mass transport Flashcards by Daisy Ruffell

describe the structure of haemoglobin

globular
water soluble
4 polypeptide chains
each chain carries a haem group

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describe the role of haemoglobin

in red blood cells

- oxygen molecules bind to haem groups + are carried around the body to respiring tissues

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name three factors affecting oxygen - haemoglobin binding

partial pressure / concentration of oxygen
partial pressure / concentration of carbon dioxide
saturation of haemoglobin with oxygen

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how does partial pressure of oxygen affect oxygen-haemoglobin binding?

as partial pressure of oxygen increases - affinity of haemoglobin for oxygen increases
so oxygen binds TIGHTLY to haemoglobin
when partial pressure is LOW - oxygen is RELEASED from haemoglobin

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how does partial pressure of carbon dioxide affect oxygen - haemolobin binding?

as partial pressure of carbon dioxide increases - conditions = ACIDIC so haemoglobin CHANGES SHAPE
affinity for haemoglobin decreases
oxygen released from haemoglobin
BOHR EFFECT

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how does saturation of haemoglobin with oxygen affect oxygen - haemoglobin binding?

hard for first molecule to bind
once it does - changes shape so easier for 2nd and 3rd
this = POSITIVE COOPERATIVITY
harder for 4th oxygen molecule to bind as low chance of finding empty binding site

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why does oxygen bind to haemoglobin in the lungs?

high partial pressure of oxygen
low concentration of carbon dioxide - high affinity
positive cooperativity

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why is oxygen released from haemoglobin in respiring tissues?

low partial pressure of oxygen

high concentration of CO2 in respiring tissues - decreased affinity

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how does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?

curve shifts to the right because haemoglobin’s affinity for oxygen decreases

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relate structure of the atria to their function

atria are thin walled and elastic so can stretch when filled with blood

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relate the structure of the ventricles to their function

thick + muscular walls
pump blood under high pressure
LEFT ventricle is THICKER as it has to pump blood all around the body

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relate the structure of the arteries to their function

the arteries have thick walls to handle HIGH PRESSURE without tearing
muscular and elastic to control blood flow

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relate the structure of the veins to their function

thin walls due to lower pressure
VALVES to ensure blood doesn’t flow backwards
less muscular and elastic tissue as they don’t have to control blood flow

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describe what happens during cardiac diastole

heart = RELAXED
blood enters atria - increases pressure - pushes open atrioventricular valves
blood can flow to ventricles
pressure in heart is LOWER than in arteries - semilunar valves remain CLOSED

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what happens during atrial systole?

atria CONTRACT

- pushing and remaining blood into the ventricles

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what happens during ventricular systole?

ventricles CONTRACT
pressure increases - closing atrioventricular valves to prevent backflow
opening semi-lunar valves
blood flows into the arteries

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what does myogenic mean?

the heart’s contraction is initiated from within the muscle itself, rather than by nerve impulses

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how is the structure of the capillaries suited to their function?

walls one cell thick - short diffusion distance
narrow - can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
numerous + HIGHLY BRANCHED = large surface area

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what is tissue fluid?

watery substance containing glucose, amino acids, oxygen and other nutrients
it supplies these to the cells and removes any waste materials

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how is tissue fluid formed?

as blood is pumped through increasingly small vessels
hydrostatic pressure created
forces fluid out of the capillaries
bathes the cells then returns to the capillaries when hydrostatic pressure is low enough

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how is water transported in plants?

xylem vessels
long, continuous columns
also provide structural support to the stem

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explain the cohesion - tension theory

COHESION - hydrogen bonds between water molecules mean that they stick together
surface TENSION of the water also creates sticking effect
- so as water is lost through transpiration, more can be drawn up the stem

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name the three components of phloem vessels

sieve tube elements
companion cells
plasmodesmata

what is translocation?

the process whereby organic materials are transported around the plant

what are the sieve tube elements

component of phloem vessel | - form a tube to transport sucrose in dissolved form of sap

what are the companion cells

involved in ATP production for active loading of sucrose into sieve tubes

evidence for mass flow hypothesis of translocation?

- sap is released when a stem is cut so there must be pressure in phloem - higher conc of sucrose in leaves than in roots

evidence against mass flow hypothesis of translocation

- structure of sieve tubes seem to hinder mass flow | - not all solutes move at same speed

describe ringing experiments to investigate transport in plants

- bark and phloem of tree removed in a ring - leaving XYLEM behind - tissues above missing ring SWELL due to accumulation of sucrose - tissues below begin to die - sucrose must be transported in PHLOEM

how can tracing experiments be used to investigate plant transport?

- plants grown in presence of RADIOACTIVE CO2 - this will be incorporated into plants sugars - using AUTORADIOGRAPHY we can see that areas exposed to radiation correspond to where PHLOEM is

in humans where does oxygen association occur?

lungs

in humans where does oxygen dissociation occur?

tissues

what is positive cooperativity?

a smaller increase in the partial pressure or oxygen is needed for the oxygen to bind to the SECOND oxygen molecule

why does the curve flatten off in an oxygen dissociation curve?

majority of binding sites occupied | less likely that a single O2 molecule will find empty one to bind to

why is it hardest for first oxygen molecule to bind to haemoglobin?

shape of haemoglobin | four polypeptide subunits are CLOSELY UNITED

common features of organisms transport systems

- suitable medium to carry materials - transport medium moved in bulk over large distances - closed system of TUBULAR vessels which form BRANCHING network

what type of circulatory system do mammals have?

a closed, double circulatory system - blood is confined to vessels and passes twice through heart per circuit)

why does the blood pass through the heart twice in one circuit?

- as blood is passed through lungs the pressure is REDUCED - low pressure would make circulation very slow - blood is RETURNED to heart to boost pressure before being circulated to other tissues

name the two valves between the atria and ventricle which prevent BACKFLOW of blood into atria when ventricles contract

- left atrioventricular - BICUSPID | - right atrioventricular - TRICUSPID

what pumps blood away from the heart and into the arteries?

ventricles

what are the vessels connecting the heart to the lungs called?

pulmonary vessels

what is the aorta?

connected to left ventricle | carries oxygenated blood to all parts of body EXCEPT LUNGS

what is the vena cava?

connected to right atrium | bring deoxygenated blood back from tissues in blood EXCEPT FOR LUNGS

what is the pulmonary artery?

connected to right ventricle | carries deoxygenated blood to lungs

what is the pulmonary vein?

connected to LEFT ATRIUM | bring oxygenated blood back from lungs

what is the function of the coronary arteries?

supply oxygenated blood to tissues in the heart

risk factors associated with cardiovascular disease

smoking high blood pressure diet blood cholesterol

equation to calculate cardiac output?

CO = heart rate x stroke volume

define translocation

movement of organic molecules through sieve tubes from a source to a sink - requires energy

why are sieve tube cells tall cylinders stacked end on end?

continuous flow of solutes

why do sieve tube cells have perforated cell walls?

allow fast transport, doesn’t restrict large molecules

why are sieve tube cells elongated?

fewer end walls to restrict flow

why are sieve tube cell walls made of cellulose?

allows loading and unloading of solutes

what is a source in mass flow?

cells that photosynthesise and make sugar

what are sinks in mass flow?

part of plants that remove sugar from the phloem

give some problems with the Mass Flow Theory

- sucrose and AA move too quickly for passive transport - solutes can travel at different speeds - solutes can travel in different directions