Topic 3B - more exchange and transport systems DVY * Flashcards
digestion and absorption haemoglobin the circulatory system the heart transport in plants - xylem transport in plants - phloem
what happens to food so it can be absorbed?
too big to fit across cell membranes
hydrolysed in digestion so they are smaller and can be easily absorbed from gut to blood and transported around the body
what is used to break down food?
a variety of different digestive enzymes are produced by specialised cells in the digestive system
they are specific
what enzymes break down carbohydrates?
amylase, membrane-bound disaccharidases
what does amylase do?
breaks down starch into maltose
breaks α-1,4 and α-1,6 glycosidic bonds
what does maltase do?
breaks down maltose into α-glucose
breaks α-1,4 and α-1,6 glycosidic bonds
where is amylase found?
produced in the salivary glands and pancreas
acts in the mouth and ileum
where is maltase found?
attached to the cell membrane of epithelial cells lining the ileum
what does sucrase do?
breaks down sucrose into α-glucose and fructose
breaks α-1,4 and α-1,6 glycosidic bonds
what does lactase do?
breaks down lactose into galactose and α-glucose
breaks α-1,4 and α-1,6 glycosidic bonds
where is sucrase found?
attached to the cell membrane of epithelial cells lining the ileum
where is lactase found?
attached to the cell membrane of epithelial cells lining the ileum
what happens after disaccharides have been hydrolised?
they can be absorbed into the ileum epithelial cells via co-transport
what enzymes break down lipids?
lipase
what does lipase do?
breaks down triglycerides into 2 fatty acids and a monoglyceride
breaks ester bonds
where is lipase found?
produced in the pancreas and ileum and acts in the ileum
other than lipase, what can be used to break down lipids?
bile salts
what do bile salts do?
produced in liver, and emulsify lipids into small droplets
why are bile salts really important in lipid digestion?
several small lipid droplets have a bigger surface area than a single large droplet, so lipase can work on a larger area.
after being broken down, monoglycerides and fatty acids stick with the bile to form micelles
what enzymes break down proteins?
endopeptidase, exopeptidase, dipeptidase
what does endopeptidase do?
hydrolyses protein into peptides by breaking peptide bonds between inner amino acids
what does exopeptidase do?
hydrolyses peptides into amino acids and dipeptides by breaking peptide bonds between outer amino acid and rest of peptide
what does dipeptidase do?
hydrolyses dipeptides into amino acids by breaking peptide bonds
where is endopeptidase found?
trypsin and chymotrypsin - made in pancreas act in ileum
pepsin - made in stomach and act in the stomach
where is exopeptidase found?
made in the stomach and pancreas
act in the stomach and ileum
where is dipeptidase found?
attached to the cell membrane of epithelial cells lining the ileum
how are monosaccharides absorbed across the ileum epithelium into the bloodstream?
glucose is absorbed by active transport with sodium ions via a co-transporter protein. galactose is absorbed in the same way
fructose is absorbed via facilitated diffusion through a different transporter protein
how are monoglycerides and fatty acids absorbed across the ileum epithelium into the bloodstream?
micelles help to move them towards the epithelium
micelles constantly break up and reform, allowing them to release them so they can be absorbed - micelles aren’t taken up
across the epithelium,
monoglycerides and fatty acids are lipid-soluble, so can diffuse directly across the membrane
how are amino acids absorbed across the ileum epithelium into the bloodstream?
absorbed via co-transport, similarly to glucose
sodium diffuse into epithelial cells through sodium dependent transporter proteins, carrying the amino acids with them
what is the structure of the ileum?
walls folded into villi walls are 1 cell thick epithelial cells of villi have microvilli many capillaries muscle in villi
how does the ileums structure aid its function?
villi - increased surface area for max absorption
thin walls - short diffusion distance
microvilli - increased SA for max absorption
capillaries - rich blood supply maintains diffusion gradient
muscle - maintains diffusion gradient
how do monosaccharides co-transport with sodium?
Na+/K+ pump actively transports Na+ into blood creating low conc. in cell
Na+ enter cell with glucose via cotransporter carrier
glucose enters blood via facilitated diffusion
what is digestion?
the hydrolysis of large, insoluble food molecules into smaller, soluble food molecules that can be absorbed into the blood
what makes up the digestive system?
salivary glands teeth oesophagus stomach liver pancreas ileum large intestine rectum and anus
what do the salivary glands do?
produce salivary amylase
what do the teeth do?
physically break down food into smaller pieces
what does the oesophagus do?
carries food to the stomach
what does the stomach do?
produces hydrochloric acid and protease enzymes. also physically churns food
what does the liver do?
produce bile
what does the pancreas do?
produce pancreatic amylase, protease and lipase
what does the ileum do?
absorbs products of food digestion into the blood
what does the large intestine do?
absorb water
what does the rectum and anus do?
the rectum stores faeces before they exit through the anus
what are the 2 types of digestion?
physical - breaking food into smaller pieces e.g. chewing, stomach churning
chemical - enzyme action
What is haemoglobin?
A large protein with a quaternary structure found in the blood.
What is the structure of haemoglobin?
Made up of 4 polypeptide chains - 2 α, 2 β
Each chain has a haem group which contains an Fe 2+ ion that combines with O2 and gives haemoglobin its red colour
What does it mean that haemoglobin has a high affinity for oxygen?
It has a high tendency to combine with oxygen - each molecule can carry 4 oxygen molecules
What happens to haemoglobin in the lungs?
Oxygen joins to haemoglobin to form oxyhemoglobin
The oxygen then dissociates at the body cells, and it turns into haemoglobin again
What is the equation for the association and dissociation of oxygen from haemoglobin?
Hb + 4O2 HbO8
Haemoglobin + oxygen oxyhaemoglobin
What is the partial pressure of oxygen?
It’s a measure of oxygen concentration, it’s the amount of pressure exerted by oxygen relative to the total pressure exerted by all the gases in a mixture. The higher the concentration of dissolved oxygen in cells, the higher the partial pressure.
measured in kilopascals (kPa)
denoted P(O2)
How does haemoglobin’s affinity for oxygen depend on its partial pressure?
Oxygen loads onto haemoglobin to form oxyhemoglobin where there’s a high pO2
Oxyhemoglobin unloads it’s oxygen where there’s a low pO2
How is oxygen carried out of the lungs?
It enters the capillaries at the alveoli. The alveoli have a high pO2 so oxygen loads onto haemoglobin readily
How do body cells take on oxygen?
When cells respire they use up oxygen lowering the pO2. This means red blood cells deliver oxyhemoglobin to respiring cells where it unloads its oxygen
What does the dissociation curve show?
Where pO2 is high, haemoglobin has a high affinity for oxygen - readily combines so has high saturation
Where pO2 is low, haemoglobin has a low affinity - readily releases oxygen so has low saturation of oxygen
Why is the dissociation curve s shaped?
at low P(O2) its hard for haemoglobin to take up oxygen due to its shape - shallow gradient
as it starts to load positive cooperativity takes place - steeper gradient
harder for 4th O2 molecule to bind because majority of sites are occupied - gradient flattens
What does haemoglobin do when there’s a high pCO2?
It gives up oxygen more readily
What is the Bohr effect?
Respiring cells produce CO2, raising pCO2
This increases the rate at which oxygen is unloaded
The dissociation curve shifts to the right
The saturation of blood with oxygen is lower for a given pO2, meaning more oxygen is released
Why do different organisms have different types of haemoglobin?
Different types of haemoglobin have different oxygen transporting capacities. This is an adaptation that helps an organism to survive in a particular environment
What is the haemoglobin like for organisms in environments with a low concentration of oxygen?
They have haemoglobin with a higher affinity for oxygen than human haemoglobin - the curve lies to the left
This means oxygen is picked up more easily from the lungs
What is the haemoglobin like for organisms that are very active?
They have a high oxygen demand so their haemoglobin has a lower affinity to oxygen then human haemoglobin - the curve lies to the right
This means oxygen dissociates more easily at respiring cells
What is the circulatory system?
A specialised transport system to carry raw materials from specialised exchange organs to the body cells
Why is the circulatory system needed?
Multicellular organisms have a low surface area to volume ratio. So can’t rely on diffusion through their body surface to deliver the required gases to and from body cells.
or the organism is more active so it needs a better mass transport system
What does the blood transport?
proteins e.g. antibodies, clotting proteins heat energy nutrients salts hormones waste carbon dioxide (plasma) oxygen (red blood cells)
What is the double circulatory system?
Humans have 2 circuits.
One takes blood from the heart to the lungs, then back to the heart.
The other takes blood around the rest of the body
the blood passes through the heart twice for each circuit of the body
What is the name of the blood vessels entering and leaving the heart?
Aorta - oxygenated blood to the body
Vena cava - deoxygenated blood from the body
Pulmonary artery - deoxygenated blood to lungs
Pulmonary vein - oxygenated blood from lungs
What are the blood vessels around the kidneys called?
Renal artery - oxygenated blood to kidneys
Renal vein - deoxygenated blood from kidneys
What are the coronary arteries?
The blood vessels that supply the heart with oxygenated blood
What do arteries do?
They carry blood from the heart to the rest of the body
All arteries except the pulmonary artery carry oxygenated blood
What is the structure of arteries?
Thick muscular walls
Elastic tissue in walls
Folded inner endothelium
Why do arteries have a thick, muscular wall?
To contract to maintain blood pressure
Why do arteries have elastic tissue?
To stretch and recoil as the heart beats, which helps maintain the high pressure
Why is the inner lining of arteries folded?
To allow the artery to stretch to help maintain high pressure
What are arterioles?
Arteries divide into smaller vessels called arterioles these form a network through the body
What do arterioles do?
Muscles inside the arterioles direct blood to areas of demand in the body, by contracting to restrict blood flow and relax to allow full blood flow
What do veins do?
They take blood back to the heart under low pressure
All veins except pulmonary veins carries deoxygenated blood
What is the structure of the veins?
Wider lumen than arteries
Very little muscle or elastic tissue
Valves
Thinner walls
Why do veins have valves?
To stop the blood flowing backwards
Why do veins have a wider lumen then arteries?
Blood flows slower at a lower pressure so a wider lumen is needed to carry more blood at once so that it doesn’t all build up
How is blood flow helped in the veins?
small amount of pressure from capillaries keeps blood moving
Contractions of the body muscles surrounding them help blood along
reduced pressure at the atria create a suction force in the vena cava and veins, pulling blood towards the heart
What do arterioles branch in to?
Capillaries - the smallest of the blood vessels
What do capillaries do?
Substances are exchanged between cells and capillaries, so they’re adapted for efficient diffusion
How are capillaries adapted for efficient diffusion?
Found near cells in exchange tissues, for short diffusion pathway
1 cell thick walls for short diffusion pathway
Large number of capillaries to increase surface area for exchange
What are capillary beds?
Networks of capillaries
What is tissue fluid?
the medium in which cells/ tissue bathe, provides a constant environment and allows final exchange to happen
What is tissue fluid made up of?
Small molecules that leave the blood plasma e.g. oxygen, water and nutrients
white blood cells, sugars, ions, fatty acids, amino acids, oxygen, coenzymes, hormones, neuro transmitters, waste products from cells
Not red blood cells or big proteins because they’re too large to fit through capillary walls
What interaction happens between cells and tissue fluid?
Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
How is tissue fluid formed?
At the start of the capillary bed, nearest the arteries, the hydrostatic pressure (created from ventricles contracting) inside the capillaries is greater than the osmotic pressure in vessels and the hydrostatic pressure in the tissue fluid.
This pressure difference forces the fluid out of the blood plasma in capillaries and into the spaces around the cell by ultra-filtration, forming tissue fluid
How does water re-enter the capillaries?
As fluid leaves, hydrostatic pressure decreases so it’s lower at the venule end
so tissue fluid forced back into capillaries
Due to fluid loss blood has an increasing concentration of plasma proteins, so water potential is lower at venule end then in tissue fluid
This means some water re-enters the capillaries by osmosis
What happens to excess tissue fluid?
It drains into the lymphatic system, which transports excess fluid from the tissues back into the circulatory system near the vena cava via the thoracic duct, close to the heart
What is the lymphatic system?
A network of tubes that acts a bit like a drain
what does the left side of the heart do?
receives oxygenated blood from the lungs and pumps it to the whole body
What does the right side of the heart do?
receives deoxygenated blood from the body and pumps it to the lungs
What path does blood take through the right side of the heart heart?
Deoxygenated blood from the body enters through the vena cava Into right atrium Through right atrioventricular valve Into right ventricle Through semi-lunar valve Out the pulmonary artery to the lungs
What path does blood take through the left side of the heart heart?
Oxygenated blood from the lungs enters through the pulmonary vein
Into left atrium
Through left atrioventricular valve
Into left ventricle
Through semi-lunar valve
Out of heart through aorta to rest of the body
How is the left ventricle adapted for its function?
Thicker, more muscular walls then right, because it needs to contract powerfully to pump blood all the way round the body
How are ventricles adapted to their function?
Thicker muscular walls than the atria, so contract stronger/ harder, because they have to push blood out of the heart but atria just have to push blood into ventricles
What do the valves do?
They allow blood to flow into the ventricles from the atria or to the arteries from the ventricles but don’t let it flow backwards
What do the cords do in the heart?
They attach the atrioventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract
How are valves adapted to their function?
Valves only open one way
If there’s higher pressure behind a valve, it’s forced open
If the pressure is higher in front of the valve it’s forced shut.
This means blood only flows on 1 direction
What is the proper name for contraction and relaxation in the heart?
Cardiac contraction - systole
Relaxation - diastole
What happens during the atrial systole?
The ventricles are relaxed. The atria contract.
pressure is higher in atria than in ventricles
AV valves forced open
This pushes blood into the ventricles
There’s a slight increase in ventricular pressure and chamber volume as blood enters
What happens during the ventricular systole?
atria relax. , ventricles contract.
in ventricles volume decreases, pressure increases
pressure higher in ventricles than atria
AV valves forced shut to prevent back-flow
pressure higher in ventricles than arteries, forcing open SL valves and pushing out blood
what happens during atrial and ventricular diastole?
both atria and ventricle muscles are relaxed
higher pressure in arteries, forcing SL valves closed to prevent backflow
higher pressure in veins than atria, blood returns to heart and atria fill again.
as ventricles relax, pressure gets lower than that of the atria so AV valves open.
blood flows passively into ventricles.
Analysis of pressure/time and volume/time of heart graph?
PIC
what does the xylem tissue do?
transports water and mineral ions in solution
what does the phloem tissue do?
transports organic substances like sugars in solution and other solutes both up and down the plant
what are xylem vessels?
part of the xylem tissue that transports the water and ions.
how are xylem vessels structured?
they are very long, tube-like structures formed from dead cells joined end to end. there are no end walls to these dead cells, making an uninterrupted tube for water to pass through easily
how does water move up a plant?
cohesion and tension help water move up plants against the force of gravity
what is the cohesion-tension theory of water transport?
water evaporates from leaves at the top of the xylem
this creates tension, pulling water into the leaf
water molecules are cohesive, so the whole column of water in the xylem moves up
water enters the stem through the roots
what is transpiration?
the evaporation of water from a plants surface (at the stomata)
how does transpiration occur?
water evaporates from moist cell walls and accumulates in the spaces between cells in the leaf.
when the stomata open, it moves out of the leaf down the concentration gradient
what are the 4 main factors that affect transpiration rate?
light - positive correlation
temperature - positive correlation
humidity - negative correlation
wind - positive correlation
how does light affect transpiration rate?
the lighter it is the faster the rate - stomata open when its light to let in CO2 for photosynthesis. when its dark they’re closed so there’s little transpiration
how does temperature affect transpiration rate?
the higher the temperature the faster the rate - warmer water molecules have more energy so evaporate from cells inside leaf faster. this increases concentration gradient between inside and outside of leaf, making water diffuse out of leaf faster
how does humidity affect transpiration rate?
the lower the humidity, the faster the rate - if the air around the plant is dry, the concentration gradient between the leaf and air is increased, increasing transpiration
how does the wind affect transpiration rate?
the windier it is, the faster the rate - lots of air movement blows away water molecules from around the stomata, this increases the concentration gradient, increasing rate of transpiration
what is a potometer?
a piece of apparatus used to estimate transpiration rates. it measures water uptake by a plant
how to set up an experiment to estimate transpiration rate using a potometer?
cut a shoot at a slant underwater
assemble potometer in water and insert shoot underwater
remove apparatus from water but keep the end of capillary tube submerged in a beaker of water
check apparatus is water and air tight
dry leaves, give time to acclimatise, then shut the tap
remove capillary tube from beaker until an air bubble is formed
record starting position of air bubble
start stopwatch, record distance moved by bubble per unit time (this is an estimate of transpiration rate)
change 1 variable at a time and keep others constant to find affect of that variable on transpiration rates
why must you cut the shoot at a slant?
to increase the surface area available for water uptake
why must you cut the shoot underwater?
to prevent air from entering the xylem
what does a potometer look like?
PIC
how to dissect a plant?
use scalpel to cut cross sections of the stem as thinly as possible
use tweezers to place the cut sections in water until needed to stop them drying out
transfer each section to a dish containing a stain and leave for 1 min
rinse off sections in water and mount each 1 onto a slide
what stain is used to see the xylem in a plant?
toluidine blue O (TBO)
it stains the lignin in the walls of the xylem vessels blue-green.
this lets you see the position of the xylem vessels and examine their structure
what are solutes?
dissolved substances.
sometimes called assimilates
what is the structure of the phloem?
formed from cells arranged in tubes, contains sieve tube elements and companion cells
what are sieve tube elements?
living cells that form the tube for transporting solutes. they have no nucleus and few organelles
what’s a companion cell?
there’s a companion cell for each sieve tube element. they carry out living functions for sieve cells. e.g. providing the energy needed for the active transport of solutes
what is translocation?
the bidirectional movement of solutes to where they’re needed in a plant. its an energy-requiring process that happens in the phloem.
what does translocation do in the phloem?
it moves solutes from ‘source’ to ‘sink’. the source is where the solute is made (so there’s a high concentration). the sink is where its used up (so there’s a lower concentration)
what is the source and sink for sucrose in translocation?
usually the leaves are the source and the sinks are the other parts of the plant, especially the food storage organs and the meristems in the roots, stems and leaves
how are concentration gradients maintained in the phloem?
enzymes maintain a concentration gradient from the source to sink by changing the solutes at the sink. this makes sure there’s always a lower concentration at the sink than at the source
what is the mass flow hypothesis?
the best supported theory for how solutes are transported from source to sink
describe what happens at the source end in the mass flow hypothesis
active transport is used to actively load solutes from companion cells into sieve tubes at source
this lowers water potential inside sieve tubes, so water enters tubes by osmosis from the xylem and companion cells
this creates a high pressure inside sieve tubes at source end
describe what happens at the sink end in the mass flow hypothesis?
at the sink end, solutes are removed from the phloem to be used up
this increases water potential inside the sieve tubes, so water leaves tubes by osmosis
this lowers pressure inside sieve tubes
what happens as a result of different pressures being formed at source and sink in the mass flow hypothesis?
a pressure gradient is formed
this gradient pushes solutes along the sieve tubes towards the sink
when they reach the sink the solutes will be used or stored
what is the supporting evidence for the mass flow hypothesis?
removing ring from bark of tree
radioactive tracer
aphid test
metabolic inhibitor
how can removing a ring of bark from a tree prove the mass flow hypothesis?
the bark includes the phloem, but not xylem. so when its removed, a bulge forms above the ring. the fluid from the bulge has a higher concentration of sugars than the fluid from below the ring - this proves there’s a downward flow of sugars
how can a radioactive tracer prove the mass flow hypothesis?
a radioactive tracer such as radioactive carbon can be used to track the movement of organic substances in a plant
how can aphids be used to prove the mass flow hypothesis?
pressure in the phloem can be investigated using aphids.
they pierce the phloem, then their bodies are removed leaving the mouthpart behind, the sap flows out of it quicker nearer the leaves than further down the stem - this is evidence of a pressure gradient
how can a metabolic inhibitor prove the mass flow hypothesis?
if a metabolic inhibitor is put in the phloem it stops the production of ATP and translocation stops. this proves active transport is involved
what are some objections against the mass flow hypothesis?
sugar travels to many different sinks, not just the one with the highest water potential
the sieve plates would create a barrier to mass flow. a lot of pressure would be needed for the solutes to get through at a reasonable rate
what can radioactive tracers do?
it can model the translocation of solutes in plants
how can radioactive tracers be used as a model?
this can be done by supplying part of a plant with an organic substance that has a radioactive label. e.g. CO2 with 14C
radioactive carbon will be incorporated into organic substances produced by the leaf which will be moved around by translocation
the movement of these substances can be tracked using autoradiography. to reveal where the tracer has spread to the plant is killed and placed on photographic film
the radioactive substance is present where the film turns black
the results demonstrate the translocation of substances from source to sink - plants killed at different times show an overall movement of solutes
what is positive cooperativity?
when haemoglobin combines with the 1st O2, it’s shape alters in a way that makes it easier for more molecules to join.
what factors affect the shape of haemoglobin?
pH, carbon dioxide concentration, temperature
how does carbon dioxide affect the shape of haemoglobin?
respiring tissues produce CO2
dissolved CO2 is acidic - lowers pH
lower pH causes haemoglobins shape to change
so it has reduced affinity for oxygen
so O2 is unloaded to cells that need it with high CO2
what does a shift to the right of the dissociation curve mean?
it has a reduced affinity for oxygen - more readily unloads it to respiring tissues
what does a shift to the left of the dissociation curve mean?
it has an increased affinity for oxygen - more readily loads oxygen at the lungs
how is foetal haemoglobin different to adult haemoglobin?
it has a higher affinity for O2
this helps maximise oxygen uptake from the mother’s bloodstream, which has already lost some of its oxygen by the time it reaches the placenta
how is myoglobin’s affinity different to to haemoglobin?
it has a very high affinity for oxygen, even at low partial pressures
this means oxymyoglobin will only dissociate when oxygen levels are really low
what is myoglobin?
a molecule similar in structure to haemoglobin but with 1 haem group.
found in muscle cells where it acts as an oxygen reserve
what are the features of a mass transport system?
suitable medium to carry the materials
a form of mass transport system
closed system of vessels containing transport medium
a pump, muscle contractions or passive processes such as evaporation
valves
to control the flow of transport medium
why do mass transport systems need suitable medium to carry the materials?
e.g. blood or air. blood is usually water based to allow substances to dissolve and can move easily
why do mass transport systems need a form of mass transport system?
so materials can be moved over large distances - faster than diffusion
why do mass transport systems need closed system of vessels containing transport medium?
to carry the materials around the body and distribute to where it is needed e.g. arteries, veins, capillaries
why do mass transport systems need a pump, muscle contractions or passive processes such as evaporation?
to be able to move the transport medium in the vessels.
this creates a pressure difference between 1 part of the system and another
why do mass transport systems need valves?
ensure a 1 way flow of mass flow/ transport
why do mass transport systems need to control the flow of transport medium?
to suit the changing needs of the organism e.g. change of heart rate, vasoconstriction, vasodilation, contraction of diaphragm and intercostal muscles
what is the heart made up of?
it mostly consists of cardiac muscle tissue, which like smooth muscle, contracts involuntarily
what is cardiac muscle made up of?
its made up of cells that are connected by cytoplasmic bridges. this enables electrical impulses to pass through the tissue.
it contains a large number of mitochondria and myoglobin molecules
what do the atria do?
receive blood from the body/lungs before pushing it into the ventricles
what do the ventricles do?
contract forcefully pushing blood to the lungs/ body
why is the lymphatic system so important?
water, etc. are continuously leaking out of tiny blood vessels into surrounding body tissues
if lymphatic system didn’t drain the excess, it would build up and cause swelling
what is lymph?
a colourless/ pale yellow fluid similar to tissue fluid but containing more lipids. formed from excess tissue fluid draining into the lymphatic system
what route does lymph take around the body?
interstitial spaces
lymph vessels
subclavian veins
back to bloodstream
how is lymph moved through the system?
it isn’t pumped around by the heart, just pressure differences and motions of muscle
where does lymph from the heart drain?
into the right subclavian vein
where does lymph from the leg and digestive system drain?
lymph vessels from the legs and digestive system form the thoracic duct, which ultimately drains the lymph into the left subclavian vein
what can cause lymph/ tissue fluid to build up in the body?
Kwashiorkor
high blood pressure medications
high blood pressure
how can Kwashiorkor cause tissue fluid to build up?
severe malnutrition
lack of protein in diet
causes osmotic imbalance as the lack of proteins means water potential of the blood is not lowered
tissue therefore retains fluid
how can high blood pressure medications cause tissue fluid to build up?
blood vessels open wider and more fluid leaks out
how can high blood pressure cause tissue fluid to build up?
more fluid forced out of capillary due to high pressure, less return of fluid into capillary due to pressure or lymphatic system can’t drain away all excess fluid
what is the cardiac cycle?
a sequence of contraction and relaxation of the heart chambers during 1 beat
how does blood move in the body?
only move if there’s a difference of pressure
changes in pressure occur when heart muscles contract and relax
blood moves from high to low pressure
what is the cardiac output?
the amount of blood pumped around the body
what does cardiac output depend on?
stroke volume
heart rate
what is the stroke volume?
the volume of blood pumped by the left ventricle in each heart beat. a typical value for an adult at rest is 75 ml
what is the heart rate?
the number of times the heart beats per minute. a typical value for an adult at rest is 70 bpm
how to calculate cardiac output?
stroke volume x heart rate
what factors affect heart rate?
autonomic innervation
hormones
fitness levels
age
what factors affect stroke volume?
heart size fitness levels gender contractility duration of contraction preload (EDV) afterload (resistance)
what are the benefits of transpiration?
it creates a transport stream from roots to leaves
it cools the plant
what is cohesion?
water molecules ‘sticking together’ hydrogen bonds allow a continuous column of water
what is tension?
as water is pulled up through xylem - their xylem are put under tension (like water being sucked up a straw) its a ‘negative pressure’
what is the supporting evidence for the cohesion-tension theory?
when transpiration rate is high during the day, there is more tension so the diameter of a tree is smaller
during night there is less transpiration, so less tension and diameter increases
what is the evidence for cohesion?
if a xylem breaks and air enters, a tree can no longer draw water up the trunk, the air pocket prevents cohesion
how is water taken up from the soil?
passive uptake by osmosis into long thin root hair cells with large surface area
what is an apoplastic pathway?
water soaks into the porous cellulose walls and travels through cortex
cohesive forces between water molecules pulls more water along
little or no resistance
what is a symplastic pathway?
water travels through the cell membranes, across the cytoplasm and through plasmodesmata to reach adjacent cells
osmosis causes water to move between cells, continuous flow of water moving down osmotic gradient
more resistance
what are root hair cells?
extension of epidermis providing large surface area for water uptake
what is the cortex (parenchyma)?
bulky ‘standard’ plant cells
what is the casparian strip?
it acts as a barrier to prevent the backflow of water into cortex and prevents loss of accumulated ions. water forced to go through membrane so it’s selective to what enters the xylem
what is the pericycle?
a cylinder of parenchyma cells that lies just inside the endodermis
How can smooth muscle reduce blood flow to the small intestine?
It can contract
Causing vasoconstriction, narrowing the lumen
What information is required to calculate the mean rate of movement of CO2 down a tree trunk?
The length of the trunk
The mean amount of CO2 released from the tree
The time after the CO2 is given to the tree
why does hydrostatic pressure fall from atriole end to venule end?
friction of blood against the capillary wall decreases pressure
what happens if damage occurs to the endothelium?
white blood cells (mostly macrophages) and lipids from the blood, clump together under the lining to form fatty streaks
what is an atheroma?
a fibrous plaque formed when more white blood cells, lipids and connective tissue build up over time from fatty streaks
what does an atheroma do?
it partially blocks the lumen of the artery and restricts blood flow, which causes blood pressure to increase
what is coronary heart disease?
CHD is a type of cardiovascular disease
when does CHD occur?
when the coronary arteries have lots of atheroma’s in them, which restricts blood flow to the heart muscle. can lead to myocardial infraction
what do atheroma’s increase the risk of?
aneurysm - a balloon-like swelling of the artery
thrombosis - formation of a blood clot
how are aneurysms caused?
atheroma plaques damage, weaken and narrow arteries, increasing blood pressure
when blood travels through a weakened artery at high pressure, it may push the inner layers of the artery through the outer elastic layer to form a balloon-like swelling
what danger do aneurysm’s have?
it may burst, causing a haemorrhage (bleeding)
how is thrombois caused?
an atheroma plaque can rupture the endothelium of an artery
this damages the artery wall and leaves a rough surface
platelets and fibrin accumulate at the site of damage and form a blood clot (thrombus)
what danger does thrombosis do?
this blood clot can cause a complete blockage of the artery, or it can become dislodged and block a blood vessel elsewhere in the body.
debris from the rupture can cause another blood clot to form further down the artery
what happens when a coronary artery becomes completely blocked?
an area of the heart muscle will be totally cut off from its blood supply, receiving no oxygen. causing a myocardial infraction
what is a myocardial infraction?
a heart attack
what problem does a myocardial infraction cause?
a heart attack can cause damage and death of the heart muscle.
if large areas of the heart are affected complete heart failure can occur, which is often fatal
what are the symptoms of a myocardial infraction?
pain in the chest and upper body, shortness of breath and sweating
What are the most common risk factors of cardiovascular disease?
High blood cholesterol and poor diet
Cigarette smoking
High blood pressure
How does high blood cholesterol increase the risk of cardiovascular disease?
Cholesterol is 1 of the main constituents of the fatty deposits that form atheromas
These can lead to increased blood pressure and blood clots
This can block blood flow to coronary arteries and cause myocardial infarction
How does poor diet increase the risk of cardiovascular disease?
A diet high in saturated fats is associated with high blood cholesterol levels
A diet high in salt also increases the risk of cardiovascular disease because it increases the risk of high blood pressure
How does cigarette smoking increase the risk of cardiovascular disease?
Nicotine and carbon monoxide in cigarette smoke both increase the risk of cardiovascular disease
Smoking decreases amount of antioxidants in blood
How does nicotine increase risk of cardiovascular disease?
It increases risk of high blood pressure
How does carbon monoxide increase risk of cardiovascular disease?
It combines with haemoglobin and reduces the amount of oxygen transported in the blood
So reduces the amount of oxygen available to to tissues
If heart muscle doesn’t receive enough oxygen it can lead to a heart attack
How does less antioxidants increase risk of cardiovascular disease?
They’re important for protecting cells from damage
Fewer antioxidants means cell damage in the coronary artery walls is more likely, and this can lead to atheroma formation
How does high blood pressure increase the risk of cardiovascular disease?
Increases risk of damage to the artery walls
Damaged walls have increased risk of atheroma formation, causing a further increase in blood pressure and blood clots
Blood clots can cause myocardial infraction
What are some examples of things that increase risk of cardiovascular disease?
Anything that increases blood pressure
e.g. being overweight, not exercising and expressive alcohol consumption
What risk factors of cardiovascular disease can’t be controlled?
Genetic disposition to coronary heart disease or having high blood pressure as a result of another condition e.g. diabetes. But risk can be reduced by removing risk factors
