Topic 3 Organisms exchange substances. Mass transport

Question 1

What is the structure of haemoglobin

Answer 1

globular, water soluble.
consists of four polypeptide chains each carrying a haem group (quaternary structure)

Question 2

DEscribe the role of haemoglobin

Answer 2

present in red blood cells. oxygen molecules bind to haem groups and are carried around the body to where they are needed in respiring tissues

Question 3

What is the affinity of haemoglobin for oxygen

Answer 3

ability of haemoglobin to attract or bind oxygen

Question 4

what is the saturation of haemoglobin with oxygen

Answer 4

when haemoglobin is holding the maximum amount of oyxgen it can bind

Question 5

what is loading/assosaitation of haemoglobin

Answer 5

binding of oxygen to haemoglobin

Question 6

what is unloading dissociation of haemoglobin

Answer 6

when oxygen detatches or unbinds from haemoglobin

Question 7

What does the oxyhaemoglobin dissociation curve show?

Answer 7

saturation on the side oxygen oartial pressure on the bottom of graph steady increase curve

oxygen is loaded in regoins with a high partial pressure of oxygen (e.g. alveoli) and is unloaded in regioins of low partial pressue of oxygen (respiring tissue). at a lower partial pressure haemoglobin has a lower affinity and as aresult will unload oxygen in those regions.

Question 8

What is cooperative binding

Answer 8

the cooperative nature of oxygen binding to haemoglobin is due to the haemoglobin changing shape (confromational change) when the first oxygen binds) making it easier for further oxygens to bind. 3d structure slighty changes. explains steep curve on graph

Question 9

What is the bohr effect

Answer 9

the bohr effect is when a high carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right. the affinty of oxygen decreases because the acidinc carbon dioxies changes the shape of haemoglobin slightly.

when partial pressue of carbon dioxide increases conditions become acidic causing haemoglovin to change shape. affinty decreases.

Question 10

How does saturation of haemoglobin with oxygen affect oxygen haemoglobin binding

Answer 10

difficult for the first oxygen molecule to bnd. then it changes shape to make it easier for second and third. it is slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site

Question 11

how does partial pressure of oxygen affect oxygen haemoglobin binding?

Answer 11

as partial pressure of oxygen increases the affinity of oxygen also increases so oyxgen binds to haemoglobin. when partial pressure is low oxygen is relaesed from haemoglobin

Question 12

Describe what the bohr effect would look like on a graph

Answer 12

line shift left:low partial pressue of carbon dioxide in alevoli curve shifts left increased affinty and therefore more oxygen uploaded

line shifts right: higher partial pressure of carbon dioxide at resporing tissues curve shifts right. decreased affinity and unloads more oxygen

Question 13

Describe the oxihameoglobin disocciation curve for fetal haemoglobin

Answer 13

Foetal haemoglobin:shift to left of adults. even at same partial pressue of oxygen the curve has shifted so it has a higher affinity and is more saturated with oxygen.
higher affinity for oxygen advantaged because foetus cannot exhale and inhale. only source of oxygen is from the mothers haemoglobin via placenta

Question 14

Describe llama and earthworm haemoglobin dissociation curve

Answer 14

llamas live at higher alitudes where there is a lower partial pressure of oxygen.

curve shifts to the left: higher affinity for oxygen. even at a low partial pressue high affintiy allows of effiecent oxgen saturation

earthworms live underground at lower partial presssure.

Question 15

describe oxyhaemoglobin dissociation curve for dove

Answer 15

line on graph shifts to the right: lower/decreased affinity. mroe likely to unload oxygen at same partial pressure. advantageous due to faster metabolism so needs more oxygen for respiration to provide energy for contracting muscles.

Question 16

Describe the propeties of the cardiac muscle and how it is myogenic

Answer 16

Thick muscular layer of the walls of the heart.

Myogenic meaning it can contract and relax without nervous or hormone stimulation,

It never fatigues as long as it has an oxygen supply.

Question 17

Describe cornary arteries

Answer 17

Cornary arteries supply cardiac muscle with oxygenated blood
these branch off from the aorta

if they become blocked cardiac muscle wnt recieve oxygen therefore will not be able to respire and the cells will die (myocardial infarction) heart attack

Question 18

Describe and name the four changes of the heart and their properties

Answer 18

Left atrium and right atrium
left ventricle and right ventricle

atria
have thin muscular walls.
because they do not need to contract as jard as they are only pumping blood to ventricles
elastic walls that stretch when blood enters

ventricles
have thick muscuar walls to enable bigger contraction
creates a high blood pressure to enable blood to flow longer distances (lungs and rest of body)
right ventricle thinner muscular wall compared to lefft as pumps blood to lungs at a lower pressure to prevent capillary damage and so blood flows slwoly allowing time for gas exchange

Question 19

Describe arteries and veins in the heart and the movement of blood within them

Answer 19

arteries (away): pulmonary arteries (carries deoxygenated blood from the right ventricle to the lungs) and aorta (carries oxygenated blood from left ventricle to the rest of the body)

veins (in): pulmonary vein (oxygenated blood from lungs to left atrium) and venca cava(carried deoxyginate dblood from body into right atrium)

Question 20

relate the structure of the vessels to their function

Answer 20

• arteries have thick walls to handle high pressure without tearing. muscular and elastic to control blood flow
• veins have thin walls due to lower pressure therefore requiring valves to ensure blood doesn’t flow backwards.

Question 21

Describe and name the valves in the heart

Answer 21

semi-lunar valves: in aorta and pulmonary artery
atriventricular:between atria and ventricles
bicuspid:left side (two flaps)
tricuspid:right side (three flaps)

function:prevent back flow of blood. open when pressure is higher behind the valve. close when pressure is higher in front of valve

Question 22

What is the function of the septum

Answer 22

septum separates deoxygenated and oxygenated blood in the heart.

maintains high concentration of oxygen in oxygenated blood t mainrain conc gradient to enable diffusion at repsiring cells

Question 23

what are the three stages of teh caridac cycle

Answer 23

diastole
atrial systole
ventricular systole

Question 24

Describe what happens during caridac diastole (cardical cycle)

Answer 24

The atria and ventricular msucles are relaxed.
blood enters atria increasing pressure in atria. pushing open atrioventricular valves. allowing blood to flow into ventricles.
pressure in the heart is lower than in arteries so semi lunar valves remain closed

Question 25

Describe what happens in the atrial systole of the cardiac cycle

Answer 25

artia muscular walls contract increasing pressure further. causing atrioventricular valves to open and blood flow into ventricles. ventricular muscual walls relax

Question 26

Describe what happens during ventricular systole

Answer 26

ventricles contract. pressure increases closing atrioventricular valves (prevnt back flow) and opening semi lunar valves. blood pushed out of ventricles into arteries

Question 27

how do you calculate the cardica output

Answer 27

cardiac output=heart rate X stroke volume heart rate-heartbeats per min -1 stroke volume-volume of blood that leaves heart each beat dm3

Question 28

What causes atriventricular valves to open

Answer 28

when pressure is higher in the atria compared to the ventricles. close when pressure is higher in ventricles than atria

Question 29

what causes semi-lunar valves to open

Answer 29

when pressure is higher in the ventricles than the arteriies. close when pressure is higher in the arteries compared to ventricles

Question 30

How to interpretate pressure changes of cardiac cycle graphs

Question 31

How is the structure of capillaries suited to their function

Answer 31

capillaries form capillary beds as exchange surfaces which are many branched capillaries. these have a narrow diameter to slow blood flow (one cell thick) red blood cells can only just fir through maximising diffusion * one cell thick short diffusion pathway * very narrow so can permate rissues and redblood cells lie flat against wall effectively delivering oxygen to tissues * numerous and highly branched large sa

Question 32

What is tissue fluid

Answer 32

watery substance containing glucose amino acids,fatty acids, ions ,oxygen and other nutrients. it supplies these to the cells whilst also removing any waste materials bathes tissues

Question 33

How is tissue fluid formed

Answer 33

Capillaries have small gaps in the walls so that liquid and small molecules can be forced out. as blood enters the capillaries from arterioles the smaller diamter results in a hig hydrostatic pressure so water, glucose amino acids ions and oxygen are forced out of capillaries (ultrification) ut bathes the cells and returns to capillaries when hydrostatic pressure is low enough. red blood cells platelets and large proteins remians in capillary

Question 34

How is tissue fluid reabsorbed

Answer 34

large molecules that remain in the capillaries create a lowered water potential towards the venule end of capillaries the hydrostatic pressure is lowered due to loss of liquid but water potential is very low. water re inters the capillaries via osmosis

Question 35

what happens to rest of tissue fluid that is not re absorbed

Answer 35

not all liquid will be reabsorbed by osmosis as equilibrium will be absorbed rest of tissue fluid is absorbed into lymphatic system and eventuall drains back into blood stream near the heart

Question 36

What is transpiration

Answer 36

loss of water vapour from the stomata by evaporation. *

Question 37

What are four factors which affect the rate of tranpsiration

Answer 37

* increased light intensity: more light causes stomata to open=large surface area for evaporation * increased temperature-more heat more kinetic energy faster moving molecles and therefore more evaporation * increased wind intensity. more wind will blow away humid air containing water vapour therefore maintaining water potential gradient * decreased humitity more water vapour in the air will ake water potential more positive outside of the leaf therefore reducing water potential gradient.

Question 38

Explain the cohesion of water allowing for cohesion tension theory and water to be pulled up the xylem

Answer 38

water is dipolar (made of slightly negative oxygen and slightly positive hydrogen) enabling hydrogen bonds to form between oxygen and water of different water molecules. this creates cohesion between water molecules and sticks them together.surface tension of water also creates sticking effect. therefore water travels up the xylem as a continous water column and as water is lost through transpiration more can be drawn up the stem

Question 39

Explain the capillarity/adhesion of water allowing for cohesion tension theory and water to be pulled up the xylem

Answer 39

adhesion of water is when water sticks to other molecules. water adheres to xylem walls. narrower xylem bigger impact of adhesion

Question 40

Describe how the root pressure in a plant allows for cohesion tension and for water to be drawn up the xylem

Answer 40

as water moves into the roots via osmosis it increases the volume of liquid inside the root and therefore pressure inside the root increases. this increase in pressure in the root forces water above it (positive pressure)

Question 41

Describe the movement of water up the xylem

Answer 41

1. Water vapour evaporates out of stomata in leaves. loss in water creates lower pressure (transpiration) 2. more water is pulled up xylem to replace water loss 3. due to hydrogen bonds between water molecules they are cohesive creating a collumn of water within xylem (stick together) 4. water molecules also adhere to walls of xylem helping pull water column upwards 5. creating tension pulling xylem to be narrower

Question 42

Describe the potometer experiment measuring the rate of transpiration

Answer 42

a potometer measures the rate of uptake of water form a plant. water uptake is proportional to transpiraion 1. sample of plant cut underwater to prevent air from entering xylem and breaking water column 2. potometer is filled with water and air bubbles removed 3. cut leafy plant attached and sealed with petrolium jelly to make air tight 4. one air bubble is then introduced and distance bubble has moved towards plant is recorded 5. rate of transpiration=volume of water/timetaken control variable:surface area of leaves (number and size of leaves)

Question 43

Compare sieve tube elements and companion cells

Answer 43

sieve tube elements: living cells contain no nucleus contain few organelles. companion cells: provide atp required for active transport of organic substances.

Question 44

describe the mass flow hypothesis from source to sieve plate elements

Answer 44

* photosynthesis occuring in the chloroplasts leaves create organic substances e.g sucrose * this creates a high concentration of sucrose at site of production so sucrose diffuses down conc gradient into companian cells via facilitated diffusion * active transport of hydrogen ions occurs from companian cells into spaces within cell walls (using energy) * establishing conc gradient H+ move down conc gradient via carrier proteins into the sieve tube elements * co transoirt of sucrose with H+ions occurs via protein co transporters to transport sucrose into sieve tube element

Question 45

explain the source to sink model

Answer 45

at source cell-photosynthesising cell glusoce/surcrose lowers water potential of source cell. water enters via osmosis. at sink cell-respiring cell is using up sucrose has more positive water potential. water leaves the sink cell via osmosis. this increases hydrostatic pressure in source cell and decreases hydrostatic pressure in sink cell. source cell has higher hydrostatic pressure so the solution is forced towards sink cell via phloem