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biology > 4.1 - exchange and transport > Flashcards

4.1 - exchange and transport Flashcards

1
Q

what are the 3 passive transport mechanisms

A

diffusion
facilitated diffusion
osmosis

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2
Q

what are the 3 active transport mechanisms

A

endocytosis
exocytosis
active transport

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3
Q

what is the definition of simple diffusion

A

the movement of particles in a liquid or gas down a concentration gradient from an area of high concentration to an area of low concentration
it is a passive mechanism so doesn’t require ATP

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4
Q

what is the definition of facilitated diffusion

A

the movement of particles in a liquid or gas down a concentration gradient from an area of high concentration to an area of low concentration through carrier proteins or protein channels
it is a passive mechanism so doesn’t require ATP

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5
Q

what is the definition of osmosis

A

the movement of solvent molecules down a concentration gradient through a partially permeable membrane
it is a passive mechanism so doesn’t require ATP

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6
Q

what is the definition of endocytosis

A

the movement of large molecules into cells through vesicle formation
it is an active mechanism so requires ATP

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7
Q

what is the definition of exocytosis

A

the movement of large molecules out of cells through vesicle formation
it is an active mechanism so requires ATP

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8
Q

what is the definition of active transport

A

the movement of substances into or out of a cell though a membrane using ATP

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9
Q

describe what happens during simple diffusion

A

-small molecules in a liquid or gas move around randomly and are able to pass through the cell membrane
-initially there is a net movement from an area of high concentration to an area of low concentration until a uniform distribution of molecules is reached
-the molecules continue to move randomly but there is no net movement
-hydrophilic molecules cannot pass through the cell membrane because the center of the phospholipid bilayer is hydrophobic so have to be transported by facilitated diffusion

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10
Q

describe overall how facilitated diffusion works

A

hydrophilic substances cross the cell membrane without interacting with the hydrophobic center of the phospholipid bilayer by using channel proteins or carrier proteins

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11
Q

why can water pass through the cell membrane but other hydrophilic substances cannot

A

water molecules are very small so can pass through the phospholipid bilayer
other hydrophilic substances cannot pass through the phospholipid bilayer becuase the center is hydrophobic due to the fatty acid tails

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12
Q

explain facilitated diffusion using carrier proteins

A

-each carrier protein has a specific shaped binding site for a specific molecule
-when the molecule binds to it’s complementary carrier protein the tertiary structure of the protein changes, which carries the molecule to the other side of the membrane
-the carrier protein changes back to its original tertiary structure, allowing more molecules to pass through the membrane

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13
Q

explain facilitated diffusion using channel proteins

A

-the protein channel is lined with hydrophilic amino acids and contains water
-protein channels are selective to the type of molecules than can pass through from one side of the membrane to the other
-some protein channels are always open and others only open in response to a trigger
e.g. a neurotransmitter binding to the protein or a change in voltage across the membrane

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14
Q

what is osmotic concentration

A

a measure of the concentration of solutes in a solution that have an osmotic effect
large insoluble molecules are not considered when calculating osmotic concentration

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15
Q

what is the definition of an isotonic solution

A

the osmotic concentration of the solutes in the solution outside the cell is equal to the osmotic concentration of solutes inside the cell

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16
Q

what is the definition of an hypotonic solution

A

the osmotic concentration of solutes in the solution outside the cell is lower than that in the cytoplasm inside the cell

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17
Q

what is the definition of an hypertonic solution

A

the osmotic concentration of solutes in the solution outside the cell is higher than that in the cytoplasm inside the cell

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18
Q

explain what happens when a plant cell is placed in a hypotonic solution

A

-water enters the cell by osmosis
-because the cytoplasm swells and presses against the cell wall it generates hydrostatic pressure
-pressure potential (inward pressure of the cell wall on the cytoplasm) increases until it cancels out the tendency for water to move into the cell
-when the osmotic force moving water into the cell is balanced by the pressure potential forcing water out, the plant cell is rigid and in turgor state

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19
Q

explain what happens when a plant cell is placed in a slightly hypertonic solution

A

-what moves out of the cell by osmosis and turgor is lost
-incipient plasmolysis occurs where the cell membrane just begins to pull away from from the cell wall as the protoplasm shrinks

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20
Q

explain what happens when a plant cell is placed in a hypertonic solution

A

-what moves out of the cell by osmosis and turgor is lost
-plasmolysis occurs where the vacuole will reduce in size and the protoplasm will shrink completely away from the cell wall
-the cell is fully plasmolysed
-the shape of the overall cell doesn’t differ much from being turgid or fully plasmolysed due to the cell wall

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21
Q

can animal cells and plant cells lysis

A

animal cells can lysis if too much water enters by osmosis
plant cells cannot lysis because of the rigid cell wall

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22
Q

what is the definition for water potential
and explain the meaning

A

ψ
-a measure of the potential for water to move out of a solution by osmosis
-pure water has the greatest possible water potential because water molecule will always move from pure water to any solution on the other side of a partially permeable membrane
-maximum water potential /pure water is 0
-so all other solutions have a lower water potential than pure water so their water potential will be negative

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23
Q

what is the definition for turgor pressure
and explain the meaning

A

P
-the inward pressure exerted by the cell wall onto the protoplasm as cell contents expands and presses outwards due to water entering the cell
-turgor pressure rises until the osmotic force pulling water into the cell is balanced by the turgor pressure opposing entering water
-at this point turgor pressure=osmotic potential of the cell so tugor remains constant
-turgor pressure usually has a positive value

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24
Q

how can tugor pressure be measured

A

using a pressure probe in 1 individual plant cell

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25
Q

what is the definition for osmotic potential
and explain the meaning

A

π
-osmotic potential is the potential of water to move across a partially permeable membrane from a hypotonic solution to a hypertonic solution
-pure water has the highest osmotic potential and a solution containing dissolved solutes has a lower osmotic potential
-osmotic potential is always 0

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26
Q

what is the definition of water potential

A

a measure of the potential for water to move out of a solution by osmosis

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27
Q

when is the cell at full turgor

A

when the osmotic potential and turgor are equal
the cell is also at 0 water potential

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28
Q

what is the equation for water potential

A

water potential (-) = turgor pressure (+) + osmotic potential (-)

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29
Q

explain what happens in active transport

A

-a molecule which is specific to the carrier protein binds onto the carrier protein
-ATP binds onto the carrier protein
-the ATPase enzyme catalyses the hydrolysis of the ATP molecule which produces ADP and a phosphate, one bond is broken and 2 new bonds are made which provides energy needed by the carrier protein
-the phosphate attaches to the carrier protein causing it to change shape, which causes the molecule to be transported to the other side of the membrane and released
-the phosphate leaves the carrier protein causing it to change back into its original shape
-these carrier proteins can only transport molecules in 1 direction

30
Q

explain what happens in the sodium-potassium pump

A

-potassium ions move into the cell and sodium ions move out of the cell through active transport
-used in the nervous system, a nerve impulse requires an influx of sodium ions though the axon membrane, which need to be actively pumped out after so another nerve impulse can be created

31
Q

what are the 4 peices of evidence that link active transport and ATP

A

-active transport only takes place in living respiring cells
-the rate of active transport depends on temperature and oxygen concentration, these factors also affect the rate of respiration and so ATP production
-cells that carry out lots of active transport have lots of mitochondria
-poisons that stop respiration also stop active transport

32
Q

are exocytosis, endocytosis and pinocytosis passive or active processes

A

examples of active transport
so require ATP

33
Q

what is the definition of exocytosis

A

an active process where materials are removed from the cell
vesicles containing the substance fuse with the cell membrane to release their contents

34
Q

what is the definition of endocytosis

A

an active process where materials are engulfed by the cell membrane and then taken into vesicles, the released into the cell

35
Q

what is the definition of pinocytosis

A

an active process where extracellular fluid is taken in by vesicles, the released into the cell

36
Q

why do single-celled organisms and very small multi-cellular organisms not have a gas exchange system

A

-oxygen which is required for aerobic respiration can diffuse directly into cells from the environment
–carbon dioxide as a waste product can diffuse directly out of cells and into the environment

37
Q

what features of single-celled organisms and very small multi-cellular organisms allow oxygen and carbon dioxide to diffuse into and out of cells directly without the need for a gas exchange system

A

-the diffusion distance from the outside of the organism to the innermost cells is very small
-very big surface area to volume ratio, so there is a very big surface area to which substances can diffuse into
-low metabolic demands, organisms don’t regulate their internal temperature, cells don’t require a lot of oxygen or food, cells don’t produce a lot of carbon dioxide

38
Q

what 3 factors affect the rate of gas exchange

A

-surface area to volume ration, the greater it is the greater the rate of diffusion
-concentration gradient, the greater the difference in concentration of a substance the greater the rate of diffusion of that substance towards the area with the lower concentration
-diffusion distance, the shorter the diffusion distance the greater the rate of diffusion

39
Q

what features does the mammalian effective gas exchange system have that makes it effective

A

-large surface area, allows sufficient diffusion of gases to supply all cells,
-thin layers for a short diffusion distance
-rich blood supplly to the alveoli, transports oxygen away and brings carbon dioxide to maintain steep concentration gradient
-moist surfaces, diffusion takes place when the gases are dissolved in a solution
-permeable surfaces, allows oxygen and carbon dioxide to diffuse

40
Q

what is the role of the nasal cavity in the human gas exchange system

A

-the nasal passage has a good blood supply, the lining secretes mucus and is covered in hairs
-the hairs and mucus remove any dust or pathogens
-the mucus increases the level of water vapour in the air
-the blood supply raises the temperature of the air
-this means the air entering the lungs has as little effect as possible on the internal body environment

41
Q

what is the function of the epiglottis

A

a flap of tissue that closes over the glottis in a reflex reaction when swallowing food
it prevent food entering the gas exchange system

42
Q

what is the function of the trachea

A

airways to the bronchi
lined with cilia that move dust and pathogens away from the lungs
has cells which secrete mucus, keeping the lining moist

43
Q

what is the function of the rings of cartilage

A

prevent the trachea and bronchi from collapsing
c-shaped to allow flexibility, can contract to push food down the oesophagus

44
Q

what structures in the gas exchange system have rings of cartilage

A

trachea and bronchi

45
Q

what are the function of the pleural membranes

A

surround the inside of the lungs and line the chest cavity
reduces friction during breathing
prevents the lungs from collapsing
in between the pleural membranes there is the pleural cavity

46
Q

what is the function of the pleural cavity

A

filled with a lubricating fluid that allows the membranes to slide with breathing movements

47
Q

what lines the inside of alveoli
what is its function

A

-lung surfacant lines the inside of alveoli
-made of phospholipids
-prevents the alveoli from collapsing

48
Q

explain how and why oxygen and carbon dioxide diffuse between the alveoli and capillaries

A

-the alveolar air contains a high concentration of oxygen and low concentration of carbon dioxide
-the deoxygenated blood in the capillaries contain a low concentration of oxygen but high concentraion of carbon dioxide
-so there is a steep concentration gradient
-oxygen diffuses by simple diffusion from the alveoli to the capillaries
-carbon dioxide diffuses by simple diffusion from the capillaries to the alveoli

49
Q

capillaries and alveoli are 1 cell thick, true or false
what are these cells

A

-true
-capillaries are made from endothelial cells
-alveoli are made from squamous epithelial cells

50
Q

state the adaptations of the alveoli for gas exchange

A

-large surface area
-short diffusion distance
-steep concentration gradient

51
Q

explain why alveoli have adapted to have a large surface area

A

-theres a greater surface area for diffusion of gases
-so rate of diffusion increases

52
Q

explain why alveoli have adapted to have a steep concentration gradient

A

-blood is continueously flowing
-the deoxygenated blood in the capillaries contain a low concentration of oxygen but high concentraion of carbon dioxide
-expired air is being breathed out and fresh air is inspired in
-the alveolar air contains a high concentration of oxygen and low concentration of carbon dioxide
-this steep concentration gradient increases the rate of diffusion

53
Q

explain why alveoli have adapted to have a short diffusion distance

A

-alveoli walls are 1 squamous epithelial cell thick
-the capillaries surround the alveoli and are 1 endothelial cell thick
-so gases only need to diffuse a short distance
-so rate of diffusion increases

54
Q

explain what happens during inhalation

A

-active process
-muscles around the diaphragm contract
-causing the diaphragm to move down and flatten
-the external intercostal muscles contract
-raising the rib cage up and outwards
-the pressure of the chest cavity is now lower than the pressure of air outside
-so air moves into the lungs to equalise the pressure

55
Q

explain what happens during passive exhalation

A

-passive process
-the muscles surrounding the diaphragm relax
-causing the diaphragm to move up and into a resting domed shape
-internal intercostal muscles relax
-rib cage moves down and in
-the pressure in the chest cavity is now greater than the pressure of air outside
-so air moves out of the lungs

56
Q

how is forced exhalation different from passive exhalation

A

-internal intercostal muscles contract instead of relax
-abdominal muscles contract forcing the diaphragm upwards

57
Q

how does the gas exchange system prevent pathogens, dust, smoke etc from infecting the body

A

-the airways are lined with mucus to trap pathogens
-which is usually runny so it can be moved by cilia up the airways into the throat
-where it can be swallowed, enter the stomach and be killed by the hydrochloric acid or digestive enzymes

58
Q

do insects have a mass transport system

A

no, oxygen is delivered directly to cells and carbon dioxide is removed directly from cells

59
Q

state the structures present in the insect gas exchange system

A

exoskeleton
spiracles
tracheae
tracheoles
muscle fibres

60
Q

what is the function of spiracles

A

-where oxygen enters and carbon dioxide exits
-can be opened or closed by spiracle sphincters, which is useful to control water loss

61
Q

what is the function of tracheae

A

-carries air directly into the body and along the body (cross shape)
-lined with spirals of chitin
-these hold the tracheae open
-chitin is impermeable to gases so no gas exchange occurs in the tracheae

62
Q

what is the function of tracheoles

A

-each tracheole is a single elongated cell
-tracheoles have no chitin, so are permeable to gases so this is where gas exchange occurs
-the tracheoles are so small that they run between cells and some run into cells
-contain tracheole fluid which doesn’t allow gases to diffuse through

63
Q

describe the pathway for gas exchange in an insect

A

-when the insect needs to respire the spiracle sphincter open
-the spiracles open to allow oxygen ti diffuse into the tracheae and tracheoles
-the amount of tracheal fluid inside the tracheoles determines how much oxygen can diffuse into the muscle cells
-CO2 diffuses from muscle cells, into the tracheoles, tracheae and then out the spiracles
-but CO2 can also diffuse directly out of the cuticle

64
Q

what 2 things control the rate of gas exchange in insects

A

-the amount of tracheal fluid in the tracheoles
-if the insect is very active the muscle cells will undergo anaerobic respiration if there is a lack of oxygen
-so lactic acid is produced in cells, causing the water potential of these cells to decreases
-tracheal fluid diffuses from the tracheoles into the muscle cells though osmosis down the concentration gradient
-so there is a large surface area in the tracheoles that is permeable to oxygen, increasing the rate of gas exchange
-the opening and closing of spiracles
-controlled by the nervous system
-the nervous system is stimulated when there are increasing CO2 levels and a build up of lactic acid, it then stimulates the spiracles to open

65
Q

what adaptations do very active insects have to increase the rate of gas exchange

A

-mechanical ventilation, when the spiracles open insects make muscular pumping movements of the thorax and abdomen, these movements change the volume and therefore pressure inside the body, drawing air into and out the tracheae and tracheoles
-collapsible tracheae that act as air reservoirs, ventilating muscle movements of the thorax and abdomen inflate and deflate them, increasing the volume of air moved in

66
Q

what challenges do bony fish face in terms of gas exchange

A

-bony fish are very active so have a high oxygen requirement
-their scaly external covering is impermeable to gases
-very low surface area to volume ratio
-the concentration of oxygen in water is much lower than in air

67
Q

describe the journey of water through the gas exchange system of a bony fish

A

-the mouth opens and the operculum closes
-water enters the mouth, and goes into the buccal cavity
-then passes over the gills
-on the gills are made up of many gill arches which extend into gill filaments, and on each filament there are many lamellae
-the operculum opens and the mouth closes
-water exits out the operculum cavity

68
Q

how does oxygen diffuse into the blood stream of a bony fish

A

-the flow of water keeps the gill filaments apart, increasing surface area
-water flows between the lamellae
-lamellae contain capillaries with deoxygenated blood, low concentration of O2 high concentratation of CO2
-blood in the lamellae flows in the opposite direction to the flow of water, this is a countercurrent exchange system
-this maintains a steep concentration gradient
-oxygen diffuses from the water into the blood
-CO2 diffuses from the blood into the water

69
Q

can bony fish ventilate their gills even if they aren’t moving
explain why

A

-yes
-when the mouth water flows into the buccal cavity
-the floor of the buccal cavity drops down, increasing the volume of the buccal cavity
-the operculum closes, increasing the volume of the operculum cavity, and the pressure drops
-the floor of the buccal cavity lifts upwards, increasing the pressure of water, causing water to flow over the gills into the operculum cavity
-the mouth closes and operculum opens, the sides of the operculum cavity squeeze inwards, increasing the pressure of water so it flows out

70
Q

what adaptation slows the flow of water in the gas exchange system of bony fish

A

-the tips of adjacent gill filaments overlap
-increasing the resistance of water flow
-this slows the flow of water allowing more time for gases to diffuse

71
Q
A

biology (7 decks)

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