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AQA ALEVEL BIOLOGY P1/P2 > 3. EXCHANGE AND TRANSPORT > Flashcards

3. EXCHANGE AND TRANSPORT Flashcards

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1
Q

How do Microorganisms Obtain Nutrients & Remove Waste?

A
  • by exchange via their surface
  • nutrients (e.g. glucose, oxygen) move in by diffusion via their surface
  • waste (e.g. carbon dioxide) move out by diffusion via their surface
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2
Q

Why are Microorganisms able to perform exchange via their surface?

A
  • have a large surface area to volume ratio
  • have a short diffusion distance
  • have low demand
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3
Q

Why can’t Animals/Plants perform exchange via their surface?

A
  • have a small surface area to volume ratio
  • multicellular (large diffusion distance and high demand)
  • impermeable surface (prevent pathogens entering and reduce water loss)
  • therefore, require specialised Exchange & Transport systems
  • exchange system = increases rate of diffusion of nutrients in and wastes out
  • transport system = deliver nutrients and remove waste from all cells
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4
Q

Why do Fish have Specialised Gas Exchange Systems?

A
  • multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable
  • therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills
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5
Q

Structure of Gills in Fish?

A
  • many gill filaments and gill lamellae = large surface area
  • gill lamellae have a thin wall (short diffusion distance) and are permeable
  • ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains concentration gradient all the way along the gill lamellae
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6
Q

Why do Insects have Specialised Gas Exchange Systems?

A
  • multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)
  • therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System
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7
Q

Structure of Tracheal System in Insects?

A
  • starts with openings on body surface called Spiracles
  • spiracles contain valves, open = gas exchange, closed = prevent water loss
  • spiracles connect to Trachea
  • trachea connect to Tracheoles
  • tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)
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8
Q

How does Gas Exchange occur in Tracheal System of Insects?

A
  • at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion
  • when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
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9
Q

Function of Lungs?

A

site of gas exchange in mammals (oxygen into blood – used in cells for respiration,

-carbon dioxide out of the blood – toxic waste product of respiration

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10
Q

What is Lungs made up of?

A

Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)

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11
Q

Function of trachea, bronchi, bronchioles?

A

transport of air and filter air, (bronchioles also controls amount of air reaching alveoli)

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12
Q

Structure of trachea/bronchi?

A
  • wall made of c-shaped cartilage
  • cartilage is strong so trachea/bronchi do not collapse
  • cartilage is c-shaped to give flexibility
  • lining made of goblet cells and ciliated epithelial cells
  • goblet cells make mucus, which traps pathogens/particles
  • ciliated epithelial cells have cilia, which pushes mucus up and out of lungs
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13
Q

Structure of bronchioles?

A
  • wall made of smooth muscle
  • smooth muscle contracts, lumen narrows, bronchiole constricts
  • (occurs when surrounded by noxious gases – reduces amount reaching alveoli)
  • lining made of goblet cells and ciliated epithelial cells
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14
Q

Adaptation of alveoli?

A
  • millions of tiny alveoli that are folded (large surface area)
  • thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
  • elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)
  • ventilation maintains concentration gradient (high oxygen, low carbon dioxide)
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15
Q

Adaptation of capillaries?

A
  • millions of tiny capillaries (large surface area)
  • thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
  • narrow lumen (increases diffusion time, decreases diffusion distance)
  • circulation maintains concentration gradient (low oxygen, high carbon dioxide)
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16
Q

How O2 moves from the alveoli to the capillaries

A

by simple diffusion passing thru the alveolar epithelium and capillary epithelium

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17
Q

How CO2 moves from capillaries to the alveoli?

A

by simple diffusion passing thru the capillary epithelium and alveoli epithelium

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18
Q

Describe the process of Breathing/Ventilation?

A
  • Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in
  • Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)
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19
Q

Formula for Pulmonary Ventilation?

A
  • PV = tidal volume x ventilation rate
  • tidal volume = volume of air breathed in/out in one breath
  • ventilation rate = number of breaths per minute
  • Pulmonary Ventilation = volume of air breathed in/out per minute
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20
Q

Function of Intestines?

A

site of exchange of digested nutrients in mammals

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21
Q

What is Digestion?

A
  • Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)
  • Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase/Lactase/Sucrase (on lining of small intestine)
  • Proteins into Amino Acids by Endopeptidase/Exopeptidase/Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine)
  • Lipids into Monoglyceride and 2 Fatty Acids by Lipase (in small intestine)
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22
Q

What do Intestine Absorb?

A
  • Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals)
  • Large Intestine absorbs water
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23
Q

Why do Humans/Mammals require a Specialised Transport System?

A
  • multicellular organisms therefore have large diffusion distances and high demand
  • need a transport system to deliver nutrients and remove waste from all cells
  • transport system in humans/mammals called Circulatory System
  • Circulatory System made of heart, blood vessels, blood (heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)
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24
Q

Why is the transport system in mammals called a double circulatory system?

A

the heart pumps twice, the blood goes through the heart twice – generates enough pressure to supply all body cells

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25
Q

Why is the transport system in mammals called a closed circulatory system?

A

blood is transported in blood vessels – helps to maintain pressure and redirect blood flow

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26
Q

Layout of Circulatory System?

A
  • heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart
  • Artery to Arterioles to Capillaries to Venules to Veins
  • Artery/Arterioles carry blood away from the hear (arterioles are small arteries)
  • Capillaries are the site of exchange (nutrients out, waste in)
  • Veins/Venules return blood back to the heart
    (venules are small veins)
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27
Q

Heart?

A
  • job is to pump blood around the body (delivers nutrients to cells and remove waste)
  • made of 4 muscular chambers (2 atria, 2 ventricles)
  • atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body)
  • ventricles thicker then atria (has to pump blood further)
  • left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can generate higher pressure and pump the blood further around the body
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28
Q

Blood vessels of the heart?

A
  • artery takes blood away from the heart, vein returns blood to the heart
  • Vena Cava supplies R atrium (with deoxygenated blood from body)
  • Pulmonary Vein supplies L atrium (with oxygenated blood from lungs)
  • R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs)
  • L ventricle supplies Aorta (oxygenated blood to body)
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29
Q

Job of valves in heart?

A
  • Ensure one way flow of blood, no backflow
  • (blood flows from atria to ventricles to arteries)
  • 2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve
  • AV valve = between atria and ventricles
  • SL valve = between ventricles and arteries
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30
Q

When are AV valves open or closed?

A

Open = pressure in atria greater then pressure in ventricles,
Closed = pressure in ventricles greater then pressure in atria

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31
Q

When are SL valves open or closed?

A

Open = pressure in ventricles greater then pressure in arteries,

Closed = pressure in arteries greater then pressure in ventricles

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32
Q

Describe the processes of the cardiac cycle?

A
  • Filling Stage = atria relaxed, ventricles relaxed, AV valve open, SL valve closed
  • Atria Contracts = the SAN located in the R atrium initiates the heart beat and sends the impulse across both atria making them contract, this pushes all the remaining blood into the ventricles so it becomes full
  • Ventricles Contract = the AVN picks up the impulse, delays it (stops the atria and ventricles contracting at the same time, so the atria empties and the ventricles fill), sends the impulse down the septum in the Bundle of His, then at the apex the impulse goes up both walls of the ventricles in the purkine fibres, so the ventricles contract from the base upwards, pushing the blood up thru the arteries, when the ventricles start to contract the AV valve closes then the SL valve opens and blood leaves the heart
  • Ventricles Relax = the SL valve closes then the AV valve opens and filling starts again
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33
Q

What causes the Heart Sounds?

A
  • when the valves close
  • 1st = AV closes
  • 2nd = SL closes
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34
Q

Formula for Cardiac Output?

A
  • CO = Stroke Volume x Heart Rate
  • stroke volume = volume of blood pumped out of the heart in one beat
  • heart rate = number of beats per minuted
  • Cardiac Output = volume of blood pumped out of the heart in one minute
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35
Q

Coronary Heart Disease and Myocardial Infarction?

A
  • high blood pressure damages lining of coronary artery
  • fatty deposits/cholesterol builds up beneath the lining, in the wall = Atheroma
  • the atheroma breaks thru the lining forming a Atheromatous Plaque on the lining, in the lumen
  • this causes turbulent blood flow
  • a blood clot (thrombus) forms
  • this block the coronary artery
  • therefore less blood flow to the heart muscle
  • less glucose and oxygen delivered
  • the heart muscle cannot respire
  • so it dies (myocardial infarction)
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36
Q

Risk Factors of Cronary Heart Diease?

A
  • Age, gender, ethnicity
  • Saturated fats (increases LDL, LDL deposits cholesterol in the arteries to form atheroma - clogs the arteries)
  • Salts (increases blood pressure – lowers water potential of the blood so it holds the water in the bloodstream)
  • Smoking (nicotine = increase Heart Rate and makes platelets more sticky – blood clot, carbon monoxide = permanently blocks haemoglobin)
  • Obesity and Lack of Exercise
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37
Q

Atheroma & Aneurysm?

A

atheroma weakens wall of artery, blood builds up in the wall, the wall swells then bursts = aneurysm

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38
Q

Role of Arteries/Arterioles?

A
  • generally carry oxygenated blood away from the heart
  • for example, Coronary Artery to heart muscle Hepatic Artery to liver Renal Artery to kidneys
  • exception = Pulmonary Artery carries deoxygenated blood to lungs
39
Q

Role of Veins/Venules?

A
  • generally carry deoxygenated blood back to the heart
  • for example, Coronary Vein from heart muscle
    Hepatic Vein from liver Renal Vein from kidneys
  • exception 1 = Pulmonary Vein carries oxygenated blood back to the heart
  • exception 2 = Hepatic Portal Vein carries deoxygenated blood from digestive system to liver (for filtering)
40
Q

Function of Arteries/Arterioles?

A

carry blood away from the heart so should be able to withstand high blood pressures & maintain high blood pressures

41
Q

Structure of Arteries/Arterioles?

A
  • narrow lumen = maintains pressure
  • lining made of squamous epithelial cells = smooth lining to reduce friction
  • thick wall = withstand pressure
  • elastic tissue in wall,
    ventricles contract – elastic tissue stretches to withstand pressure ventricles relax – elastic tissue recoils to maintain pressure and smooth out flow
  • smooth muscle in wall (particularly in arterioles),smooth muscle contracts – lumen narrows and arteriole constricts smooth muscle relaxes – lumen widens and arteriole dilates
  • collagen in wall prevents artery from tearing
42
Q

Function of Veins/Venules?

A

return blood back to the heart, the blood is under low pressure

43
Q

Structure of Veins/Venules?

A
  • wide lumen = ease of blood flow
  • lining made of squamous epithelial cells = smooth lining to reduce friction
  • thin wall = vein can be squashed by skeletal muscle pushing blood back to the heart
  • valves in lumen = prevents backflow of blood
44
Q

Function of Capillaries?

A
  • site of exchange
  • 3 locations,

With Alveoli, takes in O2 and removes CO2

With Microvilli, takes in glucose/amino acids/monoglyceride and fatty acids/vitamins/minerals

With All Cells, deliver nutrients and remove waste

45
Q

Adaptation of Capillaries?

A
  • many small capillaries = large surface area
  • thin wall, one cell thick, squamous epithelial cells = short diffusion distance
  • pores between cells = allows fluid to move in and out
  • narrow lumen = increase diffusion time and decrease diffusion distance
46
Q

Content of Blood?

A
  • main component = Plasma (fluid)
  • plasma carries,
  • Cells = red blood cells, white blood cells, platelets
  • Solutes = nutrients, waste, protein
47
Q

How does exchange occur between Capillaries & All Cells?

A
  • by mass flow
  • fluid moves out of the blood in the capillaries carrying the nutrients
  • fluid moves back into blood in the capillaries carrying the waste
  • (fluid in the blood called plasma, fluid surrounding cells called tissue fluid, fluid in lymph system called lymph)
48
Q

How is tissue fluid formed and returned to circulatory system?

A
  • at the start of the capillary (arterial end) there is a build up hydrostatic pressure
  • this pushes fluid out of the capillary via the pores
  • the fluid carries the nutrients with it
  • the fluid surrounds the cells, this is called tissue fluid
  • at the finish of the capillary (venous end) the fluid moves back in by osmosis
  • the capillary has low water potential due to the presence of proteins (too large to move out of capillaries)
  • any excess tissue fluid is picked up by the lymph system and deposited in the vena cava
49
Q

Why does high blood pressure cause accumulation of tissue fluid?

A

increases hydrostatic pressure, so more tissue fluid is formed – not as much can be returned to the circulatory system

50
Q

Why does diet low in protein cause accumulation of tissue fluid?

A

the water potential in the capillary is not as low as normal, so not as much fluid can move back into the capillary by osmosis

51
Q

Blood Pressure changes along the Circulatory System?

A

Arteries =
- highest pressure (connects directly with heart/ventricles)
- pressure fluctuates (increases when ventricles contract
- which causes the elastic tissue to stretch, decreases when ventricles relax
- which causes the elastic tissue to recoil)
- overall decrease in pressure due to friction

Arterioles =
- large decrease in pressure due to increase in total cross-sectional area
(ensures pressure is not to high to damage capillaries)

Capillaries = pressure here is called hydrostatic pressure (decreases due to a loss in fluid)

Venules/Veins = blood under low pressure

52
Q

Job of Red Blood Cells?

A
  • found in humans/mammals (animals)
  • carries haemoglobin
  • haemoglobin carries oxygen
53
Q

Structure of Haemoglobin?

A
  • globular protein (soluble & specific 3d shape)
  • quaternary structure made of 4 polypeptide chains (2α, 2β)
  • each chain carries a haem group
  • each haem group carries Fe2+
  • each Fe2+ carries an O2
  • therefore, each haemoglobin carries 4 lots of O2
54
Q

What is Affinity?

A

the level of attraction haemoglobin has to oxygen (high affinity = strong attraction, low affinity = weak attraction)

55
Q

Role of haemoglobin in oxygen transport?

A
  • haemoglobin has High Affinity in the lungs – due to high partial pressure of oxygen and low partial pressure of carbon dioxide, so haemoglobin loads/associates oxygen in the lungs and becomes saturated (full)
  • the haemoglobin is transported in the blood in the red blood cell
  • at the respiring tissues, haemoglobin has Low Affinity – due to low partial pressure of oxygen and high partial pressure of carbon dioxide, so oxygen is unloaded/dissociated/delivered and haemoglobin becomes unsaturated
56
Q

Relationship between O2 Partial Pressure & Affinity/Saturation of Haemoglobin?

A
  • positive correlation
  • as O2 partial pressure increases, affinity/saturation of haemoglobin increases
  • the correlation is not linear but is curved (produces a s-shaped, sigmoid curve called Oxygen Dissociation Curve)
  • middle portion of ODC has a steep gradient so when respiring tissues change from resting to active and partial pressure of O2 falls, there is a large drop in affinity, so more O2 would be delivered to the respiring tissues
57
Q

Relationship between CO2 Partial Pressure & Affinity/Saturation of Haemoglobin?

A
  • negative correlation
  • as CO2 partial pressure increases, affinity/saturation of haemoglobin decreases
  • this occurs at the site of respiring tissues = the carbon dioxide lowers the pH of the blood, makes the haemoglobin change shape, so oxygen is released, lowering affinity. this shifts the ODC to the right, called the bohr shift. benefit = more oxygen delivered to respiring cells
58
Q

How does a Fetus receive oxygen?

A

from mother’s blood, oxygen dissociates from mother’s haemoglobin and associates with fetal haemoglobin in the placenta – fetal haemoglobin has a higher affinity compared to mother’s haemoglobin

59
Q

Benefit of fetal haemoglobin having high affinity

A

fetal haemoglobin’s ODC will be to the left, it has high affinity – so the oxygen will dissociate from the mother’s haemoglobin and associate with the fetal haemoglobin at the low partial pressures of oxygen in the placenta, so it has enough oxygen for its needs

60
Q

Why do adults not keep with fetal haemoglobin?

A

the high affinity will mean less oxygen will be unloaded at the respiring tissues

61
Q

Affinity of Organisms in a Low Oxygen Environment

A

has a high affinity, curve to the left, therefore it can readily associate oxygen at the low oxygen partial pressures

62
Q

Affinity of Active Organisms?

A

has a low affinity, curve to the right, therefore more oxygen can be unloaded to meet the cell’s demand for more respiration

63
Q

Affinity of Small Organisms?

A

have a large surface area to volume ratio, lose a lot of heat, needs to respire to generate heat, therefore has a low affinity, curve to the right, so unloads enough oxygen for the cells demand of more respiration

64
Q

What are the Exchange & Transport Systems in Plants?

A
  • exchange systems = leaf and root
  • leaf to absorb light and CO2 for photosynthesis
  • roots to absorb water and minerals
  • transport systems = xylem and phloem
  • xylem transports water and minerals
  • phloem transports glucose/sugars
  • xylem transports in one direction from roots to leaves, phloem transports in both directions
65
Q

Job of the Roots?

A
  • absorb water and minerals
  • absorbs water by osmosis
  • absorbs minerals by active transport
  • plants need water for photosynthesis, cytoplasm hydration, turgidity of cells
  • plants need magnesium, nitrate, phosphate (magnesium to make chlorophyll, nitrate to make amino acids, phosphate to make phospholipids/ATP/DNA)
66
Q

Function of the Xylem?

A

transport water and minerals from roots, up the plant, to the leaves

67
Q

Structure of the xylem?

A
  • long continuous hollow tube (no resistance to water flow)
  • narrow lumen
  • wall made out of lignin
  • lignin: strong, waterproof, adhesive
  • wall contains pits/pores (water and minerals can leave)
68
Q

How does water move up the xylem?

A
  • loss of water at the leaves (transpiration)
  • water moves from the top of the xylem into the leaf by osmosis (transpirational pull)
  • this applies TENSION to the column of water in the xylem
  • the column of water moves up as one as the water particles stick together, COHESION
  • this is is the cohesion-tension theory
  • it is supported by capillary action, adhesion and root pressure
  • (capillary action = water automatically moves up narrow lumen of xylem)
  • (adhesion = water particles stick to lignin in wall of xylem)
  • (root pressure = water absorbed at the roots pushes the column of water up slightly by hydrostatic pressure)
69
Q

Why does the diameter of a tree decrease during the day?

A
  • more light and higher temperature
  • increase rate of transpiration
  • increase transpirational pull
  • water pulled up xylem by cohesion-tension
  • because the water particles stick to the wall of the xylem (adhesion)
  • the walls of the xylem are pulled inwards
70
Q

Structure of Leaves?

A
  • upper layer called Upper Epidermis
  • waxy cuticle on upper epidermis (barrier to reduce water loss)
  • beneath the upper epidermis are Palisade Cells
  • palisade cells are were photosynthesis takes places
  • beneath palisade cells are Spongy Mesophyll Cells
  • are loosely packed leaving air spaces to allow ease of gas exchange
  • lower layer called Lower Epidermis
71
Q

Adaptation of palisade cells for photosynthesis?

A
  • located near top of leaf, closer to light
  • large size, large surface area for light
  • thin cell wall, short diffusion distance for carbon dioxide
  • contains many chloroplasts, site of photosynthesis
  • large vacuole, pushes chloroplast to the edge of the cell closer to light
72
Q

Structure of chloroplast?

A
  • organelle for photosynthesis
  • has double membrane
  • contains discs called thylakoids
  • thylakoids contain chlorophyll
  • stack of thylakoids called granum
  • thylakoids surrounded by a fluid called stroma
73
Q

How does Exchange occur in Leaves?

A
  • lower epidermis of leaf contains pairs of cells called Guard Cells
  • when turgid, guard cells form an opening called Stomata
  • gas exchange occurs via the stomata
  • In Day, plant photosynthesises and respires, CO2 moves in for photosysnthesis and O2 moves out (some is used in respiration)
  • At Night, plant only respires, O2 moves in for respiration and CO2 moves out
74
Q

What is Transpiration?

A

loss of water vapour from the leaf via the stomata

75
Q

How does Transpiration occur?

A
  • moist lining of spongy mesophyll cells evaporate forming water vapour
  • water vapour builds up in air spaces
  • if water vapour concentration is high enough & stomata is open, water vapour diffuses out
76
Q

Factors that increase rate of transpiration?

A
  • light = more light, more stomata open, increase surface area for transpiration
  • temperature = more temperature, more evaporation (increase water vapour concentration) & more kinetic energy
  • wind = more wind, maintains concentration gradient
  • humidity = less humidity, less water vapour in the surrounding air, increase in water vapour concentration gradient
77
Q

What is a Potometer?

A

apparatus used to measure rate of transpiration

78
Q

Principle of potometer?

A
  • as transpiration occurs from the leaves, the plant will pull up more water from the potometer by cohesion-tension causing the bubble to move towards the plant
  • the more water lost by transpiration, the more water taken up, the further the bubble moves
79
Q

Measuring Rate of Transpiration?

A
  • rate of transpiration = volume of transpiration divided by time
  • for volume of transpiration, distance bubble moved x cross-sectional area of tube (πr2)
80
Q

How to set up a potometer?

A
  • choose healthy leaf and shoot
  • cut shoot underwater and connect to potometer underwater (prevents air bubbles entering/blocking xylem)
  • ensure potometer is air tight and water tight
81
Q

What does a potometer actually measure?

A

measures rate of water uptake as a result of water loss from plant
(water loss can be due to: transpiration, photosynthesis, making cells turgid, loss from potometer)

82
Q

What is a Xerophyte?

A

a plant adapted to reduce water loss (reduce transpiration)

83
Q

Adaptations of Xerophyte?

A
  • spiky, needle like leaves = reduced surface area
  • thick waxy cuticle = waterproof, impermeable barrier
  • densely packed spongy mesophyll = less air spaces, less water vapour build up
  • sunken stomata/hairy leaves/rolled up leaves = traps moist layer of air, reduces concentration gradient
84
Q

Function of Phloem?

A

transport organic material (e.g. Sucrose) up and down a plant

85
Q

Structure of phloem?

A

made of 2 parts (Sieve Tube with Companion Cells alongside)

86
Q

How does phloem transport organic material like sucrose?

A
  • by principle of Mass Flow (mass flow of water carries the sucrose)
  • Sucrose loaded into Phloem at Source
  • Hydrogen Ions (H+) actively transported from companion cells into source
  • therefore, H+ diffuses back into companion cells from source
  • as they do, they pull in sucrose with them by co-transport
  • sucrose then diffuses into sieve tube
  • this lowers the water potential of sieve tube so water follows by osmosis
  • this water will carry the sucrose by hydrostatic pressure (mass flow)
  • Sucrose unloaded from Phloem at Sink
  • sucrose moves out of phloem/sieve tube into sink by diffusion
  • water follows by osmosis
87
Q

Enzymes of Carbohydrate Digestion?

A
  • Starch/Glycogen (Salivary Amylase in Mouth, Pancreatic Amylase in Small Intestine) into Maltose
  • Maltose (Maltase on lining of Small Intestine) into Glucose
  • Lactose (Lactase on lining of Small Intestine) into Glucose and Galactose
  • Sucrose (Sucrase on lining of Small Intestine) into Glucose and Fructose
88
Q

Enzymes of Protein Digestion?

A
  • Endopeptidase (in stomach), hydrolyses peptide bonds in middle of polypeptide chain into many smaller chains
  • Exopeptidase (in small intestine), hydrolyses peptide bonds at end of chains to leave dipeptides
  • Deipeptidase (on lining of small intestine), hydrolyse dipeptides into amino acids
89
Q

Enzymes of Lipid Digestion?

A
  • Lipase in Small Intestine leaves Monoglyceride and 2 Fatty Acids
90
Q

Adaptations of SI for Absorption?

A
  • folded to form Villus (large surface area)
  • cells lining SI have Microvilli (large surface area)
  • wall of SI is thin (short diffusion distance)
  • rich blood supply (maintains concentration gradient)
  • cells lining SI have transport proteins, enzymes (maltase, lactase, sucrase, didpeptidase) and many mitochondria
91
Q

Absorption of Glucose and Amino Acids in SI?

A
  • sodium ions are actively transported from the cells lining the SI into the blood
  • lowers the sodium ion concentration in the cell
  • therefore sodium ions move from the lumen of the SI into the cell
  • this pulls in glucose and amino acids via a cotransport protein
  • therefore glucose and amino acids builds up in the cell and moves into the blood by diffusion
92
Q

Absorption of Monoglyceride and Fatty Acids?

A
  • Lipids initially emulsified by Bile into Micelles (smaller droplets)
  • Micelles digested by Lipase into Monoglyceride and 2 Fatty Acids
  • Monoglyceride and Fatty Acids absorbed by Cells lining SI by simple diffusion
  • Form a Chylomicron (lipid + cholesterol + lipoprotein)
  • Enters Lymph as Lacteal, then enters Blood
93
Q

What is Lactose Intolerance

A
  • Person does not make Lactase Enzyme
  • Lactose remains Undigested
  • Leads to Diarrhoea and Flatulence
  • Undigested Lactose in Lumen of Intestine lowers it’s water potential, so water enters the lumen by osmosis leading to water faeces (Diarrhoea)
  • Undigested Lactose brokendown by micro-organisms in Large Intestine, giving off gas (Flatulence)

AQA ALEVEL BIOLOGY P1/P2 (8 decks)

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