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[ GCSE ] biology > B4: Bioenergetics > Flashcards

B4: 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

carbon dioxide + water → glucose + oxygen
(light)
symbol: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 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 by photosynthesis
  • the gas will relight a glowing splint as it contains oxygen
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6
Q

Give 6 examples of lead 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 and food substances from xylem and 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

give 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
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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 and light intensity

A

inverse square law
- light intensity = 1/distance₂

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16
Q

State 5 uses of the glucose produced during photosynthesis

A
  • respiration
  • starch for storage
  • cellulose for strength
  • amino acid and protein synthesis ( with nitrates)
  • lipids for energy storage in seeds
17
Q

what is aerobic respiration? is it exo or endo

A
  • an exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells
18
Q

What are the equations for aerobic respiration? chemical and symbol

A

glucose + oxygen → carbon dioxide + water ( + energy)
C₆H₁₂O₆ + 60₂ → 6CO₂ + 6H₂O (+ energy)

19
Q

where does anaerobic respiration take place?

A
  • in the cytoplasm
20
Q

give 4 uses of the energy released in respiration

A
  • synthesis of larger molecules
  • muscle contraction
  • maintenance of body temperature
  • active transport
21
Q

what is anaerobic respiration?

A
  • an exothermic reaction in which glucose is broken down to release energy in the absence of oxygen
22
Q

what is the equation for anaerobic respiration?

A

glucose →lactic acid (+energy)

23
Q

Why is anaerobic respiration less efficient than aerobic respiration?

A
  • it is the incomplete breakdown of glucose
  • so less energy is transferred
24
Q

Why can anaerobic respiration lead to muscle fatigue?

A
  • lactic acid builds up in muscles
  • preventing efficient contraction
25
Q

what is oxygen debt?

A

the amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration

26
Q

What is fermentation?

A
  • a type of anaerobic respiration that occurs in yeast cells
27
Q

What is the equation for fermentation?

A

glucose → ethanol + carbon dioxide ( + energy)

28
Q

what is the fermentation reaction used for

A
  • it is used in the production of bread and alcoholic drinks
29
Q

Give three 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
30
Q

How do muscles store glucose?

A

As glycogen

31
Q

Give three changes that 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
32
Q

How is lactic acid transported away from the muscles?

A
  • blood flowing through the muscles transports lactic acid to the liver, where it is oxidised back to glucose
33
Q

What is metabolism?

A
  • the sum of all the reactions that take place in a cell or an organism
34
Q

How do cells use the energy transferred by respiration?

A
  • carry out enzyme-controlled processes
  • leading to the synthesis of new molecules
35
Q

Give 6 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

[ GCSE ] biology (10 decks)

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