SB8: exchange and transport in animals Flashcards
diffusion
movement of molecules from an area of higher concentration to an area of lower concentration
important things to remember about diffusion
-particles will move in both directions, but there will be a net movement from high to low concentration
-particles will end up evenly spread throughout the liquid or gas, but will continue to move
examples of diffusion in biological systems
leaf:
oxygen out, carbon dioxide in
lungs:
deoxygenated blood in, oxygenated blood out
which organisms have a very high surface area:volume ratio?
unicellular organisms (eg: bacteria)
what does organisms having a high surface area:volume ratio mean?
-substances can diffuse in and out at a high rate and easily reach all parts of the cell
which organisms have a small surface area:volume ratio?
large organisms
what does organisms having a small surface area: volume ratio mean?
-larger organisms need transport systems to move substances around the body to where they are needed (eg: the bloodstream in most animals
-they also need specialised exchange surfaces where substances can enter and leave the transport system by diffusion (eg:
lungs in mammals)
-exchange surfaces are adapted to increase their surface area to maximise the rate of diffusion
why do cacti reduce their surface area?
to reduce loss of substances such as water
examples of a large surface area in exchange surfaces
-the flattened shape of structures such as leaves
-the alveoli in the respiratory system
examples of short distances in exchange surfaces
-the membranes of cells
-the flattened shape of leaves
-the walls of blood capillaries are one cell thick
how is a steep concentration gradient maintained in the lungs?
continuous blood flow through capillaries and ventilated of alveolus
what is the exchange surface in the lungs adapted for?
-absorbing oxygen (needed for respiration) into the blood from the air in the lungs
-transferring carbon dioxide (produced by respiration) from the blood into the lungs (which then goes into the air)
where are the lungs?
enclosed within the thorax
what is ventilation?
movement of air in and out of the lungs
what are the lungs protected by?
12 pairs of ribs
layout of the ribs
-the ribs are moved by two sets of intercostal muscles
-there is a diaphragm below the lungs
-the lungs are sealed within two airtight pleural membranes, these wrap around the lungs and line the rib cage
layout of the trachea
-branches into two bronchi, one bronchus leads to each lung
-rings of cartilage in the walls of the trachea help to keep it open as air is drawn in
bronchi
-split into smaller branches and then into smaller tubes called bronchioles
-each bronchiole ends in a cluster of microscopic air sacs called alveoli
where does gas exchange occur in the lungs?
between the alveoli and blood in the capillaries
how does the alveoli provide a large surface area for gas exchange?
-small size -> larger surface area to volume ratio than larger structures
-there are millions of alveoli
-closely associated with capillary (one cell thick) reduces diffusion distance
how is there a short diffusion pathway for gas exchange in the alveoli?
-the walls of capillaries and alveoli are just one cell thick
-the alveoli are lined with a thin layer of moisture, gases dissolve in this water, making the diffusion path even smaller
how distance affects rate of diffusion
if the diffusion distance is small, diffusion happens faster because the particles do not have as far to travel
how concentration gradient affects rate of reaction
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 surface area affects rate of reaction
the larger the surface area, the higher the number of particles that will be able to move in a given time so the faster the rate
what is fick’s law?
the rate of diffusion is proportional to both the surface area and concentration gradient and is inversely proportional to the thickness of the membrane
fick’s law equation
rate of diffusion = surface area x
concentration gradient/thickness of membrane
the rate of diffusion will double if
-surface area or concentration difference is doubled
-thickness of the exchange membrane is halved
composition of blood
55% plasma, 45% formed elements (red blood cells, white blood cells and platelets)
function of plasma
-transporting dissolved carbon dioxide, digested food molecules, urea and hormones
-distributing heat
what is function of red blood cells?
transporting oxygen
what is the function of white blood cells?
ingesting pathogens and producing antibodies
what is the function of platelets?
clot blood so that wounds close and don’t become infected
what must red blood cells be able to do?
absorb oxygen in the lungs, pass through blood capillaries and release oxygen to respiring cells
what is the other name for red blood cells?
erythrocytes
how does haemoglobin help red blood cells fulfill their purpose?
-haemoglobin gives them their red colour
-haemoglobin can combine reversibly with oxygen as blood passes through the lungs, and release the oxygen when it reaches the cells
why do red blood cells have no nucleus?
so they can contain more haemoglobin
why are red blood cells small and flexible?
they can fit through narrow blood capillaries
why do red blood cells have a biconcave shape?
to maximise their surface area for oxygen absorption
why are red blood cells thin?
so there is only a short distance for the oxygen to diffuse to reach the centre of the cell
haemoglobin + oxygen
⇌ oxyhaemoglobin
types of white blood cells
phagocytes & lymphocytes
phagocytes
-about 70% of white blood cells
-engulf and destroy unwanted microorganisms that enter the blood
lymphocytes
-make up about 25 per cent of white blood cells
-produce antibodies when a microorganism enters the body
how do lymphocytes neutralise pathogens?
-they bind to pathogens and damage or destroy them
-they coat pathogens, clumping them together so that they are easily ingested by phagocytes
-lymphocytes may also release antitoxins that stick to the toxins that the pathogen makes, which stops it damaging the body
what do platelets do (detailed)?
-they have proteins on their surface that let them to stick to cracks in a blood vessel and clump together
-they secrete proteins that result in a series of chemical reactions that make blood clot
how does blood go to and from the heart?
to: through the veins
away: through the arteries
what is blood transported in/ what are the blood vessels?
arteries, veins and capillaries
how are capillaries like a
‘bridge’?
-they connect the two types of blood vessel (veins and arteries)
-molecules are exchanged between the blood and the cells across their walls
arteries vs veins
always carry blood away from the heart (a) v always carry blood to the heart (v)
carry oxygenated blood, except for the pulmonary artery (a) v always carry deoxygenated blood, except for the pulmonary vein (v)
carry blood under high pressure (a) v carry blood under low/negative pressure (v)
have thick, muscular & elastic walls to pump and accommodate blood (a) v have thin walls & less muscular tissue than arteries (v)
called connective tissue provides strength (a) v have less connective tissue than arteries (v)
the lumen is narrow (a) v have a wide lumen (v)
lumen
the channel in a blood vessel that carries blood
capillary facts
-one cell thick
-allow the exchange of molecules between the blood and the body’s cells
-molecules can diffuse across their walls, this exchange of molecules isn’t possible across the walls of other types of blood vessel
which substances diffuse into cells?
-oxygen diffuses through the capillary wall, into the tissue fluid and then cells
-glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid, and then to the cells
which substances diffuse out of cells?
-carbon dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma
-the waste product urea diffuses from the cells of the liver, to the tissue fluid, and then across the capillary walls into the blood plasma
size of blood cells
10 um or less in diameter
how many chambers does the heart have?
four: two atria, two ventricles
how does blood enter the heart?
(through the atria)
pulmonary veins (left atrium)
vena cava (right atrium)
what order do the chambers fill in?
-the atria fill, followed by the ventricles
-blood is prevented from flowing back into the atria by heart valves
how does blood leave the heart?
-from the aorta (left side)
-from the pulmonary artery (right side)
double circulation
the heart pumps blood through two circuits:
-the pulmonary circulation
-the systematic circulation
which parts of the body are included in the pulmonary circulation?
-the right side of the heart
-the lungs
-the blood vessels that connect them together
what happens in pulmonary circulation?
-oxygen diffuses into the blood from the alveoli & the blood becomes oxygenated
-carbon dioxide diffuses from the blood into the lungs
(blood becomes oxygenated)
which parts of the body are included in the systematic circulation?
-the left side of the heart
-the rest of the body apart from the lungs
-the blood vessels that connect them together
what happens in systematic circulation?
-transports oxygen and nutrients to the body
-transports carbon dioxide and other wastes away from cells
-systemic circulation is under high pressure, it has to deliver blood around the body
-the walls of the left ventricle are thicker and contain more muscle than those of the right ventricle, this is to create more pressure on the blood ready for entering the systemic circulation
(oxygenated blood is pumped around the body)
why is the pulmonary circulation under less pressure than systematic circulation?
-blood is delivered to the lungs only, which are very close to the heart
-in a healthy person, this lower pressure is optimum for the diffusion of gases
how many times does blood pass through the heart in a circulation?
twice
following the blood through one complete circulation of the body:
-deoxygenated blood from the body enters the right atrium
-blood passes from the right atrium to the right ventricle, then to the lungs
-oxygenated blood from the lungs enters the left atrium
-blood passes into the left ventricle, through the aorta and into the body
when do the atria and ventricles contract?
the atria contract in unison, and when full, the ventricles also contract in unison
what is cardiac output?
the total volume of blood pumped out by the left ventricle every minute
cardiac output equation (CO)
stroke volume (SV/cms) × heart rate (HR/ bpm)
what is stroke volume?
the volume of blood pumped out of the left ventricle each time the heart beats
what is heart rate?
the number of beats per minute and is the same as your pulse rate
if your heart rate increases,
_____ increases
cardiac output
as stroke volume increases, _____ increases
cardiac output
how is the one way flow of blood achieved?
the closure of a valve
what is respiration?
an exothermic reaction which is continually occurring in living cells that supplies all the energy needed for living processes
are respiration and breathing the same?
no
what is the process of breathing called?
ventilation
breathing in
inhaling
breathing out
exhaling
what happens as you inhale?
-your diaphragm muscle contracts and moves downwards
-the intercostal muscles contract and move the ribs upwards and outwards, this increases the volume of the lungs, which reduces the pressure inside and so air moves into the lungs to equalise it
-air that is rich in oxygen moves into the gas exchange system and then the body when you breathe in
what happens when you exhale?
-diaphragm muscle relaxes and moves upwards
-the intercostal muscles relax and move downwards and inwards
-this reduces the volume of the lungs, which forces air outwards
-air with more carbon dioxide is then removed when you breathe out
how asthma affects breathing
-the lining of the airways from the mouth to the lungs become irritated and swells up
-this reduces the air that can move in and out from the lungs
how smoking affects breathing
-smoking irritates the bronchi which can lead to bronchitis
-smoking also breaks down the lining of the alveoli, which means less gas exchange can occur
-smoking damages the lining of the arteries
-inhalation of carbon monoxide in cigarette smoke reduces the amount of oxygen that can be carried by the blood
-the nicotine in cigarette smoke increases the heart rate, putting strain on the heart
why do all organisms need energy?
-to drive the chemical reactions needed to keep organisms alive
-movement -> energy is needed to make muscles contract
-for cell division
-homeostasis
-active transport
-for the transmission of nerve impulses
what is the heat released in respiration used for?
this heat is distributed around the body by the blood and helps to maintain a constant internal temperature
aerobic respiration
respiration that requires oxygen
what happens in aerobic respiration?
-glucose (the main respiratory substrate) is oxidised to release its energy
-the first stages of respiration occur in the cytoplasm of cells
-most of the energy released is in the mitochondria
word equation for aerobic respiration
glucose + oxygen -> carbon dioxide + water + (energy)
chemical equation for cellular respiration
C6H1206 + 602 - 6C02 + 6H20
anaerobic respiration
-respiration in the absence of oxygen, this produces lactic acid
-the oxidation of glucose is incomplete
-animal muscles can respire anaerobically for short periods of time - even though the process is relatively inefficient, it’s better to continue respiring and be able to run away from danger - or run a race
where does anaerobic respiration happen?
cytoplasm
can only animals respire anaerobically?
no, some plants and fungi (yeast) can respire anaerobically
anaerobic yeast
-glucose in yeast cells is converted to carbon dioxide and ethanol, which we refer to simply as ‘alcohol’
-this reaction is also called fermentation
equation of anaerobic respiration in yeast
glucose -> ethanol + carbon dioxide (+ energy released
while exercising, the muscles need additional energy to contract muscles, several changes take place in the body to enable this:
-the breathing rate and volume of each breath increases to bring more oxygen into the body and remove the carbon dioxide produced
-the heart rate increases, to supply the muscles with extra oxygen and remove the carbon dioxide produced
during long periods of vigorous activity:
-lactic acid levels build up
-glycogen reserves in the muscles become low as more glucose is used for respiration, and additional glucose is transported from the liver
what does the build up of lactic acid cause?
-oxygen debt
-as body stores of glycogen become low, the person suffers from muscle fatigue
