Bioenergetics

Question 1

What is photosynthesis?

Answer 1

The process by which plants make glucose from sunlight
Light energy is converted into chemical energy

Question 2

Where does photosynthesis take place?

Answer 2

Within chloroplasts in leaf palisade cells
They contain chlorophyll a pigment which absorbs sunlight

Question 3

State equation for photosynthesis

Answer 3

Carbon dioxide +water light->glucose +oxygen
6CO2 + 6H2O -> C6H12O6 +6O2

Question 4

Is photosynthesis an endothermic or exothermic reaction?

Answer 4

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

Question 5

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

Answer 5

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

Question 6

Give examples of leaf adaptions which maximise the rate of photosynthesis

Answer 6

-broad leaves- maximise surface area
-thin leaves- short diffusion pathway
-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

Question 7

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

Answer 7

Temperature
Light intensity
Carbon dioxide concentration
Amount of chlorophyll

Question 8

How does temperature affect the rate of photosynthesis?

Answer 8

Increasing temperature increases the rate of photosynthesis as kinetic energy increases until it reaches optimum temperature
The rate decreases past a certain required as enzymes become denatured
If temp decreases too much the particles lack kinetic energy so there are fewer collisions so lower rate of photosynthesis

Question 9

How does light intensity affect the rate of photosynthesis?

Answer 9

Increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting
Then plateaus as chloroplasts can only absorb a certain amount of light and other factors like co2 or temperature are limiting factors meaning reaction can’t continue

Question 10

How does carbon dioxide concentration affect the rate of photosynthesis?

Answer 10

Increasing co2 concentration increases rate of photosynthesis until another factor becomes limiting as co2 is required to make glucose
Then plateaus as other factors like light or temperature are limiting it further, are limiting factors

Question 11

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

Answer 11

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

Question 12

What is a limiting factor?

Answer 12

When a process depends on 2 or more factors the rate of a process is limited by the factor which is in shortest supply
Is an environmental factor which can restrict the rate of photosynthesis( light intensity)

Question 13

How can you calculate the rate of photosynthesis by measuring oxygen production?

Answer 13

-pondweed is placed in a test tube full of water. The top is raked with bung. A capillary tube also containing water leads into a test tube and is attached to a syringe
- a lamp is placed at a measured distance from test tube
- as it photosynthesises oxygen is produced forming a gas tube into the capillary tube
- the distance the bubble has moved is measured using a ruler to calculate the volume of oxygen produced
-many variables can be changed to observe their effect on photosynthesis: the temp (using water bath) , time pondweed is left, the light intensity (varied by distance of lamp from plant)

Question 14

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

Answer 14

Can control temperature, light intensity and co2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield

Question 15

State the law which described the relationship between the distance of a light source from a plant and light intensity

Answer 15

The light intensity is inversely proportional to the square of the distance
Inverse square law - light intensity inversely proportional 1/distance squared

Question 16

State uses of the glucose produced during photosynthesis

Answer 16

Respiration
Starch for storage
Cellulose for strength
Amino acid and protein synthesis
Lipids for energy storage in seeds

Question 17

What is aerobic respiration?

Answer 17

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

Question 18

What are the equations for aerobic respiration?

Answer 18

Glucose +oxygen -> carbon dioxide +water (+energy)
C6H12O6 + 6O2 -> 6CO2+ 6H2O

Question 19

Where does aerobic respiration take place?

Answer 19

In the mitochondria

Question 20

Why do organisms require the energy released by respiration?

Answer 20

Synthesis of larger molecules
Muscle contraction
Maintenance of body temperature
Active transport

Question 21

What is anaerobic respiration?

Answer 21

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

Question 22

What is the equation for anaerobic respiration?

Answer 22

Glucose -> lactic acid (+energy)

Question 23

Why is anaerobic respiration less efficient then aerobic respiration?

Answer 23

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

Question 24

Why can anaerobic respiration lead to muscle fatigue?

Answer 24

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

Question 25

What is an oxygen debt?

Answer 25

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

Question 26

What is fermentation?

Answer 26

A type of anaerobic respiration that occurs in yeast cells

Question 27

What is the equation for fermentation?

Answer 27

Glucose -> ethanol * carbon dioxide

Question 28

Why is the fermentation reaction important?

Answer 28

It’s used in the production of bread and alcoholic drinks

Question 29

What are the differences between aerobic and anaerobic respiration?

Answer 29

Aerobic requires oxygen
Aerobic produced co2 and water, anaerobic produces lactic acid
Aerobic transfers a greater amount of energy

Question 30

How do muscles store glucose?

Answer 30

As glycogen

Question 31

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

Answer 31

-heart rate increases and arteries dilate to increase the flow of oxygenated blood to muscles
-breathing rate increases and breathing so deeper - increases the rate of gaseous exchange
- stored glycogen is converted back into glucose

Question 32

How is lactic acid transported away from the muscles?

Answer 32

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

Question 33

What is metabolism?

Answer 33

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

Question 34

How do cells use the energy transferred by respiration?

Answer 34

To continuously carry out enzyme controlled processes which lead tit he synthesis of new molecules

Question 35

Give examples of metabolic processes

Answer 35

-glucose into starch/glycogen/cellulose by being joined together
-glycerol and fatty acids into lipids
-glucose and nitrate ions into amino acids
-photosynthesis
-respiration
- breakdown of excess proteins into urea

Question 36

What is the difference between breathing and respiration

Answer 36

Breathing- physical process which occurs at lungs, exchange of gases
Respiration- chemical reaction, occurs on every cell and relies on diffusion

Question 37

What are tree roots important?

Answer 37

Phloem- transports sugars which cells need for photosynthesis
Anchorage- support the plant and keep it in ground
Xylem water- needed for photosynthesis to produce glucose which is needed for respiration. For new cell walls and for amino acids