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Biology AS > Mass Transport > Flashcards

Mass Transport Flashcards

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1
Q

Haemoglobin

A
  • Found in red blood cells
  • Large protein with a quaternary structure
  • Four polypeptide chains linking in a globular shape
  • Each chain has a haem group
  • Which contains an iron ion that can combine with a single oxygen molecule
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2
Q

Formation Of Oxyhaemoglobin

A
  • Haemoglobin has a high affinity (tendency to combine with) for oxygen
  • Each molecule can carry four oxygen molecules
  • In the lungs oxygen joins to haemoglobin in red blood cells to form oxyhemoglobin
  • Reversible reaction; oxygen can dissociate from oxyhemoglobin

Hb + 4O2 = HbO8

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3
Q

Partial Pressure Of Oxygen

A
  • Measure of oxygen concentration
  • The greater the concentration of dissolved oxygen, higher the partial pressure
  • There is high partial pressure in the lungs so haemoglobin has a high affinity for oxygen there
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4
Q

Loading & Unloading Of Oxygen

A
  • Oxygen enters blood capillaries at the alveoli in the lungs
  • Alveoli have a high partial pressure of oxygen so oxygen loads onto haemoglobin to form oxyhemoglobin
  • Respiring cells use up oxygen, this lowers the partial pressure of oxygen
  • Red blood cells deliver oxyhemoglobin to respiring tissues where it unloads its oxygen
  • Haemoglobin returns to the lungs to pick up more oxygen
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5
Q

Haemoglobin In Different Organisms

A
  • Different structures because of different DNA
  • Form different primary structures and have different numbers of polypeptide chains in the tertiary structure
  • Organisms in environments with low concentration of oxygen (partial pressure) have haemoglobin with a higher affinity for oxygen than human haemoglobin
  • This dissociation curve is to the left of the human one
  • Organisms that are active with high oxygen demand have haemoglobin with a lower affinity for oxygen than human (so it can dissociate more easily for use in respiration)
  • This curve is to the right of the human one
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6
Q

Dissociation Curves Show Affinity For Oxygen

A
  • Lungs: partial pressure is high so haemoglobin has a high affinity for oxygen; it readily combines to oxygen as there is a high saturation of it
  • Respiring Cells: partial pressure is low in respiring tissue so haemoglobin has a low affinity for oxygen; it releases oxygen as there is a low saturation of it
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7
Q

S-shape Of Dissociation Curves

A
  • When haemoglobin combines with the first oxygen molecule it’s shape alters
  • It makes it easier for other oxygen molecules to then join too
  • As haemoglobin becomes more saturated it gets harder for more oxygen molecules to join
  • The curve has a steep middle where it’s easy for oxygen molecules to join and shallow ends parts where it’s harder
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8
Q

Haemoglobin & Carbon Dioxide

A
  • Respiring cells produce carbon dioxide
  • This decreases blood pH and makes it slightly acidic
  • Haemoglobin is a protein so its shape is changed as hydrogen bonds are broken
  • This decreases it’s affinity for oxygen and allows oxygen to unload more easily and be used up by respiring cells
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9
Q

The Bohr Effect

A
  • Respiring cells produce carbon dioxide which increases the partial pressure of carbon dioxide
  • At higher partial pressures of carbon dioxide haemoglobin unloads it’s oxygen more easily
  • This increases the rate at which oxygen dissociates from oxyhemoglobin
  • The dissociation curve shifts to the right because the saturation of blood with oxygen is lower for a given partial pressure of oxygen as more is being released for use by respiring cells
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10
Q

The Circulatory System

A
  • There are two circuits
  • One circuit takes blood from the heart to the lungs then back to the heart
  • The other takes blood around the rest of the body
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11
Q

Coronary Arteries

A
  • Supply the heart with oxygenated blood
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12
Q

Arteries

A
  • Carry blood from the heart to the rest of the body
  • All carry oxygenated except for pulmonary arteries (take deoxygenated blood to the lungs)
  • Have thick walls to maintain high pressure
  • Branch into arterioles
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13
Q

Arterioles

A
  • Form a network throughout the body
  • Muscles inside arterioles direct blood to areas of demand in the body
  • By contracting to restrict blood and relaxing to allow full blood flow
  • Branch into capillaries
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14
Q

Capillaries

A
  • Smallest blood vessels
  • Found near exchange tissues e.g. alveoli
  • One cell thick walls for a short diffusion pathway
  • Large number of capillaries to increase surface area for exchange
  • Network of capillaries in a tissue are called capillary beds
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15
Q

Veins

A
  • Take blood back to the heart
  • Under low pressure so have a wider lumen than arteries and little muscle tissue
  • All carry deoxygenated blood except pulmonary veins (carry oxygenated blood to the heart from the lungs)
  • Have valves to prevent blood flowing backwards
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16
Q

Tissue Fluid

A
  • Surrounds cells in tissues
  • Made from small molecules that leave the blood plasma e.g. water, oxygen and nutrients
  • Tissue fluid forms because of the high hydrostatic pressure of blood at the arteriole end of the capillary that pushes fluid out of the blood
  • Most fluid re-enters the capillaries e.g. the water by osmosis
  • Excessive tissue fluid is drained into the lymphatic system
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17
Q

The Heart

A
  • Consists of two muscular pumps
  • The right-side pumps deoxygenated blood to the lungs
  • The left-side pumps oxygenated blood to the whole body
  • Diastole is a period of relaxation
  • Systole is a period of contraction
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18
Q

The Heart [Process]

A
  • Right atrium contracts and opens AV valves
  • Deoxygenated blood flows into the right ventricle
  • Right ventricle contracts opening AL valves
  • Blood flows into the pulmonary artery then to the lungs
  • Oxygenated blood from the lungs enters the left atrium via the pulmonary vein
  • Left atrium contracts opening AV valves
  • Blood enter the left ventricles
  • These are thicker than the right; contract powerfully to pump blood around the body (all ventricles have thicker walls than atria; they push blood out of the heart)
  • Left ventricle contracts
  • Blood goes to the aorta via SL valve where it goes to the rest of the whole body at a high pressure
19
Q

The Cardiac Cycle

A
  • When the ventricles are relaxed the atria contract
  • This causes pressure in the atrium to increase so AV valves open
  • Pushing blood into ventricles
  • The ventricles contract once atria relax
  • This increases pressure in the ventricles so the SL valves open after the AV valves shut (prevent back flow)
  • Blood is forced into the arteries
  • The ventricles and atria relax
  • Pressure increases in the pulmonary artery and aorta so SL valves close to prevent back flow into ventricles
20
Q

Cardiovascular Disease

A
  • Most start with atheroma formation
  • When damage is caused to the arteries endothelium by high blood pressure
  • White blood cells, lipids and connective tissue build up overtime
  • They harden and form a fibrous plaque called an atheroma
21
Q

Coronary Disease

A
  • Type of cardiovascular disease
  • Caused when coronary arteries have lots of atheroma
  • Restricting blood flow
22
Q

Aneurysm

A
  • Atheroma cause capillaries to narrow
  • Blood travelling at a high pressure can push the inner layers through the outer layer
  • Forming a swelling which bursts and causes a haemorrhage
23
Q

Thrombosis

A
  • Atheroma plaques can rupture the endothelium of an artery
  • Causing platelets and fibrin to accumulate and form a blood clot
  • This blocks the artery
24
Q

Myocardial Infarction

A
  • When a coronary artery is blocked
  • The area is cut off from blood supply and oxygen
  • Causing a heart attack [myocardial infarction]
25
Q

High Blood Cholesterol & Poor Diet

A
  • Cholesterol is on the main constituents of the fatty deposits which form atheroma
  • A diet high in fat is linked to high blood cholesterol levels
  • A diet high in salt increases risk of cardiovascular disease due to increased risk of high blood pressure
26
Q

Cigarette Smoking

A
  • Nicotine increases risk of high blood pressure; it causes adrenaline
  • Carbon monoxide combines with haemoglobin reducing the amount of oxygen transported the blood and available to tissues
  • If the heart muscle doesn’t receive enough oxygen it can lead to heart attack
27
Q

High Blood Pressure

A
  • Increases risk of damage to artery walls; increases risk of atheroma formation
  • Atheroma lead to blood clots which block flow of blood to the heart muscle
  • May result in myocardial infarction
  • High blood pressure can be caused by being overweight, not exercising and excessive alcohol consumption
28
Q

Xylem

A
  • Tissue that transports water and mineral ions in solution

- These substances move up the plant from the roots to the leaves

29
Q

Structure Of Xylem

A
  • Hollow lumen (formed from dead cells with no cytoplasm): allows water to move in a continuous column using the cohesion-tension theory
  • Pits in their walls: allows lateral movement of water so it reaches other parts of the leaf
  • Lignified walls: kill the xylem and make it water proof
  • Thick walls: strengthens the xylem to prevent bursting under pressure
30
Q

Root Pressure

A
  • When an influx of water from soil creates a hydrostatic pressure
  • Water is forced into the roots
  • The pressure is enough to move water up the xylem by a small amount
31
Q

Root Pressure Evidence

A
  • If the leaves are removed
  • A monometer is added below
  • There is still water movement up the monometer which acts as the roots
32
Q

Capillary Action

A
  • Water adheres to the sides of the xylem and moves upwards

- Adhesive properties of water allow it to stick to the xylem and move upwards

33
Q

Capillary Action Evidence

A
  • The meniscus of water in glassware shows how it sticks to the sides of the tube
  • Creating a curve and in smaller test-tubes this curve is bigger
  • As the space is more confined there is more capillary action
34
Q

Cohesion Tension

A
  • Water is polar
  • Slightly negative oxygen attracts to slightly positive hydrogen of another water molecule
  • This forms hydrogen bonds
  • Within a xylem, the water is held together by hydrogen bonds so water moved upwards by tension created by evaporation from leaves
35
Q

Cohesion Tension Evidence

A
  • If the roots are taken off and a monometer is added
  • Water still moves up as there is still tension from the leafs
  • If the leaves are removed there is less water movement due to less tension
  • If the temperature is increased there is more water movement as the molecules have more kinetic energy to move up the stem
36
Q

Transpiration

A
  • When water evaporates from the plants surface
  • Stomata open and water moves out of the leaf down a concentration gradient
  • This is due to there being more water inside the leaf than in the air outside
37
Q

Transpiration Process

A
  • Water moves out of the soil into the roots by osmosis
  • Water moves from the roots into the xylem
  • This movement is all down a concentration gradient
  • Water molecules are cohesive so they form a continuous column of water up the xylem
  • It is also moved up by root pressure and capillary action
  • Water evaporates through stomata in the leafs
  • As each water molecule evaporates the column of water is pulled up the xylem by cohesion-tension
38
Q

Factors Affecting Transpiration Rate

A
  • Light: the lighter it is the faster the rate; stomata open when it gets light to release CO2 for photosynthesis
  • Temperature: the higher the temperature the faster the rate; water molecules have more energy to evaporate from cells in the leaf faster
  • Humidity: the lower the humidity the faster the rate; the concentration gradient between the leaf and air increases as the air around the plant is dry
39
Q

Phloem

A
  • Tissue that transports organic substances e.g. sugars up and down the plant
40
Q

Structure Of Phloem

A
  • Phloem tube is made from sieve tubes which are living cells
  • These sieve tubes have mitochondria; energy is needed
  • There’s a companion cell for each sieve tube element
  • Companion cells carry out living functions for sieve tubes e.g. providing energy needed for active transport of solutes
41
Q

Translocation

A
  • The movement of solutes to where they’re needed in a plant
  • Moves solutes from sources to sinks
  • Source is where the solute is made so it’s at a high concentration there
  • Sink is the area where its taken up so its at a lower concentration there
  • It’s an energy requiring process that happens in the phloem
42
Q

Mass Flow Hypothesis

A
  • Explains the movement of sap through the phloem
  • Solutes are loaded into sieve cells from companion cells at the phloem’s source
  • Through active transport
  • This lowers the water potential in the sieve tubes so water enters them from the xylem and companion cells by osmosis
  • Creates high pressure inside sieve tubes at the source
  • At the sink solutes are removed from the phloem to be used up
  • Increasing water potential inside the sieve tubes so water leaves them by osmosis
  • This lowers pressure inside the sieve tubes at the sink
  • There is a pressure gradient from the source end to the sin end
  • This pushed solutes towards the sink
  • Where they are used for respiration or stored as starch
  • The higher the concentration of sucrose at the source, the higher the rate of translocation
43
Q

Evidence For Mass Flow

A
  • Downward flow of sugars: when a ring of bark is removed from a woody stem a bulge forms above the ring and fluid inside the bulge has a higher concentration of sugars than food below the ring
  • A pressure gradient: when a phloem is pierced by aphids, the sap flows out quicker nearer the leaves than further down the stem
  • Active transport is involved: when a metabolic inhibitor which stops ATP production is put into the phloem, translocation stops
44
Q

Evidence Against Mass Flow

A
  • Sugar travels to many different sinks not just one with the highest water potential
  • The sieve plates would create a barrier to mass flow; a lot of pressure would be needed for solutes to get them through at a reasonable rate
  • Not all solutes move at the same speed and they should do if the mass flow theory is correct

Biology AS (7 decks)

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