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A Level Biology > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

Small organism

A

-Large SA:V ratio.
-Shorter distance from middle to edge of organism.
-More heat loss.

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2
Q

Large organism

A

-Small SA:V ratio.
-Longer distance from middle to edge of organism.
-Less heat loss.

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3
Q

Gas exchange in single-celled organisms

A

-Large SA:V ratio.
-Gases move by diffusion quicker.
-No additional barrier to diffusion of gases.

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4
Q

Gas exchange in insects

A

-Internal network of tubes called tracheae.
-Tracheae split up into tracheoles.
-Extend to the respiring tissues of the insect.
-Direct connection for diffusion of gases.

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5
Q

Gases move in and out the tracheal system in 3 ways:

A

-Along a diffusion gradient
-Mass transport
-The end of the tracheoles are filled with water

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6
Q

Limiting water loss in insects (3 ways)

A

-Small surface area to volume ratio.
-Waterproof coverings.
-Spiracles.

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7
Q

Structure of gills

A

-Gill filaments
-Gill lamellae
-Gill bar

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8
Q

How water is passed in water gills

A

-Buccal cavity opens.
-Pressure in buccal cavity decreases so water flows into mouth.
-Buccal cavity closes and pressure increases so therefore water flows into the gill cavity.
-Operculum opens and water flows out of gills.

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9
Q

Parallel flow vs countercurrent flow

A

PF- water and blood moves in one direction.
CF- water and blood move in opposite directions.

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10
Q

How countercurrent flow increases rate of gas exchange

A

-Contains different concentrations of exchange substances.
-Maintains a concentration gradient as it is constantly flowing.

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11
Q

Plants gas exchange

A
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12
Q

Structure of dicotyledonous plant leaf

A
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13
Q

Adaptations of leaves for efficient gas exchange

A
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14
Q

Limiting water loss in plants

A
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15
Q

Structure of human gas exchange system

A

Mouth/nose —> trachea —> bronchi —> bronchioles —> alveoli.

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16
Q

Lungs

A

Pair of lobed structures made up of a series of branched structures.

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17
Q

Trachea

A

-Flexible airway supported by rings of cartilage which prevent it collapsing.
-Tracheal walls is made up of muscle, lined with ciliated epithelium and goblet cells.

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18
Q

Bronchi

A

-Two divisions of the trachea leading to each lung.
-Amount of cartilage decreases as bronchi size decreases.

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19
Q

Bronchioles

A

-Branching subdivisions of the bronchi.
-Walls are made of muscles lined with epithelial cells.
-Muscles means that the walls are able to constrict to control air flow in and out of alveoli.

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20
Q

Alveoli

A

-Minute air sacs at the end of the bronchioles.
-Collagen and elastic fiber between alveoli meaning it can expand when filled with air as breathing in.
-Lots of caplilaries.
-Exchange surface between alveolar membrane and capillary endothelium.

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21
Q

How and why air is moved into lungs when breathing in?

A

-Mouth/nose –> Trachea —> Bronchi –> Bronchioles –> Alveoli.
-From the alveoli, gases travels into the bloodstream.

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22
Q

Inspiration

A

-Active process
-External intercostal muscle contract, internal intercostal muscles relax.
-Ribs are pulled upwards and outwards, increasing volume of the thorax.
-Diaphragm muscles contract, causing it to flatten which increases free volume of thorax.
-Increased volume of thorax means less pressure in the lungs.
-Atmospheric pressure is greater than pulmonary pressure so air is forced into the lungs.

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23
Q

Expiration

A

-Largely passive process.
-Internal intercostal muscles contract, external intercostal muscles relax.
-Ribs move downwards and inwards, decreasing volume of the thorax.
-Diaphragm muscles relax causing it to be pushed up which decreases the free volume of the thorax.
-Decreased volume of thorax means more pressure in the lungs.
-Pulmonary pressure is now greater than atmospheric pressure so air is forced out the lungs.

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24
Q

Pulmonary ventilation

A

Total volume of air that is moved in or out the lungs in a given time.

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25
Q

Pulmonary ventilation equation

A

pulmonary ventilation rate= tidal volume x breathing rate

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26
Q

Essential features of human exchange surfaces

A
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27
Q

Gas exchange in alveoli

A
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28
Q

Oesophagus

A

-Carries food from mouth to stomach.
-Physical

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29
Q

Stomach

A

-Muscular sac.
-Inner layer of enzymes.
-Store and digest foods.

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30
Q

Ileum

A

-Long muscular tube.
-Enzymes produced in walls.
-Walls folded in villi (absorb products of digestion).

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31
Q

Large intestines

A

-Absorbs water.
-Secretion of many digestive glands.

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32
Q

Rectum

A

-Faeces are stored here.
-Removed vias anus in process called egestion.

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33
Q

Salivary glands

A

-Situated near mouth.
-Pass secretions via duct.
-Amylase- hydrolyses starch into maltose

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34
Q

Pancreas

A

-Large gland situated below stomach.
-Secretes enzymes.

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35
Q

Physical digestion

A

-Large food molecules are broken down into smaller food molecules.
-By structures like teeth.

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36
Q

Chemical digestion

A

-Large food molecules are broken down into smaller food molecules.
-Carried out by enzymes (hydrolysis reactions).

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37
Q

Carbohydrates digestion

A

-Salivary amylase hydrolyses any starch into maltose during chewing.
-It also contains mineral salts that help maintain pH around neutral (optimum).
-Food is swallowed and enters the stomach where it is acidic and enzyme is denatured preventing hydrolysis.
-Food passed to small intestines where it mixes with pancreatic juice containing pancreatic amylase.
-Amylase continues hydrolysis of starch into maltose.
-Alkaline salts are produced by pancreas and intestinal wall to maintain pH around neutral (optimum).
-Muscles in intestinal wall push down food along the ileum.
-Membrane of ileum contain membrane-bound disaccharidases like maltase.
-Maltase hydrolyses maltose into alpha-glucose.

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38
Q

Sucrase

A

-Hydrolyses sucrose into alpha glucose and fructose.
-Membrane-bound disaccharidases.

39
Q

Lactase

A

-Hydrolyses lactose into alpha glucose and galactose.
-Membrane-bound disaccharidases.

40
Q

Protein digestion

A

-Endopeptidases- hydrolyse bonds in central regions of polypeptide chain.
-Exopeptidases- hydrolyse terminal ends of the broken down chains.
-Dipeptidases- hydrolyse peptide bond between two amino acid (membrane-bound- found in ileum).

41
Q

Lipids digestion

A

-Lipids are combined with bile salts.
-Emulsified into micelles.
-Increase surface area for lipase to act on.

42
Q

Structure of ileum

A

-Last portion of the small intestines.
-Villi, microvilli.

43
Q

Ileum adaptations

A

-Increase surface area for diffusion.
-Thin walled- decreasing distance over which diffusion takes place.
-Muscles so they are able to move.
-Well supplied with blood vessels to maintain a conc gradient.
-Epithelial cells lining the villi possess microvilli which increase surface area.

44
Q

Absorption of amino acids and monosaccharides

A

Co-transport.

45
Q

Absorption of triglycerides

A

-Monoglycerides and fatty acids combine with bile salts forming micelles.
-Micelles come into contact with the epithelial cells lining the villi of the ileum.
-Broken down and monoglycerides and fatty acids enter the epithelial cell.
-Transported to ER where they recombine.
-Moved to golgi where it associates with cholesterol and lipoproteins creating chylomicrons.
-Chylomicron moves out the cell by exocytosis.
-Enter lymphatic system by capillaries called lacteals.

46
Q

Primary structure of haemoglobin

A

Sequence of amino acids in the four polypeptide chains.

47
Q

Secondary structure of haemoglobin

A

One of the polypeptide chains is coiled in a helix.

48
Q

Tertiary structure of haemoglobin

A

Each polypeptide chain is folded into a precise shape- important for ability to carry oxygen.

49
Q

Quaternary structure of haemoglobin

A

All four polypeptides are linked together to form almost spherical molecule. Each polypeptide is associated with a haem group- which contains a ferrous(Fe2+) ion. Each Fe2+ can combine with a single O2.

50
Q

Loading/associating

A

Haemoglobin binds with oxygen. Takes place in lungs.

51
Q

Unloading/dissociating

A

Haemoglobin releases its oxygen. Takes place in tissues.

52
Q

High affinity

A

Haemoglobins with high affinity for oxygen takes up oxygen more easily and releases it less easily.

53
Q

Low affinity

A

Haemoglobins with low affinity for oxygen takes up oxygen less easily and releases it more easily.

54
Q

Role of haemoglobin

A

To transport oxygen efficiently.

55
Q

How does haemoglobin transport oxygen efficiently?

A

-Readily associates with oxygen at surface where gas exchange takes place.
-Readily dissociates from oxygen at those tissues requiring it.

56
Q

Why are there different haemoglobins?

A

-Each species produces a haemoglobin with a slightly different amino acid sequence.
-Slightly different tertiary and quaternary structure.
-Different oxygen binding properties.
-Structure gives them high or low affinity for oxygen.

57
Q

Oxygen dissociation curves

A

-x-axis- partial pressure of oxygen(kPa).
-y-axis- saturation of haemoglobin with oxygen (%).
-Relationship between them.

58
Q

Shape of oxygen dissociation curve

A

-Initially shallow.
-Steep increase.
-Graph plateaus.

59
Q

Explanation for initially shallow-

A

-Shape of haemoglobin makes it difficult for first oxygen molecule to bind to one of the sites as they are closely united.

60
Q

Explanation for steep increase-

A

-Quaternary structure changes shape which makes it easier for other subunits to bind.
-A smaller increase in partial pressure in needed to bind second oxygen than first (positive cooperativity).

61
Q

Explanation for graph plateaus-

A

-After third molecule is bound, fourth is very hard to bind.
-Due to probability.
-Majority of binding sites are occupied.
-Less likely for oxygen to find empty site.

62
Q

Position of dissociation curve

A

-The further left the curve is, the greater the affinity of haemoglobin for oxygen (loads oxygen more easily and unloads less easily.)
-The further right the curve is, the lower the affinity of haemoglobin for oxygen (loads oxygen less easily and unloads more easily).

63
Q

Bohr effect

A

The greater the concentration of CO2, the lower the pH, the more readily haemoglobin releases its oxygen.

64
Q

Transport of oxygen

A

-At exchange surface, CO2 is constantly being removed so concentration of CO2 is very low.
-pH is slightly raised which changes the shape of the haemoglobin to have a higher affinity to oxygen and also load oxygen more easily.
-In the tissues, CO2 is being produced so the concentration of CO2 is very high.
-pH is lowered which changes the shape of the haemoglobin to have a lower affinity for oxygen and therefore unloads oxygen more easily.

65
Q

Why do large organisms have transport systems?

A

-Take substances from cells to exchange surfaces.
-Organisms evolved into more complex and larger species.
-Tissues and organs they’re made of have become more complex and dependent on one another.

66
Q

Features of transport systems

A

-Suitable medium to carry materials.
-Form of mass transport.
-Closed system of tubular branching vessels.
-Mechanism of moving the transport medium within vessels (muscle contraction or passive processes).
-Mass flow in one direction.
-Means of controlling flow to suit needs of organism.
-Mass flow of water or gases.

67
Q

Circulatory system in mammals

A

-Closed, double circulatory system.
-Blood confined within vessels.
-Blood passes through heart twice in one circuit.
-High body temperature and therefore high metabolic rate.

68
Q

Structure of the heart

A

-Left atrium
-Right atrium
-Left ventricle
-Right ventricle
-Inferior vena cava
-Superior vena cava
-Pulmonary artery
-Pulmonary vein
-Aorta
-Bicuspid valve
-Tricuspid valve
-Semi lunar valves
-Septum

69
Q

Supplying heart muscle with oxygen

A

-Oxygen is supplied via heart’s own blood vessels called coronary arteries.
-When they get blocked, leads to myocardial infraction.
-Part of heart is deprived of oxygen so muscles in that area cannot respire so part of heart dies.

70
Q

Risk factors associated with cardiovascular disease

A

-Smoking
-High blood pressure
-Blood cholesterol
-Diet

71
Q

Smoking

A
72
Q

High blood pressure

A
73
Q

Blood cholesterol

A
74
Q

Diet

A
75
Q

Stages of cardiac cycle

A

-Diastole
-Artial systole
-Ventricular systole

76
Q

Diastole

A

-Relaxation of the heart
-Blood enters the atria via pulmonary vein and vena cava.
-Atria fills- pressure rises.
-Pressure exceeds ventricular pressure and AV valve opens and blood flows into ventricles.
-Muscular wall of atria and ventricles are both relaxed at this moment.
-Relaxation of ventricle wall causes it to recoil and reduce pressure.
-Pressure lower than aorta and pulmonary artery so semilunar valves close.

77
Q

Atrial systole

A

-Contraction of atria
-Contraction of atrial walls and recoil of ventricle walls (while relaxed).
-Forces blood into ventricle.

78
Q

Ventricular systole

A
79
Q

Atrioventricular valves

A
80
Q

Semi lunar valves

A
81
Q

Pocket valves

A
82
Q

Pressure and volume changes of the heart

A
83
Q

Cardiac output

A
84
Q

Arteries

A
85
Q

Arterioles

A
86
Q

Capillaries

A
87
Q

Veins

A
88
Q

Artery structure related to function

A

Transport blood rapidly under high pressure from heart to tissues.
-Thick muscle layer- smaller arteries can be constricted or dilated in order to control volume of blood passing.
-Thick elastic layer- keep blood pressure high to reach all extremities of body, stretching and recoil helps maintain high pressure and smooth pressure surges created by beating heart.
-Thickness of wall- resists the vessel bursting under pressure.
-No valves- under constant high pressure so doesn’t require valves.

89
Q

Arteriole structure related to function

A

Carry blood, under lower pressure than arteries, from arteries to capillaries, control flow of blood.
-Thick muscle layer- allows constriction of the lumen, restricts flow of blood controlling movement into capillaries that supply tissues with blood.
-Thin elastic layer- blood pressure is lower.

90
Q

Vein structure related to function

A

Transports blood from tissues to heart under low pressure.
-Thin muscle layer- veins carry blood away from tissues and therefore constriction and dilation cannot control flow of blood.
-Thin elastic layer-Low pressure of blood within veins will not cause them to burst and pressure is too low to create recoil action.
-Thinness of wall- pressure too low so no risk of bursting, flattened easily.
-Valves- ensure no backflow of blood, one direction.

91
Q

Capillary structure linked to function

A

-Mostly lining layer- extremely thin- shorter diffusion distance- rapid diffusion.
-Numerous and highly branched- permeate tissues, shorter diffusion pathway.
-Narrow lumen- short diffusion distance.
-Spaces between endothelial cells (fenestrations)- allow WBCs to escape in order yo deal with infections within tissues.

92
Q

Tissue fluid

A

-The means by which substances are exchanged from blood to cells.
-It is a watery substance that contains glucose, amino acids, fatty acids, ions in solution and oxygen.

93
Q

Tissue fluid formation

A

At arteriole end:
-Higher hydrostatic pressure inside the capillary than tissue fluid.
-Forces water out the fenestrations.
-Large plasma proteins remain in the capillary lowering the water potential.
At venule end:
-Hydrostatic pressure reduces as fluid leaves capillary.
-Increased concentration of plasma proteins lowers the water potential of the capillary.
-Water enters capillary by osmosis down a water potential gradient.
-Excess water is taken up by lymph capillaries and returned to the circulatory system via veins.

94
Q
A

A Level Biology (9 decks)

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