B4 - Bioenergetics

Question 1

Where does photosynthesis take place in a plant

Answer 1

chloroplasts - they contain pigments like chlorophyll that absorb light

Question 2

What is the word equation for photosynthesis

Answer 2

carbon dioxide + water → glucose + oxygen

Question 3

What is the symbol equation for photosynthesis

Answer 3

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Question 4

What are the 5 ways plants use glucose

Answer 4

1. For respiration - this transfers energy from glucose which enables the plants to convert the rest of the glucose into various other substances
2. Making cellulose - glucose is converted to cellulose for making strong plant cell walls
3. Making amino acids - glucose is combined with nitrate ions (absorbed by the soil) to make amino acids which are then made into proteins
4. Stored as oils or fats - glucose is turned into lipids (fats and oils) for storing in seeds
5. Stored as starch - starch and stored in roots, stems and leaves ready for use when photosynthesis isn’t happening like in the winter. starch is insoluble which makes it better for storing than glucose - a cell with lots of glucose in would draw in loads of water and swell up

Question 5

What are some limiting factors of photosynthesis

Answer 5

• light intensity
• CO₂ concentration
• temperature

(lack of chlorophyll in a plant could also be a limiting factor however this is usually caused by disease like tobacco mosaic virus which damages chloroplasts so that they don’t make chlorophyll which makes the rate of photosynthesis reduce due to the plant not being able to absorb as much light)

Question 6

What does limiting factor mean

Answer 6

means that it is stopping photosynthesis from happening any faster or at all

Question 7

What is the difference between an exothermic and an endothermic reaction and given this information, is photosynthesis an exothermic or an endothermic reaction?

Answer 7

• an exothermic reaction is when energy is transferred to the surroundings (usually the reaction feel hots)
• an endothermic reaction is when energy is taken in from the surroundings (usually the reaction feels cold)

therefore, photosynthesis is an endothermic reaction because it takes in energy (light) from the surroundings

Question 8

How do farmers make sure that their crop yield will have optimum conditions for growing

Answer 8

• planting them in greenhouse - this will keep the temperature nice and warm
• buy LED lights - this will give more energy for the plants to take in
• buy heating - this will keep it trapped inside the greenhouse also increasing temperature and this is effective for growing crops even on cold days inside a greenhouse

Question 9

Why might a farmer not be able to provide optimum conditions for their plants in a greenhouse

Answer 9

cost - lighting and heating can cost a lot and if the cost of those materials will be more or near the same amount as what they will make from the crop yield then it wouldn’t be worth it

Question 10

What is the equation for inverse square law

Answer 10

light intensity = 1 / distance²

Question 11

What’s a method for investigating how light intensity affects rate of photosynthesis

Answer 11

• by using an aquatic plant like pondweed
• change the distance of a lamp from the pondweed that is inside a beaker filled with water and count the number of bubbles (these are oxygen bubbles produced as a waste product of photosynthesis) produced within a set amount of time (a minute or 2)

in this experiment, light intensity is the independent variable and the number of bubbles is the dependent variable

equipment needed for this experiment:
- beaker filled with water
- pondweed
- ruler (to measure distance lamp s away from pondweed)
- lamp
- stopwatch

Question 12

How does temperature affect the rate of photosynthesis

Answer 12

• if the temperature is colder then the rate of photosynthesis will decrease
• if the temperature is warmer the rate of photosynthesis will increase

HOWEVER, if the temperature goes above 45°C then the enzymes needed for photosynthesis will being to denature and not work anymore.

usually the outdoors won’t get up to this temperature (unless you’re in a desert) but it can get pretty warm like this temperature in greenhouses if you’re not careful

Question 13

What is respiration

Answer 13

Respiration is the process if transferring energy from the breakdown of glucose (sugar) - and it goes on it every cell in your body continuously. It also happens in plants too. ALL living things respire

Question 14

Is respiration an endothermic or an exothermic reaction

Answer 14

reparation is an exothermic reaction as it transfers energy to the environment

Question 15

What is metabolism

Answer 15

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

Question 16

Give examples of what organisms need energy for

Answer 16

• homeostasis (regulating body temperature)
• contraction (of muscles)
• construction (to make larger molecules from smaller molecules)

Question 17

What are the 2 types of respiration

Answer 17

• aerobic
• anaerobic

Question 18

What is anaerobic respiration

Answer 18

• glucose is not broken down completely, making it a less efficient way to transfer energy
• in animals, glucose is converted into lactic acid during anaerobic respiration
  glucose → lactic acid
• anaerobic respiration happens when insufficient (not enough) oxygen reaches the muscles during periods of intense activity.it is also useful for emergancies

Question 19

What is aerobic respiration

Answer 19

• aerobic respiration is respiration using oxygen and it is the most efficient way to transfer energy from glucose. it goes on all the time in plants and animals
• in aerobic respiration, glucose reacts with oxygen in the mitochondria of cells to give carbon dioxide, water and energy

Glucose + oxygen → carbon dioxide + water (+ energy)

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂0 (+ energy)

Question 20

How is anaerobic respiration different in plants compared to in animals

Answer 20

plants and yeast cells can respire anaerobically but they product ethanol (alcohol) and carbon dioxide instead of lactic acid

glucose → ethanol + carbon dioxide

anaerobic respiration in yeast is called fermentation. in the food and drinks industry, fermentation by yeast is of great value as it is used for bread making and alcoholic drinks like beer and wine

Question 21

Name some metabolic reactions:

Answer 21

making amino acids - combining glucose and nitrate ions make amino acids which can then be combined to make proteins

breaking down excess proteins - this forms urea which is excreted and gotten rid of through urine

converting glucose - converting glucose into starch (plants), glycogen (animals) and cellulose (plants)

making lipids - combining glycerol and fatty acid chains to make lipid molecules

Question 22

What responses does the body have to an increased rate of reparation during exercise

Answer 22

increase breath volume - this will also increase the rate of gas exchange

increase heart rate - an increased heart rate delivers more blood (containing more glucose and oxygen) to the muscles

blood vessels dilate - blood vessels dilate (open wider) to ensure more blood reaches the muscles

increase in breathing rate - n increase in breathing rate increases gas exchange in the lungs, with more oxygen taken in and more carbon dioxide released

Question 23

What is lactic acid

Answer 23

• lactic acid is a by-product of anaerobic respiration
• it is toxic and can build up in muscles leading to muscular pain and fatigue
• lactic acid also stops muscles contracting efficiently