Topic 8 Flashcards
what must all organisms do?
take in substances that they need from the environment and get remove any waste products
why do cells need oxygen?
for aerobic respiration which produces carbon dioxide as a waste product
how do oxygen and carbon dioxide move between cells and the environment?
by diffusion
how is water taken up by cells?
by osmosis
what substances diffuse with water in animals?
food molecules (the products of digestion) and mineral ions
what are some examples of food molecules which diffuse with water in animal cells?
glucose and amino acids
what are three substances which organisms exchange with the environment?
oxygen, water and urea
where does urea diffuse from cells to? and why?
urea diffuses from cells to the blood plasma for removal from the body by the kidneys
what does an organism’s ease to exchange substances with its environment depend on?
the organism’s surface area to volume ratio (SA:V)
what does a ratio show?
how large one value is compared to another
how does an organism’s SA:V vary with the size of the organism?
the larger an organism is, the smaller its surface area is compared to its volume
what is the equation for the area of a surface?
length x width
what is the equation for a volume of a block?
length x width x height
in single-celled/ unicellular organisms, how do substances diffuse into/ out of the cell?
the gases and dissolved substances can diffuse directly into/ out of the cell across the cell membrane because the cells have a large surface area compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell
how do multicellular organisms diffuse/ exchange substances to supply to the volume of the organism?
multicellular organisms need exchange surfaces for efficient diffusion and a mass transport system to move substances between the exchange surface and the rest of the body. this is because multicellular organisms have a smaller surface area compared do to their volume which makes it difficult to exchange substances to supply to their entire volume across their outside surface alone.
what are alveoli?
an exchange surface found in the lungs of mammals which are well-adapted for the efficient exchange of oxygen and carbon dioxide. they are in the form of small “air sacs”
how are gases exchanged in the lungs?
by diffusion
what three factors affect the rate of diffusion of any substance?
- distance
- concentration difference / concentration gradient
- surface area
how can distance affect the rate of diffusion?
substances diffuse faster when the substances don’t have to move as far
how can concentration gradient affect the rate of diffusion?
substances diffuse faster if there’s a large difference in concentration between the area the substances are diffusing from and the area the substances are diffusing to. this is because there is a greater concentration of particles to move from one side of the membrane to the other.
how can surface area affect the rate of diffusion?
the greater the surface area, the more surface there is available for the molecules to move across so the faster the molecules can travel from one side to the other.
what is the function of the lungs?
to transfer oxygen to the blood and to remove waste carbon dioxide from the blood
where does gas exchange happen in mammals?
in the lungs, in the alveoli
what is the singular form of “alveoli”?
alveolus
describe the process of gas exchange in the alveoli
- blood returning from the rest of the body and arriving at the lungs contains lots of carbon dioxide and a small amount of oxygen. this maximises the concentration gradient for the diffusion of the gases
- oxygen diffuses out of the air in the alveoli where the concentration of oxygen is is high and into the blood where the concentration of oxygen is low. carbon dioxide diffuses in the opposite direction to be breathed ou
how are the alveoli specialised to maximise the diffusion of oxygen and carbon dioxide?
- have a moist lining for dissolving gases
- have a good blood supply to maintain the concentration gradient of oxygen and carbon dioxide
- have very thin walls which minimises he distance that the gases have to move
- the alveoli have a huge surface area
what is the surface area of alveoli in humans?
75 m²
which cell membranes do oxygen and carbon dioxide diffuse across in the lungs?
the membranes of the cells which make up the walls of the capillary and alveolus.
what is Fick’s Law?
the rate of diffusion ∝ (is proportional to)
surface area x concentration difference
—————————————————
thickness of membrane
what does Fick’s Law describe?
the relationship between the rate of diffusion and the factors that affect the rate of diffusion
what would happen to the rate of diffusion if the surface area doubled?
the rate of diffusion would double
what would happen to the rate of diffusion if the difference in concentration doubled?
the rate of diffusion would double
what would happen to the rate of diffusion if the thickness of the membrane halved?
the rate of diffusion would double
what is blood?
a tissue
what one of the functions of the blood?
to act as a huge transport system in the body
what are the four main substances / cells in the blood?
- red blood cells
- white blood cells
- plasma
- platelets
what are red blood cells also known as?
erythrocytes
what is the function of red blood cells?
to carry oxygen from the lungs to all of the cells in the body
how are red blood cells adapted for their function?
- they have a biconcave shape to give a larger surface area for absorbing oxygen
- they don’t have a nucleus which allows more room to carry oxygen
- they contain haemoglobin
what is haemoglobin?
a red pigment in red blood cells which contains iron
how does haemoglobin release oxygen to the cells?
in the lungs haemoglobin binds to oxygen to form oxyhaemoglobin.
in body tissues, the oxyhaemoglobin breaks into haemoglobin and oxygen to release oxygen to the cells
what are the two types of white blood cells?
phagocytes and lymphocytes
what are phagocytes?
white blood cells which can change shape to engulf microorganisms
what is the process called when phagocytes change shape to engulf microorganisms?
phagocytosis
what are lymphocytes?
white blood cells which produce antibodies against microorganisms. some produce antitoxins as well.
why do some lymphocytes produce antitoxins?
to neutralise any toxins produced by microorganisms
state what your white blood cells do when you have an infection
the white blood cells multiply to fight the infection
when would a blood test show a high white blood cell count and why?
when you have an infection, this is because the white blood cells multiply to fight the infection off
do white blood cells contain a nucleus?
yes, unlike red blood cells
what are platelets?
small fragments of cells
do platelets have a nucleus?
no
what is the function of platelets?
to help the blood clot at a wound
why do wounds need to clot?
to stop the blood pouring out of the wound and to stop microorganisms from entering the body
what can a lack of platelets cause?
excessive bleeding and bruising
what causes excessive bleeding and bruising?
a lack of platelets in the blood
what is plasma?
a pale straw-coloured liquid which carries everything in the blood
what does plasma carry in the blood specifically?
- red blood cells,
- white blood cells,
- platelets,
- nutrients such as glucose and amino acids (the soluble products of digestion absorbed from the gut and taken to the cells in the body),
- carbon dioxide (from the organs to the lungs),
- urea (from the liver to the kidneys),
- hormones,
- proteins,
- antibodies and antitoxins (produced by the white blood cells.)
what are the three different types of blood vessel?
arteries, capillaries, and veins
what is the function of arteries?
to carry the blood away from the heart
what is the function of capillaries?
to assist in the exchange of materials at the tissues
what is the function of veins?
to carry the blood to the heart
what adaptations do arteries have for their function?
- strong and elastic walls because the heart pumps the blood out at a high pressure
- thick walls compared to the lumen
- thick layers of muscle to strengthen them and elastic fibres to allow them to stretch and spring back
what is the lumen?
the hole down the centre of arteries, capillaries, and veins
what do arteries branch into?
capillaries
what adaptations do capillaries have for their function?
- they are very narrow to squeeze into the gaps between cells to carry the blood very close to the cells for the exchange of substances
- have permeable walls for the diffusion of substances into and out of the capillaries
- walls are usually only one cell thick, increasing the rate of diffusion by decreasing the distance over which it occurs
what do capillaries do?
supply food and oxygen and remove waste such as carbon dioxide
do capillaries contain a nucleus?
yes
what joins up to form veins?
capillaries
what do capillaries eventually join up to form?
veins
what adaptations do veins have for their function?
- the walls are not as thick as the artery walls because the blood is at a lower pressure in the veins
- have larger lumen to help blood flow despite the lower pressure
- have valves to keep the blood flowing in the correct direction
what type of circulatory system do mammals have?
a double circulatory system
what is a double circulatory system?
when the heart pumps blood around the body in two circuits
what happens in the first circuit of a double circulatory system?
the heart pumps deoxygenated blood to the lungs to take on oxygen, and oxygenated blood then returns to the heart
what happens in the second circuit of a double circulatory system?
the heart pumps oxygenated blood to all of the other organs in the body to deliver oxygen to the body cells, deoxygenated blood then returns to the heart
what type of circulatory system do fish have?
a single circulatory system
what happens in a single circulatory system?
deoxygenated blood from the [fish’s] body travels to the heart, which then pumps the blood around the body again in a single circuit via the gills where oxygen is picked up
how many chambers does a fish’s heart have?
two
how many chambers does a mammalian heart have?
four
how many major blood vessels does a mammalian heart have?
four
which ventricle has a much thicker wall than the other?
the left ventricle has a much thicker wall than the right ventricle
why does the left ventricle have a much thicker wall than the right ventricle?
because the left ventricle needs more muscle because it has to pump blood around the whole body at high pressure but the right ventricle only has to pump blood to the lungs
what is the purpose of valves?
to prevent the backflow of blood in the heart
what is cardiac output?
the total volume of blood pumped by a ventricle every minute
how can you calculate cardiac output?
heart rate x stroke volume
what are the units for cardiac output?
cm³ min⁻¹
what is heart rate?
the number of beats per minute (bpm)
what is the stroke volume?
the volume of blood pumped by one ventricle each time it contracts
what are the units for heart rate?
beats per minute (bpm)
what are the units for stroke volume?
cm³
what is the formula triangle for heart rate, cardiac output and stroke volume?
cardiac output
———————
heart x stroke
rate volume
where dow energy come from?
food and it is released by respiration
what is respiration?
the process of transferring (releasing) energy from the breakdown of organic compounds (usually glucose)
NOT breathing in and breathing out
where does respiration happen?
in every cell of all living organisms
how frequently does respiration happen?
continuously
what type of reaction is respiration and why?
an exothermic reaction because energy is transferred o the environment
in what form is some of the energy from respiration transferred to the environment?
in the form of heat energy
what are the two types of respiration?
aerobic and anaerobic respiration
what are organic compounds?
compounds containing carbon, these include carbohydrates, lipids and proteins
what is energy used for?
- metabolic processes (e.g. making larger molecules from smaller ones - proteins from amino acids)
- contracting muscles in animals
- maintaining a steady body temperature in mammals and birds
when does aerobic respiration happen?
when there is plenty of oxygen available
what does “aerobic” mean?
“with oxygen”
which way is the most efficient way to transfer energy from glucose, aerobic respiration or anaerobic respiration?
aerobic respiration
what is the equation for aerobic respiration?
glucose + oxygen -> carbon dioxide + water
C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O
when does your body do anaerobic respiration?
when you do very vigorous exercise your body can’t supply enough oxygen to the muscles for aerobic respiration, even though your heart rate and breathing rate increase to the maximum. the muscles have to start respiration get anaerobically as well.
what does “anaerobic” mean?
“without oxygen”
what happens in anaerobic respiration?
the glucose is only partially broken down and lactic acid is also produced
what happens when lactic acid is produced in anaerobic respiration?
the lactic acid builds up in the muscles, becomes painful and leads to cramp
what is the equation for anaerobic respiration in animals?
glucose -> lactic acid
what is the equation for anaerobic respiration in plants?
glucose -> ethanol + carbon dioxide
what is an example of plants which do anaerobic respiration?
fungi such as yeast
name three things you could use in an experiment to measure the rate of respiration
live woodlice, germinating peas, germinating beans, mealworms
describe the step-by step method for measuring the rate of respiration using a respirometer.
1) add some soda lime granules to two test tubes.
2) place a ball of cotton wool on top of the soda lime granules in both tubes to protect you and the organisms from the soda lime,
3) put some live woodlice/mealworms/ germinating peas in top of the cotton wool in one test tube and glass beads with the same mass as the woodlice/mealworms/germinating peas on top of the cotton wool in the other tube as a control.
4) insert a bung and capillary tube (with a scale) into both test tubes
5) place both test tubes into a rack in a water bath at a set temperature (around 15°C), it is best to tilt the rack slightly so that the capillary tubes hang over the side of the water bath at an angle
6) wait for five minutes to allow the organisms to adjust to the temperature of the water bath
7) add some coloured liquid to the capillary tubes
8) during the time in the water bath there will be a decrease in the volume of air in the test tube containing the organisms because the organisms use up oxygen in the tube as they respire but the carbon dioxide will be absorbed by the soda lime. the decrease in the volume of air reduces the pressure in the tube which causes the coloured liquid to move towards the test tube containing the organisms.
mark the position of the coloured liquid in the tube and time for five minutes,
9) mark the position of the coloured liquid again and measure the distance it has travelled
10) repeat the experiment at different temperatures
what does soda lime do in the experiment to measure the rate of respiration using a respirometer?
it absorbs the CO₂ produced by the respiring woodlice/ germinating peas/germinating peas in the experiment
what hazard is soda lime? what precautions should you take to be safe with it?
soda lime is corrosive, wear safety goggles and gloves when handling it to protect your eye and skin
what can you use as a substitute for soda lime in the experiment to measure the rate of respiration using a respirometer?
cotton wool soaked in a few drops of potassium hydroxide solution to absorb the carbon dioxide
is diffusion a fast or slow process?
slow
if organisms are different sizes, do the rates of diffusion differ?
no, the rate of diffusion is always the same - no matter what size the organism is
why are cells so small?
because the distance for diffusion needs to be short so the substances can diffuse quickly
how many times does the blood pass through the heart in one circulation of the body?
two (double circulatory system)
what is an advantage which a double circulatory system has over a single circulatory system?
the blood is able to pumped at a greater pressure
in which order does the blood flow through the chambers of the heart?
right atrium, right ventricle, left atrium, left ventricle
which two chambers of the heart contain deoxygenated blood?
the right atrium and the right ventricle
what are the two chambers of the heart which contain oxygenated blood?
the left atrium and the left ventricle
what are the four major blood vessels of the heart?
pulmonary artery, aorta, vena cava, pulmonary vein
in which order does blood flow through the four major blood vessels?
vena cava, pulmonary artery, pulmonary vein, aorta,
describe the order of the blood flow through the heart
- deoxygenated blood from the head and body enters through the vena cava, flows into the right atrium, passes through the tricuspid valve, enters the right ventricle, then goes up through the semi-lunar valves, through the pulmonary artery to the lungs.
- the red blood cells collect oxygen from the lungs
- then the oxygenated blood flows through the pulmonary vein and into the left atrium, through the bicuspid valve into the left ventricle where the blood receives a large push from the left ventricular wall, to go through the semi-lunar valves and out of the aorta to the carry oxygen to the rest of the body
what is the vena cava?
a vein carrying deoxygenated blood, the vena cava is the main vein returning blood to the heart from the body
what is the pulmonary artery?
an artery carrying deoxygenated blood, the pulmonary artery takes blood from the right ventricle to the lungs
what is the pulmonary vein?
a vein carrying oxygenated blood, the pulmonary vein takes blood from the lungs to the left atrium
what is the aorta?
an artery carrying oxygenated blood, the aorta takes blood from the left ventricle to the rest of the body
what is the bicuspid valve?
the bicuspid valve is the valve between the left atrium and the left ventricle, it prevents the backflow of blood
what is the tricuspid valve?
the tricuspid valve is between the right atrium and the right ventricle, it prevents the backflow of blood
where do most of the reactions in aerobic respiration the place?
in the mitochondria
