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AQA Biology > Topic three > Flashcards

Topic three Flashcards

(47 cards)

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1
Q

Relationship between organism size and surface area

A

A larger organism will have a smaller surface area to volume ratio, larger organisms also have a higher metabolic rate

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2
Q

Adaptations of larger organisms, with small surface area to volume ratios

A

-Villi and microvilli for the absorption of food
-Alveoli and bronchioles for human gas exchange
-Spiracles and tracheoles for gas exchange in insects
-Gill filament and lamellae for gas exchange in fish
-Thin, wide leaves for gas exchange in plants
-Many capillaries in capillary networks

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3
Q

Adaptations of unicellular amoeba for gas exchange

A

-Large surface area to volume ratio
-Thin, moist membrane
-Shorter diffusion pathway

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4
Q

Adaptations of an insect to reduce water loss

A

-Small SA:V ratio for water to evaporate from
-Waterproof exoskeleton and lipid layer
-Spiracles that can open and close to limit water loss

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5
Q

Insect gas exchange: spiracle

A

-Round, valve-like openings that run along the length of the abdomen
-O2 enters
-CO2 exits

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6
Q

Insect gas exchange: trachea

A

-Network of internal tubes attached to spiracles
-Rings strengthen it, and keep it open
-Provides large surface area

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7
Q

Insect gas exchange: tracheoles

A

-When the trachea branch into smaller tubes that extend through the abdomen
-Extend through all tissues to deliver oxygen to all respiring cells
-Provides shorter diffusion pathway

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8
Q

Insect gas exchange: simple diffusion

A

As the cells respire aerobically there in less O2 and more CO2, creating a concentration gradient from tracheoles to atmosphere

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9
Q

Insect gas exchange: mass transport

A

The insect contracts and relaxes abdominal muscles to move gas on mass

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10
Q

Insect gas exchange: osmosis

A

-Insects eventually respire anaerobically, producing lactate
-This decreases the water potential, so water moves from the tracheoles to cells by osmosis
-This decreases the volume in tracheoles, creating a pressure gradient so air is drawn in from the atmosphere

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11
Q

Fish gas exchange: gill structure

A

-Four layers of gills on each side of the head, which are stacks of gill filaments
-Each gill filament is covered in a thin lamellae, that is at a right angle to the filament
-This creates a large surface area
-As the fish open their mouth, water rushes in and over the gill, and out through a hole in the head

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12
Q

Fish gas exchange: how is a short diffusion pathway created?

A

-Thin gill lamellae
-Capillary network in the lamellae

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13
Q

Fish gas exchange: counter-current principle

A

-Water flows over the gills in the opposite direction of blood flow in the capillaries
-This ensures equilibrium is never reached
-This maintains an oxygen concentration gradient across the entire length of the lamellae

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14
Q

Leaf gas exchange: structure

A

Thin and flat to allow for short diffusion pathway, and large SA:V ratio

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15
Q

Leaf gas exchange: stomata

A

-Allow CO2 in, O2 out
-Close at night to prevent water loss when photosynthesis isn’t happening
-Many to allow gas to easily enter

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16
Q

Leaf gas exchange: mesophyll

A

Air spaces allow gas to move around the leaf

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17
Q

Structural features of xerophytic plants that reduce water loss, but still allow for efficient gas exchange

A

-Curled leaves, hairs and sunken stomata to trap water, increasing local humidity. This reduces a water potential gradient, preventing evaporation
-Thicker waxy cuticle to reduce evaporation
-Longer root network to reach more water

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18
Q

Human gas exchange: trachea

A

-Wide tube supported by C-shaped cartilage to keep an open passage during pressure changes
-Lined with epithelium cells which allow mucus towards the throat the be swallowed, preventing lung infections
-Carries air to the bronchi

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19
Q

Human gas exchange: bronchi

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A

-Supported by rings of cartilage and lined with ciliated epithelium cells
-Narrower than trachea
-One for each lung
-Allows air flow to bronchioles

20
Q

Human gas exchange: bronchioles

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A

-Narrower than bronchi
-Do not need cartilage for support, they are mostly muscle and elastic fibres that can contract and relax easily during ventilation
-Allow air into the alveoli

21
Q

Human gas exchange: alveoli

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A

-Mini air sacs lined with epithelium cells, the site of gas exchange
-Walls are one cell thick, and covered with a network of capillaries
-300 million per lung, which facilitate gas diffusion

22
Q

Human gas exchange: inspiration

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A

-Internal intercostal muscles relax, external intercostal muscles contract, pulling ribs up and out
-Diaphragm contracts to flatten
-This increases volume in thorax, decreases the pressure
-This creates a pressure gradient, so air is forced into the lungs from the atmosphere

23
Q

Human gas exchange: expiration

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A

-External intercostal muscles relax, internal intercostal muscles contract, pulling ribs down and in
-Diaphragm relaxes to form a dome shape
-This decreases the volume in the thorax, which increases the pressure
-This creates a pressure gradient, so air is forced out of the lungs into the atmosphere

24
Q

Digestion of carbohydrates

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A

-Amylase in the mouth, it is produced by the pancreas and salivary glands
-Hydrolyses the polysaccharide to disaccharides by hydrolysing the glycosidic bonds
-Membrane-bound disaccharidases, such as sucrase, in the duodenum and ileum hydrolyse the disaccharides to monosaccharides

25
Digestion of proteins
-Starts in the stomach, then duodenum, then ileum -Endopeptidases-hydrolyse peptide bonds between two amino acids in the middle of the polypeptide chain -Exopeptidases-hydrolyse peptide bonds between two amino acids at the end of the polypeptide chain -Membrane-bound dipeptidases-hydrolyses the bonds in a dipeptide
26
Digestion of lipids
-Lipase is produced in the pancreas, it hydrolyses the ester bonds in triglycerides to monoglycerides and fatty acids -Bile salts are produced in the liver and emulsify lipids to form smaller lipid droplets (micelles), which increase the surface area for lipase action
27
Micelles in lipid digestion
-Water soluble vesicles that contain fatty acids, glycerol, monoglycerides, and bile salts -Deliver the fatty acids, glycerol, and monoglycerides to the epithelial cells of the ileum
28
Absorption of lipids
-Micelles include fatty acids and glycerol, and make them more water-soluble -Move to the ileum where there is a concentration gradients, so the fatty acids and monoglycerides are absorbed by diffusion -Triglycerides are reformed in chylomicrons -Vesicles from the SER move to the cell membrane, and triglycerides enter the lymphatic vesicle
29
How are amino acids and monosaccharides absorbed?
Co-transport
30
Describe the structure of Haemoglobin
-Quaternary protein with four chains -Each one contains a haem group-Fe2+ that allows the oxygen to bind (forming FE3+)
31
Describe the oxygen dissociation curve
-At low partial pressures of 0, such as 50% saturation, O unloads from the Hb. This occurs in respiring tissues -At high partial pressures of O, O loads onto the Hb, this occurs in the lungs
32
Describe co-operative binding in Haemoglobin
-When one O molecule loads, it alters the tertiary structure of the Haemoglobin, making it easier for more O to bind -Can be applied in reverse when an O molecule unloads
33
Describe the Bohr effect
-When the body is respiring more, there may be a high concentration of CO2 in the blood, this causes the affinity curve to shift to the right (Hb has a lower affinity) -This is because the CO2 makes the blood more acidic, which slightly alters the shape of the Hb
34
Describe the mammalian circulatory system
-Closed-all blood is always contained in blood vessels -Double circulatory system-blood passes through the heart twice in each cycle, one circuit takes it to the lungs and the other takes it to the body
35
Why do mammals use a double circulatory system?
-Maintains the pressure of blood flow -Lower in the lungs so as to not damage the capillaries, and to allow more time for gas exchange -Higher in the rest of the body to ensure respiring cells are getting oxygen at a sufficient rate
36
Describe the cardiac cycle
-Diastole-both the atria and ventricles are relaxed as blood enters the atria, causing a slight pressure change -Atriasystole-blood continues to flow in and the atria contracts, decreasing volume and increasing pressure. Pressure is lower in the ventricles, so the AV valves open -Ventricular systole-ventricle contracts, decreasing the volume and causing the pressure to be greater than in the atria. AV valves close and semi-lunar valves open, allowing blood flow into arteries
37
Heart structure: cardiac muscle
-Thick muscle, only found in the heart -Myogenic-can contract and relax without nervous or hormonal stimulation -Will never fatigue as long as it has a supply of oxygen
38
Heart structure: coronary arteries
-Branch off the aorta -Supply cardiac muscle with blood
39
Heart structure: atria
-Thinner muscular walls as they don't need to pump blood as far, so don't need as strong contractions -Elastic walls that can stretch
40
Heart structure: ventricles
-Thicker for stronger contraction-blood flow around the body and against gravity -Create a higher blood pressure for blood to flow longer
41
42
Xylem adaptations: long cells with no end walls
Allows for continuous water columns
43
Xylem adaptations: no cytoplasm or organelles
Nothing to obstruct the flow of water
44
Xylem adaptations: cellulose walls are thickened with lignin
Helps the cells to withstand tension
45
Xylem adaptations: pits in walls
-Lignin is waterproof, pits are spots with no lignin -Allows for the lateral flow of water out of the xylem -Allows water to bypass any blocked xylem vessels
46
Describe cohesion-tension theory
-Water is lost from the leaf by transpiration from the mesophyll -This lowers the water potential of the mesophyll -Water is pulled up the xylem, creating tension -Water molecules cohere by hydrogen bonding, forming columns -Adhesion of water molecules to xylem wall
47
Describe translocation in the phloem
-At the source, companion cells actively transport sucrose into sieve tube elements -This lowers the water potential in the sieve, so water enters sieve cells from the xylem by osmosis -This causes a high hydrostatic pressure in the sieve tube -The pressure gradient leads to the mass flow of fluid towards the sink, where the sucrose is actively transported to the sink -Due to the high water potential in the sieve tube, water moves back to the xylem by osmosis to decrease the hydrostatic pressure in the sieve

AQA Biology (16 decks)

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