B4 : Bioenergenetics

Where does photosynthesis take place?

In the chloroplast, which has a green pigment called chlorophyll which absorbs light

What type of reaction is photosynthesis?

Endothermic reaction

What is the word equation for photosynthesis?

What is the balanced symbol equation for photosynthesis?

What is a limiting factor?

A limiting factor is any factor that slows down the rate of photosynthesis if there is not enough of it

What are the 4 factors that affect photosynthesis?

• Temperature

• Light intensity

• Carbon dioxide

• Chlorophyll

When is temperature a limiting factor + how does temperature affect the rate of photosynthesis?

In winter temperature is a limiting factor but in summer photosynthesis increases because particles gain more energy in warmer temperatures

When is light intensity a limiting factor + how does light intensity affect the rate of photosynthesis?

At night light intensity is a limiting factor but in the day photosynthesis increases because there is light which is absorbed by chlorophyll

When is carbon dioxide the limiting factor for the rate of photosynthesis?

If its warm and bright enough carbon dioxide is the limiting factor

How does chlorophyll affect the rate of photosynthesis?

Chlorophyll absorbs light and if there is not enough chlorophyll the rate of photosynthesis will decrease

What effects the amount of chlorophyll? (3)

• diseases (such as tobacco mosaic virus)

• lack of nutrients (such as magnesium)

• loss of leaves (fewer leaves means fewer chloroplasts)

What are the 5 uses of glucose in plants? + explain the uses.

• Amino Acids → glucose combined with nitrate ions to form amino acids which are the building blocks for protein

• Cellulose → glucose converted into cellulose which is used to strengthen the plant cell wall

• Respiration → energy transferred from glucose

• Oils and fats → glucose converted into oils and fats for seeds

• Starch → glucose (soluble) stored as starch (insoluble) for food for plants for when photosynthesis isn’t happening

Describe the temperature limiting factor graph (3)

• The temperature of the environment affects how much kinetic energy all particles have – so temperature affects the speed at which carbon dioxide and water move through a plant

• The lower the temperature, the less kinetic energy particles have, resulting in fewer successful collisions occurring over a period of time

• At higher temperatures (45°C), however, enzymes that control the processes of photosynthesis can be denatured (where the active site changes shape and is no longer complementary to its substrate) – this reduces the overall rate

Describe the light intensity limiting factor graph (3)

• The intensity of the light available to the plant will depend on the amount of energy that it has to carry out photosynthesis

• The more light a plant receives, the faster the rate of photosynthesis

• This trend will stop if either temperature or carbon dioxide are limiting factors

Describe the carbon dioxide limiting factor graph (3)

• Carbon dioxide is one of the raw materials required for photosynthesis

• This means the more carbon dioxide that is present, the faster the reaction can occur

• This trend will stop if either temperature or light intensity are limiting factors

Describe how oxygen production shows the rate of photosynthesis. (5)

1. Source of white light placed at a specific distance from pondweed

2. Pondweed is left to photosynthesise for a set amount of time

3. As pondweed photosynthesises, O2 collected in capillary tube

4. A syringe is used to draw gas bubbles in a tube up alongside a ruler, so the length of the gas bubble can be measured. This is proportional to the volume of O2 produced

5. Experiment repeated with a light source at different distances from pondweed

How can the apparatus be altered to find and measure the effect of temperature or CO2?

Temperature

• The test tube of pondweed can be put into a water bath at a set temperature.

• The experiment can then be repeated with different temperatures of water

CO2

• A measured amount of sodium hydrogen carbonate can be dissolved in the water - this gives off CO2.

• The experiment can be repeated with different concentrations of sodium hydrogen carbonate

What is the light intensity formula?

light intensity ⍺ 1/distance² 

(⍺ → proportional to)

How is a green house adapted for ideal farming? (7)

• Greenhouses trap the sun’s heat+ make sure the temperature doesn’t become limiting

• In winter a heater is used

• In summer if it’s too hot a ventilator is used

• Artificial light is used if it is dark

• To increase CO2 a paraffin heater is used

• Plants enclosed in a greenhouse keep pests away

• Fertilisers are used to provide minerals

Why is it important that farmers make sure their greenhouse conditions are effective? (2)

• To much off light,CO2 or temperature will lead to the conditions being ineffective and waste money.

• Keep a greenhouse supplied costs a lot of money and if crop is not being produced then money is being wasted as no revenue will be collected

What is a metabolism?

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

What are chemical reactions controlled by?

Enzymes

What are the 5 larger molecules that are made from small molecules during chemical reactions?

• glucose forms starch (glucose stored in a plant)

• glucose forms glycogen (glucose stored in a human)

• glucose forms cellulose (for the cell wall)

• glucose combines with nitrate ion to form amino acids which form protein

• Lipid molecules are made from 1 molecule of glycerol and 3 molecules of fatty acids

What are the 2 larger molecules that are broken down from large molecules to smaller molecules during chemical reactions?

• Glucose is broken down in respiration to release energy for the body

• Excess protein is broken down to produce urea which is removed from the body via urine

What is respiration?

Respiration is the process of transferring energy from glucose which happens in every cell (transference of energy from food)

What type of reaction is respiration?

Exothermic

What are 3 ways the organisms use energy from respiration?

• Build up larger molecules from smaller molecules

• In animals it allows muscles to contract

• In mammals and birds the energy is used to keep their body temperature to stay warm in colder settings

What are the two types of respiration?

Aerobic respiration + anaerobic respiration

Where does aerobic respiration take place?

It happens in the mitochondria

What is the formula for respiration?

What is the symbol equation for respiration?

Why does aerobic respiration release large amounts of energy?

The glucose has been fully oxidised

Why does anaerobic respiration take place?

There is not enough oxygen supplied to the cells

What is anaerobic respiration in terms of glucose?

The incomplete oxidation of glucose

What is the word equation for anaerobic respiration in muscle cells?

How much energy does anaerobic respiration release?

Not a lot compared to aerobic respiration

When is anaerobic respiration used?

In emergencies such as during exercise

Explain respiration in terms of exercise (4)

1. Muscles need energy to contract and during exercise, muscles contract more frequently leading to increased respiration

2. An increase in respiration in cells means more oxygen is needed in them

3. Your breathing rate and breath volume increase to get more oxygen into the blood and your heart rate increases to get oxygenated blood around the body

4. This removes CO2 at the same time

Explain anaerobic respiration in terms of exercise (3)

1. When you do vigorous exercise like sprinting your body can’t supply oxygen to the body fast enough so it starts respiring anaerobically

2. This is bad because it causes a build up of lactic acid which gets painful

3. Long periods of exercise cause muscle fatigue and muscles get tired leading to inefficient contraction

What is oxygen debt?

Oxygen that needs to be paid back after anaerobic respiration

Explain oxygen debt (4)

1. After anaerobic respiration you body will need to make up all the oxygen that was lost

2. This is because it needs to react with the build up of lactic acid and remove it from cells

3. As a result after exercise you need to breathe hard to get oxygen back into your body

4. The pulse and breathing levels stay high whilst removing lactic acid and carbon dioxide

How else apart from breathing can lactic acid be removed?

The blood that enters the muscles transports the lactic acid to the liver where it is converted back to glucose

What is the word equation for anaerobic respiration in plants and yeast?

What is anaerobic respiration called in yeast cells?

Fermentation

What is fermentation used to make?

Bread + alcoholic drinks

How is fermentation used in bread + alcoholic drinks?

Bread

Carbon dioxide from fermentation is used to make bread rise

Alcoholic drinks

The fermentation process produces alcohol (ethanol) for alcoholic drinks

How can you measure the effects of exercise on the body? (2)

• Measure breathing rate by counting breaths

• Measure heart rate by taking your pulse