Exchange and Transport

Question 1

Describe what happens when a person inhales

Answer 1

1. Diaghram flattens and external intercostal muscles contract
2. this causes ribs to move up and out
3. volume in lungs increases and pressure decreases
4. air moves into lungs down pressure gradient

Question 2

why can’t insects directly exchange gases between themselves and the environment

Answer 2

they have exoskeletons which are impermeable and waterproof

Question 3

How are unicellular organisms e.g amoeba adapted for gas exchange

Answer 3

they have a very large surface area to volume ratio
so they use cell membrane as an exchange surface

Question 4

when are the internal intercostal muscles used

Answer 4

during exercise due to forced exhalation

Question 5

What happens when a person exhales

Answer 5

1. External intercostal muscles relax so diaphragm becomes dome shape
2. volume decreases pressure increases
3. so air moves out due to pressure gradient

Question 6

describe adaptations of insect gas exchange

Answer 6

spiracle opens and closes to allow gases to diffuse and prevent water loss.
trachea is lined with chitin which helps keep spiracle open
tracheoles are moist so gases dissolve which increases diffusion rate

Question 7

Describe steps of small insect gas exchange

Answer 7

Oxygen moves in through spiracle.
It travels down trachea which is lined with rings of chitin, through the air sac and into the tracheoles.
Oxygen travels directly to cells.
carbon dioxide leaves opposite way

Question 8

How can large insects draw more air in?

Answer 8

by abdominal contractions to pump air sac as pressure gradient is created by contracting and opening air sac
volume increases pressure decreases SO AIR PULLED IN from atmosphere

Question 9

Describe fish gill structure

Answer 9

Gas exchange occurs in the gills.
Each gill has 2 gill filaments
Gill filaments are covered in folds called lamella

Question 10

state diffusion adaptations in fish gill

Answer 10

As water passes through the gills, gas exchange occurs
in lamella the distance between water and blood is only 5 micrometres so faster diffusion
gills provide a VERY LARGE surface area

Question 11

State steps of fish inspiration

Answer 11

Mouth opens
Buccal muscle contracts so buccal cavity drops
Opercular muscle contracts so operculum moves out
Volume increases, pressure decreases so air moves in

Question 12

State fish exhalation steps

Answer 12

Mouth closes
Buccal muscle relaxes so buccal cavity rises
Opercular muscle relaxes so operculum moves in
volume decreases so pressure increases
so water is forced out

Question 13

Describe counter current exchange in fish

Answer 13

Water and blood travel in opposite directions
this maintains a concentration gradient
ACROSS LENGTH OF GILL

Question 14

How are plants adapted for gas exchange

Answer 14

Spongy mesophyll is loosely packed to increase surface area for diffusion
spongy mesophyll is also moist to dissolve gases so increases diffusion rate

stomata opens and closes to allow gases to enter/exit

opening and closing of stomata is controlled by guard cells: if guard cells are flaccid then stomata is closed if guard cells are turgid then stomata is open

Question 15

In fish, when blood enters gills, why does blood pressure reduce

Answer 15

capillaries are narrow so they have small lumen so b.p automatically reduces

smaller lumen size means increase in pressure but decrease in speed

Question 16

What are disadvantages of single circulation

Answer 16

Gas exchange is much slower
Less oxygen is delivered to respiring cells

Question 17

Why are fish fine with a single circulatory system

Answer 17

They don’t need to regulate a steady body temperature
Their level of activity is much lower so oxygen and glucose doesn’t need to be delivered as rapidly.

Question 18

Why do mammals need a double circulatory system

Answer 18

Their level of activity is very high so O2 and glucose needs to be delivered rapidly and CO2 and urea needs to be got rid of
They need to maintain a steady body temperature so blood travels at high pressure to all respiring cells around body

Question 19

What do mammals use as well as diffusion

Answer 19

because mammals have a low surface area to volume ratio, diffusion doesn’t produce enough oxygen.
So they use specialist exchange systems eg mass flow/transport

Question 20

Describe mass flow/mass transport

Answer 20

transports oxygen in 1 direction over a larger distance

Question 21

Compare mass transport with diffusion

Answer 21

Mass transport is faster, happens over a larger distance, happens in 1 direction and is an active method (requires energy)
Diffusion is slower, happens over smaller distance, transports both ways and is passive

Question 22

What are advantages of mammalian circulation

Answer 22

Deoxygenated and oxygenated blood don’t mix
Oxygenated blood is delivered at high pressure to all respiring cells

Question 23

How are capillaries adapted for diffusion

Answer 23

Capillaries have a very small lumen so only 1 red blood cell can go at a time
SO blood flow is slower SO diffusion happens for longer SO more oxygen diffuses into RBC

Question 24

How are arteries adapted

Answer 24

Endothelium is thin and smooth to reduce friction so blood flows easily
Elastic and muscle layers expand to prevent artery tearing under high pressure
Muscle layer also contract to provide a constant flow of blood

Question 25

How are veins adapted

Answer 25

Have valves to prevent backflow

Question 26

What is tissue fluid and what substances are found in it

Answer 26

Tissue fluid is a medium by which exchange happens. Glucose, oxygen, amino acids, fatty acids are delivered to cells Carbon dioxide, urea and water removed from cells

Question 27

What is osmotic/oncotic potential

Answer 27

its the pull on water a solute has towards it

Question 28

Describe tissue fluid formation

Answer 28

Heart pumps and lumen size decreases so hydrostatic pressure increases and becomes higher than oncotic. Causes ultrafiltration - where tissue fluid is forced out of fenestrations (pores) in capillary due to high hydrostatic pressure tissue fluid bathes around cells and gas exchange occurs glucose, oxygen, amino acids and fatty acids diffuse in AND co2 urea and water diffuse out

Question 29

describe return of tissue fluid

Answer 29

when tissue fluid leaves blood, plasma proteins in blood lower water potential of blood plasma proteins keep oncotic pressure the same but because lumen size gets bigger, hydrostatic pressure decreases so oncotic pressure is higher so water moves back in from tissue to blood by osmosis

Question 30

give adaptations for red blood cells

Answer 30

they have a biconcave shape which gives large surface area for diffusion don't have membrane bound organelles eg nucleus so more haemoglobin can fit SO more oxygen can bind to haemoglobin they are only 7micrometres and capillaries are 8 micrometres so 1 at a time so longer diffusion

Question 31

what is haemoglobin and describe its structure

Answer 31

it's a quaternary globular protein (has 4 polypeptide chains and is spherical) each polypeptide chain has a haem group haem group is iron containing

Question 32

what is an additional group in a quaternary protein called

Answer 32

prosthetic group eg haem group in haemoglobin

Question 33

what is loading and unloading in terms of oxygen

Answer 33

when oxygen binds to haemoglobin it loads when oxygen dissociates from haemoglobin its been unloaded

Question 34

where does oxygen load and unload at and why

Answer 34

oxygen loads at lungs because there is a high partial pressure of oxygen oxygen unloads at respiring cells because there is a low partial pressure of oxygen due to it all being used up in aerobic respiration

Question 35

what does oxygen and haemoglobin bind to form and when do they bind

Answer 35

they bind at partial pressures (different concentrations) to form oxyhaemoglobin

Question 36

describe generally an oxygen dissociation curve

Answer 36

the 1st molecule finds it hard to bind and load but once it does, the haemoglobin undergoes a conformational change this makes it easier for the 2nd and 3rd oxygen molecule to bind but 4th finds it difficult as haemoglobin is becoming saturated

Question 37

Describe control of cardiac cycle

Answer 37

1. sinoatrial node initiates heartbeat 2. a wave of excitation generated by SAN spreads through atrial walls. Atria contracts 3. Atrioventricular node recieves wave of excitation. A delay caused by AVN allows separation of atrial and ventricular systole. 4. From AVN, wave of excitation passed down bundle of his, down septum and along purkinje fibres in walls of ventricle from base up. 5. Ventricles contract from base (apex) upwards

Question 38

give the equation for cardiac output

Answer 38

cardiac output = heart rate x stroke volume

Question 39

how can heart rate be calculated from a pressure graph

Answer 39

by measuring time taken for 1 cardiac cycle using: heart rate (beats per min) = 60/cycle time

Question 40

what is the effect of cardiac output increasing when the body exercises

Answer 40

oxygen + glucose can get to muscles faster carbon dioxide and lactate can be carried away from muscles faster

Question 41

Explain how carrier proteins are used to transport molecules by active transport

Answer 41

1. Carrier protein binds to molecule to be brought into cell 2. ATP enables protein to change shape 3. Carrier protein releases molecule on other side 4. Proteins are highly specific so can only transport 1 molecule 1 way

Question 42

What is the enzyme used to form ATP? Name what molecules ATP is formed from.

Answer 42

ATP synthase is used to form ATP from ADP + Pi

Question 43

What is the enzyme used to break down ATP? Name what it's broken down into.

Answer 43

ATP hydrolase breaks down ATP into ADP + Pi

Question 44

Draw and label a molecule of ATP

Answer 44

Has 3 phosphate groups on left Pentose sugar in middle Base on the right

Question 45

Give definition of active transport

Answer 45

Transport of substances against conc gradient (L to H) Requires energy in the form of ATP Requires carrier proteins

Question 46

Give the equation to calculate water potential

Answer 46

Water potential = turgor pressure + osmotic potential

Question 47

What is passive transport?

Answer 47

Diffusion across a cell membrane and doesn't require any energy

Question 48

Describe simple diffusion

Answer 48

For very small molecules e.g oxygen, CO2, H2O High to low conc Passive as no energy required

Question 49

Describe facilitated diffusion

Answer 49

Transport proteins are needed to transport larger molecules. Channel proteins used for charged particles e.g Mg2+ High to low conc Passive as no energy required

Question 50

Describe how carrier proteins transport large molecules e.g glucose

Answer 50

1. The (glucose) molecule is complimentary to the binding site of carrier protein. 2. When (glucose) molecule binds, it causes carrier protein to change shape 3. (glucose) molecule is sent out other side of membrane

Question 51

How do molecules know which carrier/channel protein to go to?

Answer 51

Due to glycoproteins which are used for cell recognition

Question 52

describe the bohr affect

Answer 52

In Hb, when CO2 binds, it turns into carbonic acid which lowers pH BUT low pH can denature Hb as it's a protein so an enzyme turns carbonic acid into hydrogen carbonate ions and H+ ion H+ binds to Hb and due to this binding, oxygen is disocciated.

Question 53

why does fetal haemoglobin have a higher affinity than adult haemoglobin?

Answer 53

because more oxygen needs to load for the growth of a baby

Question 54

give similarities and differences in structures of haemoglobin and myoglobin

Answer 54

S: both are globular proteins D: haemoglobin has 4 polypeptide chains whereas myoglobin has only 1. Haemoglobin has 4 haem groups, myoglobin only has 1

Question 55

give similarities and differences between functions of haemoglobin and myoglobin

Answer 55

S: both carry oxygen D: Hb carries O2 from lungs to body tissues but myoglobin stores O2 in muscle tissue Myoglobin has a higher affinity for O2 than Hb but Hb affinity is lower as its influenced by O2, CO2 concentration

Question 56

explain how a blood clot forms

Answer 56

1. when thromboplastin comes in contact with collagen, its released 2. thromboplastin causes prothrombin to be converted into thrombin 3. thrombin causes fibrinogen to be converted into fibrin (insoluble) 4. so it forms a mesh

Question 57

what are the risk factors associated with Cardiovascular disease

Answer 57

- smoking - age, gender - diet - family history

Question 58

Describe factors affecting transpiration rate

Answer 58

Temperature: increase in temp means increase in transpiration as water molecules GAIN KINETIC ENERGY so more evaporation Air flow: increased air flow means increased transpiration to maintain concentration gradient as water moves out into atmosphere Humidity: increase in humidity decreases transpiration as concentration gradient is smaller Light: increased light increases transpiration as stomata open to let CO2 in for photosynthesis BUT WATER LEAVES AT THE SAME TIME

Question 59

How are cacti/xerophytes adapted to decrease transpiration

Answer 59

low surface area as instead of leaves they have spines SO decreases transpiration as less stomata sunken stomata increase humidity and decreases transpiration

Question 60

describe the stages of cardiovascular disease that leads to athersclerosis

Answer 60

1. smoking/high bp/old age causes damage to endothelilal lining. This causes an inflammatory response so an influx of leukocytes (WBCs) move into artery wall. 2. damage to endothelium causes cholesterol to build up in artery wall. Leukocytes + fatty deposits = atheroma IN artery wall. Artheroma reduces lumen size, reducing blood flow, reducing glucose and O2 transport. 3. atheroma collects calcium, becoming calcified which hardens artery wall. Hardening is called athersclerosis. Causes it to lose its elasticity. 4. artery wall swells due to loss of elasticity and blood still flowing under high pressure. Swelling is known as aneurism.

Question 61

what can an athersclerosis stimulate and describe the 2 types

Answer 61

stimulates the blood clotting cascade stationary blood clot is called thrombus. It grows quickly and can block a whole artery. if clot breaks off and travels around blood stream, it is called embolus

Question 62

what is a myocardial infarction and what is it caused by

Answer 62

its a heart attack. caused by athersclerosis in coronary artery. If the artery becomes blocked, the heart tissue is starved of oxygen resulting in ischaemia (cell death)

Question 63

what is a stroke

Answer 63

stroke is atherosclerosis in the brain artery. Brain tissue is incapable of anaerobic respiration so infarction quickly kills cells

Question 64

describe xylem tissue and it's role in transport

Answer 64

composed of dead cells forms long, hollow tubes cell walls contain lignin which makes xylem strong so they dont collapse under pressure used to transport water and mineral ions up the plant

Question 65

describe structure of phloem tissue and its role in transport

Answer 65

composed of seive cells which form long columns with holes in end walls (seive plates) cytoplasm is moved to edge of cell to allow for sucrose transport. seive cells have no nuclei or other organelles

Question 66

what are companion cells connected to seive cells by and what do they provide the seive cells with

Answer 66

connected by plasmodesmata provides seive cells with protein, ATP, and other nutrients

Question 67

how is water moved through symplast pathway

Answer 67

water is absorbed into root hair cells by osmosis down w.p gradient cytoplasm of all the cells in root are connected by plasmodesmata so water moves through epidermis using these

Question 68

how does water move using the apoplast pathway

Answer 68

water moves using the cell walls cell walls are fully permeable so water moves by diffusion NOT OSMOSIS because there's no partially permeable membrane apoplast pathway stops at endodermis because of waterproof casparian strip sp water crosses cell membrane by osmosis and enters symplast pathway to go to xylem.

Question 69

explain the cohesion - tension model

Answer 69

xylem vessels form continous pipes from roots to leaves water vapour in leaves diffuses from spaces in spongy mesophyll thru open stomata (TRANSPIRATION) water loss causes low pressure in leaves so water is sucked up stem to replace it as it evaporates due to cohesion between water molecules, they form many H bonds with each other so as 1 H2O molecule leaves xylem, it pulls another behind it.

Question 70

explain movement of sugars through phloem tissue

Answer 70

1. H+ ion in companion cell moves out using carrier protein by active transport. This creates a conc gradient. 2. so H+ ions move back into cell using cotransport protein. H+ ions take sucrose with it into cell. Because H+ gradient is always being maintained sucrose is constantly going into cell so 100%. 3. a carrier protein moves sucrose out of companion cell + into phloem by facilitated diffusion as its a large molecule. 4. sucrose conc is always maintained due to FLOW and phloem is bidirectional so when 1 sucrose enters phloem, it goes straight away. 5. sucrose transport into phloem lowers water potential. 6. so water moves from higher w.p in xylem to lower w.p in phloem down w.p gradient by osmosis. 7. water moving into phloem increases pressure but up/down phloem the pressure is lower. 8. pressure gradient causes sucrose to move down conc gradient 9. sucrose is moved into sink using carrier protein by facilitated diffusion. Sink is storage area for starch + is located in areas that use starch for aerobic respiration (shoots +roots) 10. removed sucrose increases w.p so xylem has lower w.p now. 11. so water moves by osmosis from phloem to xylem down w.p gradient.

Question 71

what are strengths of mass flow hypothesis

Answer 71

- explains the pressure gradient and is supported by evidence: when phloem is cut, sap oozes out showing a pressure gradient. phloem sap has high pH as H+ are actively transported out of cell ATP is also present in phloem seive elements as its required for active transport of H+ -explains directional flow as explains how substances move from source to sink

Question 72

what are weaknesses of mass flow hypothesis

Answer 72

- doesnt explain how phloem can transport substances in both directions (bidirectional)