Slides in this set
Respiration = - energy released from the breakdown of glucose from food substances in cells.
-Happens in Mitochondria.
- Makes smaller molecules into larger one e.g. Amino acids into protein molecules.
- Allow muscles to contract.
- Maintain a constant body temperature (homeostasis)
Aerobic respiration = oxygen + glucose reacts to form carbon dioxide and water.
Oxygen = breathed in.
Carbon dioxide = produced as a waste product of respiration. Breathed out.
Glucose = the breakdown of starch in food substances. Provides energy to cells through respiration.
Capillaries = tiny blood vessels close to the body's cells.
Diffusion = movement of particles from an area of higher concentration to an area of lower
Carbon dioxide diffuse from cells (an area of higher concentration) to the capillaries (an area of lower
concentration) to be removed.
Oxygen and glucose diffuse from capillaries (an area of higher concentration) to an area of lower
concentration (the cells)…read more
Effects of exercise on respiration
-Muscle cells respire more as your muscle cells contract more frequently so need more energy.
-This mean that oxygen and glucose must be delivered to cell more quickly (so the breathing rate
increases for oxygen)
-This also means carbon dioxide should be removed more quickly.
During hard exercise, the oxygen supply might not be enough to respire quickly enough to provide
energy to muscle cells. So anaerobic respiration occurs as well as aerobic.
Anaerobic respiration = glucose reacts to form lactic acid and energy.
-A build up of lactic acid causes pain in muscles e.g. Cramps.
-Releases less energy than aerobic respiration.
During hard exercise, oxygen debt builds up. This is because you are not able to breathe fast enough so
you don't take in enough oxygen. So after exercise your breathing rate is still very high, this is called
EPOC (excess post-exercise oxygen consumption) so that your body can break down lactic acid into
harmless carbon dioxide and water.
-Glucose is not broken down fully as there's not enough oxygen , so is just broken down into carbon
dioxide and water when exercising.
-Your heart rate is still at an increased rate post exercise to allow the lactic acid to be carried away by
the blood into the liver. It is broken down there.…read more
Photosynthesis equation: carbon dioxide + water react to form glucose + oxygen (oxygen is the waste
How are leafs adapted to their function:
1. They are broad, so have a larger surface area thus absorb more light hence increase the rate of
2. Contains many chloroplasts which contain chlorophyll. The more chloroplasts = the more chlorophyll
= the more sunlight absorbed = an increased rate of photosynthesis.
3. Stomata are tiny openings in the in leafs that open and close to allow the exchange of gases in and
out of the leaf (e.g. Carbon dioxide = in, oxygen = out). Water vapour is also let out.…read more
Limiting factors (means stopping photosynthesis from happening faster) of photosynthesis:
1. Sunlight: - Not enough light slows down the rate of photosynthesis.
- Only increases the rate of photosynthesis up to a certain point, after that the limiting
factor is either the Carbon Dioxide levels or the temperature.
2. Carbon Dioxide: - Not enough carbon dioxide slows down the rate of photosynthesis, however only
up to a certain point, after that the light intensity or temperature are the limiting factors.
3. Temperature: - If temperature is too low, it's the limiting factor. Enzymes works more slowly at low
temperatures for photosynthesis.
-However if you keep increasing the temperature the enzymes will work faster until they reach their
optimum temperture which is where they'll work at their fastest and so photosynthesis will occur as fast
as it can be.
-If the temperature is increased too much, the enzymes will become denatured (at about 45 degrees).…read more
Experiments for investigating photosynthesis:
1. How fast is photosynthesis happening:
-Get some Canadian pondweed put it in water. Seal with a bung containing a tube attached to a syringe.
-Measure how much oxygen is produced over a given time.
How different limiting factors affect the rate of photosynthesis:
- Do the same as above however:
1. Light Intensity: Use a bench lamp to control intensities of light. Use a light meter to measure light
intensity at the beakers.
2. Temperature: Keep the flask in different water baths to measure how temperature affects the rate of
3. Carbon Dioxide: Dissolve different amount of sodium hydrogencarbonate into the water as it
produces carbon dioxide to see how this affects the rate of photosynthesis.…read more
Movement of water molecules from an area of higher concentration to an area of lower concentration
across a semi-permeable membrane.
-Small molecules e.g. Water can get through the semi-permeable membrane, larger molecules e.g.
-Steady net flow of water molecules from an area of higher concentration to an area of lower
Practical to show Osmosis:
1. Use a cork borer to get potato cylinders. This is so they are of the same height and circumference.
2. Measure the cylinders weight and then place an equal amount of the potato cylinders into 3 different
beakers, one with pure water and another with concentrated sucrose solution..
3. Keep them in the beakers for half an hour and then measure their weight.
Pure water= Weight increases as water molecules move from an area of high concentration (pure
water) to an area of lower concentration (potato cylinders)
Concentrated sucrose solution= Weight decreases as water molecules move from an area of higher
concentration (potato cylinders) to an area of lower concentration (sucrose solution)…read more