Topic 4 - Bioenergetics

Question 1

photosynthesis Equation

Answer 1

Carbon dioxide + water ———> glucose + oxygen
sunlight

Question 2

Where does photosynthesis take place

Answer 2

In the chloroplasts which contains pigments like chlorophyll that absorb light

Question 3

What type of reaction is photosynthesis

Answer 3

Endothermic as energy is transferred from the environment into the chloroplasts

Question 4

Symbol equation for photosynthesis

Answer 4

6CO2 + 6H2O → C6H12O6 + 6O2

Question 5

What do plants use glucose for respiration

Answer 5

This transfers energy from glucose enabling the plant to convert the rest of the glucose into various other useful substances

Question 6

Why is glucose used for making cellulose

Answer 6

Glucose is converted into cellulose for making strong plant cell walls

Question 7

How is glucose used for making amino acids

Answer 7

Glucose is combined with nitrate ions to make amino acids which are then made into proteins

Question 8

Why is glucose stored as oils or fats

Answer 8

Glucose is turned into lipids for storing in seeds

Question 9

Why is glucose stored as starch

Answer 9

-Stored into starch and stored in roots, stems and leaves for use when photosynthesis isn’t happening like in winter.
-Starch is insoluble so it is better for storing than glucose - a cell with lots of glucose in would draw in loads of water and swell up

Question 10

What cour things can affect the rate of photosynthesis

Answer 10

The intensity of light, concentration of CO2 and temperature

Question 11

What is the limiting factor

Answer 11

It stops photosynthesis from happening ang faster

Question 12

Which factor limits photosynthesis at different times depending on the environmental conditions

Answer 12

-At night light is the limiting factor
-During winter it’s usually temperature
-If it’s warm and bright enough the limiting factor is usually the amount of CO2

Question 13

How is chlorophyll a limiting factor for photosynthesis

Answer 13

-The amount of chlorophyll in a plant can be affected by disease or environmental stress (e.g. lack of nutrients)
-These can cause chloroplasts to become damaged or not to make enough chlorophyll so photosynthesis is reduced as they can’t absorb as much light

Question 14

Practical for oxygen production showing the rate of photosynthesis

Answer 14

1. A source of white light is placed at a specific distance from the pondweed
2. It is left to photosynthesise for a set amount of time and as it photosynthesises the oxygen released will collect in the capillary tube
3. At the end the syringe will be used to draw the gas bubble in the tube alongside a ruler and the length will be measured
4. Any variables affecting the results should be controlled, like the temperature and time the pondweed is left to photosynthesise
5. Repeat twice with the light source at the same distance and mean volume of O2 produced calculated
6. Then the whole experiment is repeated with different light sources at different distances

Question 15

What happens in the pondweed experiment when the distance of the light increases

Answer 15

The lightly intensity decreases
The light intensity decreases in proportion to the square of the distance

Question 16

What is the inverse square law for the pondweed experiment

Answer 16

light intensity = 1 / distance (d)^2

Question 17

How do greenhouses artificially create the ideal conditions for farming

Answer 17

Greenhouses trap the suns heat and make sure that temperature doesn’t become limiting so in Winter a farmer or gardener might use a heather to keep temperature at ideal level. In summer it could get too hot so they might use shades and ventilation

Question 18

How do farmers artificially create the ideal light conditions for farming

Answer 18

Supply artificial light for plants after the sun goes down to give their plants more quality photosynthesis time

Question 19

How do farmers artificially create the ideal carbon dioxide conditions for farming

Answer 19

By using a paraffin heater to heat the greenhouse as the paraffin burns it makes carbon dioxide as a by-product

Question 20

How does keeping plants enclosed in a greenhouse artificially create the ideal conditions for farming due to pests

Answer 20

Keeps them free from pests and disease and the farmers can add fertilisers to the soil to provide minerals needed for healthy growth

Question 21

How is light a limiting factor for photosynthesis

Answer 21

-Light provides energy needed for photosynthesis
-As the light level is raised, the rate of photosynthesis increases steadily- but only up to a certain point
-Beyond that it won’t make any difference - as light intensity increases, the rate will no longer increase. This is because it’ll be either be the temperature or the CO2 level which is now the limiting factor, not light.

Question 22

How is CO2 a limiting factor for photosynthesis

Answer 22

-CO2 is one of the raw materials needed for photosynthesis
-The amount of CO2 will only increase the rate of photosynthesis up to a certain point. After this the rate no longer increases showing that CO2 is no longer the limiting factor
-As long as light and CO2 are in plentiful supply then the factor limiting photosynthesis must be temperature

Question 23

How is temperature a limiting factor for photosynthesis

Answer 23

-Usually if the temperature is the limiting factor it’s because it’s too low and enzymes needed for photosynthesis work more slowly at low temperature
-If the plant gets too hot the enzymes it needs for photosynthesis will be denatured
-This happens at about 45°C

Question 24

What is respiration

Answer 24

The process of transferring energy from the breakdown glucose and it goes on in every cell in your body continuously

Question 25

What kind of reaction is respiration

Answer 25

Exothermic - it transfers energy to the environemtn

Question 26

How do organisms use the energy transferred by respiration

Answer 26

-To build up larger molecules from smaller ones
-In animals it’s use to allow the muscles to contract
-In mammals and birds the energy is used to keep their body temperature steady in colder surroundings

Question 27

What is metabolism

Answer 27

The sum of all reactions that happen in a cell or the body

Question 28

Outline reactions where larger molecules are made from smaller ones

Answer 28

-Lots of small glucose molecules are joined together in reactions to form starch, glycogen and cellulose
-Lipid molecules are each made from one molecule of glycerol and three fatty acids
-Glucose is combined with nitrate ions to make amino acids, which are then made into

Question 29

Outline reactions where larger molecules are broken into smaller molecules

Answer 29

-Glucose is broken down in respirations which transfers energy to power all the reactions in the body that make molecules
-Excess protein is broken down in a reaction to produce urea which is then excreted in urine