Organisms exchange substances with their environment Flashcards
Generally is it good or bad to have a large SA:volume ratio?
Generally the larger the better
What adaptation may an organism have to maximise SA to volume ratio?
Flattened shape
Specialised exchange surface (e.g. lungs) which are also often adapted to maximise diffusion
Having large ears would do what to the heat loss of an organism?
Increase it
Describe the gas exchange system in insects
Each segment has spiracles (pair of lip like opening)
These lead to trachea, which are supported by strengthened rings to stop the from collapsing
These divide into smaller tubes called tracheoles which lead to each individual cell
Give the three ways in which respiratory gases move in and out of the tracheal system
Along a diffusion gradient
Mass transport
Ends of tracheoles filled with water
Describe how respiratory gases move in and out of the tracheal system along a diffusion gradient
Cells respire and use up O2, therefore the O2 conc. towards the tracheal ends fall
Creates a diffusion gradient whereby O2 gas diffuses for the atmosphere along the trachea and tracheoles to the cells
Also creates diffusion gradient in opposite direction involving CO2
Describe how respiratory gases move in and out of the tracheal system by mass transport
Muscles contract and squeeze the trachea
Allows mass movement of air
Speeds it up
Describe how respiratory gases move in and out of the tracheal system due to the end of the tracheoles are filled with water
During major activity the muscle cells around the tracheoles carry out some anaerobic respiration
The lactate produced leaves the water potential of the cells, therefore water moves into the cells from the tracheoles by osmosis
Water vol. in tracheoles decreases therefore air drawn in
Describe and explain the adaptations of the fish gas exchange system
Gills made of lamellae which are covered in filaments - increase SA
Thin epithelium - short diffusion distance
Counter current flow, water pumped over gills - maintain conc. gradient
How do fish ventilate their gills?
By moving their mouths and opercula, they pump water over their gills, which ventilate them
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish (3) PPQ
Water and blood flow in opposite directions;
- Maintains concentration/diffusion gradient / equilibrium not reached / water always next to blood with a lower concentration of oxygen;
- Along whole/length of gill/lamellae;
How do insects prevent water loss?
Spiracles are able to close
Body covered with waterproof waxy cuticle
Small SA : V ratio
How are leaves adapted for diffusion?
Many stomata - more gas in, short diffusion distance
Many interconnecting air spaces - gases readily in contact with cells
Large SA of mesophyll cells
How is gas exchange in plants similar to that in insects?
No living cell is far from the external air (and therefore a O2 and CO2 source)
Diffusion takes place in the gas phase (quicker than in water)
Describe and explain the way xerophytic plants are adapted
Rolled up leaves Hairy leaves Stomata in pits/grooves All these reduce by transpiration by reducing the gradient of water potential by trapping moist air to the surface Thick waxy cuticle A reduced SA:V of the leaves
What is a xerophyte?
A plant adapted to dry conditions
How does rolled up leaves prevent water loss?
Protects lower epidermis from outside
Helps trap air inside
As inside becomes saturated with water, conc. gradient decreases
How do hairy leaves prevent water loss?
Traps moist air next to leaf surface
Reduces water potential gradient b/wn inside and outside of leaf
Less water loss by transpiration
How does having stomata in pits prevent water loss?
Protects stomata from outside
Traps moist air in gap - reduces water potential gradient
Why are lungs located inside the body?
Air not dense enough to support these delicate structure
Body as a whole would lose a lot of water
How are the alveolus adapted to aid diffusion?
Lined with epithelium (site of gas exchange)
++ SA
Lined with ++ capillary network - maintains good conc. gradient
Describe how inhalation occurs
External intercostal muscles contract whilst the internal intercostal muscles. relax
Ribs are pulled upwards and outwards, increasing the volume of the thorax
Diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax
Increased vol of thorax results in reduction of pressure in the lungs
Atmospheric pressure is now greater than pulmonary pressure, and so air is forced into the lungs
Describe how expiration occurs
Internal intercostal muscles contract, external ones relax
Ribs move downwards and inwards –> decrease vol of thorax
Diaphragm muscles relax - pushed up against abdo –> decreases vol of thorax
Decreased vol of thorax increases pressure in lungs
Pulmonary pressure now greater than atmos - air forced out of lungs
How do you calculate pulmonary ventilation rate?
PVR = breathing rate x tidal volume
How is the body adapted for gas exchange?
RBCs slowed –> ++ time for diffusion
RBCs flattened against capillary walls –> reduces distance b/w RBC and alveolar air
Thin alveoli and capillary wall –> reduces diffusion distance
Alveoli and pulmonary capillaries both have large overall SA
Lungs constantly ventilated and constant blood circulation –> steep conc. gradient
What is the function of the oesophagus?
Carries from the mouth to the stomach
What is chemical digestion?
The process by which large, insoluble molecules are hydrolysed into smaller, soluble ones
What is the role of the stomach in digestion?
Store and digest food (especially proteins)
What is the role of the ileum in digestion?
Releases more enzymes to further digest
How is the ileum adapted for diffusion?
Villi and microvilli increases SA
Good blood supply maintain high gradient
Thin walled - short diffusion distance
Contain muscle and so are able to move - maintain diffusion gradient, mixes content
Lipases do what to lipids?
Hydrolyse them into glycerol and fatty acids
Proteases do what?
Hydrolyse proteins ultimately into amino acids
Carbohydrases do what?
Hydrolyse carbohydrates ultimately into monosaccharides
Describe the process of carbohydrate digestion
Salivary glands release saliva which contain salivary amylase - hydrolyse starch to maltose
Also mineral salts which maintain neutral pH (optimum)
Food swallowed and enters stomach, acid denatures
Moves into small intestine, where it mixes with pancreatic juice that contains pancreatic amylase - hydrolyses any remaining
Reaches ileum - membrane disaccharidase - maltose to a glucose
Why is the maltase in the ileum known as a membrane bound disaccharidase?
It is part of the cell-surface membranes of the epithelial cells rather than being released
Describe the process of lipid digestion
Lipids firstly split into micelles by bile salts from the liver in a process known as emulsification - increases SA and so hydrolysis into fatty acids and monoglycerides by lipases
Where are lipase produced?
Pancreas
Proteins are hydrolysed by a group of enzymes known as peptidases. What is an endopeptidase?
Enzymes which hydrolyse peptide bonds b/w amino acids in the central region of a protein molecule forming a series of peptide molecules
Proteins are hydrolysed by a group of enzymes known as peptidases. What is an exopeptidase?
Enzymes which hydrolyse peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases - progressively release dipeptides and single amino acids
Proteins are hydrolysed by a group of enzymes known as peptidases. What is a dipeptidase?
Enzymes which hydrolyse the bond b/w 2 amino acids of a dipeptide
How are amino acids and monosaccharides absorbed?
Diffusion and co-transport
How are triglycerides absorbed?
Monoglycerides and fatty acids in combo w/ bile salts –> micelles
Micelles come into contact w/epithelial cells and break down - release fatty acids and monoglycerides - non-polar and so can diffuse into cell
Transported to ER - recombo as triglycerides
Associate w/ cholesterol and lipoproteins to form chlorymicrons (adapted for lipid transport)
Chloryms move out of cell by exocytosis
Enter lymphatic capillaries called lacteals
Pass into blood system
Triglycerides hydrolysed in endothelial cell - diffuse in
How do chylomicrons move out of epithelial cells?
Exocytosis
Where do chylomicrons go after leaving the epithelial cell (during digestion)?
Lacteals (lymphatic capillaries)
What is haemoglobin?
A protein with a quaternary structure that transports oxygen in animals
Describe the structure of haemoglobin
Quaternary structure which forms an almost spherical molecule
Polypeptides associated w/ a haem group containing a ferrous ion (Fe 2+)
What is the role of haemoglobin?
To transport oxygen in the blood (in animals)
What is loading/associating (with regards to Hb)?
The process by which Hb binds with oxygen
Where does loading take place? (Hb)
In the lungs
What is unloading/dissociating (with regards to Hb)?
The process by which Hb releases O2
What does it mean when Hb has a high affinity?
It has a strong chemical attraction to O2 and so can take up O2 easily
However, releases less easily
What does in mean when Hb has a low affinity?
It has a weak chemical attraction to O2 and so can take up O2 less easily
However, releases more easily
What will the O2 affinity of Hb be like for an animal living in an area with low oxygen levels?
High affinity - needs to be able to take up easily
What will the O2 affinity of Hb be like for an animal that has a low metabolic rate?
Low affinity - needs to be able to release easily, but doesn’t necessarily need to be able to take up easily
How does Hb affinity change under acidic conditions?
Decreases (low affinity)
How does Hb affinity change under low CO2 conditions?
Increases (high affinity)
What is the Bohr effect?
The observation that Hb’s O2 binding affinity is related to acidity and the conc. of CO2
Give a general formula to show the association and dissociation of Hb with oxygen
Hb + 4O2 <==> Hb(O2)4
Describe and explain Hb’s O2 loading affinity at the gas exchange surface
High affinity
High O2 conc and low CO2 conc
O2 easily associates
Describe and explain Hb’s O2 loading affinity at the respiring tissues
Low affinity
Low O2 conc but high CO2 (Bohr effect, acidity decrease affinity)
O2 readily dissociates
The positive cooperative nature of oxygen means what? (With regards to Hb binding)
The binding of the first oxygen makes binding of further oxygens easier
Why is it difficult for the 4th O2 molecule to bind to Hb?
The low probability of O2 finding an empty site to bind to
Describe and explain a general oxygen dissociation curve
- Hb shape makes it hard to bind (all subunits close together) therefore at low O2 conc, little O2 binds (shallow gradient)
- 1st O2 binding changes 4* structure and so shape - makes it easier for other to bind (positive cooperativity), therefore a smaller increase in partial pressure of O2 is required to bind the 2nd O2 than the 1st
- 4th molecule hard to bind bc low probability of O2 finding an empty binding site - increase decreases to straight line (‘tails off’)
Why is blood passed through the heart twice in mammals?
When blood passed through lungs, its pressure is reduced
If pressure was not increased via the heart, circulation would be v. slow
What kind of circulatory system do mammals have?
Closed, double circulatory
Which blood vessel carries deoxygenated blood from the heart to the lungs?
Pulmonary artery
Which blood vessel carries deoxygenated blood from the body to heart?
Vena cava
Which blood vessel carries deoxygenated blood from the kidneys to the main venous system?
Renal veins
What general system of vessels carries deoxygenated from the respiring tissues to the heart?
Veins
Which blood vessel carries oxygenated blood from the lungs to the heart?
Pulmonary vein
Which blood vessel carries oxygenated blood from the heart to the kidneys?
Renal artery
What is the general name of blood vessels that carry blood away from the heart to the respiring tissues?
Arteries
What does the pulmonary vein do?
Carry oxygenated blood from the lungs to the heart
What does the pulmonary artery do?
Carry deoxygenated blood from the heart to the lungs
What does the vena cava do?
Carry deoxygenated blood from the rest of the body to the heart
What do veins do?
Carry deoxygenated blood from the rest of the body to the heart
What do arteries do?
Carry oxygenated blood away from the heart, to the respiring tissues
If you were standing opposite someone and looking at their heart, what is the name of the bottom left chamber?
Right ventricle
If you were standing opposite someone and looking at their heart, what is the name of the bottom right chamber?
Left ventricle
If you were standing opposite someone and looking at their heart, what is the name of the top right chamber?
Left atrium
If you were standing opposite someone and looking at their heart, what is the name of the top left chamber?
Right atrium
Which blood vessel carries oxygenated blood away from the heart to all parts of the body except the lungs?
The aorta
What does the aorta do?
Carries oxygenated blood away from the heart to all parts of the body except the lungs
Where is the bicuspid valve found?
Between the left atrium and left ventricle
Where is the tricuspid valve found?
Between the right atrium and right ventricle
Where is the pulmonary valve found?
In the pulmonary artery
Which chamber of the heart is the vena cava connected to?
The right atrium
Which chamber of the heart is the aorta connected to?
Left ventricle
Which chamber of the heart is the pulmonary artery connected to?
Right ventricle
Which chamber of the heart is the pulmonary vein connected to?
Left atrium
Describe the general structure of the atria
Thin walled, elastic
The atria are thin walled and elastic. Explain why
Able to expand as they are filled with blood
Describe the general structure of the ventricles
Thick, muscular wall
The ventricles have a thick, muscular wall. Explain why
They have to contract to pump the blood round the heart.
The left ventricle has a thicker, more muscular wall than the right ventricle. Why is this?
The right ventricle is just contracting enough to push blood to the lungs. The left has to contract enough to push blood round the whole body
What is the role of coronary arteries?
They supply the heart with blood
What are the sounds the heart makes during its cardiac cycle?
Lub-dupp
The ‘lub’ sound refers to what part of the cardiac cycle?
Contraction of ventricles and closing of AV valves
The ‘dupp’ refers to what part of the cardiac cycle?
Semilunar valves closing
Describe what happens during atrial diastole
All muscles relaxed and all heart valves closed
Blood returns to atria so pressure in atria increases
Describe what happens during atrial systole
Atria contracts
AV valves open
Blood moves into the ventricles and so pressure in the atria decreases, in the ventricle increases
Describe what happens during ventricular systole
Ventricles contracting
Semilunar valves open
Blood passed to arteries
What are the two atrioventricular valves?
Tricuspid and bicuspid/(mitral) valve
What are the two semilunar valves?
Aortic valve and pulmonary valve
Describe what happens during ventricular diastole
All heart muscles in relaxation and all heart valves closed
Blood returning to atria
How do you calculate cardiac output?
Heart rate x stroke volume
How do you calculate heart rate?
Cardiac output divided by stroke volume
What are the units for cardiac output?
dm-3 min-1
What are the four phases of the cardiac cycle?
Atrial diastole, atrial systole, ventricular systole, ventricular diastole
How does the structure of an artery relate to its function?
Thicker muscle than veins - smaller can be constricted/dilated to control blood flow
Relatively thick elastic layer - maintain high blood pressure
Overall thick wall - prevent bursting
Generally no valves - high pressure so little risk of back flow
Why do arteries have a relatively thicker muscle layer than veins?
So the smaller arteries can be constricted and dilated in order to control the volume of blood passing through them
Why do arteries have relatively thick elastic layers?
In order to maintain a high pressure - stretch and recoil action
Why are arteries relatively thick walled?
Prevent bursting under high pressure
Why don’t (most) arteries require valves?
Blood is constantly kept under high pressure
How does the structure of an arteriole relate to its function?
Relatively thicker muscle layer than arteries - control of blood flow into capillaries
Relatively thinner elastic layer than in arteries - blood pressure is lower
Why do arterioles have a relatively thicker muscle layer than arteries?
Contraction allows constriction/dilation of arteriole lumen - control of blood flow into capillaries
Why do arterioles have a relatively thinner elastic layer than in arteries?
Blood pressure is lower than in arteries
How does the structure of a vein relate to its function?
Relatively thinner muscle layer than arteries - veins carry blood away from heart so construction/dilation can’t control blood flow
Relatively thin elastic layer compared to arteries - low pressure of blood
Overall thickness of wall is small - no need for thicker, flattened easily to aid flow
Valves throughout - prevent back flow
Why do veins have a relatively thinner muscle layer than arteries?
Veins carry blood away from the heart, therefore constriction/dilation can’t control blood flow to tissues
Why do veins have a relatively thin elastic layer compared to arteries?
Low pressure of blood
Won’t burst and too low a pressure to recoil
Why do veins have an overall small wall thickness?
No need for thicker as the blood pressure is low
Can be flattened easily to aid flow
Why do veins have a valves throughout?
To ensure there is no back flow
How is the structure of a capillary related to its function?
Walls mostly consist of lining layer - v. thin so short diffusion distance
Numerous and highly branched - can permeate tissues so no cell far from capillary so short diffusion distance
Narrow lumen - RBCS squeezed flat which increases SA and shortens diffusion distance
Spaces between lining cells - allows WBCs to escape to deal w/ infections in the tissue
Why do capillary walls consist mostly of the lining layer?
V. thin so short diffusion distance
Why does the numerous number and branches of capillaries aid it with its function?
Large SA
Why do capillaries have narrow diameter?
So they can permeate tissues
This means no cell is far from a capillary and so there is a short diffusion distance
Why do capillaries have a narrow lumen?
RBCs are squeezed flat against the capillary sides
This increases SA and reduces diffusion distance
Why do capillaries have spaces between their endothelial (lining) cells?
To allow WBCs to escape to deal with infections within the tissue
What does tissue fluid supply to the tissues?
Amino acids, glucose, fatty acids, ions in soln. and oxygen
What is the role of tissue fluid?
The medium in which materials are exchanged between blood and cells
Provides constant surrounding cell environment
What is tissue fluid formed from?
Blood plasma
Describe how proteins are digested in the human gut PPQ
- Hydrolysis of peptide bonds;
- Endopeptidases break polypeptides into smaller peptide chains;
- Exopeptidases remove terminal amino acids;
- Dipeptidases hydrolyse/break down dipeptides into amino acids;
