B8 | exchange & transport in animals Flashcards
what is the definition of diffusion?
the net movement of particles (gas or liquid) from an area of high concentration to an area of low concentration
how does distance affect the rate of diffusion?
smaller distance to travel = faster rate of diffusion
how does the concentration gradient affect the rate of diffusion?
greater difference in concentration = faster rate of diffusion
how does the temperature affect the rate of diffusion?
higher temperature = faster rate of diffusion because high thermal energy = high kinetic energy = particles move more/faster
how does surface area affect the rate of diffusion?
larger surface area = faster rate of diffusion because there is more surface space for the particles to move across
what is the equation for Fick’s Law?
rate of diffusion (a.u) ≈ surface area x concentration difference / thickness of membrane
what is the relationship between rate of diffusion and surface area/concentration difference?
directly proportional
what is the relationship between the rate of diffusion and the thickness of membrane?
inversely proportional
how to calculate surface area:volume ratio?
1) calculate area of one side
2) multiply this by the number of sides (surface area)
3) calculate volume of the shape
4) write out SA:V ratio
5) divide both sides by the volume (n:1)
what is the relationship between cell size and the SA:V ratio?
as the cell increases in size, the SA:V ratio decreases
what can cells do to increase their SA:V ratio?
- divide into smaller cells
- change shape to increase surface area
why is the SA:V ratio important for living cells?
- a high SA:V ratio means substances diffusing into the cell can reach all parts of it
- if the ratio is too low/the cell is too big, substances such as oxygen cannot reach all parts of the cell
- leading to cell death
what is the pulmonary circuit?
the circuit between the heart and the lungs which transports deoxygenated blood from the heart to the lungs and oxygenated blood from the lungs back to the heart
what happens when deoxygenated blood arrives at the lungs from the heart?
- carbon dioxide diffuses from the blood into the air in the alveoli
- oxygen diffuses from the air in the alveoli into the blood and is absorbed by haemoglobin in the red blood cells
- oxygenated blood is carried back into the heart
what is the systemic circuit?
the circuit between the heart and the other organs which transports blood around the body in order to:
- transport oxygen and nutrients to the body tissues
- carry away deoxygenated blood containing carbon dioxide and other waste materials
which side of the heart carries deoxygenated blood?
right side
which side of the heart carries oxygenated blood?
left side
how does the left side of the heart transport oxygenated blood to the rest of the body?
1) oxygenated blood from the lungs enters the left atrium via the pulmonary vein
2) left atrium contracts (beats)
3) oxygenated blood passes through the bicuspid valve into the left ventricle
4) left ventricle contracts
5) oxygenated blood passes through the semi-lunar valve, then through the aorta and travels to the rest of the body
how does the right side of the heart transport deoxygenated blood to the lungs?
1) deoxygenated blood from the body enters the right atrium via the vena cava
2) the right atrium contracts (beats)
3) deoxygenated blood passes through the tricuspid valve into the right ventricle
4) right ventricle contracts
5) deoxygenated blood passes through the semi-lunar valve, then through the pulmonary artery and travels to the lungs
what is the function of the bicuspid valve?
prevents oxygenated blood from flowing back into the left atrium from the left ventricle which increases flow of oxygenated blood around the body
what is the function of the tricuspid valve?
prevents deoxygenated blood from flowing back into the right atrium from the right ventricle
what is the function of the semi-lunar valve?
prevents blood from flowing back into the ventricles after it moves into the blood vessels
why are atrium walls thinner than ventricle walls?
- atrium walls are thin because the blood only needs to be pumped a short distance which doesn’t require much muscle
- ventricle walls are thicker because the blood has to be pumped further
why are the walls of the left ventricle thicker than the right ventricle?
- left ventricle walls are thickest because the muscle has to pump blood around the entire body under high pressure
- right ventricle walls are thinner because it only needs to pump blood to the lungs
why is the circulatory system of a frog less efficient at carrying oxygen to the body tissues than the human system?
- frogs have one ventricle whereas humans have two
- unlike humans, frogs have no septum to separate their ventricles which leads to oxygenated and deoxygenated blood mixing together
what is the function of the septum?
separates the right and left side of the heart, preventing oxygenated and deoxygenated blood from mixing
how does the nervous system control the beating of our heart?
sends electrical impulses to the heart causing it to contract
what is the definition of stroke volume?
the volume of blood (cm3) pumped from the left ventricle to the rest of the body
what is the definition of cardiac output?
the volume of blood pumped into the aorta from the left ventricle per minute
what is the formula for cardiac output?
cardiac output = stroke volume x heart rate
compared to a fit person, what is an unfit person’s heart rate like at rest?
an unfit person’s heart rate is always higher than a fit person at rest because the heart has to work harder
does a fit person have a shorter or longer recovery period than an unfit person?
a fit person has a shorter recovery period because they have a higher stroke volume and therefore a higher cardiac output allowing oxygen (for respiration) to move around the body quicker
what is the definition of recovery time?
the time it takes for a person’s heart rate to return to rest heart rate after exercise
how does exercise affect cardiac output?
exercise increases stroke rate which increases cardiac output
what is plasma?
- a clear liquid portion of the blood which carries everything in the blood
- makes up 55% of blood and is made up of 90% water
what substances does plasma carry?
red blood cells white blood cells platelets dissolved carbon dioxide dissolved glucose & amino acids urea (waste product of digestion) antibodies antitoxins hormones proteins
what are red blood cells?
cells which carry oxygen around the body and make up 45% of blood
what are the adaptations of red blood cells?
- no nucleus to allow more space for haemoglobin
- biconcave shape to increase surface area to absorb/release oxygen quicker
- small & smooth to be able to fit through capillaries
- contain haemoglobin in order to carry oxygen
how is oxygen transported to body tissues by haemoglobin?
- in the lungs, oxygen diffuses into the blood
- oxygen combines with haemoglobin to make oxyhaemoglobin
- when oxyhaemoglobin reaches tissue, the oxygen and haemoglobin separate and oxygen is released into the tissues
what are white blood cells?
phagocytes and lymphocytes which combat pathogens and make up less than 1% of blood
what do phagocytes do?
change shape to engulf and digest/destroy pathogens
what do lymphocytes do?
produce antibodies and antitoxins that bind to viruses to destroy them
what are platelets?
small fragments of other cells which make up less than 1% of blood
what do platelets do?
responsible for creating blood clots
what happens if a person has a lack of platelets?
a lack of platelets causes excessive bleeding and bruising
what is a group of the same type of cells known as?
a tissue
what is the function of the arteries?
carry oxygenated blood away from the heart at high pressure
what is the function of veins?
carries deoxygenated blood towards the heart at low pressure
what is the function of the capillaries?
carries blood to and from cells via diffusion at low pressure
why does the blood in the arteries need to be at a high pressure?
because the blood has to be pumped all around the entire body against the resistance from muscles and body tissue
why do arteries need thick elastic walls?
- to allow them to stretch and spring back to push blood around the body
- to withstand high blood pressures
why do arteries have small lumen?
to maintain high blood pressure
why do veins have a large lumen?
to help blood flow because the pressure is lower
why are capillaries only one cell thick?
- to maximise diffusion of substances in and out of the capillary due to the shortened diffusion distance
- slows down blood flow so more substances can diffuse
why do veins have valves?
- to stop the back flow of blood
- to make sure blood only flows towards the heart since the blood is under low pressure
what happens in the alveoli?
1) deoxygenated blood from the pulmonary artery enters the capillary
2) carbon dioxide is released from the red blood cells and diffuses a short distance into the air sac, and then travels out into the bronchiole
3) at the same time, oxygen brought into the air sac from the bronchiole diffuses across the alveolus membrane
4) oxygen binds to the haemoglobin in red blood cells creating oxygenated blood
5) oxygenated blood moves into the pulmonary vein to be taken to the heart
what are alveoli?
very small air sacs at the end of each bronchiole where gas exchange in the lungs takes place
adaptations of alveoli:
- large combined surface area (many small air sacs) to increase rate of diffusion
- moist surface to allow oxygen and carbon dioxide to easily dissolve so they can diffuse through the cell membrane
- a thin membrane for easy diffusion of gases
- a large network of blood capillaries surrounding them to maintain the concentration gradient
what is cellular respiration?
the process of transferring energy from the breakdown of organic compounds for use by metabolic processes
is cellular respiration an endothermic or exothermic reaction?
exothermic because it releases energy to the surroundings
where does cellular respiration take place?
mitochondria
what is the equation for aerobic respiration?
glucose + oxygen —> carbon dioxide + water + energy
what is the equation for photosynthesis?
carbon dioxide + water —> glucose + oxygen + energy
why does oxygen uptake increase when we exercise?
- during exercise our muscles contract more
- this means that they are doing more work which requires more energy
- so aerobic respiration in the cells in our muscles increases which increases the amount of energy released
what happens to the oxygen in our body is we exercise too much?
oxygen is used faster than it can be replaced
what is anaerobic respiration?
the release of energy from the incomplete breakdown of glucose in the absence of oxygen
what is the equation of anaerobic respiration in animals?
glucose —> lactic acid + energy
what is the equation of anaerobic respiration in plants?
glucose —> ethanol + carbon dioxide + energy
why does anaerobic respiration produce less energy than aerobic respiration?
because the breakdown of glucose is incomplete
what does anaerobic respiration allow our muscles to do?
to continue to contract for a short while after our oxygen stores have been depleted
what does a build up of lactic acid cause?
causes muscles to stop contracting and relaxing which causes them to eventually seize up and experience a cramp
how might we prevent a cramp?
stretch/warm up before exercise in order to increase the oxygen store in cells which limits anaerobic respiration and therefore the build up of lactic acid
what is oxygen debt?
the amount of extra oxygen needed by muscle tissue in order to remove lactic acid
why do we breathe heavily after exercise?
to increase the volume of oxygen to repay oxygen debt
what does excess oxygen taken in after exercise do to lactic acid?
oxidises it into carbon dioxide and water
what does soda lime do?
absorbs carbon dioxide
when using a respirometer, why does the volume of the air in the test tube containing the woodlice decrease?
because the wood lice use up oxygen as they respire and the CO2 they produce is absorbed by the soda lime so it doesn’t affect the experiment
when using a respirometer, what happens to the colour liquid in the manometer?
the decrease in volume in the test tube containing wood lice causes pressure to reduce in the tube which causes the liquid to move towards the tube with the lice
