B4 BIOENERGETICS

Question 1

what do plants use light for?

Answer 1

for their source of energy ( the reaction that plants use for to trap this light energy is called photosynthesis)

Question 2

is photosynthesis endothermic reaction or exothermic reaction

Answer 2

endothermic because photosynthesis takes in energy

Question 3

where does photosynthesis takes place?

Answer 3

leaves of the plant ( leave contains the green chemical chlorophyll which absorbs light energy)

Question 4

stages of photosynthesis?

Answer 4

the plants takes in carbon dioxide and water into the leaf , light energy is absorbed by chlorophyll, the light energy is then used to convert carbon dioxide and water into the sugar glucose, oxygen is also produced.

Question 5

word equation for photosynthesis?

Answer 5

carbon dioxide + water ————–>glucose + oxygen
light/chlorophyll

Question 6

factors affecting photosynthesis?

Answer 6

light intensity , amount of co2 , temperature , amount of chlorophyll

Question 7

how does light intensity affect photosynthesis?

Answer 7

increase light intensity = increase photosynthesis
(because the plant has more light energy to carry out the photosynthesis reaction so the reaction gets faster)

increase the light intensity = rate of photosynthesis increases = light intensity was limiting (photosynthesis was not as fast as it could have been because there was not enough light)

if we keep increasing light intensity there comes a point where rate of photosynthesis no longer increases

Question 8

how does the amount of carbon dioxide affect photosynthesis?

Answer 8

increase carbon dioxide = increase photosynthesis (carbon dioxide is the limiting factor , however at some point the rate of photosynthesis no longer increases)

Question 9

how does the amount of chlorophyll affect photosynthesis?

Answer 9

less chlorophyll = lower rate of photosynthesis (because the leaves can trap less energy)

Question 10

how does temperature affect photosynthesis?

Answer 10

increase the temperature = rate of photosynthesis increases (because enzymes work faster)

however if we keep increasing temperature the enzyme will denature and the rate of photosynthesis decreases.

Question 11

uses of glucose?

Answer 11

release energy in respiration (takes place in mitochondria)

produce insoluble storage molecule starch (can be converted back to glucose when it is needed)

produce fat or oil for storage.

produce cellulose, which strengthens the cell wall

Combined with nitrate ions (absorbed from the soil) to produce amino acids for protein synthesis

Question 12

explain how greenhouses are used to increase the rate of photosynthesis

Answer 12

increase the yields of crop = increase the rate of photosynthesis.
farmers use light and heat to their greenhouse gases they also add extra carbon dioxide.
some gardeners use oil burners which release heat and carbon dioxide

problems
extra cost has to be justified by the increase in yield.

Question 13

key facts about respiration

Answer 13

• the energy we need
• an exothermic reaction because it releases energy.
  -takes place continually in cells

Question 14

word equation for aerobic respiration

Answer 14

glucose + oxygen —> carbon dioxide + water

Question 15

key facts about aerobic respiration

Answer 15

releases a great deal of energy (because the glucose molecule has been fully oxidised)

Question 16

balanced equation for aerobic respiration

Answer 16

C6H12O6 + O2 —–> CO2 + H20

Question 17

word equation for anaerobic respiration in muscles.

Answer 17

glucose —-> lactic acid
energy

Question 18

key facts about anaerobic respiration in muscles

Answer 18

does not require oxygen.
releases much less energy (that is because in anaerobic respiration the oxidation of glucose is incomplete)

Question 19

word equation for anaerobic respiration in plants and yeast cells

Answer 19

glucose —-> ethanol + carbon dioxide

Question 20

fermentation?

Answer 20

anaerobic respiration in yeast cells

Question 21

uses of fermentation?

Answer 21

alcoholic drinks e.g beer
(alcohol contains ethanol which is produced by fermentation)
make bread (this creates bubbles in the dough causing the bread to rise)

Question 22

describe what happens in the body during exercise

Answer 22

during exercise the body needs a great deal of energy for muscle contraction.
- has to react to the increased demand for energy (aerobic respiration) = more oxygen is needed
- breathing rate increases = breathing volume increases ( to provide extra oxygen)
- we breathe more frequently = we take deeper breaths = gets more oxygen into the bloodstream.
- heart rate increases to pump the oxygenated blood around the body.

Question 23

what does lactic acid cause the muscles

Answer 23

to become fatigued (this causes muscles to stop contracting efficiently)
at this point the body has to remove lactic acid from muscles this causes oxygen debt

Question 24

oxygen debt?

Answer 24

the amount of extra oxygen needed to react with lactic acid in muscles and remove it from cells

Question 25

what happens after oxygen debt?

Answer 25

lactic acid is transported out of the muscles by blood.

taken to the liver = converted back to glucose with a series of chemical reactions.

reacting with accumulated lactic acid = removing it from the cells require oxygen

Question 26

metabolism?

Answer 26

sum of all the chemical reactions in a cell or body.

Question 27

what is glucose in humans?

Answer 27

glycogen - storage form of glucose

Question 28

how is protein connected to metabolism?

Answer 28

• don’t need to eat much protein
  -excess protein broken down by the chemical urea
• urea is excreted by the kidneys

Question 29

describe how to investigate the effect of light intensity on the rate of photosynthesis

Answer 29

1. place cut pondweed in a boiling tube at a fixed distance from a light source.
2. count the number of bubbles produced in one minute using stopwatch
   3.repeat several times at different distances/light intensities and calculate a mean for each distance.
3. plot a graph of light intensity (x) against rate of photosynthesis (bubbles per min, y)

Question 30

problems with this photosynthesis practical?

Answer 30

too fast to count
bubbles aren’t same size.

Question 31

how do you measure the volume of bubbles produced?

Answer 31

place the pond weed under a funnel

catch the bubbles in a measuring cylinder.

then measure the volume of the oxygen gas produced.

Question 32

inverse square law?

Answer 32

the relationship between the intensity of light and the distance from its source.

if we double the distance, the light intensity falls falls by four times.

Question 33

How does the inverse square law apply to photosynthesis?

Answer 33

The inverse square law applies to photosynthesis because the amount of light energy that reaches a plant decreases as the distance from the light source increases.

This means that plants need to be close to a light source in order to perform photosynthesis effectively.

Question 34

photosynthesis?

Answer 34

the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Question 35

limiting factor?

Answer 35

an environmental factor which can restrict the rate of photosynthesis e.g light intensity

Question 36

what is aerobic respiration?

Answer 36

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

Question 37

what is anaerobic respiration?

Answer 37

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

Question 38

why can anaerobic respiration lead to muscle fatigue?

Answer 38

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