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AQA A Level Biology 2018 > More Exchange & Transport Systems > Flashcards

More Exchange & Transport Systems Flashcards

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1
Q

How is food broken down?

A

Into smaller molecules during digestion.

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2
Q

Why can some food not be absorbed from the gut into the blood?

A

The large biological molecules are too big to cross cell membranes do they can’t be absorbed from the gut into the blood.

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3
Q

What happens to the large molecules?

A

They are broken down into smaller molecules which CAN move across cell membranes - so they can be easily absorbed from the gut into the blood.

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4
Q

How are the large biological molecules broken down?

A

Into monomers using hydrolysis reactions.

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5
Q

What are fats broken down into?

A

Fatty acids and monoglycerides.

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6
Q

How are digestive enzymes produced?

A

By specialised cells in the digestive system of mammals.

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7
Q

Different enzymes are needed to…

A

Catalyse the breakdown of different food molecules.

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8
Q

What is Amylase?

A

A digestive enzyme that catalysed the conversion of starch into the smaller sugar maltose.

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9
Q

What does Amylase converting starch into maltose involve?

A

The hydrolysis of glycosidic bonds in starch. I’m

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10
Q

Where is Amylase produced?

A

In the salivary glands and pancreas.

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11
Q

What are membrane bound disaccharides?

A

Enzymes that are attached to the cell membranes of epithelial cells lining the ileum ( part of small intestine)

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12
Q

What do membrane bound disaccharides do?

A

They help to break down disaccharides into Monosaccharides.

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13
Q

How can Monosaccharides can be transported?

A

Across the cell membrane of the ileum epithelial cells via specific transporter proteins.

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14
Q

What do Lipase enzymes do?

A

They catalyse the breakdown of lipids into monoglycerides and fatty acids - hydrolysises the ester bonds in lipids.

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15
Q

Where are Lipase made and where do they work?

A

In the pancreas

Work in small intestine

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16
Q

Where produced Bile salts?

A

The liver and the bile emulsify lipids - cause lipids to be in small droplets.

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17
Q

Why are Bile salts important?

A

In lipid digestion - several small lipid droplets have a bigger surface area than a single large droplet.

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18
Q

What happens once a lipid has been broken down?

A

The monoglycerides and fatty acids stick with the Bile salts to form tiny structures called micelles.

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19
Q

What breaks down proteins?

A

By a combination of different proteases or peptides.

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20
Q

What are proteases?

A

Enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids.

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21
Q

Name the two molecules which break down Proteins:

A

Endopeptidases

Exopeptidases

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22
Q

Explain Endopeptidases?

A

They act to hydrolyse peptide bonds WITHIN a protein.

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23
Q

Give 2 examples of Endopeptidases:

A

a Trypsin

a Chymotrypsin

Synthesised in the pancreas and secreted into the small intestine.

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24
Q

Give another example of another Endopeptidase:

A

Pepsin

Released into the stomach by cells in the stomach lining - given acidic conditions.

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25
Q

Explain what Exopeptidases do?

A

They hydrolyse peptide bonds at the ends of the protein molecules - remove single amino acids from proteins.

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26
Q

What are Dipeptidases?

final part of digestion of proteins

A

Exopeptidases that work specifically on dipeptides - act to seperate two amino acids that make up a dipeptide by hydrolysing the peptide bond between them.

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27
Q

Where are Dipeptidases located?

A

Located in the cell-surface membrane of epithelial cells in the small intestine.

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28
Q

Products of digestion are absorbed across…

A

Cell membranes.

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29
Q

How are Monosaccharides absorbed across the ileum epithelium?

A

Glucose and Galactose absorbed by active transport with sodium ions via a co-transporter protein.

Fructose is absorbed via facilitated diffusion.

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30
Q

How are Monoglycerides and fatty acids absorbed across cell membranes?

A

Micelles help to move monoglycerides and fatty acids towards the epithelium.

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31
Q

What can Micelles do?

A

They can release monoglycerides and fatty acids allowing them to be absorbed - they are lipid soluble so they can diffuse directly through.

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32
Q

How are Amino acids absorbed across cell membranes?

A

Via co-transport. Sodium ions are actively transported out of the ileum epithelial cells into the blood - creates a sodium ion concentration gradient.

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33
Q

Sodium ions can…

A

Diffuse from the lumen of the ileum into the epithelial cells through the sodium dependent transporter proteins, carrying the amino acids with them.

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34
Q

Describe the role of enzymes in the complete breakdown of starch: (3)

A
  • analyse breaks down starch into maltose.
  • maltase breaks down maltose into glucose.
  • this happens with hydrolysis which removes a glycosidic bond.
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35
Q

Describe the process involved in the absorption of the products of starch digestion: (4)

A
  • sodium is removed from epithelial cells by active transport via the sodium potassium pump into the blood.
  • this maintains a low conc of sodium in epithelial cell compared to lumen.
  • glucose moves into the blood by facilitated diffusion.
  • glucose moves in with the sodium to the epithelial cell via a carrier protein.
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36
Q

How is starch absorbed?

A

Glucose (the product) passes through the small intestine into the blood supply.

it passes through the epithelial cells (which have microvilli) to go into the blood stream where there is a low conc of glucose usually.

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37
Q

What is the most important part of the small intestine and what does it do?

A

The Villi - provides a large surface area.

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38
Q

What breaks down the Disaccharides Maltose, Sucrose and Lactose?

A

Disaccharidases

  • maltAse
  • sucrAse
  • lactAse
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39
Q

What happens after the Fatty acids and glycerol are diffused across the small intestine? (4)

A
  • they combine again in the ER.
  • assosciate with cholesterol and proteins - form chylomicrons.
  • they leave cells via exocytosis which enter lacteal of lymphatic system, the enter blood via the thoracic duct.
  • then diffuse into the body cells.
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40
Q

Red blood cells contain…

A

Haemoglobin - a large protein with a quaternary structure (made up of 4 polypeptide chains)

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41
Q

Each polypeptide chain in Haemoglobin contains…

A

A Haem group which contains an iron ion.

42
Q

What does AFFINITY mean?

A

The tendency to combine with oxygen.

43
Q

What’s Haemoglobin’s affinity for oxygen like?

A

High - each molecule can carry four oxygen molecules.

44
Q

In the lungs, oxygen joins to haemoglobin in red blood cells to form…

A

Oxyhaemoglobin.

45
Q

What is the partial pressure of oxygen?

A

A measure of oxygen concentration - the greater the concentration of dissolved oxygen in cells, the higher the partial pressure.

46
Q

What is the partial pressure of carbon dioxide?

A

A measure of the concentration of carbon dioxide in a cell.

47
Q

When does oxygen load onto haemoglobin?

A

Where there’s a high partial pressure of oxygen.

48
Q

Where does oxyhemoglobin unload it’s oxygen?

A

Where there’s a lower partial pressure of oxygen.

49
Q

Give the 3 step process of oxygen loading and unloading around the body:

A
  • oxygen enters blood capillaries at the alveoli = loads oxygen
  • when cells respire, this oxygen used - lowers partial pressure oxygen. Red blood cells deliver oxyhaemoglobin to respiring tissues to unload it.
  • haemoglobin then returns to the lungs to pick up more oxygen.
50
Q

How does carbon dioxide concentration affect oxygen unloading?

A

Haemoglobin gives up its oxygen more readily at a higher partial pressure of carbon dioxide.

51
Q

How does exercise affect oxygen unloading: (3)

A

Cells respire producing carbon dioxide increasing the conc

Increases rate of O2 unloading so the curve shifts to the right

Saturation of blood with oxygen is lower for a given O2 meaning more oxygen is released = this is called the Bohr effect.

52
Q

How is Haemoglobin different in different organisms?

A

Organisms that live in environments with a low concentration of oxygen have a higher affinity for oxygen so their curve is to the left.

Oxygens which are active and have a higher oxygen demand have Haemoglobin with a low affinity for oxygen - curve to the right.

53
Q

Why do multicellular organisms need a specialised transport system?

A

Because they have a low surface area to volume ratio.

54
Q

The circulatory system is made up of…

A

Heart and blood vessels

55
Q

Double Circulatory System:

A

Two circuits

One takes blood from the heart to the lungs (picks up O2 then back to heart)

Other one takes blood around the rest of the body.

56
Q

The heart has its own blood supply…

A

Coronary arteries.

57
Q

What do Arteries do?

A

Carry blood from the heart to the rest of the body.

58
Q

Adaptations of Arteries: (3)

A
  • thick and muscular walls - strong.
  • elastic tissue to stretch and recoil as the heart beats which maintains the high pressure.
  • inner lining (endothelium) is folded allowing the artery to stretch to maintain pressure.
59
Q

What kind of blood do arteries carry?

A

Oxygenated blood

Except for the pulmonary artistes which take deoxygenated blood to the lungs.

60
Q

Arteries divide into…

A

Smaller vessels called arterioles which form a network throughout the body.

Blood is directed to different areas of demand in the body by muscles inside the arterioles.

61
Q

What do the muscles inside the arterioles do? (2)

A

They contract to restrict the blood flow

Or

Relax to allow full blood flow

62
Q

What do veins do?

A

They take blood back to the heart under low pressure.

63
Q

Adaptations of Valves: (2)

A
  • contain valves to stop blood flowing backwards.

- wider lumen with very little elastic or muscle tissue because of low pressure blood.

64
Q

What type of blood do Veins carry?

A

Deoxygenated blood except for the pulmonary veins which carry oxygenated blood to the heart from the lungs.

65
Q

Where are Capillaries found?

A

Very near cells in exchange tissues.

66
Q

Adaptations of Capillaries: (2)

A
  • only one cell thick, short diffusion pathway.

- large number of them to increase surface area for exchange.

67
Q

Networks of capillaries in tissue are called…

A

Capillary beds.

68
Q

What is Tissue Fluid?

A

The fluid that surrounds cells in tissues - made from small molecules that leave blood plasma.

69
Q

How is Tissue Fluid formed: (3)

A
  • near the arteries, the high hydrostatic pressure is greater inside the capillaries then after causing fluid to move out of the capillaries.
  • as the Fluid leaves, hydrostatic pressure reduces in the capillaries so the hydrostatic pressure is much lower at the Venule end of the capillary bed.
  • now the water potential at the venule end is lower than in the Tissue Fluid so water is reabsorbed in.
70
Q

What happens to any excess tissue fluid?

A

It is drained into the lymphatic system.

71
Q

Heart Structure:

A

RIGHT A LEFT A

RIGHT V LEFT V

72
Q

What is special about the left ventricle of the heart?

A

It is thicker and has more muscular walls than the right - because it needs to contract powerfully to pump blood all the way around the body.

73
Q

Why does the right ventricle not need to be as thick?

A

Because it is only pumping blood to the lungs which are nearby.

74
Q

Why do ventricles have thicker walls than the atria?

A

Because they have to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles.

75
Q

Where are the Atrioventricular valves?

A

They link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract.

76
Q

What are the Semi-Lunar valves?

A

They link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract.

77
Q

What do the cords in the heart to?

A

They attach the AV valves to the ventricle to stop them being forced up into the atria when the ventricles contract.

78
Q

The valves only open one way

When do they open/close?

A

If there’s a higher pressure behind a valve, it’s forced open but if pressure is higher in front of the valve, it’s shut.

79
Q

Blood only flows in …

A

ONE DIRECTION to the heart.

80
Q

The cardiac cycle is an ongoing sequence of…

A

Contraction and relaxation of the atria and ventricles.

81
Q

3 stages of the Cardiac Cycle:

GIVE THE FIRST STAGE

A

1) ventricles relax, atria contract decreasing the volume of chambers and increasing pressure of the chambers pushing blood into the ventricles.

Slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracting atria.

82
Q

3 stages of the Cardiac Cycle:

GIVE THE SECOND STAGE

A

2) atria relax and ventricles contract decreasing their volume and increasing their pressure.

Pressure is higher in ventricles than in atria which forces the AV valves shut but the pressure is higher than in the aorta and pulmonary artery so SL valves are open and blood is forced out into these arteries.

83
Q

3 stages of the Cardiac Cycle:

GIVE THE THIRD STAGE

A

3) the ventricles and atria both relax.

The higher pressure in the pulmonary artery and aorta closes the SL valves and blood returns back to the heart and atria fill again due to high pressure in vena cava and pulmonary vein = increases pressure of atria.

As the ventricles continue to relax, pressure falls below the pressure of the atria so the AV valves open allowing blood to flow passively. The atria contract and whole process begins again.

84
Q

What do Xylem Tissue do?

A

Transports water and mineral ions in the solution.

85
Q

What do Phloem Tissue do?

A

Transports organic substances like sugars both up and down the plant.

86
Q

Xylem and Phloem are M…

A

Mass transport systems - they move substances over large distances.

87
Q

What are Xylem Tissues?

A

The part of the xylem Tissue that actually transports the water and ions.

Long tube-like structures formed from dead cells with no end walls.

88
Q

How does water move up a plant against the force of gravity? (3)

A
  • water evaporates from the leaves creating tension which pulls more water into the leaf.
  • cohesive water molecules stick together so the whole column of water in the xylem moves upwards.
  • water enters the stem through the roots.
89
Q

What is Transpiration?

A

The evaporation of water from a plant’s surface especially the leaves.

90
Q

Evaporation: (2)

A
  • water evaporates from the moist cell walls and accumulated in the spaces between cells in the leaf.
  • when the stomata open, moves out the leaf down the conc gradient.
91
Q

4 main factors which affect Transpiration Rate:

A
  • light = makes it faster as stomata are open.
  • temperature = warmer water molecules evaporate faster increasing concealer gradient so diffusion is faster.
  • humidity = the lower, the faster = if the air round the plant is dry, the conc gradient between the leaf and air is increased which increases transpiration.
  • wind = the windier, the faster = lots of air movement blows away water molecules from around the stomata increasing the conc gradient = increases the rate of transpiration.
92
Q

Phloem Tissue transport S…

A

Solutes = dissolves substances.

93
Q

Give 2 cell types in Phloem Tissue:

A
  • sieve tuve elements are living cells that form the tube = few
    organelles so more space.
  • companion cell for each sieve tube element = carry out living functions e.g. providing the energy needed for the active transport of solutes.
94
Q

What is Translocation?

A

The movement of solutes to where they’re needed in a plant.

This requires energy.

95
Q

Translocation moves solutions…

A

From ‘sources’ to ‘sinks’

96
Q

What is the source of a solute?

A

Where it’s made

97
Q

What is the sink?

A

The area where it’s used up.

98
Q

How do enzymes maintain a concentration gradient from the source to the sink?

A

By changing the solutes at the sink (e.g. breaking them down) this makes a lower concentration at the sink.

99
Q

What is the Mass Flow Hypothesis?

(1)

A
  • active transport used to move solutes from companion cells into the siege tubes of the Phloem at the source
  • lowers the water potential inside the sieve tubes so water enters the tubes by osmosis from the xylem and companion cells creating a high pressure inside the sieve tubes at the source end of the tube.
100
Q

What is the Mass Flow Hypothesis?

(2)

A
  • at the sink end, solutes ate removed from the Phloem increasing the water potential inside the sieve tubes so water also leaves the tubes by osmosis.
  • this lowers the pressure inside the sieve tubes.
101
Q

What is the Mass Flow Hypothesis?

(3)

A
  • the result is a pressure gradient from the source end to the sink end - the gradient pushes solutes along the sieve tubes towards the sink.
  • when they reach the sink the solutes will be used or stored.

AQA A Level Biology 2018 (17 decks)

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