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biology > mass transport- chapter 7 > Flashcards

mass transport- chapter 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the primary structure of a haemoglobin molecule

A

sequence of amino acids in the four polypeptide chains

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2
Q

what is the secondary structure of a haemoglobin molecule

A

in which each of these polypeptide chains is coiled into a helix

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3
Q

what is the tertiary structure of a haemoglobin molecule

A

each polypeptide chain is folded into a precise shape- important in its ability to carry oxygen

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4
Q

what is the quaternary structure of a haemoglobin molecule

A

all four polypeptides are linked together to form an almost spherical molecule. Each polypeptide is associated with a haem group- which contains a ferrous (Fe2+) ion. Each Fe2+ ion can combine with a single oxygen molecule (O2) making a total of four oxygen molecules that can be carried by a single haemoglobin molecule in humans

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5
Q

what is loading/associating

A

haemoglobin binding with oxygen

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6
Q

what is unloading/dissociating

A

haemoglobin releases its oxygen

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7
Q

what does high affinity mean for haemoglobin

what does low affinity mean for haemoglobin

A

high affinity for oxygen take up oxygen more easily and release it less easily

low affinity for oxygen take up oxygen less easily and release it more easily

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8
Q

what is the role of haemoglobin

A

The shape changes in the presence of certain substances, such as carbon dioxide. In the presence of carbon dioxide, the new shape of the haemoglobin molecule binds more loosely to oxygen. As a result haemoglobin releases its oxyge

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9
Q

what are there different species of haemoglobins

A
  • Each species produces a haemoglobin with a slightly different amino acid sequence.
  • The haemoglobin of each species therefore has a slightly different tertiary and quaternary structure resulting in different oxygen binding properties
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10
Q

explain the oxygen dissociation curve

A
  • The shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits because they are closely united.
  • The binding of the first oxygen molecule changes the quaternary structure which makes it easier for the other subunits to bind to an oxygen molecule. This is known as positive cooperativity.
  • The situation changes after the binding of the third molecule. While in theory it is easier for haemoglobin to bind the fourth oxygen molecule, it is harder
  • Further to the left of the curve, the greater is the affinity of haemoglobin for oxygen.
  • The further to the right the curve, the lower the affinity of haemoglobin for oxygen
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11
Q

explain the loading, transport and unloading of oxygen

A
  • At the gas-exchange surface carbon dioxide is constantly being removed.
  • The pH is slightly raised due to the low concentration of carbon dioxide.
  • The higher pH changes the shape of the haemoglobin into one that enables it to load oxygen readily.
  • This shape also increases the affinity of haemoglobin for oxygen, so it is not released whilst being transported in the blood to the tissues.
  • In the tissues, carbon dioxide is produced by respiring cells.
  • Carbon dioxide is acidic in solution, so the pH of the blood within the tissues is lowered.
  • The lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen.
  • Haemoglobin releases its oxygen into the respiring tissues
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12
Q

the higher the rate of respiration……
(terms of loading, transport and unloading)

A

The more carbon dioxide the tissues produce = the lower the pH = the greater the haemoglobin shape change = the more readily oxygen is unloaded = the more oxygen is available for respiration

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13
Q

what is the circulatory system in mammals and why

A

closed, double circulatory system- blood is confined to vessels and passes twice through the heart for each complete circuit of the body

why= this stops the oxygenated and deoxygenated blood from mixing and ensures blood is under a high pressure

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14
Q

what side of the heart has oxygenated blood

what side of the heart has deoxygenated blood

A

left side, from the lungs and pumps to the rest of the body, the ventricle has a thicker muscular wall

right side, from the body and pumps to the lungs, ventricle has a thinner muscular wall

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15
Q

what is the atrium

A

a thin-walled and elastic and stretches as it collects the blood

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16
Q

what is the ventricle

A

has a much thinner muscular wall as it has to contract strongly to pump blood some distance

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17
Q

what do valves do and what 2 are there

A

prevent back flow of blood in the heart

  • left atrioventricular (bicuspid) valve
  • right atrioventricular (tricuspid) valve
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18
Q

what is the aorta

A

connected to the left ventricle and carries oxygenated blood to all parts of the body

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19
Q

what is the vena cava

A

connected to the right atrium and bring deoxygenated blood back from the tissues of the body

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20
Q

what is the pulmonary artery

A

connected to the right ventricle and carries deoxygenated blood to the lungs

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21
Q

what is the pulmonary vein

A

connected to the right atrium and brings oxygenated blood back from the lungs

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22
Q

how is the heart supplied with oxygen

A
  • supplied by the coronary arteries, which branch off the aorta shortly after it leaves the heart
  • a blockage of these may lead to myocardial infarction or a heart attack as an area of the heart muscle is deprived of blood and oxygen also
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23
Q

explain the relaxation of the heart (diastole)

A
  • As the atria fill, the pressure in them rises.
  • When the pressure exceed the pressure in the ventricles the atrioventricular valves open allowing the blood to pass into the ventricles.
  • The muscular walls of both the atria and ventricles are relaxed at this stage.
  • The relaxation of the ventricle walls causes them to recoil and reduces the pressure.
  • This causes the pressure to be lower than that in the aorta and the pulmonary artery, and so the semi-lunar values in the aorta and the pulmonary artery close (dub sound of the heart beat)
24
Q

explain the contraction of the atria (atrial systole)

A

contraction of the atrial walls, along with the recoil of the relaxed ventricle walls forces the remaining blood into the ventricles from the atria

25
Q

explain the contraction of the ventricles (ventricular systole)

A
  • After a short delay to allow the ventricles to fill with blood, their walls contract simultaneously.
  • Increasing the blood pressure within them forcing shut the atrioventricular valves and preventing backflow of blood into the atria. (Lub sound of heart beat)
  • With the atrioventricular valves closed the pressure in the ventricles rise further.
  • Once it exceeds that in the aorta and pulmonary artery, blood is forced from the ventricles into these vessels
26
Q

what are the atrioventricular valves

A

between the atrium and ventricles, prevent back flow when contraction of the ventricles means the ventricular pressure exceeds atrial pressure

27
Q

what are the semi-lunar valves

A

in the aorta and pulmonary artery. Prevent backflow of blood into the ventricles when the pressure in these vessels exceed that in the ventricles. This happens when the elastic walls of the vessels recoil and the ventricle walls relax

28
Q

what are the pocket valves

A

found in veins that occur throughout the venous system. This ensure blood flows back to the heart rather than away from it when the veins are squeezed

29
Q

how do valves work

A
  • Values are flaps of tough, but flexible fibrous tissues which are cusp shaped.
  • When pressure is greater on the convex side they move apart to let blood pass between the cusps.
  • When pressure is greater on the concave side, blood collects within the ‘bowl’ of the cusps and pushes them together
30
Q

what is the cardiac output

how is cardiac output calculated

A

volume of blood pumped by one ventricle of the heart in one minuite

heart stroke x stroke volume

31
Q

what is cardiac output measured in and what does it depend on

A

dm3min-1

heart rate
strike volume (volume of blood pumped out at each beat)

32
Q

what are arteries

A

carry blood away from the heart and into the arterioles

33
Q

what are arterioles

A

smaller arteries that control blood flow from arteries to capillaries

34
Q

what are capillaries

A

tiny vessels that link arterioles to veins

35
Q

what are veins

A

carry blood from capillaries back to the heart

36
Q

what is the structure of blood vessels (5 layers)

A
  1. Tough fibrous outer layer- resists pressure changes from both within and outside.
  2. Muscle layer- contract and so control the flow of blood.
  3. Elastic layer- helps to maintain blood pressure by stretching and springing back (recoiling)
  4. Thin inner lining (endothelium)- smooth to reduce friction and thin to allow diffusion.
  5. Lumen- central cavity of the blood vessel through which the blood flows.
37
Q

explain the artery and how its related to its function

A
  • Muscle layer is thick compared to veins.
  • Elastic layer is relatively thick compared to veins. The elastic wall is stretched at each beat of the heart (systole), it then springs back when the heart relaxes (diastole). The stretching and recoiling action helps to maintain high pressure and smooth pressure surges created by the beating of the heart.
  • The overall thickness of the wall is great- resists the vessel bursting under pressure.
  • There are no valves because blood is under constant high pressure
38
Q

explain the arterioles and how its related to its function

A
  • The muscle layer is relatively thicker than in arteries. The contraction of this muscle allows constriction of the lumen of the arteriole. This restricts the flow of blood and so controls its movement into the capillaries that supply the tissues with blood.
  • The elastic layer is relatively thinner than in arteries because blood pressure is lower
39
Q

explain the vein and how its related to its function

A
  • The muscle layer is relatively thin because their constriction and dilation cannot control the flow of blood to the tissues.
  • The elastic layer is relatively thin because the low pressure of blood will not cause them to burst and pressure is too low to create a recoil action.
  • The overall thickness of the wall is small because there is no need for a thick wall as the pressure within the veins is too low to create any risk of bursting. Also allows them to be flattened easily, aiding the flow of blood.
  • There are valves at intervals throughout to ensure that blood does not flow backwards. When body muscles contract, veins are compressed, pressurising the blood within them. The valves ensure that this pressure directs the blood in one direction only
40
Q

explain the capillaries and how its related to its function

A
  • Their walls consist mostly of the lining layer making them extremely thin, so the distance over which diffusion takes place is short.
  • They are numerous and highly branched, which provides a large surface area for exchange.
  • They have a narrow diameter and so permeate tissues, which means that no cell is far from a capillary and there is a short diffusion pathway.
  • Their lumen is so narrow that red blood cells are squeezed flat against the side of a capillary. This brings them even closer to the cells they supply oxygen too reducing the diffusion distance.
  • Space between the lining cells that allow white blood cells to escape in order to deal with infections within tissues

capillaries do not serve every cell directly, therefore the final journey of metabolic materials is made in tissue fluid

41
Q

explain tissue fluid and its formation

A
  • Contains glucose, amino acids, fatty acids, ions in solution and oxygen which is delivers to tissues.
  • It returns carbon dioxide and other waste materials from tissues.
  • It is the immediate environment of all cells.
42
Q

what is the formation of tissue fluid

A
  • Pumping the blood through the arteries, arterioles and capillaries creates a pressure called hydrostatic pressure.
  • This causes tissue fluid to move out of the blood plasma.
  • The outward pressure is opposed by:
  • Hydrostatic pressure of the tissue fluid outside the capillaries, which resists outward movement of liquid.
  • The lower water potential of the blood, due to the plasma proteins, that causes water to move back into the blood within the capillaries.
  • Pressure is only enough to force small molecules out of the capillaries not larger proteins. This is called ultrafiltration
43
Q

explain the return of tissue fluid to the circulatory system

A
  • Most tissue fluid returns to the blood plasma via capillaries
  • The loss of the tissue fluid from the capillaries reduces the hydrostatic pressure inside them.
  • As a result, by the time the blood has reached the venous end of the capillary network its hydrostatic pressure is usually lower than that of the tissue fluid outside it.
  • Therefore tissue fluid is forced back into the capillaries by the higher hydrostatic pressure outside them.
  • The plasma has also lost water and still contains proteins so the water potential is lower than the tissue fluid.
  • As a result, water leaves the tissue by osmosis down a water potential gradient.
  • Not all tissue fluid is returned to the capillaries the remaining is carried back via the lymphatic system.
  • These vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart.
  • The contents of the lymphatic system are moved by hydrostatic pressure (of the tissue fluid that has left the capillaries) and the contraction of body muscles (that squeeze the lymph vessels- values!)
44
Q

explain the movement of water out through the stomata

A
  • Humidity of the atmosphere is usually less than that of the air spaces next to the stomata.
  • This means there is a water potential gradient from the air spaces through the stomata to the air.
  • When the stomata are open, water vapour molecules diffuse out of the air spaces.
  • Water lost is replaced by water evaporating from the cell walls of the surrounding mesophyll cells.
  • By changing the size of the stomatal pores, places control that rate of transpiration
45
Q

explain the movement of water across the cells of a leaf

explain why the water movement occurs through the cytoplasmic route

A

Water reaches the mesophyll cells from the xylem either via cell walls or via the cytoplasm

*Mesophyll cells lose water to the air spaces by evaporation.
*Cells now have a lower water potential and so water enters by osmosis from neighbouring cells.
* Loss of water from these neighbouring cells lowers their water potential
* They, in turn, take water from their neighbours by osmosis

46
Q

explain the movement of water up the stem in the xylem

A
  • Water evaporates from mesophyll cells.
  • Water molecules form hydrogen bonds between one another and hence tend to stick together. This is known as cohesion.
  • Water forms a continuous, unbroken column across the mesophyll cells and down the xylem.
  • As water evaporates from the mesophyll cells in the leaf, more molecules are drawn up behind it.
  • A column of water is therefore pulled up the xylem, this is called the transpiration pull.
  • Transpiration pull puts the xylem under tension, creating a negative pressure within the xylem. Cohesion-tension theory
47
Q

what is the evidence to support the cohesion tension theory

A
  • change in the diameter of tree trunks according to the rate of transpiration. When transpiration is at its greatest there is more tension in the xylem which causes the diameter of the trunk to shrink.
  • If a xylem vessel is broken and air enters it, the tree can no longer draw up water. Water molecules can not stick together.
  • When a xylem vessel is broken, water does not leak out
48
Q

what type of process is transpiration

A

passive so does not require metabolic energy to take place but energy is needed to drive the process which comes from the sun in the form of heat that evaporates water

49
Q

why is it good that xylem vessels are dead and have no end walls

A

means that xylem forms a series of continuous, unbroken tubes from root to leaves

50
Q

explain the phloem

A
  • organic molecules (sucrose and amino acids) and some mineral ions are transported from one part of a plant to another by translocation
  • phloem is made up of sieve tube elements, long thin structures arranged end to end
  • their end walls are perforated with the sieve tube elements
    -sugar produced during photosynthesis are moved from sources to sinks
  • translocation in the phloem can take place in either direction
51
Q

what does the phloem transport

A

inorganic ions such as potassium, chloride, phosphate and magnesium ions

52
Q

what are the 3 steps to the mechanism of translocation- mass flow theory

A
  1. transfer of sucrose into sieve elements from photosynthesising tissues
  2. mass flow of sucrose through sieve tube elements
  3. transfer of sucrose from the sieve tube elements into storage or other sink cells
53
Q

explain the step of transfer of sucrose into sieve elements from photosynthesising tissue

A
  • Sucrose is made from the products of photosynthesis
  • Sucrose diffuses down a concentration gradient by facilitated diffusion from the photosynthesising cells into companion cells.
  • Hydrogen ions are actively transported from companion cells into the spaces within cell walls using ATP.
  • These hydrogen ions then diffuse down a concentration gradient through carrier proteins into the sieve tube elements.
  • Sucrose molecules are transported along with the hydrogen ions in a process known as co-transport. The protein carriers are therefore also known as co-transport proteins
54
Q

explain the step of mass flow of sucrose through sieve tube elements

A
  • The transfer of sucrose into sieve elements causes the sieve tubes to have a lower water potential.
  • As the xylem has a much higher water potential, water moves from the xylem into the sieve tubes by osmosis creating high hydrostatic pressure within them.
  • At the respiring cells (sink), sucrose is either used up during respiration or converted to starch.
  • These cells therefore have a low sucrose content and so sucrose is actively transported into them from the sieve tubes lowering their water potential.
  • Water also moves into these respiring cells, from the sieve tubes, by osmosis.
  • The hydrostatic pressure of the sieve tubes in this region is therefore lowered.
  • There is a high hydrostatic pressure at the source, so mass flow of sucrose occurs into the sieve tubes
55
Q

explain the step of transfer of sucrose from the sieve tube elements into storage or other sink cells

A

The sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells

biology (11 decks)

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