Paper 1 - bioenergetics

is photosynthesis an endothermic or exothermic reaction, why

endothermic because energy is transferred from the environment to the chloroplasts

how is energy transferred to the chloroplasts

by light

five main ways plants use glucose

• for respiration

• to produce amino acids for protein synthesis

• converted into soluble starch for storage

• to produce cellulose, which strengthens cell wall

• to produce oil or fat for storage

what are the limiting factors that can affect the rate of photosynthesis

• light intensity

• carbon dioxide concentration

• temperature

• Amount of chlorophyll

What is the limiting factor of photosynthesis at night

Light intensity

What is the limiting factor of photosynthesis when it is warm and bright

Concentration of carbon dioxide

What is the limiting factor of photosynthesis when it is warm and bright

Concentration of carbon dioxide

How can the amount of chlorophyll in a plant be affected

Disease or environmental stress

How does chlorophyll affect the rate of photosynthesis

Reduces the rate because plants can’t absorb as much light

How does light intensity affect the rate of photosynthesis

• light provides energy needed for photosynthesis

• As light intensity increases, rate of photosynthesis increases steadily up to a certain point

• Beyond that, as light intensity increases, the rate no longer increases

• Another limiting factor will then affect the rate of photosynthesis

How does carbon dioxide concentration affect the rate of photosynthesis

• Concentration of carbon dioxide only increases the rate of photosynthesis up to a point

• After this the graph plateaus, as the concentration of CO2 increases, rate no longer increases as CO2 is no longer the limiting factor

  
  

How is temperature a limiting factor of photosynthesis when temp is too low

• the enzymes needed for photosynthesis work more slowly at low temperatures

How does temperature affect the rate of photosynthesis when temp is too high

• the enzymes the plant needs for photosynthesis and other reactions will be damaged

  
  

How are greenhouses used to prevent temperature becoming a limiting factor

• help to trap the suns heat

• In winter, farmers/gardeners may use heaters

• In summer, use shades and ventilation

How are greenhouses used to provide enough light for plants

• artificial light after sun sets to give plants more quality photosynthesis time

How are greenhouses used to increase CO2 concentration

• Using a paraffin heater to heat

• As paraffin burns, makes CO2 as a by-product

Apart from limiting factors, why might plants be kept in a greenhouse

• makes it easier to keep them free fro, pests and diseas3s

• Farmers can add fertilisers to the soil, to provide all minerals needed for growth

Why is maintaining the conditions of greenhouses important for farmers that sell crops

• if conditions are kept right for photosynthesis the plants grow much faster, so decent crop can be harvested more often to be sold

  
  

Where does the energy that’s transferred in respiration come from

The breakdown of glucose

Is respiration endothermic or exothermic

Exothermic, transfers energy to the environment

What are three ways that organisms use the energy transferred by respiration

• chemical reactions to build larger molecules

• Muscle contraction (movement)

• In mammals and birds to keep warm

What is metabolism

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

Describe how larger molecules are made from smaller ones like glucose

• lots of small glucose molecules are joined together in reactions to form starch (a storage molecule in plant cells),

• Glycogen (a storage molecule in animal cells)

• And cellulose (a component of plant cell walls)

Describe how larger molecules like lipids are made from smaller ones

• each made from one molecule of glycerol and three fatty acids

Describe how large molecules like proteins are made from smaller ones

• glucose is combined with nitrate ions to make amino acids which in turn are used to synthesise proteins

What process of glucose broken down in

Respiration

Describe what happens when excess protein is broken down in a reaction

• urea is produced, which is excreted in urine

What is the most efficient way to transfer energy from glucose

Aerobic respiration

When might anaerobic respiration take place

When doing vigorous exercise and your body can’t supply enough oxygen to your muscles

What is produced in anaerobic respiration (humans)

Lactic acid

What is produced in anaerobic respiration in plants and yeast

Ethanol and carbon dioxide

What is anaerobic respiration in yeast cells called

Fermentation

What is fermentation by yeast used for in the food and drinks industry

To make bread and alcoholic drinks like beer and wine

Why is fermentation by yeast important for bread making

The carbon dioxide from fermentation makes bread rise

Why is fermentation by yeast important in beer and wine making

Fermentation is what produces alcohol

Why do you respire more when you exercise

• muscles need energy from respiration to contract

• When you exercise, some of your muscles contract more frequently so more energy is needed

• This energy comes from increased respiration

Why do you need to get more oxygen into your cells when exercising

Because of the increased rate of respiration

How does your body supply the muscles with more oxygenated blood during exercise

• breathing rate and breath volume increase → more oxygen into the blood

• Heart rate increases → more oxygenated blood around the body faster

What is oxygen debt

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells

What happens to your muscles during long periods of vigorous activity

Muscles become fatigued and stop contracting efficiently

How does the body cope with the high level of lactic acid

Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose