B4- Bioenergetics

What is photosynthesis

Photosynthesis uses energy to change carbon dioxide and water into oxygen and glucos

Is photosynthesis an endothermic or exothermic reaction

Endothermic as light energy is absorbed from its environment

What is the word equation for photosynthesis

Light

Carbon Dioxide +Water → Oxygen + Glucose

What is the balanced equation for photosynthesis

Light

6CO2 + 6H2O → C6H12O6 +6O2

What uses do plants have for glucose

Plants use glucose for:

• Respiration- transfers energy from glucose and the rest is turned into useful substances

• Making cellulose- Makes the plants cell walls strong

• Making amino acids- combined with nitrate ions to make amino acids

• Stored as fats and oils- turned into lipids for storing in seeds

• Stored as starch- glucose turned into (starch as it is insoluble so won’t swell up like glucose) starch ready to be used when photosynthesis isn’t possible like in the winter

What are the factors that may limit the rate of photosynthesis

Light- night

Temperature- winter

CO2- when it is warm and bright enough CO2 is most likely the limiting factor

chlorophyll- IF plant has a disease or lack of nutrients can’t produce enough chlorophyll which limits sunlight absorption limiting rate of photosynthesis.

What practical measures rate of photosynthesis

Pondweed in test tube

1. Boiling tube set 10cm away from light source ideally LED

2. Fill boiling tube with sodium hydrogen carbonate solution which releases CO2 needed for photosynthesis

3. Put a piece of pondweed into the boiling tube with the cut end on the top

4. Leave for 5 minutes to acclimatise to the conditions of the boiling tube

5. Start a stopwatch and count the number of bubbles produced in one minute

6. Repeat twice before finding the mean number of bubbles produced in one minute

7. Then repeat the experiment with the light source at different distances from the light source. 20cm , 30cm, 40 cm

How can issues with the practical be solved

Measure the volume of gas produced with a gas syringe

What is the Inverse square law

Light intensity: equivalent 1

distance (d)2

How does distance affect Light intensity

As distance increases light intensity increases.

What is the most common way to artificially create the ideal environment for plants

Greenhouse

• Trap the suns heat (in winter may use heater or in summer cooler or ventilator to get ideal temperature)

• Artificial light may be added to give plants more time for photosynthesis

• May use Paraffin heater as it gives off CO2 as a bi product increases CO2 level

• Keeps them enclosed from pests

• Add fertilisers to provide minerals for healthy growth

• All this allows plants to grow faster and a decent crop can be harvested more often

• Conditions have to be perfect in order to ensure farmer isn’t wasting money

What is respiration

The process of transferring energy from the breakdown of glucose - occurring in every cell in the body continuously. It is an exothermic reaction as it releases energy into the environment

What do organisms use the energy transferred from respiration for

1. To build up larger molecules from smaller ones( like proteins from amino acids)

2. In animals it’s used to allow the muscles to contract (so they can move about)

3. In mammals and birds the energy is used to keep their body temperature steady in colder surroundings. (Unlike other animals, mammals and birds keep their bodies constantly warm)

How are larger molecules formed

From the combination of lots of smaller molecules e.g. 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)

What are examples of when larger molecules are broken down

• Glucose is broken down in respiration. Respiration transfers energy to power all the reactions in the body that make molecules

• Excess protein is broken down in a reaction to produce urea. Urea is then excreted in urine.

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

Metabolism

What is metabolism

Metabolism is all the chemical reactions in a an Organism

Where does aerobic respiration occur

The mitochondria and occurs all the time in plant and animals

What is the equation for aerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

What is anaerobic respiration

The incomplete breakdown of glucose which causes lactic acid production

glucose → lactic acid

Why does Anaerobic respiration not transfer as much energy as aerobic

As it isn’t oxidised

How is anaerobic respiration different in plants and yeast to animals

• Plants and yeast respire without oxygen but produce ethanol and carbon dioxide instead of lactic acid

• The word equation is: glucose → ethanol + carbon dioxide

• Anaerobic respiration in yeast cells is called fermentation

What is fermentation used for

• to make bread and alcoholic drinks e.g. beer and wine

• In bread making the carbon dioxide from fermentation makes the bread rise

• In beer and wine making the fermentation process produces alcohol ( ethanol)

What happens to respiration when you exercise

It increases to compensate for the increased amount of energy needed

What increases during exercise

Breathing rate and breath volume as well as heart rate helping to remove CO2 quicker

What causes Lactic acid build up

Anaerobic respiration

What can long periods of exercise cause

Muscle Fatigue- which is when muscles get tired and then stop contracting efficiently.

What does anaerobic respiration lead to a debt in

Oxygen

What is an oxygen debt

The amount of extra oxygen needed to react with the build up of lactic acid and remove it from the cells (Oxygen reacts with lactic acid to form harmless CO2 and water)

• Lungs heart and blood couldn’t keep up with the demand so the oxygen has to be ‘repayed’

• This is why you have to keep breathing hard after you stop, to get more oxygen into the blood

• The pulse and breathing rate stay higj whilst there are high levels of lactic acid and CO2

• Additionally the body also transports the lactic acid that enters your muscle to the liver where it is converted back into glucose

How can you measure the effects of exercise on the body

By taking your pulse and/or breathing rate by counting breaths at different levels of exercise

rest, gentle walking, slow jogging and running.