Exchange and Transport in Animals Flashcards
Describe what substances organisms exchange with their environment and why
- Cells need oxygen for aerobic respiration which produces carbon dioxide as a waste product
- Water is taken up by cells by osmosis. In animals, dissolved food molecules and mineral ions diffuse along with it
- Urea diffuses from cells to the blood plasma for removal from the body by kidneys
Why are exchange surfaces and a transport system important in multicellular animals?
- because it would take too long for materials to diffuse through cells on the outside of a tissue to reach the cells on the inside
What is surface to volume ratio?
- the larger a cell’s surface area, the more of a substance can diffuse in and out of it in a certain time
- however, if a cell’s volume is too big, the cell cannot fill up quickly enough with the materials it needs
- surface area : volume = surface area/volume
- if the ratio is too small, cannot get enough raw materials fast enough, so there is a limit to the size of cells
Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries.
- Alveoli increase the surface area : volume ratio of the lungs making it more efficient for gas exchange
- It does this by having a higher concentration of oxygen and a lower concentration of carbon dioxide than the blood
- also had a one cell thick wall with the capillaries , alllowing for oxygen to move to the blood quickly and CO2 from the blood to move into the lungs quickly
- has a moist lining for dissolving gases
What does the Rate of Diffusion depend on?
Distance- substances diffuse more quickly when they haven’t as far to move
Concentration gradient - substances diffuse faster if there is a bigger difference in concentration between the area they are diffusing from and the area they are diffusing to
Surface area- the more surface there is available for molecules to move across, the faster they can get from one side to the other
How do you calculate the rate of diffusion with Fick’s Law?
rate of diffusion α (surface area x concentration) / thickness of membrane
Explain how the structure of the blood is related to its function:
a) Red blood cells
a) - the job of the red blood cells (erythrocytes) is to carry oxygen from the lungs to all the cells in the body
- they have a biconcave disc shape to give a large surface area for absorbing the most amount of oxygen
- they don’t have a nucleus which allows for more room to carry oxygen
- they contain haemoglobin which contains iron
- In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin
- In body tissues, the reverse happens - oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells
Explain how the structure of the blood is related to its function:
a) White blood cells
- Phagocytes are white blood cells that can change shape to engulf foreign organisms - this is called phagocytosis
- Lymphocytes are white blood cells that produce antibodies against microorganisms . Some also produce antitoxins to neutralise any toxins produced by microorganisms
- When you have an infection, your white blood cells multiply to fight it off - so a blood test will show a high white blood cell count
Explain how the structure of the blood is related to its function:
a) Platelets
b) Plasma
a) - platelets are small fragments of cells. they have no nucleus
- they help the blood to clot at a wound - to stop all your blood pouring out and microorganisms getting in
- lack of platelets can cause excessive bleeding and bruising
b) plasma is a pale, straw-coloured liquid that carries just about everything:
- Red and white blood cells and platelets
- Nutrients like amino acids and glucose
- Carbon dioxide from organs to lungs
- Urea from liver to the kidneys
- Hormones
- Proteins
- Antibodies and antitoxins produced by the white blood cells
Explain how the structure of the blood vessels is related to
their function:
a) Arteries
a) - The heart pumps the blood out at high pressure so the artery walls are strong and elastic
- The walls are thick compared to the size of the hole down the middle (the “lumen”)
- They contain thick layers of muscle to make them strong, and elastic fibres to allow them to stretch and spring back
Explain how the structure of the blood vessels is related to
their function:
a) capillaries
a) - Arteries branch to capillaries
- Capillaries are really tiny and are too small to see
- They are very narrow, so they can squeeze into the gaps between cells. This means they can carry the blood really close to every cell in the body to exchange substances with them
- They have permeable walls, so substances can diffuse in and out, they supply food and oxygen, and take away waste like CO2
- Their walls are usually only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs
Explain how the structure of the blood vessels is related to
their function:
a) veins
a) - capillaries eventually join up to form the veins
- the blood is at lower pressure in the veins so the walls don’t need to be as thick as artery walls
- they have a bigger lumen than arteries to help the blood flow despite the lower pressure
- they also have valves to help keep the blood flowing in the right direction
Explain how the structure of the heart and circulatory system
is related to its function
The mammal heart has four chambers and four major blood vessels…
Right atrium- receives deoxygenated blood from the body through the vena cava
Right ventricle- deoxygenated blood moves through the right ventricle, which pumps it to the lungs via the pulmonary artery
Left atrium- receives oxygenated blood from the lungs through the pulmonary vein
Left ventricle- oxygenated blood then moves through the left ventricle, which pumps it out round the whole body via the aorta
a) Why does the left ventricle have a much thicker wall than the right ventricle?
b) What do valves do?
a) - Because it needs more muscle because it has to pump blood around the whole body at high pressure
- whereas the right ventricle only has to pump blood to the lungs
b) - Valves prevent the backflow of blood in the heart
Describe cellular respiration
- An exothermic reaction that happens continuously in living cells to release energy for metabolic processes
- Examples include aerobic and anaerobic respiration
Compare the process of aerobic respiration with the process of
anaerobic respiration
Aerobic Respiration:
- happens when there is plenty of oxygen available
- aerobic is the most efficient way to transfer energy from glucose
- Glucose + oxygen → carbon dioxide + water (is the reverse equation of photosynthesis)
Anaerobic Respiration:
- when your body can’t supply enough oxygen to your muscles for aerobic respiration - even though your heart rate and breathing rate increase as much as they can
- your muscles have to start respiring anaerobically
- anaerobic respiration transfers much less energy thana erobic respiration so its much less efficient
- in anaerobic respiration the glucose is only partly broken down, and lactic acid is produced which leads to pain and cramps
- Glucose → lactic acid
SB8e Core practical - Respiration
Describe the core practical to investigate the effect temperature has on rates of reaction in living organisms.
Aim - Investigate the rate of reaction in living organisms
- A: Collect a tube with a volume of soda lime, held in place with cotton wool. The soda lime absorbs carbon dioxide.
- B: Carefully collect and place some of the small organisms into the tube after weighing them.
- C: Insert the bung and capillary tube, then set up a control tube with the same apparatus but no organism.
- D: Place both tubes into a rack in a water bath at a set temperature. It’s best to tilt the rack slightly, so the capillary tubes hang over the side of the water bath at an angle.
- E: Wait for 5mins to let the organisms adjust to the temperature of the water bath.
- F: Hold a beaker of coloured liquid to the ends of the capillary tubes, so that liquid enters
- G: Mark the position of the liquid before & after 5mins & measure distance moved.
- H: Repeat at different temperatures.
How to calculate heart rate, stroke volume and cardiac output
cardiac output = stroke volume x heart rate
- heart rate is the number of beats per minute
- the stroke volume is the volume of blood pumped by one ventricle each time it contracts
