Mass Transport Systems

Question 1

Why do humans require transport system?

Answer 1

-low surface area to volume ratio to diffuse substance and remove waste such as urea and carbon dioxide
-the transport system can carry raw materials from specialised organs to body cells and carry waste away

Question 2

What is mass transport?

Answer 2

The bulk movement of substances in a fluid involving a mechanism of moving the fluid around the body

Question 3

What does mass transport help to do?

Answer 3

-move substances quickly from in exchange surface to another
-maintain diffusion distance/gradients at a surface
-ensure effective cell activity by keeping the immediate fluid environment of cells within a metabolic range

Question 4

Name the features within a circulatory system

Answer 4

-liquid transport medium which can readily dissolve substances due to presence of water
-vessels to carry transport medium
-pumping mechanism to move the medium around the body

Question 5

What are the features of a closed circulatory system?

Answer 5

-transport medium enclosed in vessels
-blood pigments
-heart pumps blood under pressure
-blood pumped into small vessels until it can diffuse out
-volume of blood can be adjusted

Question 6

What is the difference between a single and double circulatory system?

Answer 6

-singles have a heart with 2 chambers and so blood flows through heart once
-doubles have a heart with 4 chambers so blood flows through heat twice

Question 7

What are the advantages of a double circulatory system?

Answer 7

-maintain body temperature
-increases pressure and speed of oxygenated blood to tissues
-as blood travels through lungs pressure decreases
-one capillary network so high pressure

Question 8

Types of capillary networks from the aorta are called…..

Answer 8

Hepatic artery to the liver
Renal artery to the kidneys

Question 9

What is transported in the blood?

Answer 9

Glucose,ions,amino acids,oxygen,albumin,platelets,fibrinogen

Question 10

What are the 3 main components of the structure of a blood vessel and their jobs?

Answer 10

Smooth muscle layer- contracts to control the flow of blood in arteries,arterioles and veins
Elastic layer- vessel can stretch and recoil in arteries,arterioles and veins
Endothelium- thin inner lining which is smooth to reduce friction in all types of blood vessel

Question 11

Describe the flow of blood through the different types of blood vessels.

Answer 11

First in the arteries then into the arterioles which branch of forming a network contracting and restricting controlling blood flow depending on the demand into the capillaries where after exchange deoxygenated blood flows into the venules joining the veins back to the heart

Question 12

Describe the structure and function of an artery

Answer 12

-carries oxygenated blood
-small lumen so has high pressure
-pulse can be felt

Question 13

Describe the structure of an arterioles

Answer 13

-less elastin and more smooth muscle
-vasoconstriction of arterioles reduce blood entering the capillaries

Question 14

Describe the structure and adaptations of a vein

Answer 14

-carry deoxygenated blood under pressure
-no pulse felt
-medium size

Adaptations:
-valves maintain flow
-larger near active muscles for contractions to push the blood
-breathing movements move blood in chest and abdomen
-when skeletal muscles contract they compress veins helping to increase pressure and push blood against gravity

Question 15

Describe the structure of a capillary

Answer 15

-diameter of a red blood cell
-site of substance exchange
-short diffusion pathway close to cell which is one cell thick
-gaps called fenestrations between endothelial cells allow for diffusion
-large number increases SA
-larger cross section than arterioles to decrease flow rate for more diffusion time

Question 16

comparison of veins to arteries

Answer 16

-veins blood towards in arteries away from heart
-narrow lumen with high pressure in artery
-wider lumen and lower pressure in vein
-thick walls in artery but thinner walls in veins
-folded endothelium in artery so it can stretch and recoil
-valves in veins

Question 17

describe the pressure changes of blood flow throughout the body

Answer 17

-flows from high to low pressure
-vena cava has the lowest pressure
-highest pressure is in the aorta after ventricular contraction
-blood looses pressure as it moves along vessels from aorta due to branching increasing lumen and friction

Question 18

Why does the blood pressure fluctuate in the arteries?

Answer 18

elastic fibres stretches when flow is at high pressure and recoils at lower pressure helping to even out the change

Question 19

what is tissue fluid?

Answer 19

-formed by blood plasma which leaks from capillaries
-surrounds cells in tissue providing them with oxygen and nutrients

Question 20

How is tissue fluid moved around?

Answer 20

• via mass flow down a pressure gradient
  -there is a net outflow at the arterial end of capillary due to higher bp creating hydrostatic pressure

Question 21

What is the lymph?

Answer 21

-colourless fluid containing high amounts of lipids that passes through lymphatic system passing into blood at the vena cava.
-composition similar to blood plasma but more lipids and less oxygen and nutrients

Question 22

What are the semi lunar valves

Answer 22

Found between aorta and pulmonary artery to prevent backflow

Question 23

Name 4 features of the heart specific to its function

Answer 23

-mainly cardiac muscle which contracts in voluntary
-myogenic
-muscle made of cells that are connected by cytoplasmic bridges which enables electrical impulses to pass through the tissue
-large no. of mitochondria and myoglobin and oxygen binding protein molecule

Question 24

What are the 3 stages of the cardiac cycle?

Answer 24

1- Arterial systole
2- Ventricular systole
3- Diastole

Question 25

What are the function of the valves in the heart?

Answer 25

-prevent back flow of blood -controlled via changes in pressure -high pressure causes opening

Question 26

Describe atrial systole

Answer 26

-ventricles relax and atria contract -increased pressure due a decreased volume which causes valve to open -blood flows into ventricles

Question 27

Describe ventricular systole

Answer 27

-atria relax and ventricles contract -increased pressure due to decreased volume which causes AV valves to close -SL valves open and blood enters pulmonary artery

Question 28

Describe diastole

Answer 28

-both atria and ventricles relax -increased pressure in arteries so SL valves relax -blood enters atria and pressure increases causing AV valves to open and blood flows into ventricle

Question 29

Describe atrial pressure during the cardiac cycle

Answer 29

-Always relatively low as the thin walls of the atria cannot create much force -Pressure is highest when they are contracting (around 1.5 kPa) -Pressure drops when the left AV valve closes and its wall relaxes (<0 kPa) -Pressure increases gradually as the atria fills with blood (around 1 kPa) -Slight drop in pressure as the AV valve opens as some blood moves into the ventricle

Question 30

Describe ventricular pressure during the cardiac cycle

Answer 30

-Low at first and gradually increases as the ventricles fill with blood as the atria contracts • Left AV valve closes and pressure rises dramatically as the thick walls of the ventricle contracts (›15 kPa) • When the pressure rises above aortic pressure blood is forced into the aorta past the semilunar valves • Pressure falls as the ventricles empty («0 kPa)

Question 31

Describe aortic pressure throughout the cardiac cycle

Answer 31

-Rises when the muscle in the wall of the ventricles contract as blood is forced through the aorta (›15 kPa) -This recoil produces a temporary rise in pressure at the start of the relaxation phase -Gradually falls (never below 12 kPA as the elasticity of the walls creates a recoil action to constantly deliver blood)

Question 32

What is haemoglobin?

Answer 32

-globular quaternary protein -4 polypeptide chains each with a haem group which contains an Fe+ ion making the pigment red -can bind on up to 4 oxygens

Question 33

State the adaptations of red blood cells

Answer 33

-biconcave shape gives large surface area to volume ratio -flat and thin so short diffusion pathway -no nucleus so can store increased amounts of haemoglobin

Question 34

Explain oxygen loading and unloading

Answer 34

Oxygen loading is the process of which oxygen assosiates to the haemoglobin forming oxyhaemoglobin (usually in the lungs) Oxygen unloading is the process of which oxygen disassociates forming haemoglobin (usually in respiring cells)

Question 35

What 3 conditions does haemoglobins oxygen affinity depend on?

Answer 35

-partial pressure of oxygen -haemoglobin saturation -partial pressure of carbon dioxide

Question 36

How does the partial pressure of oxygen affect its affinity to haemoglobin?

Answer 36

the higher the concentration of oxygen the higher the pO,and as pO increases haemoglobins affinity increases. This means: haemoglobin will have a higher affinity for O, in oxygen-rich areas (e.g lungs) where there is a high po., promoting oxygen loading. haemoglobin will have a lower affinity for O, in oxygen-starved areas (e.g respiring tissues) where there is a low po., promoting oxygen unloading. This ensures oxygen is always picked up by red blood cells in the lungs and released in respiring cells where it is needed

Question 37

How does haemoglobin saturation affect oxygens affinity?

Answer 37

- as each oxygen molecule binds it changes the shape of the haemoglobin in a way that makes it easier for further oxygen molecules to bind (this is known as co-operative binding) -However, as the saturation of haemoglobin increases it becomes harder for the final oxygen molecules to bind

Question 38

How does the partial pressure of carbon dioxide affect hemoglobins affinity for oxygen?

Answer 38

-When pCO,is high (e.g in respiring tissues) oxygen dissociates from haemoglobin more easily, this allows more oxygen to be unloaded to cells during intense activity, - an increase in carbon dioxide production leads to a decrease in blood pH as it reacts with water to form carbonic acid. -The low pH causes the tertiary structure of the haemoglobin to be altered, decreasing its affinity for oxygen so increasing the dissociation of oxygen. -This ensures that where there is the most respiration occurring (more CO, produced) more oxygen will be released to help maintain the level of metabolic activity.

Question 39

How is the Bohr effect shown on the disassociation graph?

Answer 39

-an increase in CO, or a decrease in pH shits the normal oxygen dissociation curve to the right. -It stays the same shape, but it shows that for the same po, the saturation of blood with oxygen is lower as more oxygen is being released from the haemoglobin.

Question 40

Describe how the haemoglobin in the foetus has different affinity to oxygen

Answer 40

-higher affinity so the curve is shifted to the left -Oxygen binds to foetal haemogiobin more easily and is more reluctant to dissociate. -This is important, as foetal haemoglobin needs to "steal" oxygen away from the mother's haemoglobin when they pass in the placenta. -If the foetal and maternal haemoglobin had the same affinity for oxygen, there would be no incentive for the oxygen to switch from the maternal blood to foetal blood.

Question 41

Describe how haemoglobins affinity for oxygen is changed in organisms living in low oxygen environments

Answer 41

-higher affinity so graphic shifts to the left -Organisms can live at high altitudes where there Is lower atmospheric pressure so low po, -This means there is less oxygen available so need to be able to load more oxygen at lower po, to make sure it is absorbed

Question 42

Describe how haemoglobins affinity to oxygen is changed in organisms with a high surface area to volume ratio or metabollic rate

Answer 42

-Small mammals that have a higher SA than larger mammals so will lose heat more quickly so they have a higher metabolic rate to help maintain their body temperature. Other high activity organisms will also have a higher metabolic rate. -Higher metabolic rate = more respiration = greater oxygen demand. This means the organisms need haemoglobin with a lower affinity for oxygen as they need it to easily unload oxygen to meet their high oxygen demand and allow a faster respiration rate.

Question 44

Describe the features of the lymphatic system

Answer 44

-use muscle contractions to help flow -valves -lymphnodes produce lymphocytes and contain phagocytes to remove bacteria from lymph -subclavian glands to enter the blood at

Question 45

What is the hydrostatic pressure at the arterial and ventless end of the capillary?

Answer 45

Arterial end- high hydrostatic pressure so lower oncotic pressure so fluid moves out of capillary Venule end- lower hydrostatic pressure so higher oncotic pressures so fluid absorbed in capillary

Question 46

What is the equation for filtration pressure?

Answer 46

Higher pressure - lower pressure

Question 47

Describe the steps for the formation of tissue fluid

Answer 47

1) at the arteriole end the hydrostatic pressure inside the capillary is greater than the tissue fluid and greater than osmotic pressure 2)the difference in hydrostatic pressure forces the fluid contains small molecules through fenestrations causing tissue fluid to form 3)red blood cells platelets and plasma proteins remain in blood as they are too large to leave 4)exchange occurs between tissue fluid and cells via diffusion, facilitated and active transport of oxygen and nutrients and waste leaves cells entering the tissue fluid 5)as fluid leaves capillary at arteriole end it reduces hydrostatic pressure and bp at the venule ends of the capillary is greater 6)as water leaves capillary but plasma remains this lowers the wp of the blood so it is lower than the wp in the tissue fluid and venule ends of capillary 7)osmotic pressure is higher than hydrostatic pressure at venule ends of capillary so water moves in via osmosis carrying carbon dioxide and waste 8)any excess tissue fluid that is not reabsorbed is returned and collected into the lymphatic system to be transported to circulatory system

Question 48

What is cardiac muscle?

Answer 48

muscle made up of cardiomyotypes which are specialised myogenic cells meaning they contract without a nervous system

Question 49

What are atrioventricular valves?

Answer 49

Found between atrium and ventricle and only open one way to prevent the back flow of blood when vessels contract They allow pressure to build in ventricles as they shut when pressure exceeds atrium pressure

Question 50

Why do plants need water?

Answer 50

-photosynthesis -transport minerals -maintain structure by keeping cells turgid -regulate tempreture

Question 51

Why do plants need nitrates and phosphates?

Answer 51

nitrates- for DNA, amino acids, chlorophyll phosphates- DNA, ATP

Question 52

State the 4 steps in the water transport in plants

Answer 52

1. absorption in roots 2. movement of water from root to xylem 3. movement into xylem 4.cohesion tension theory

Question 53

Explain the absorption of water into the roots

Answer 53

-water is absorbed via osmosis into the root hair cell -mineral ions are absorbed via active transport and dissolved in water

Question 54

How are root hair cells adapted?

Answer 54

-large surface area -short diffusion distances -many carrier protiens -minerals to maintain low wp

Question 55

State the 3 pathways of which water can move from the root to the xylem

Answer 55

symplast pathway vacuolar pathway apoplast pathway

Question 56

Explain the symplast pathway

Answer 56

-through cytoplasm -flows via plasmodesmata -each cell further away from the root as lower wp so water drawn up -slower pathway

Question 57

Explain the vacuolar pathway

Answer 57

-moves through cytoplasm and vacuole

Question 58

Explain the apoplast pathway

Answer 58

-through cell wall and intracellular spaces (non living) between cellulose fibres -pulled up plant due to cohesion and tension -faster route

Question 59

Explain the movement of water into the xylem

Answer 59

-water via apoplast pathway reaches endodermal cells and is blocked by waxy caspirian strip -water forced in to cytoplasm by cell membrane -means all water passes through partially permeable membrane removing any toxins before entering living part of plant

Question 60

Describe the xylem structure

Answer 60

-elongated tubes of dead cells -no end walls and hollow lumen allowing for continuous flow -lignin that forms walls is strong preventing collapse and is waterproof preventing adhesion -gaps in lignin allow for water to leave/enter vessel -no cytoplasm

Question 61

Define cohesion

Answer 61

attraction between like molecules

Question 62

Define adhesion

Answer 62

attraction between non-like molecules

Question 63

Explain how water potential effects transpiration

Answer 63

-movement of water increases and transpiration increases -water evaporates through stomata moving down a wp gradient as there is less water than atmosphere than in leaf

Question 64

State and explain the 4 steps to the cohesion tension theory

Answer 64

1. water evaporates from mesophyll due to heat from the sun and leaves cells with a negative water potential causing more water to enter via osmosis 2.this increase in water tension pulls more water into the leaf known as transpiration pull 3.water is cohesive so as they form hydrogen bonds they undergo adhesion this pulls the whole column of water in the xylem up from mesophyll tissues in the leaves 4.water enters stem through roots

Question 65

Evidence for the transport in water in plants

Answer 65

1. day time transpiration is at its greatest and the adhesion of water to xylem causes tension narrowing the xylem 2. night time transpiration is at its lowest and less tension so diameter increases 3.Trunk damage and broken xylem water does not leak prooving it is not due to pressure and when air enters tree it cannot draw water up as column has broken

Question 66

Describe the heart.

Answer 66

A muscular organ that lies in the thoracic clarity behind the sternum.

Question 67

Explain why the ventricles have much thicker muscle wall compared to atrium

Answer 67

Has two contract strongly to pump blood some distance to the rest of the body and right side of the lungs.

Question 68

What is translocation?

Answer 68

-process where assimilates are transported from source to sink via the phloem in a bidirectional way which is an active process

Question 69

Why is glucose converted to sucrose for transport?

Answer 69

less likely to be metabolised or oxidised as it is much less reactive

Question 70

Describe the structure of the phloem

Answer 70

-elongated sieve tubes with no nuclei or organelles just as small amount of cytoplasm to maximise space -each tube has a companion cell with organelles and mitochondria for ATP -end walls with holes called sieve plates let solutes pass through

Question 71

Give some examples of sources

Answer 71

-roots -meristems -storage locations

Question 72

Explain what happens at the source during mass flow

Answer 72

-high sucrose concentration so sucrose is moved into sieve cells via active loading decreasing the water potential of the phloem so water moves in from the xylem via osmosis. This causes an increased volume of water and therefore increased hydrostatic pressure.

Question 73

Explain what happens at the sink during mass flow

Answer 73

-low sucrose concentration as sucrose moves out of the sieve tubes down a concentration gradient as cells convert it to glucose this increases the water potential of the phloem so water moves back into the xylem via osmosis causing a reduction in pressure due to a decrease in volume

Question 74

Describe the overall mass flow of solutes around the plant

Answer 74

hydrostatic pressure gradient between source and sink causes a continuous flow and the concentration gradient of sucrose in created due to the constant need for glucose in respiring cells and storage.

Question 75

Explain the process of active loading

Answer 75

-H+ ions actively pumped out of the companion cells using ATP into the source creating a concentration gradient -H+ ions can diffuse back down a concentration gradient through transport proteins which require sucrose molecules to be transported -this increases the concentration of sucrose in the companion cells which then diffuse into the sieve tubes

Question 76

Explain one advantage of the capilliaries being narrow

Answer 76

-short diffusion distance of blood -large surface area -increases the rate of diffusion

Question 77

What factor limits the minimum internal diameter of a capillary lumen?

Answer 77

thickness/width of blood cell wall

Question 78

Explain why the pressure in a dogs ventricle is related to the thickness of the wall

Answer 78

-the thicker wall enables the ventricle to contract -the thicker the muscle the grater the pressure as internal volume is decreased

Question 79

Explain how the pressure in a dogs ventricle is related to the blood flow in the aorta

Answer 79

-as pressure in ventricle increases blood flow to aorta increases -semi lunar valves open due to the increased pressure

Question 80

Explain how the changes in shape of haemoglobin result in the s-shaped graph

Answer 80

The first oxygen is difficult to initially bind however this causes the later oxygen molecules to bind much more easily due to cooperative binding which makes it easier to bind except for the last oxygen

Question 81

State how the change in a babies haemoglobin from fetal to adult is an advantage for the baby.

Answer 81

-adult haemoglobin has a lower affinity for oxygen at low partial pressures so the oxygen unloads more easily at respiring cells

Question 82

Explain how cardiac output can remain the same even when resting heart rate decreases

Answer 82

increase in ventricular volume

Question 83

Why is the water potential of the blood plasma more negative at venule end than arteriole end?

Answer 83

water has left the capillary meaning many blood proteins are present as they cannot leave the blood vessel creating a negative water potential

Question 84

Explain why people with higher ventricular blood pressure have a higher buildup of tissue fluid

Answer 84

the increase in pressure forces more fluid out of the blood however not all the fluid can be returned due to pressure and the lymphatic system cannot drain all the fluid away

Question 85

What is the equation for the percentage saturation of haemoglobin with oxygen equation?

Answer 85

oxygenated Hb / maximum saturation X 100

Question 86

State the way in which the structure of the aorta is related to its function

Answer 86

Elastic tissue to allow stretching / recoil / smooths out flow of blood / maintains pressure; 2. Elastic tissue stretches when ventricles contract OR Recoils when ventricle relaxes; 3. Muscle for contraction / vasoconstriction; 4. Thick wall withstands pressure OR stop bursting; 5.Smooth endothelium reduces friction; 6.Aortic valve / semi-lunar valve prevents backflow.

Question 87

Explain why a small increase in and rate of flow in the aorta occurs and its importance

Answer 87

occurs due to the elastic recoil of the aortic wall which allows for blood flow and pressure to be maintained

Question 88

Evidence towards mass flow

Answer 88

-when sieve tubes are cut sap is released due to being under pressure -excretion of sap from an aphid when it goes to the phloem to feed as sap flows into the body demonstrating pressure as it flows faster at the top of the plant due to a pressure gradient -electrical potential difference between companion and source cells -downward flow mostly in the day due to photosynthesis -

Question 89

Evidence against mass flow

Answer 89

-sugar travels to many different sinks but not always the first or fastest to one with a higher water potential -sieve plates create a barrier to mass flow

Question 90

Ringing experiment

Answer 90

Remove bark including the phloem -stem above the ring swells with liquid containing a high concentration of sugars and organic substances suggesting an accumulation of sugars in the phloem -some non-photosynthetic tissues below the ring wither and die

Question 91

Tracer experiment

Answer 91

1) grow a plant in radioactive carbon 2)the carbon is incorporated into glucose via photosynthesis 3)traced as it travels through the phloem 4)done by taking cross sections of the plant and x-raying them as film blackens if exposed to radiation

Question 92

Explain the use of a potometer

Answer 92

can be used to measure the rate of transpiration via the uptake of water from a plant and several environmental factors can be changed.

Question 93

Explain how environmental factors effect the rate of transpiration

Answer 93

light- increases the rate as stomata remain open temperature increases so does kinetic energy so therefore transpiration rate increases if less humid the rate increases low carbon dioxide means stomata are open for longer and wider so increases rate wind increases rate as it steepens the gradient