B2 Topic 2 - Life Processes

Respiration is the process of breaking down glucose to release energy which goes on in every living cell.

Aerobic respiration is respiration using plenty of oxygen. This is the most efficient way to release energy from glucose:

• Glucose + Oxygen → Carbon Dioxide + Water + Energy

Anaerobic respiration happens when there's not enough oxygen available. It doesn't release as much energy as aerobic respiration. It produces a build-up of lactic acid in the muscles which can cause cramp, but anaerobic respirations is advantageous as you can continue using your muscles for longer:

• Glucose → Lactic Acid + Energy

Once exercise is stopped, the person will have oxygen debt. The amount of oxygen required is called excess post-exercise oxygen consumption (EPOC). Breathing will be harder for a while after stopping to get more oxygen to the blood. The heart rate stays high to get the oxygen to the muscles where it's converted from lactic acid into CO₂
and water.

When you exercise you respire more. Muscles need energy from respiration to contract. Your muscles contract more frequently than normal during exercise so need more energy which comes from increased respiration.

More oxygen is needed in cells so the breathing rate increases to get more oxygen into the blood. The blood becomes oxygenated and travels around the body faster, as your heart rate increases. This removes CO₂ more quickly at the same time.

The rate of diffusion of CO₂ and O₂ at the lung surface and in muscle calls increase to keep up with demand.

During vigorous exercise, your body can't supply oxygen to your musces quickly enough so begin to respire anaerobically.

Cardiac Output = Heart Rate x Stroke Volume

Investigating the effect of exercise on breathing and heart rate:

1. You can measure breathing rate by counting breaht, and heart rate by taking the pulse

2. You could take your pulse after:

• sitting down for 5 minutes
• then after 5 minutes of gentle walking
• then again after 5 minutes of slow jogging
• then again after running for 5 minutes

3. Plot the results in a bar chart

4. Your pulse rate will increase the more intense the exercise is as your body needs to get more oxygen to the muscles and take more carbon dioxide away from the muscles

5. To make the experiment more reliable, do this as a group and plot the average pulse rate for each exercise

Raw materials and waste diffuse in and out of cells.

• The circulatory system carries glucose, oxygen and carbon dioxide around the body in the blood
• The glucose needed for respiration come from breaking down food in the digestive system
• The oxygen come from air breathed into the lungs and carbon dioxide is breathed out
• The smallest blood vessels in the body are called capillaries. All the cells in the body have capillaries nearyby to supply them with glucose and oxygen, and to take away the waste carbon dioxide

These substances move between cells and capillaries by a process called diffusion. Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.

• The bigger the different in concentration, the faster the rate of diffusion

Photosynthesis is the process that produces glucose in plants. This process happens in the leaves of all green plants and inside of the chloroplasts that contain chlorophyll which absorbs energy in sunlight and uses it to convert carbon dioxide and water into glucose. Oxygen is produced as a by-product.

Carbon Dioxide + Water → Glucose + Oxygen

Leaves are adapted for photosynthesis by:

• Broad leaves - large surface area exposed to light
• Contain lots of chlorphyll in chloroplasts - absorb light
• Stomata - little holes to let gases like carbon dioxide and oxygen in and out; also to let water vapour escape (transpiration)

Limiting factors:

• Light intensity
• Concentration of carbon dioxide
• Temperature

You can discover the ideal conditions for photosynthesis in a certain plant. In this case it's the Canadian pondweed.

1. You can measure the amount of oxygen produced in a given time to show how fast photosynthesis is happening

2. You could count the bubbles given off or, to be more accurate, collect the oxygen in a gas syringe

3. You can measure how different factors affect the rate of photosynthesis

Light intensity:

• The rate steadily increases up to a certain point
• After that, the other limiting factors need to be increased (carbon dioxide or temperature)

Carbon dioxide concentration:

• The rate steadily increases up to a certain point
• After that, the other limiting factors need to be increased (light or temperature)

Temperature:

• If temperature is the limiting factore, it's usually because the temperature is too low
• If the temperature is too hot, the enzymes it needs for photosynthesis will be denatured. This happens around 40-45°C
  

Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.

Practical:

Dependant variable - chip length

Independant variable - concentraion of sugar solutions

1. Cut up a potato into identical cylinders and measure the length of them

2. Gather some beakers with different sugar solution in them - one of pure water and the others of varied sugar concentrations

3. Leave some of the cylinders in each beaker for around 30 minutes and measure the lengths of the cylinders again.

If the water has moved into the cylinders by osmosis, they will be longer. If water has moved out, they will be shorter.

Root hairs take in water by osmosis:

• The cells on the plant roots grow into long branches which stick out into the soil covered in millions of microscopic hairs
• This gives the plant a large surface area for absorbing water from the soil
• There's usually a higher water concentration in the soil than inside the plant, so water enters the root hair cell by osmosis

Root hairs take in minerals using active transport

• Root hairs absorb minerals from the soil
• The concentration of minerals in the soil is usually low. It's normally higher in the root hair cell than in the soil
• Normal diffusion doesn't explain how minerals are taken up into the root hair cell
• A different process is used called ACTIVE TRANSPORT
• Active transport uses energy from respiration to help the plant pull minerals into the root hair against the concentration gradient which is essential for its growth

Plants have tube networks to move substances to and from the cells quickly:

• Xylem tubes transport water and minerals from the root to the rest of the plant
• Phloem tubes transport sugars from the leaves to growing and storage tissues

Transpiration is the loss of water from the plant that is caused by the evaporation and diffusion of water from inside the leaves.

This creates a shortage of water in the leaf and so more water is drawn up from the xylem vessels to replace it.

More water is drawn up from the roots and so there's a constant transpiration stream of water through the plant.

Transpiration is a side-effect of how leaves are adapted for photosynthesis. They have stomata in so gases can be easily exchanged. As there is more water inside the plant than in the air outside, the water escapes through the stomata in the leaves.

Transpirations does provide the plant with a constant supply of water for photosynthesis.

Pooters - jars that collect ground insects

• The jar has rubber bungs sealing the top and two tubes stuck through the bung
• If you **** on the shorter tube and put the end of the longer tube over an insect it will be ****ed into the jar

Pitfall traps - steep-sided containers that are sunk into a hole in the ground to collect ground insects

• The top is partially open to let insects fall into the container and can't get out, so you can count them

Sweep nets - collecting animals from long grass

Pond nets - collecting animals from ponds and rivers

Quadrats are used to study the distribuation of small organisms

• A quadrat is a square frame that encolses an area to compare how common an organism is from two different areas

1. Place the quadrat on the ground at a random point within the first sample area

2. Count all the organisms you're interested in within the quadrat

3. Work out the mean number of organisms per quadrat within the first sample area

4. Repeat steps 1-3 in the second sample area

5. Compare the two means

Population size = mean number of organisms per m² x total are in m²

If there is a distribution of organisms you can investigate the environmental factors that might be causing it.

Environmental factors:

• Temperature - use a thermometer
• Light intensity - use an electronic device called a light sensor
• pH levels - you can measure the soil's pH using indicator liquid that changes colour depending on the pH. Electronic pH monitors can also be used