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AQA Biology Paper 1: Combined Science > Topic 4: Bioenergetics > Flashcards

Topic 4: Bioenergetics Flashcards

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1
Q

What is photosynthesis?

A

The process by which plants synthesise glucose using light energy from the Sun. Light energy is converted into chemical energy.

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2
Q

Where does photosynthesis take place?

A

Within chloroplasts in leaf palisade cells.They contain chlorophyll, a pigment which absorbs light energy.

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3
Q

State the equations for photosynthesis (word and symbol)

A

Word: carbon dioxide + water →light glucose + oxygen

Symbol: 6CO2 + 6H2O → Clight 6H12O6 + 6O2

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4
Q

Is photosynthesis an endothermic or exothermic reaction, and why?

A

Endothermic - energy is transferred from the environment to chloroplasts by light.

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5
Q

How can you show that a plant gives off oxygen during photosynthesis?

A

Using a water plant (eg. Elodea), collect gas bubbles produced during photosynthesis. The gas will relight a glowing splint as it contains oxygen.

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6
Q

Give examples of leaf adaptations which maximise the rate of photosynthesis

A
  • Broad leaves - maximise surface area.
  • Thin leaves - short diffusion distance.
  • Chlorophyll present - trap light energy.
  • Veins - transport water to leaves via xylem, remove photosynthesis products via phloem.
  • Air spaces - allow CO2 to enter and O2 to leave.
  • Guard cells - control opening of stomata for gaseous exchange and prevent water loss.
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7
Q

What are the four main factors that affect the rate of photosynthesis?

A
  • Temperature
  • Light intensity
  • Carbon dioxide concentration
  • Amount of chlorophyll
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8
Q

How does temperature affect the rate of photosynthesis?

A

Increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased. The rate decreases past a certain temperature as enzymes become denatured.

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9
Q

How does light intensity affect the rate of photosynthesis?

A

Increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting.

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10
Q

How does carbon dioxide concentration affect the rate of photosynthesis?

A

Increasing the carbon dioxide concentration increases the rate of photosynthesis (until another factor becomes limiting) as CO2 is required to make glucose.

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11
Q

How does the amount of chlorophyll affect the rate of photosynthesis?

A

Decreasing the amount of chlorophyll (eg. due to a lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy.

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12
Q

What is a limiting factor?

A

An environmental factor which can restrict the rate of photosynthesis eg. light intensity.

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13
Q

Explain how you can calculate the rate of photosynthesis by measuring oxygen production

A
  • Set up bubble potometer apparatus (pondweed in a sealed tube of water, attached to a capillary tube and a gas syringe).
  • Oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen produced.
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14
Q

How can farmers use their knowledge of limiting factors to increase their profits?

A

They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield.

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15
Q

State the law which describes the relationship between the distance of a light source from a plant

A

Inverse square law - light intensity∝1 / distance2

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16
Q

What is aerobic respiration?

A

An exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells.

17
Q

What are the equations for aerobic respiration? (word and symbol)

A

Glucose + oxygen → carbon dioxide + water (+energy)

C6H12O6 + 6O2 → 6CO2 + 6H2O (+energy)

18
Q

Where does aerobic respiration take place?

A

In the mitochondria

19
Q

Why do organisms require the energy released by respiration?

A
  • Synthesis of larger molecules
  • Muscle contraction
  • Maintenance of body temperature
  • Active transport
20
Q

What is anaerobic respiration?

A

An exothermic reaction in which glucose is broken down to release energy in the absence of oxygen.

21
Q

What is the equation for anaerobic respiration?

A

Glucose → lactic acid (+energy)

22
Q

Why is anaerobic respiration less efficient than aerobic respiration?

A

Glucose is not completely broken down, so less energy is transferred.

23
Q

Why can anaerobic respiration lead to muscle fatigue?

A

Lactic acid (product of anaerobic respiration) builds up in muscles, preventing efficient contraction.

24
Q

What is fermentation?

A

A type of anaerobic respiration that occurs in yeast cells.

25
Q

What is the equation for fermentation?

A

Glucose → ethanol + carbon dioxide (+energy)

26
Q

Why is the fermentation reaction important?

A

It is used in the production of bread and alcoholic drinks.

27
Q

What are the differences between aerobic and anaerobic respiration?

A
  • Aerobic requires oxygen; anaerobic does not.
  • Aerobic produces CO2 and water; anaerobic produces lactic acid or ethanol + CO2.
  • Aerobic transfers a greater amount of energy.
28
Q

How do muscles store glucose?

A

As glycogen

29
Q

What changes take place when muscular activity increases in the body?

A
  • Heart rate increases and arteries dilate - increases flow of oxygenated blood to muscles.
  • Breathing rate increases and breathing is deeper - increases the rate of gaseous exchange.
  • Stored glycogen is converted back into glucose.
30
Q

How is lactic acid transported away from the muscles?

A

Blood flow through the muscles transports lactic acid to the liver, where it is oxidised back to glucose.

31
Q

What is metabolism?

A

The sum of all the reactions that take place in a cell or an organism.

32
Q

How do cells use the energy transferred by respiration?

A

To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules.

33
Q

Give examples of metabolic reactions

A
  • Glucose into starch/glycogen/cellulose
  • Glycerol and fatty acids into lipids
  • Glucose and nitrate ions into amino acids
  • Photosynthesis
  • Respiration
  • Breakdown of excess proteins into urea

AQA Biology Paper 1: Combined Science (7 decks)

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