3B more exchange Flashcards
why is food broken down into smaller molecules during digestion
as the large biological molecules are to big to cross cell membranes and be absorbed from the gut into the blood
what are digestive enzymes produced by
specialised cells in the digestive system
why do different enzymes needed to catalyse the breakdown of different food molecules
as enzymes only work with specific substrate
what are carbohydrates broken down by
amylase and membrane bound disaccharide
what does amylase catalyse starch conversion into
maltose
where is amylase produced
salivary glands- into mouth
pancreas- into small intestine
what are membrane bound disaccharide
enzymes which are attached to the cell membranes of epithelial cells lining the ileum
what do membrane bound disaccharide do
help break down disaccharide into monosaccharides
involves hydrolysis
what is the ileum
final part of small intestine
how can monosaccharides be transported across cell membrane of the ileum epithelium cells
via transporter proteins
what are lipids broken down by
lipase with the help of bile salts
what does lipase catalyse the breakdown of lipids into
monoglycerides and fatty acids
where is lipase made
made in pancreas
works in small intestine
where are bile salts produced
liver
what does bile slats do
emulsifies lipids into small droplets
why are bile salts so important
as they emulsify lipid into small droplets which largely increases the surface area and therefore increases the rate of diffusion as there is more area for lipase to work on
once lipids are broken down what do monoglycerides and fatty acids stick to bile salts to form
micelles
what are proteins broken down by
endopeptidases and exopeptidase
what are endopeptidases
they act to hydrolyse peptide bonds within a protein
what are two examples of endopeptidases
and where are they found
chymotrypsin and trypsin
both synthesised in pancreases and secreted in small intestine
details on pepsin (another endopeptidase)
released into stomach by cells in the stomach lining
only works in acidic conditions- what hydrochloric acid is for in the stomach
what is exopeptidase
acts to hydrolyse peptide bonds at the end of protein molecules
removes single amino acid from proteins
what are dipeptidases
exopeptidase that only work on dipeptides
how do dipeptidases work
they separate the two amino acids which make up the dipeptide by hydrolysing the peptide bond between
where are dipeptidases located
found on cell surface membrane of epithelial cells in small intestine
what are the products of digestion absorbed across
the ileum epithelium into the blood stream
how is glucose and galactose absorbed
by active transport with sodium ions via co transporter proteins
how are monoglycerides and fatty acids absorbed
micelles help move them towards epithelium
micelles release them allowing them to be absorbed
why can monoglycerides and fatty acids be absorbed across the epithelial cell membrane
as they are lipid soluble
how are amino acids absorbed
absorbed via co transport
sodium ions actively transported out of the ileum epithelial cells into the blood
creates sodium conc grad
Sodium ions diffused from lumen of ileum into epithelial cells through sodium dependent transporter proteins carrying amino acids with
How are proteins digested
Hydrolysis of peptide bonds
Endopeptidases breaks down polypeptides into smaller peptides
exopeptidases removes terminal Amino acid
Dipeptidase breaks down dipeptides into amino acids
Why is maltose only digested by Maltese
Maltase has specific active site shape
Only binds to maltose
To form an enzyme substrate complex
describe haemoglobin
large protein with quaternary structure
what does quaternary structure mean
made up of more than one polypeptide chain
in haemoglobin what is a haem group and what does it contain
each chain has haem group
contains an iron ion giving the red colour
why is haemoglobin described as having a high affinity for oxygen
each molecule can carry four oxygen molecules
how and where is oxyhemoglobin formed
oxygen joins to haemoglobin in red blood cells forming oxyhemoglobin
this takes place in the lungs
what is the equation of the reversible reaction oxyhaemaglobin to haemoglobin
Hb + 4O2 Hb08
what is the partial pressure of oxygen
pO2
measure of oxygen concentration
higher conc of dissolved o2 in cells= higher partial pressure
what is the partial pressure of c02
pCO2 measure of concentration of carbon dioxide in cell
how does haemoglobin affinity for oxygen depend on the partial pressure of oxygen
oxygen loads onto haemoglobin to form oxyhemoglobin where there’s a high po2
oxyhemoglobin unloads its oxygen when there is a low pO2
why does oxygen load onto haemoglobin in the alveoli
as The alveoli have a high p02
where does oxyhemoglobin unload its oxygen
in respiring cells as they have low pO2
how does pCO2 effect oxygen unloading
haemoglobin gives up its oxygen more readily at higher partial pressures of carbon dioxide
explain the bohr effect
1- when cells respire they produce co2 which increases pco2
2- this increases rate of oxygen unloading so dissacosiation curve moves to right
more oxygen released
what is the circulatory system
a mass transport system
what is the circualtory system made up of
heart and blood vessels
what does the heart do in the circulatory system
pumps bloood through blood vessels to reach different parts of body
what does the blood do in the circulatory system
transports respiratory gases, products of digestion,metabolic wastes, hormones around the body
what are the two circuits
1st- takes blood from heart to lungs
2nd- takes blood around the rest of the body
what is the hearts blood supply
left and right coronary arteries
what do arteries do
carry blood from heart to rest of body
describe arteries
thick muscular and have elastic tissue to stretch and recoil as heart beats
what is the inner lining of the artery called
endothelium
describe endothelium in the artery
folded allowing artery to stretch
also helps maintain high pressure
what do pulmonary arteries carry
deoxygenated blood to the lungs
all other arteries carry oxygenated blood
what do arteries divide into
aterioles
what do aterioles form and what do they do
forms network throughout body
blood is directed to areas of demand in body by muscles in aterioles
these muscles contract or relax to allow full blood flow
what do veins do
take blood back to heart under low pressure
describe veins
wider lumen , little elastic or muscle tissue
have valves to prevent blood flowing backwards
how is bloodflow through veins helped
by surrounding body muscle
what does the pulmonary vein carry
oxgenated blood to heart from lungs
all other veins carry deoxygenated
what do aterioles branch into
cappilleries
how are capilleries adapted for efficient diffusion
1) found near cells in exchange tissue so very short difffusion pathway
2) walls are one cell thick so short diffusion pathway
3) large number of cappileries so large SA
what is the network of capilleries in tissue called
capillary beds
what is tissue fluid
fluid which surrounds cells in tissues
what is tissues fluid made up from
made from small molecules that leave the blood plasma like oxygen water and nutrients
why cant tissue fluid contain red blood cells or big proteins
as too big to be pusshed through capillary wals
what do cells take in and release into tissue fluid
take in - oxygen and nutrients
release- metabolic waste
process of pressure filtration
1) (artery)at start of capillary bed, hydrostatic pressure is higher in capilleries than in tissue fluid
2) this difference in pressure means an overall outward pressure forces fluid out of cap into spaces around the cells forming tissue fluid
3) as fluid leaves pressure in reduces in cap so pressure is lowest now at venule end of capillary bed( near vein)
4) due to fluid loss &increasing concentration of plasma proteins -water potential at venue end of cap bed is lower than water potential in tissue fluid
5) this means some water re-enters capillaries from the tissue fluid at venue and by osmosis
Where is excess tissue fluid drained
Lymphatic system which transports it from tissues and dumps it back into circulatory system
what is lymphatic system
network of tubes acting like drains
what does the right side of heart do
Pumps deoxygenated blood to the lungs
what does left side of heart do
Pumps oxygenated blood to the whole body
what are the for blood vessels in the heart and what do they pump
Vena cava and pulmonary veins carry blood to the heart
pulmonary artery and aorta carry blood away from her
quick heart summmary blood flow
Deoxygenated blood pumped through vena cava to right atrium to right ventricle then out of the pulmonary artery
oxygenated blood flows in through the pulmonary vein into the left atrium into right left ventricle out of aorta
describe difference between right and left ventricle
Left ventricle is thicker more muscular as it needs to contract powerfully to pump blood all around the body
right ventricle only need to get blood lungs
why do the ventricles have thicker walls than the atria
As they need to push blood out of the heart where as atria just need to push blood a short distance into ventricles
what do atrioventricular valves do
link atria to ventricles and stop blood flowing back into atria when the ventricles contract
what do semi lunar valves do
Link the ventricles to the pulmonary artery and aorta
stop blood flowing backwards into heart after ventricles contract
what do cords in the heart do
attach atrioventricular valves to the ventricles to stop them being forced up into atria when ventricles contract
why can blood only flow in one direction in the heart
Valves only open one way
if there is pressure behind a valve it’s forced open
but if there is pressure in front of the valve it’s forced shut
first step of the cardiac cycle
atria contracts, ventricle relaxed
causing higher pressure in the atria so blood moves down the pressure gradient into the ventricles
second step of the cardiac cycle
atria relax, ventricle contracts
increases pressure in ventricle , forcing AV valve shut( prevents back flow)
presure in ventricle higher than that in aorta and pulmonary artery so forces SL valve open so blood forced out
third step of the cardiac cycle
atri and ventricle relax
higher pressure in pulmonary artery and aorta now forcing semi lunar valves to close preventing back flow
blood returns and fills atria due to higher pressure in the pulmonary vein and vena cava this increases pressure of atria opening AV valve
What is a atheroma
Fibrous plaque
How is a atheroma formed
If damage occurs to endothelial lipids from the blood come together forming fatty streaks overtime this will harden to a atheroma
What is a aneurysm and has it formed
Atheroma plaques damage the arteries and narrows them
so when blood travels through narrowed artery at high-pressure it can push the inner layers of the artery through the outer elastic layer to form a lballoon like swelling
aneurysm can burst causing haemorrhage
What is thrombosis and how is it formed
Atheroma plaque can rupture the endothelial and this causes damage
platelets and fibre in accumulate at cited damage forming blood clot this can block an artery
What is a myocardial infarction
If coronary artery becomes completely blocked area of heart muscle will be cut off from blood supply is receiving no oxygen so can’t respire causing heart attack
What are three risk factors of cardiovascular disease
High blood cholesterol and poor diet
cigarette smoking
a high blood pressure
How does high blood pressure and poor diet lead to cardiovascular disease
As cholesterol is one of the main constitutions of fatty deposits that from atheroma is leading to blood clots
How does cigarette smoking need to cardiovascular diseases
Nicotine increases risk of high blood pressure
carbon monoxide binds the haemoglobin reducing the amount of oxygen in the blood can lead to a heart attack
smoking decreases about antitoxin dents in the bloods
How can hide blood pressure need to cardio vascular diseases
Increases risk of damage to artery walls increasing risk of atheroma formation
what does xylem tissue transport
water and mineral ions
what does phloem tissue transport
sugars
describe xylem vessels
long tube like made up of dead cells
no end walls making uninterrupted tube so water can pass through easier
how does water move up the plant
Water evaporates from the leaves at top of xylem
- creates tension pulling up more water
- as water is cohesive it pulls up even more water
- water enter stem from roots
whats transpiration
1- water evaporates from voice cells and accumulates in spaces between cells in the leaf
2-when stomato open water moves out of leaf down concentration gradient
how does light effect transpiration rate
more light means faster rate of transpirations as photosynthesis happens more in light
how does temperature effect transpiration rate
higher temp means faster rate of transpiration as molecules have more energy so can evaporate quicker
how does humidity effect transpiration rate
lower humidity the faster the transpiration rate as higher concentration gradient
how does wind effect the rate of transpiration
more windy means faster rate of transpiration as the wind can blow away more water molecules
what are seive tube cells and companion cells
seive tube elements are living cells which form the phloem tube but they have no nucleus so there is a companion cell for each of them to provide energy needed for active transport
what is translocation
the movement of solutes in a plant to where they are needed
does transloctaion require energy
yes
how do enzymes maintain the concentration gradient from source to sink
by changing (breaking down the solutes) the sloutes at the sink so there is always a lower concentration at the sink
what is the first step of mass flow hypothesis
1- active transport loads the solutes from companion cells into the sieve tube of p[phloem at the source
2- this lowers water potential inside the sieve tubes so water enters the tubes by osmosis from the companion cells and the xylem
3-this creates high pressure at the source end f the phloem and in the sieve tubes
what is the second step of the mass flow hypothesis
1- at the sink end solutes are removed from phloem to be used up
2- this increases water potential inside the sieve tubes so water leaves by osmosis
3-this loweres the pressure insed the sieve tubes
what is the third step of the mass flow hypothesis
1- this results in a pressure gradient from the sink to source end of the phloem
2- the gradient pushes the solutes from the source to sink end of the sieve tubes
3- when the solutes reach the sink they will be used or stored
what are two objections to the mass flow hypothesis
1- sugar and solutes travel to many different sinks not just the one with the highest water potential
2- the sieve plates would create a barrier to mass flow , a lot of pressure would be needed for solutes to get through at a reasonable rate
what are 4 supporting evidences for the mass flow hypothesis
1-tree ringing
radioactive tracker
aphids
metabolic inhibitir
