Topic 8 - Exchange and transport in animals Flashcards
Which substances may need to be transported into and out of organisms and why?
Oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea.
This is to prevent them from accumulating. We need to intake oxygen and get rid of waste products
What is the equation for surface area to volume ratio and what does it mean?
Surface area = length x width
Volume = length x width x height
Write the ratio in the smallest whole numbers.
If the ratio is large the organism is less likely to require specialised exchange surfaces and a transport system because the rate of diffusion is sufficient in supplying and removing the necessary gases.
Describe villi
In the small intestine, cells have projections called villi. Digested food is absorbed over the membrane of these cells, into the bloodstream. Microvilli increase surface area for absorption
Why is having an efficient blood supply/being ventilated (in animals) a beneficial adaptation?
It creates a steep concentration gradient, so diffusion occurs faster
Why is having a thin membrane a beneficial adaptation?
It provides a short diffusion pathway, allowing the process to occur faster e.g. villi
Explain how alveoli are adapted for gas exchange
Alveoli are small ‘air sacs’ in the lungs.
-They are very small and arranged in clusters, creating a large surface area for diffusion to take place over
-The capillaries provide a large blood supply, maintaining the concentration gradient
-The walls between the alveoli and blood vessels are very thin, meaning there is a short diffusion pathway
They gas exchange by diffusion between air in the lungs and blood in the capillaries.
How does surface area affect the rate of diffusion?
The larger the surface area, the higher the number of particles that will be able to move in a given time (more space for particles to move through) so the rate of diffusion is faster
How does concentration gradient affect the rate of diffusion?
Diffusion is faster if there is a big difference in the concentration between the area the substance travels from and the area that it is moving to
How does diffusion distance affect the rate of diffusion?
If the diffusion distance is small, diffusion happens faster because the particles do not have as far to travel
What is Fick’s law?
rate of diffusion ∝ surface area*concentration difference/thickness of membrane
Explain how the structure of red blood cells (erythrocytes) is related to its function
Its function is to carry oxygen molecules from the lungs to all the cells in the body
-They have no nucleus so they can contain more haemoglobin (a red pigment which can transport oxygen around the body)
-They have a biconcave disc shape to maximise their surface area for oxygen absorption
-They are thin so there is only a short distance for the oxygen to diffuse to reach the centre of the cell
Explain the function of white blood cells (phagocytes and lymphocytes)
They are a part of the immune system, which defends against pathogens.
-70% of white blood cells are phagocytes which engulf and destroy unwanted microorganisms that enter the blood by the process of phagocytosis
-25% are lymphocytes which produce soluble proteins called antibodies when a foreign body such as a microorganism enters the body.
Explain plasma’s function
It’s the liquid that carries components in the blood including red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
Explain how the structure of platelets is related to its function
Platelets are cell fragments produced by giant cells in the bone marrow which help stop bleeding.
-They have proteins on their surface that enable them to stick to breaks in a blood vessel and clump together
-They secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound
-The clot dries and hardens to form a scab, this allows new skin to grow underneath while preventing microorganisms from entering
-They have no nucleus
Explain how the structure of the arteries is related to their function
Arteries carry oxygenated blood away from the heart
-Layers of muscles in the walls make them strong
-Elastic fibres allow them to stretch
-This helps the vessels withstand the high pressure created by the pumping of the heart
Explain how the structure of the veins is related to their function
Veins carry blood towards the heart
-The lumen is wide to allow the low pressure blood to flow through
-They have valves to ensure the blood flows in the right direction
Explain how the structure of the capillaries is related to their function
Capillaries allow the blood to flow very close to cells to enable substances to move between them
-One cell thick walls (very thin) create a short diffusion pathway
-Permeable walls so substances can move across them
What is the purpose of the circulatory system?
To carry oxygen and nutrients to every cell in the body and remove the waste products
Describe the structure of the double circulatory system in relation to the heart
Deoxygenated blood flows through the vena cava into the right atrium and then into the right ventricle and through the pulmonary artery which pumps it to the lungs to undergo gaseous exchange.
Oxygenated blood flows through the pulmonary vein, into the left atrium, then into the left ventricle and through the aorta, which pumps oxygenated blood around the body
Describe how the structure of the heart is adapted to fulfil its function
-It has muscular walls to provide a strong heartbeat
-The muscular wall of the left ventricle is thicker because blood needs to be pumped all around the body rather than just to the lung like the right ventricle.
-There are 4 chambers that separate the oxygenated blood from the deoxygenated blood.
-Valves make sure blood does not flow backwards
-Coronary arteries cover the heart to provide its own oxygenated blood supply.
Describe the process which the circulatory system goes through
-Blood flows into the right atrium through the vena cava and left atrium through the pulmonary vein.
-The atria contract, forcing the blood into the ventricles
-The ventricles then contract, pushing the deoxygenated blood in the right ventricle into the pulmonary artery to be taken to the lungs, and oxygenated blood in the left ventricle to the aorta to be taken around the body.
-As this happens, valves close to make sure the blood does not flow backwards.
Define cellular respiration
An exothermic reaction which occurs continuously in living cells to release energy for metabolic processes, including aerobic and anaerobic respiration
Describe aerobic respiration in comparison to anaerobic
It uses oxygen. It yields the most energy. Most of the reactions that make up aerobic respiration occur in the mitochondria.
glucose + oxygen –> carbon dioxide + water
Describe anaerobic respiration in comparison to aerobic
It occurs when body cells do not have enough oxygen for aerobic respiration, such as during vigorous exercise. It does not yield as much energy as aerobic respiration.
The oxidation of glucose is complete.
In animals:
glucose –> Lactic acid
In plants and yeast cells (fermentation):
Glucose –> Ethanol + carbon dioxide
Describe the core practical for investigating the rate of respiration in living organisms
-Pick a small organism (e.g. maggots, leaves)
-Place soda lime into a test tube, this absorbs carbon dioxide so any volume changes are only due to oxygen uptake
-Place gauze on top and a small amount of the organism being tested on top of this
-Attach a capillary tube and bung to the test-tube.
-Set up a control tube with glass beads
-Place both tubes in a water bath and wait for the temperature to adjust
-Insert a small amount of coloured liquid into the capillary tube.
-Mark the position of the coloured-liquid in the tube
-After 5 minutes, record how far the coloured liquid has moved
-Calculate the volume of oxygen taken in by the insect per minute (V = πr²h where h is distance moved by coloured liquid) in cm³/min
What is the equation for cardiac output?
cardiac output = stroke volume*heart rate
