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GCSE Biology > B4 - Bioenergetics > Flashcards

B4 - Bioenergetics Flashcards

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1
Q

What is photosynthesis?

A

A process in plants which uses solar energy to react carbon dioxide and water to form glucose and oxygen

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2
Q

Where does photosynthesis take place, and how do plants take in energy for it?

A

In chloroplasts in green plant cells. Chloroplasts contain pigments (like chlorophyll) that absorb light. Energy is transferred to the chloroplasts by light.

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3
Q

Energy is transferred to plants, from the environment, in what form?

A

Light / solar energy.

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4
Q

What type of reaction is photosynthesis?

A

Endothermic (energy is transferred to plants, from the environment).

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5
Q

What is the word and symbol equation for photosynthesis?

A

Carbon dioxide + water →light→ glucose + oxygen

6CO2 + 6H2O →light→ C6H12O6 + 6O2

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6
Q

In what 5 main way do plants use glucose?

A
  • Respiration: to generate energy that allows the plant to convert the rest of the glucose to the below substances
  • Making cellulose: for cell walls
  • Making amino acids: to make proteins
  • Converted to lipids (oils or fats): for storing in seeds
  • Stored as starch: for a source of energy in the winter etc
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7
Q

What is glucose combined with to make amino acids, and what is it then turned into?

A

Combined with nitrate ions, which are absorbed from the soil.

The amino acids are then made into proteins.

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8
Q

Where do plants store lipids?

A

In seeds.

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9
Q

What is cellulose used for in plants?

A

Making strong cell walls.

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10
Q

Where is starch stored in plants?

A

Roots, stems and leaves.

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11
Q

Why do plants store starch?

A

It is a source of stored energy ready for when photosynthesis isn’t happening, like in winter.

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12
Q

Why do plants store energy as starch, rather than glucose?

A

Starch is insoluble, which is better for storing; a cell with lots of (soluble) glucose in it would draw in lots of water and swell up.

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13
Q

What are the 3 main limiting factors of photosynthesis? Name one other potential factor.

A
  • Light
  • CO2 concentration
  • Temperature
    (Chlorophyll can also be a factor)
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14
Q

How could chlorophyll be a limiting factor of photosynthesis?

A

The amount of chlorophyll in a plant can be inhibited by disease, or a lack of nutrients.

These things can damage chloroplasts themselves, or cause leaves to drop off - both scenarios limiting the amount of chlorophyll produced.

The rate of photosynthesis is therefore reduced, as the plant can’t absorb as much light.

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15
Q

Why is temperature a limiting factor of photosynthesis?

A

If the temperature is low, the enzymes needed for photosynthesis work more slowly.

If the plant gets too hot (around 45°C), the enzymes become damaged. Other reactions can also be affected.

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16
Q

Describe how you would investigate the effect of light intensity on the rate of photosynthesis.

A

1) Place a boiling tube a specific distance away from an LED light source (doesn’t release much heat).
2) Fill the tube with water or sodium hydrogencarbonate solution (releases CO2) and place a piece of pondweed in it.
3) Connect the boiling tube, using a bung, to a water filled capillary tube and syringe.
4) Use the syringe to draw the oxygen bubble in the tube alongside a ruler and measure its length.
5) Controls = temperature and time given to photosynthesise.
6) Do several readings to get a mean.
7) Repeat with varying distances between the tube and light source.
8) Use the inverse square law to calculate the change in light intensity for each experiment.

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17
Q

Give the law that links light intensity and distance.

A

The inverse square law:

Light intensity is inversely proportional to the square of the distance.

In other words, light intensity = 1/d2.

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18
Q

How do farmers make sure temperature isn’t a limiting factor of photosynthesis?

A

Growing plants in greenhouses, which trap the sun’s heat.

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19
Q

How do farmers make sure carbon dioxide isn’t a limiting factor of photosynthesis?

A

Using paraffin heaters to heat greenhouses. As the paraffin burns, it produces CO2.

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20
Q

What is respiration?

A

The process by which energy is transferred from the breakdown of glucose; it happens in every cell. All living things respire.

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21
Q

What type of a reaction is respiration?

A

Exothermic.

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22
Q

Give 3 examples of how organisms use energy transferred by respiration.

A

Synthesising and breaking down large molecules.
Contracting muscles.
In mammals and birds: to keep their bodies constantly warm.

23
Q

What is aerobic respiration?

What is anaerobic respiration?

A

Respiration using oxygen: the most efficient way to transfer energy from glucose
Respiration without oxygen: the incomplete breakdown of glucose into lactic acid.

24
Q

Where does aerobic respiration happen?

A

The mitochondria.

25
Q

Where does anaerobic respiration happen?

A

The cytoplasm.

26
Q

Give the word and symbol equation for aerobic respiration.

A

Glucose + oxygen → carbon dioxide + water

C6H12O6 + 6O2 → 6CO2 + 6H2O

27
Q

What is the word equation for anaerobic respiration in humans?

A

Glucose → lactic acid (+ energy)

28
Q

When and why do cells start to respire anaerobically?

A

When you do vigorous exercise and your body can’t supply enough oxygen to your muscles, cells start to anaerobically respire as well as aerobically.

29
Q

Why is anaerobic respiration undesirable and only used by body cells in emergencies?

A

It doesn’t transfer nearly as much energy as aerobic respiration, because glucose isn’t fully oxidised.
It causes lactic acid to build up in the muscles, which is painful.

30
Q

What is the name given to anaerobic respiration in yeast cells?

A

Fermentation.

31
Q

What is the word equation for anaerobic respiration in plants and yeast cells?

A

Glucose → ethanol + carbon dioxide

32
Q

Give two industrial uses of fermentation.

A
  • Bread making: the carbon dioxide released from fermentation makes bread rise.
  • Making alcoholic drinks, e.g. beer and wine: fermentation produces ethanol.
33
Q

What is metabolism?

A

The sum of all the chemical reactions occuring in an organism.

34
Q

Give 6 examples of metabolic reactions which make larger molecules from smaller ones, or that break larger ones down into smaller ones.

A 
Glucose ⇌ starch (plants)
Glucose → cellulose (plants)
Glucose ⇌ glycogen (animals)
Glycerol + 3 fatty acids ⇌lipids
Glucose + nitrates ⇌ amino acids
Amino acids ⇌ proteins
35
Q

When you exercise, your muscle cells need more energy from respiration to contract. How does your body increase the amount of oxygen that gets to your cells?

A

Breathing rate and depth increases (to get more oxygenated blood to cells)
Heart rate increases (to get oxygenated blood to cells quicker, and to remove CO2 quicker)

36
Q

What can long periods of exercise cause?

A

Muscle fatigue, where muscles get tired and stop contracting efficiently.

37
Q

Explain what an oxygen debt is and what it is caused by.

A

After cells have respired anaerobically, your body needs a certain amount of oxygen (known as an oxygen debt) to react with the buildup of lactic acid to remove it from cells (forming CO2 and water).

38
Q

How does the body “repay” its oxygen debt?

A

Breathing rate and depth remains high to get more oxygen to the blood and to cells
You continue to breathe hard until all the lactic acid has been converted to CO2 and water

39
Q

How could you measure breathing rate?

A

By counting the number of breaths taken in a certain period of time.

40
Q

How could you measure heart rate?

How could you reduce the effect of any random errors in your results?

A
  • Counting the number of pulses on your wrist/neck in one minute.
  • Do the experiment as a group and calculate the average pulse rate.
41
Q

What are the raw materials needed by a plant to photosynthesise?

A

Water and carbon dioxide

42
Q

What is the green pigment found in plant cells?

A

Chlorophyll

43
Q

What is the role of chlorophyll?

A

To transfer energy from the environment and use it to synthesise glucose from carbon dioxide and water

44
Q

List 3 ways in which commercial farmers improve the environmental conditions to maximize photosynthesis

A
  • Increase the air temperature with heaters
  • Provide artificial lighting to supplement the sunlight and through the night
  • Increase the amount of carbon dioxide in the atmosphere
45
Q

How is the glucose produced by photosynthesis used in plants?

A

Used:

  • for respiration
  • to produce fats / oils for storage
  • to produce amino acids for protein synthesis
  • converted into insoluble starch for storage
  • to produce cellulose to strengthen cell walls
46
Q

What is the equation that links light intensity and distance?

A

light intensity ∝ 1 ÷ distance 2

47
Q

Name 3 processes that organisms require energy for

A
  • Chemical reactions to build larger molecules
  • Keeping warm
  • Movement
48
Q

Describe three ways in which the body responds to vigorous exercise in order to ensure sufficient oxygen reaches the muscle cells

A
  • Increased heart rate
  • Increased breathing rate
  • Increase in breath volume
49
Q

If exercise carries on for a long time, what happens to the muscles?

A

Muscles become fatigued and stop contracting efficiently

50
Q

What kind of reaction is respiration (endo / exothermic)? Why?

A

Exothermic - it transfers energy to the environment

51
Q

Describe the process for removing lactic acid from the body

A

Blood flows through the muscle cells and transports the lactic acid
to the liver where it is converted back into glucose. The glucose is
then used in aerobic respiration or stored as glycogen

52
Q

What does ‘oxygen debt’ mean?

A

The amount of extra oxygen which is needed to remove all lactic
acid from the body is known as the oxygen debt

53
Q

Give 2 ways in which the body removes the buildup of lactic acid which results from anaerobic respiration.

A

1) Oxygen reacts with lactic acid to remove it from cells (forming CO2 and water).
2) Blood transports lactic acid to the liver, where it is converted back to glucose.

GCSE Biology (7 decks)

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