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GCSE Biology > Bioenergetics > Flashcards

Bioenergetics Flashcards

1
Q

What is meant by photosynthesis?

A

An endothermic reaction by which energy is transferred from the environment to the chloroplasts by light to make nutrients such as glucose.

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2
Q

Where does photosynthesis occur?

A

In the chloroplasts of a plant.

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3
Q

Explain how plants make glucose

A
  • Photosynthesis occurs in the chloroplasts, which contain a green pigment responsible for the absorption of light to provide energy for photosynthesis to occur. This is called chlorophyll
  • Light energy is absorbed by plants chlorophyll.
  • Light energy is then uses CO2 from air, and H2O from soil to produce glucose and oxygen.
  • This is an endothermic reaction because energy is transferred from surroundings to the reaction.
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4
Q

Equation for photosynthesis:

A

Carbon dioxide + Water -> Glucose and Oxygen

6CO2 + 6H2O -> C6H12O6 + 6O2.

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5
Q

True or false, photosynthesis is endothermic?

A

True. Photosynthesis is an endothermic reaction.

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6
Q

State and explain
6 ways leaves are adapted for photosynthesis.

A

(Love To Chomp Very Amazing Grapes)

Large surface area/Broad - more sunlight can fall onto is so more light energy can be absorbed by chlorophyll, so photosynthesis occurs quicker

Thin - shorter distance for diffusion of gases, eg CO2 and waste O2 - so photosynthesis occurs quicker.

Chlorophyll - Pigment responsible for light energy absorption, for photosynthesis to occur

Veins - Used to transport ALOT of WATER from xylem to cells, so photosynthesis occurs quicker, and used to remove WASTE products of photosynthesis through the phloem.

Air spaces - more CO2 and can enter cells, and more O2 can leave cells, via diffusion so photosynthesis rate increases+ maintains conc gradient to increase diffusion rate

Guard cells - Open and closes stomate to regulate gas exchange to MAKE THE MOST of photosynthesis.

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7
Q

Give a short explanation as to how algae are adapted to photosynthesis in water?

A
  • Large surface area/broad - so can absorbed more CO2 DISSOLVED IN WATER AROUND THEM. and more O2 can dissolved in water around them to be released as a waste product.
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8
Q

State 4 factors affecting the rate of photosynthesis:

A
  • Light intensity
  • Carbon dioxide concentration
  • Temperature of surroundings.
  • Amount of chlorophyll in leaves
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9
Q

How can chlorophyll be reduced in leaves? x3 ways.

A

1 - Diseases.
2 - Lack of nutrients
3 - Environmental stress (eg pollutants etc)

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10
Q

If the 4 factors affecting the rate of photosynthesis are REDUCED below the optimal requirement, what will happen to the rate of photosynthesis?

A

It will decrease.

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11
Q

How can CO2 conc be increased for photosynthesis? X3

A
  • Respiration
  • Combustion of fossil fuels
  • Putting plant in a dark place.
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12
Q

A student places a plant in a dark environment and notices that carbon dioxide conc in surroundings increases after measuring it - suggest why.

A
  • Bc dark, less light absorbed.
  • Less photosynthesis (so CO2 is used less)
  • But still respiration still occurs (so CO2 in surroundings increases)
  • So CO2 made is more than being used
  • So conc of CO2 in surroundings increases.
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13
Q

Explain how temperature affects photosynthesis? - you must refer to enzymes in your answer.

A
  • Temperature increase means more thermal energy provided so no. of collisions between reacting particles (CO2 AND H2O) increases so rate of photosynthesis increases.
  • Temp increase also means enzyme activity increases, so does rate of reaction.
  • If temp increase too high, past optimal level (45 deg celc), enzymes will begin to denature, so rate of photosynthesis decreases.
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14
Q

At night a limiting factor for photosynthesis would be?

A

Light intensity.

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15
Q

In the winter, what would be a limiting factor for photosynthesis?

A

Temperature of surroundings

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16
Q

In light and warm conditions what would be a limiting factor for photosynthesis?

A

Carbon dioxide concentration.

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17
Q

In mineral-deficient soil what would be a limiting factor for photosynthesis?

A

Chlorophyll (less minerals absorbed by plants, so less chlorophyll made)

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18
Q

What is meant by a limiting factor?

A

A factor that if in low levels, it restricts the increase in rate of reaction as well as the reaction from occurring at the maximum rate.

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19
Q

On a graph, which axis will the ‘factor’ and ‘rate of photosynthesis’ go on.

A

X-axis - factor (CO2 conc, light intensity etc)

Y-axis - rate of photosynthesis

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20
Q

How are greenhouses used to make the most of photosynthesis? (Think of photosynthesis factors and apply)

A
  • To increase light intensity - artificial light sources eg LED as well as natural light.
  • Temperature - from heat sources eg electric heater and paraffin heats
  • extra CO2 - paraffin heaters (fossil fuel burnt - CO2 produced)
  • Ventilation - Temperature is regulated - for optimal enzyme activity
  • Watering system
  • Greenhouse glass - traps heat, light can enter
  • Plants kept inside green houses - away from pests, can be monitored and controlled w pesticides and fertilisers

IN AN EXAM: state, explain how this makes the most of photosynthesis + state how that prevents a particular factor from being a limiting factor.

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21
Q

What is a disadvantage of using a greenhouse? x 1

A
  • Expensive, because a lot of energy (thermal and light) is required.
  • So extra cost must be justified by the yield of plants produced.
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22
Q

what are the advantages of greenhouses? x 2

A
  • Increase in crop yield, so more profitable.
  • Plants can be closely monitored away from pests.
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23
Q

How do plants use glucose?

A
  • Respiration glucose + oxygen -> CO2 + H2O
  • To make cellulose (for cell structure - to strengthen cell wall)
  • To make starch (to be converted intro insoluble starch for storage, so when conditions aren’t favourable for PS, they still have food)
  • To make amino acids to make proteins - (glucose combines w nitrate ions which are absorbed from soil to make ACs)
  • To make oils and fats (store of energy in plant seeds, this is useful bc when planted, the new plant will hv energy to respire as it germinates, leading to healthy growth)
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24
Q

Why is starch sometimes more ideal than glucose?

A
  • Starch is insoluble so will not absorb water from soil via osmosis, while glucose would.
  • So starch is a more reliable and better energy source for plants.
  • Especially when photosynthesis isn’t occurring due to unfavourable conditions.
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25
Q

Why are algal cells considered a source of biofuels?

A

Because they are rich in fats and oils, so can be burnt to produce energy.

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26
Q

How can we test for the presence of starch in plants?

A

1 - Drop leaf into BOILING water. (to kill the cells and break down membranes - to extract chlorophyll and allow iodine to enter into cells to react w starch)

-2 Remove leaf and place into hot ethanol for 10-15 minutes (longer time means colour change is seen more clearly).

  • Leaf becomes whiter when ethanol is added (bc ethanol dissolves the chlorophyll

-3 Now place leaf on a white tile and add 1-2 drops of iodine.

  • If starch is present leaf becomes orange-red (if kept in the dark) or blue-black (if kept in light)
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27
Q

Describe a practical to investigate the effect of light intensity on the rate of photosynthesis.

A
  • AIM - to investigate the effect of light intensity on the rate of photosynthesis.

1) Place a piece of pondweed with a cut into a beaker of water, 10cm away from an LED light source (measure distance using a ruler).

2) Add sodium hydrogen carbonate to the water - this produces CO2 gas for plant to photosynthesise to produce O2 gas

3) Once the sodium hydrogen carbonate is added, leave plant to acclimatise to its new conditions for 5 minutes.

4) Now, count the number of O2 gas bubbles produced in one minute - repeat this step 2 more times and calculate a mean.

5) Repeat the previous steps using different distances away from the LED light source.

6) Record date on a table and plot on a graph - we should notice that as distance increases, light intensity decreases, less O2 gas produced so rate of PS falls.

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28
Q

What is meant by the inverse square law?

A

The law that states light intensity and distance are inversely proportional.

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29
Q

Describe the relationship between light intensity and distance.

A

Inversely proportional

30
Q

What units are used to measure intensity, for instance light intensity?

A

au = Arbitary units.

31
Q

Why do we use an LED light instead of a regular lamp when investigating the effect of light intensity on the rate of photosynthesis?

A
  • LED light emits less heat energy than a lamp.
  • So the rate of photosynthesis will not be affected by temperature from lamp.
  • This makes data will be more reliable and valid.
32
Q

How can we see if a plant has carried out photosynthesis?

A
  • By testing for starch (we cannot test for glucose/sugar bc glucose is quickly used up during respiration)
33
Q

What mineral ions are used to make chlorophyll?

A

Magnesium ions from soil (absorbed in roots).

34
Q

Why can’t we test for glucose in plants?

A

It is quickly used up via cellular respiration.

35
Q

What does ethanol do when testing for the presence of starch in a leaf?

A
  • Dissolves chlorophyll removing the green pigment from the leaf.
  • This makes it easier to see a colour change.
36
Q

Formula to calculate light intensity:

A

Light intensity = 1/distance^2

37
Q

Limitations and improvements of photosynthesis experiment:

A
  • miscounting O2 gas bubbles produces - solution: use a gas syringe instead to measure volume of gas produced.
  • Heat from lamp can affect rate - put glass tank between lamp and plant OR use an LED light source.
  • Repeat experiment twice for each distance and calculate the mean no. of gas bubbles produced.
38
Q

Independent, dependent and control variables of photosynthesis practical

A
  • INDEPENDENT: light intensity
  • DEPENDENT: no. of O2 bubbles produced.
  • CONTROL: size of pondweed, volume of water its kept in, temperature of water.

IDC

39
Q

Safety precautions for ethanol test for starch:

A
  • keep away ethanol from naked flames; it is flammable. - so use hot water bath instead of Bunsen burner.
  • wear eye protection (ethanol is harmful to eyes).
40
Q

What is meant by (cellular) respiration?

A

an exothermic reaction which is continuously occurring in living cells.

41
Q

What is the energy transferred in respiration used for?

A

(METABOLIC REACTIONS) for living processes - enzyme metabolic reactions that synthesise proteins.

42
Q

What is aerobic respiration?

A

respiration that occurs using oxygen.

glucose + oxygen -> carbon dioxide + water

43
Q

What is anaerobic respiration?

A

respiration that occurs without oxygen.

glucose -> lactic acid (in ANIMALS ,MUSCLE CELLS)

OR

glucose -> ethanol + carbon dioxide (in PLANT and YEAST CELLS)

44
Q

Compare aerobic and anaerobic respiration (diff and sims)

A

Differences
- aerobic respiration occurs w oxygen, anaerobic respiration occurs w/o O2

  • aerobic respiration produces a greater yield of energy because glucose molecules are fully oxidised, while anaerobic produces less energy bc glucose molecules are incompletely oxidised (bc not a lot of O2 present).
  • aerobic takes place in mitochondria, anaerobic takes place in cytoplasm.

similarities
- both provide energy.

45
Q

State 3 reasons why organisms need energy?

A
  • chemical reactions to build larger molecules
  • movement
  • keeping warm.
46
Q

formula for aerobic respiration

A

C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water).

47
Q

formula for anaerobic respiration

A

in plants : glucose -> ethanol + carbon dioxide.

in animals (muscle cells) : glucose -> lactic acid

48
Q

why is there a lower yield of energy transfer in anaerobic respiration than aerobic respiration?

A

Because glucose molecules aren’t fully oxidised.

49
Q

Where does anaerobic respiration occur?

A

in the cytoplasm of a cell.

50
Q

Where does aerobic respiration occur?

A

in the mitochondria of a cell.

51
Q

Uses of anaerobic respiration in industry.

A

Fermentation = anaerobic respiration in yeast cells)

this produces:

ethanol - in alcoholic drinks
CO2 - used to make bread

EQUATION:
glucose -> ethanol + carbon dioxide

52
Q

What is meant by fermentation?

A

anaerobic respiration in yeast cells.

53
Q

Under what circumstances does anaerobic respiration occur?

A

when there is not enough oxygen to oxidise glucose - it is the last resort.

Anaerobic respiration can occur during a sprint.

54
Q

How does the body keep up w the demands for energy during oxygen - x3 ways.

A
  • The heart rate
  • Breathing rate
  • Breath volume increase during exercise to supply the muscles with more oxygenated blood.
55
Q

What are the consequences of anaerobic respiration?

A

If insufficient oxygen is supplied anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently.

56
Q

What is meant by oxygen debt?

A

Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.

57
Q

What is meant by metabolism?

A

Metabolism is the sum of all the reactions in a cell or the body.

58
Q

what is energy from respiration used for?

A
  • keeping warm
  • active transport
  • building larger molecules eg making proteins
  • movement/muscle contraction

DO NOT SAY METABOLISM

59
Q

5 examples of metabolic reactions:

A

Metabolism includes:
* conversion of glucose to starch, glycogen and cellulose
* the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
* the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins
* respiration
* breakdown of excess proteins to form urea for excretion.

60
Q

anaerobic respiration in animal cells equation

A

glucose -> lactic acid

(glucose breaks down to produce lactic acid in muscle cells - leading to lactic acid build up -> o2 debt))

61
Q

anaerobic respiration in plant/yeast cells equation

A

glucose -> ethanol + carbon dioxide

ethanol - used in alcoholic drinks
CO2 - used to make bread.

62
Q

A guy is sprinting, and notices over time he becomes tired and his muscles don’t contract properly - suggest why.

A
  • Not enough O2 for aerobic respiration
  • So anaerobic respiration occurs for energy to be supplied to body cells.
  • Anaerobic respiration in humans results in glucose being broken down to produce lactic acid.
  • Lactic acid builds up in muscles
  • So over a period of exercise, muscles become fatigued and stop contracting efficiently.
63
Q

How does the body get rid of lactic acid build up and how may this lead to O2 debt?

A
  • Blood flowing thru muscles transport lactic acid to liver and convert it back to glucose (by reacting lactic acid w O2 which is contained in the liver).
  • Oxygen debt is the amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells.
64
Q

what is the balanced equation for respiration?

A

6O2 + C6H12O6 → 6H2O + 6CO2

65
Q

What is the balanced equation for photosynthesis?

A

6H2O + 6CO2 -> 6O2 + C6H12O6

66
Q

Differences between aerobic and anaerobic respiration in animals

don’t refer to oxygen.

A
  • aerobic respiration produces water and anaerobic respiration does not.
  • anaerobic respiration produces lactic acid and aerobic does not.

other
MUST INCLUDE AND

  • anaerobic produces lactic acid and aerobic does not
    allow anaerobic creates an oxygen debt
    and aerobic does not
  • aerobic produces carbon dioxide and anaerobic does not
  • aerobic produces water and anaerobic does not
  • aerobic occurs (mainly) in the mitochondria and anaerobic
    does not
    allow anaerobic only occurs in the
    cytoplasm
  • anaerobic releases less energy than aerobic
    allow anaerobic releases less ATP (than anaerobic)
    do not accept anaerobic produces / makes / creates less energy
67
Q

On day 10, the pond snail died.
Explain why the death of the pond snail caused the concentration of
carbon dioxide to increase after day 10. 3 marks

A

snail is being decayed 1
by decomposers 1
so respiration of decomposers releases CO2 1

68
Q

True or false, all living organisms respire?

A

TRUE - this includes algae, plants and animals, bacteria etc.

69
Q

Explain the lock and key theory of enzyme action: 3 marks

A
  • Enzyme binds to substrate because they are complementary shapes
  • So substrate fits perfectly into enzyme and is broken down
  • So products are released as smaller molecules and enzymes aren’t changed
70
Q

Suggest why anaerobic respiration is less efficient than aerobic respiration.

A

Glucose isn’t fully oxidised/broken down (1)
So less energy is transferred (1)

71
Q

Why does anaerobic respiration lead to muscle fatigue?

A

Anaerobic respiration produces lactic acid which builds up in muscles preventing efficient contraction.

72
Q

What is meant by oxygen debt?

A

The amount of oxygen needed to convert lactic acid into glucose after anaerobic respiration.

GCSE Biology (9 decks)

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