

Question 14

What is the Phloem?

Answer 14

Transports sugars (like glucose) made in the leaves to the rest of the plant. The process is called translocation.

Question 15

What is aerobic respiration?

Answer 15

an exothermic reaction in which glucose is broken down using oxygen to produce carbon dioxide and water and release energy for the cells

Question 16

How is aerobic respiration an exothermic reaction?

Answer 16

In the process of glucose and oxygen combining to form carbon dioxide and water and releasing energy for metabolism, the release of energy is the same as energy transfer from the reaction to the environment. This means also more bonds are formed in this reaction than chemical bonds broken.

Question 17

What is the equation for aerobic respiration?

Answer 17

C6H12O6 + 6O2 -> 6CO2 + 6H2O (and energy is produced; some to the environment)

Question 18

What happens in the mitochondria?

Answer 18

The mitochondria holds enzymes needed for aerobic respiration. Their folded inner membrane provides a large surface area for the enzymes to work to allow the reaction of glucose and oxygen to happen. The number of mitochondria in a cell shows you how active the cell is.

Question 19

Name four uses for aerobic respiration (energy)

Answer 19

• For synthesis of new molecules and to break them down too; e.g. in digestion
• For muscle contraction
  -To maintain body temperature
  -To move mineral ions like nitrates in plants from the soil

Question 20

Why do muscle cells have many mitochondria whilst fat cells have few?

Answer 20

Muscle cells need a lot of energy for contraction, which is provided by mitochondria through aerobic respiration. Fat cells store energy rather than use it, so they require fewer mitochondria.

Question 21

What are muscle tissues made up of?

Answer 21

Muscle tissues are made up of muscle cells (muscle fibers) that can contract and relax to produce movement.

Question 22

What is glycogen?

Answer 22

It is a carbohydrate store in animals.

Question 23

What does the body need to do in terms of respiration when exercising?

Answer 23

The body will require more glucose and oxygen and will need to clear away the additional carbon dioxide produced from aerobic respiration ( glucose + oxygen -> carbon dioxide and water)

Question 24

What changes happen in the body when exercising?

Answer 24

• The heart rate increases as arteries dilate to increase blood flow and oxygen supply to muscles, and increases rate of removing carbon dioxide from the cells, carried away in the blood.
• Rate of breathing increases and breathing is deeper to inhale more air and oxygen to be supplied to the muscles ( more O2 molecules picked up by red blood cells), and for carbon dioxide to be breathed out faster
  -Glycogen stored in the muscles is converted back to glucose to supply the cells for respiration

Question 25

Explain why muscles contain a store of glycogen but most other tissues of the body do not.

Answer 25

Muscles store glycogen as an energy reserve because they need a quick supply of glucose for respiration during movement. Most other tissues do not require as much immediate energy, so they do not store glycogen in large amounts.

Question 26

Define anaerobic respiration

Answer 26

an exothermic reaction in which glucose is broken down in the absence of oxygen to produce lactic acid in animals (and ethanol and carbon dioxide in plants and yeast.) A small amount of energy is transferred to the cells.

Question 27

What is lactic acid?

Answer 27

The end product of anaerobic respiration ( in animals)

Question 28

What is the equation for human anaerobic respiration?

Answer 28

glycogen -> lactic acid + energy (glucose)

Question 29

Explain the process of muscle fatigue

Answer 29

When you exercise, muscles use up a lot of energy in contraction and require more oxygen for aerobic respiration. When aerobic respiration alone can't meet the muscle's demand for energy, the body begins to respire anaerobically, producing lactic acid and energy instead of carbon dioxide and water. An oxygen debt is accumulated, as oxygen will still be required to clear out the lactic acid afterwards.

Question 30

What is oxygen debt?

Answer 30

The extra oxygen that must be taken into the body after exercise has stopped to complete the aerobic respiration of lactic acid.

Question 31

How is anaerobic respiration different in plants and microorganisms compared to humans?

Answer 31

Plants and microorganisms respire without oxygen, they respire anaerobically only. However, some plants and microorganisms form ethanol and carbon dioxide as waste products when respiring. anaerobic respiration in yeast is known as fermentation.

Question 32

What is the equation for anaerobic respiration in plants and microorganisms?

Answer 32

glucose -> ethanol + carbon dioxide + energy

Question 33

Why after exercising do we pant for air after stopping?

Answer 33

To inhale more air and absorb more oxygen to pay off the oxygen debt, which is to convert the lactic acid built up from anaerobic respiration into glucose, a process which requires oxygen.

Question 34

List 4 common metabolic reactions

Answer 34

-the conversion of glucose to starch, glycogen and cellulose -the formation of lipid molecules from a molecule of glycerol and 3 fatty acid molecules ( a triglyceride) -The reactions of respiration -The reactions of photosynthesis

Question 35

Describe the role of the liver

Answer 35

- Detoxifying poisonous substances such as ethanol from alcohol - Passing the breakdown products into the blood so they can be excreted in urine via the kidneys - Breaking down old, worn out blood cells and storing the iron until we need to make more red blood cells

Question 36

How is lactic acid removed from the body by the liver?

Answer 36

Blood flowing through the muscles transports lactic acid to the liver where it is converted back into glucose, if the glucose isn't still needed for respiration, it is converted to glycogen and stored in the liver for future use.

Question 37

Define metabolism

Answer 37

The sum of all the reactions taking place in a cell or the body of an organism.

Question 38

The liver is an organ of respiration. Evaluate this statement.

Answer 38

The liver is not directly involved in respiration like the lungs (not involved in gas exchange there), but it plays a key role in respiration by regulating blood glucose levels. It stores glycogen and releases glucose when needed for cellular respiration. It also detoxifies lactate from anaerobic respiration.

Question 39

What is the energy transferred by respiration used for?

Answer 39

Muscle contraction (e.g., movement) Maintaining body temperature (in warm-blooded animals) Active transport (moving substances against a concentration gradient) Building large molecules (e.g., proteins from amino acids)