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A Level Biology > Unit 3 > Flashcards

Unit 3 Flashcards

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
Pulmonary ventilation equation
pulmonary ventilation rate= tidal volume x breathing rate
26
Essential features of human exchange surfaces
27
Gas exchange in alveoli
28
Oesophagus
-Carries food from mouth to stomach. -Physical
29
Stomach
-Muscular sac. -Inner layer of enzymes. -Store and digest foods.
30
Ileum
-Long muscular tube. -Enzymes produced in walls. -Walls folded in villi (absorb products of digestion).
31
Large intestines
-Absorbs water. -Secretion of many digestive glands.
32
Rectum
-Faeces are stored here. -Removed vias anus in process called egestion.
33
Salivary glands
-Situated near mouth. -Pass secretions via duct. -Amylase- hydrolyses starch into maltose
34
Pancreas
-Large gland situated below stomach. -Secretes enzymes.
35
Physical digestion
-Large food molecules are broken down into smaller food molecules. -By structures like teeth.
36
Chemical digestion
-Large food molecules are broken down into smaller food molecules. -Carried out by enzymes (hydrolysis reactions).
37
Carbohydrates digestion
-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.
38
Sucrase
-Hydrolyses sucrose into alpha glucose and fructose. -Membrane-bound disaccharidases.
39
Lactase
-Hydrolyses lactose into alpha glucose and galactose. -Membrane-bound disaccharidases.
40
Protein digestion
-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
Lipids digestion
-Lipids are combined with bile salts. -Emulsified into micelles. -Increase surface area for lipase to act on.
42
Structure of ileum
-Last portion of the small intestines. -Villi, microvilli.
43
Ileum adaptations
-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
Absorption of amino acids and monosaccharides
Co-transport.
45
Absorption of triglycerides
-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
Primary structure of haemoglobin
Sequence of amino acids in the four polypeptide chains.
47
Secondary structure of haemoglobin
One of the polypeptide chains is coiled in a helix.
48
Tertiary structure of haemoglobin
Each polypeptide chain is folded into a precise shape- important for ability to carry oxygen.
49
Quaternary structure of haemoglobin
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
Loading/associating
Haemoglobin binds with oxygen. Takes place in lungs.
51
Unloading/dissociating
Haemoglobin releases its oxygen. Takes place in tissues.
52
High affinity
Haemoglobins with high affinity for oxygen takes up oxygen more easily and releases it less easily.
53
Low affinity
Haemoglobins with low affinity for oxygen takes up oxygen less easily and releases it more easily.
54
Role of haemoglobin
To transport oxygen efficiently.
55
How does haemoglobin transport oxygen efficiently?
-Readily associates with oxygen at surface where gas exchange takes place. -Readily dissociates from oxygen at those tissues requiring it.
56
Why are there different haemoglobins?
-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
Oxygen dissociation curves
-x-axis- partial pressure of oxygen(kPa). -y-axis- saturation of haemoglobin with oxygen (%). -Relationship between them.
58
Shape of oxygen dissociation curve
-Initially shallow. -Steep increase. -Graph plateaus.
59
Explanation for initially shallow-
-Shape of haemoglobin makes it difficult for first oxygen molecule to bind to one of the sites as they are closely united.
60
Explanation for steep increase-
-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
Explanation for graph plateaus-
-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
Position of dissociation curve
-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
Bohr effect
The greater the concentration of CO2, the lower the pH, the more readily haemoglobin releases its oxygen.
64
Transport of oxygen
-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
Why do large organisms have transport systems?
-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
Features of transport systems
-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
Circulatory system in mammals
-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
Structure of the heart
-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
Supplying heart muscle with oxygen
-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
Risk factors associated with cardiovascular disease
-Smoking -High blood pressure -Blood cholesterol -Diet
71
Smoking
72
High blood pressure
73
Blood cholesterol
74
Diet
75
Stages of cardiac cycle
-Diastole -Artial systole -Ventricular systole
76
Diastole
-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
Atrial systole
-Contraction of atria -Contraction of atrial walls and recoil of ventricle walls (while relaxed). -Forces blood into ventricle.
78
Ventricular systole
79
Atrioventricular valves
80
Semi lunar valves
81
Pocket valves
82
Pressure and volume changes of the heart
83
Cardiac output
84
Arteries
85
Arterioles
86
Capillaries
87
Veins
88
Artery structure related to function
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
Arteriole structure related to function
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
Vein structure related to function
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
Capillary structure linked to function
-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
Tissue fluid
-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
Tissue fluid formation
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

A Level Biology (11 decks)

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