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Biology - AS Level > gas exchange > Flashcards

gas exchange Flashcards

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1
Q

what is an exchange surface

A

where molecules leave and enter the cell

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2
Q

which cells can exchange materials with the environment

A

unicellular

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3
Q

which cells can not exchange materials with the environment

A

multicellular - as cells are often to far away from the surface, so takes to long for the molecules to diffuse

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4
Q

what is the relationship bwt SA and vol and exchange material

A

-amount of material an organism needs to exchange with its environment is PROPORTIONAL to its volume
-amount it can exchange is PROPORTIONAL to SA

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5
Q

what is the equation for diffusion in terms of SA:V

A

SA x difference in conc./ length of diffusion path or thickness of exchange surface

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6
Q

what is the relationship bwt SA and V

A

as volume increases SA:V decreases

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7
Q

what features do good exchange surfaces have

A

-a large SA- makes SA:V so molecules can cross the surface per unit time
-a thin surface- shorter diffusion pathway - so more molecules per unit time across surface
-a steep diffusion gradient- greater conc gradient increases rate of diffusion so more molecules across surface per unit time

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8
Q

how is a diffusion gradient maintained

A

movement of an a environmental medium (air/water) and the movement of the internal medium (blood)

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9
Q

how can certain environmental changes effect exchange surfaces

A

water and air have different properties due to heat transfer
- air - molecules apart - so air is a poor conductor
- water - molecules close- more heat conducted- loss heat more easily- so need adaptions to survive

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10
Q

what must larger organisms have to increase SA

A

-a specialised organ
-circulatory system with oxygen-carrying pigment eg Hb

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11
Q

how to calculate volume

A

length x height x width

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12
Q

how to find surface area

A

length x height x no of faces

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13
Q

how to find SA:V

A

divide SA by V

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14
Q

what type of skeleton does an insect have

A

an exoskeleton made of chitin

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15
Q

how is the exoskeleton adapted to prevent water loss

A

waxy cuticle - prevents dehydration and allows insect to live on land

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16
Q

how is the insect tracheal system structured

A

spiracles are located in the thorax and abdomen
spiracles branch into tracheoles
tracheoles surrounded by rings of chitin

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17
Q

how do the spiracles prevent water loss

A

they can open and close - short periods of gas exchange

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18
Q

what other feature of the insect prevents water loss

A

-hairs on entrance to spricale - trap layer of thin air and reduce conc gradient

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19
Q

how does the insect system allow for sufficient gas exchange

A

extensive branching system - large SA for gas exchange to occur over

maintenance of diffusion gradient - using a ventilation mechanism which increases the conc gradient- O2 used in tissues for respiration so conc is lower in the cells- higher conc of CO2 in the cells

thin membrane - shorter diffusion pathway - tracheole walls very thin and narrow which makes them permeable due to the lack of chitin
- also a withdrawal of fluid in exercise - so air reaches more cells on the exchange surface

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20
Q

what is the effect of exercise on fluid in the tracheoles

A

-at rest
tracheoles contain watery fluid
reduces SA over which diffusion can occur
this is not a problem when at rest as respiration rate is lower

-during strenuous activity
muscles respire anaerobically - produce lactate
lactate lowers water potential in the muscles
water moves from tracheole into muscle
gas diffuses faster through air than water
greater SA exposed to air
so more gas exchange occurs

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21
Q

what factors enable an organism to have a transport medium and pump

A

activity levels
SA:V ratio

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22
Q

what are some of the parts of a transport system

A

medium to transport materials
system of vessel to transport the medium
mechanism to move the medium
mechanism to maintain air flow in one direction
means of controlling the flow depending on the needs of an organism

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23
Q

what is the relationship bwt size and SA:V

A

larger the organism the smaller the SA:V

24
Q

how are the gills of fish ventilated

A

muscles in the walls of the buccal cavity and opercular cavity contract which makes the opercular cavity smaller so water can pass over

25
Q

how does inspiration occur in fish

A

-mouth and the opercular valve closes
-floor of the mouth is lowered
-buccal cavity expands- increasing the vol
-increase in vol, causes pressure in mouth to fall below that of pressure of water outside
-water enters the mouth down a pressure gradient

26
Q

how does expiration occur in fish

A

-mouth closes and opercular valve opens
-floor of mouth raises
-buccal cavity walls contract so pressure rises above the pressure of water outside
-water is forced over the gills due to increased pressure
-water leaves via opercular valve, down pressure gradient

27
Q

why is the flow of water in fish one-way

A

water is too dense to be moved two ways - so allows for maximum gas exchange

28
Q

how are the gills structured

A

–4 each side
-two piles of filaments attached to a gill arch
-MANY gill filaments attached to arches
-each filament made of MANY lamellae-provide surface for gas exchange
-rich blood supply so max gas exchange
-lamellae one cell thick - reduced diffusion distance
-conc gradient maintained

29
Q

how are the lamellae adapted for gas exchange

A

-large SA
-thin walls-short pathway
-rich blood supply
-open mouth to allow water in - ventilation mechanism
-many lamellae

30
Q

what is countercurrent flow

A

-in bony fish
-water flows over the gill lamellae in the opposite direction to the blood.
-this helps maintain a diffusion gradient all along the gill
-prevents equilibrium from being reached
-almost 100% diffusion

31
Q

what is parallel flow

A

-in cartilaginous fish
-water and blood flow in same direction
-exchange gas until conc becomes equal- no more net diffusion
-so gas exchange only occurs part way across the gills and only 50% of water diffuses

32
Q

how are fish adapted for gas exchange

A

-large SA
-each gill has MANY filaments
-each filament has MANY lamellae
-countercurrent mechanism enabling all lamellae to be used for gas exchange - prevent eq from being reached

-thickness of exchange surface is minimised
-lamellae one cell thick
-capillary walls one cell thick
-blood close to surface of gill plate
-gill plates thin so water close to the blood

-difference in conc
-constant flow of aerated water over the lamellae-caused by ventilation mechanism
-constant movement of blood removing oxygen and bringing carbon dioxide to gills
-countercurrent mechanism maintaining a difference in conc bwt water and blood - prevent eq from being reached

33
Q

how is a typical dicotyledonous leaf structured

A

central vein and branches that extend out across the leaf
2 leaves

34
Q

what is the internal structure of a leaf

A

-large internal SA compared to its vol
-large no. of mesophyll cells in the leaf
-large no. of air spaces in mesophyll

35
Q

where does gas exchange occur in the leaf

A

mesophyll cells
-walls thin and moist so permeable to gases
-walls moist as water escapes from cells but water loss is limited as exchange surface is in the leaf

36
Q

how does the process of photosynthesis and respiration maintain conc gradient

A

photosynthesis- produce more O2than needed for resp - so lost from plant
-at night produce more CO2 - not needed for photosyn- so lost from plant

37
Q

how is the flow of O2 and CO2 controlled-plants

A

by stomata and these surrounded by guard cells- can change shape which open and close stomata

38
Q

describe the mechanism for guard cell expansion

A

open

-guard cells actively take up k+ from epidermal cells using energy in the form of ATP
-water potential decreases
-water moves into guard cell by osmosis as water in the guard cell is lower than outside
-guard cells swell and buckle outwards
-inner wall is thicker than the outer wall so is less flexible and resists expansion- causes guard cell to become more curved

close
-K+ leave guard cells
-water potential increases
-water follows by osmosis
-guard cells sag together and close

39
Q

how are plants adapted to reduce transpiration

A

-thick waxy cuticle - waterproof barrier is formed
the thicker the cuticle the less water can escape through the epidermis
-rolling of the leaves- protects lower epidermis from the outside - thus traps a region of air within the leaf
region becomes saturated with water vapour, so has a very high WP
no W gradient bwt out and in so no water loss
-hairy leaves - layer of hair traps moist air next to leaf surface
WP out and in reduced so less water lost in evap
-stomata in pits - traps still moist air next to leaf surface reducing WP
-reduced SA:V- small roughly circular leaves lowers SA so less diffusion as smaller SA:V so rate of water loss decreases

40
Q

where is the human thorax

A

part of body between the head and the abdomen - contains the lungs and heart and is protected b the ribcage

41
Q

what is the role of the trachea

A

-large tube leading from the back of the nose and mouth to the lungs
-lined with ciliated columnar epithelia cels - covered with thick layer of mucus

42
Q

what are the goblet cells

A

-produce mucus to which bacteria and dirt stick
-cilia beat up and mucus is carried up the throat
-so bacteria kept out of the lungs
-stomach kills bacteria due to high acidty
-air that passes through is cleaned, warmed and moistened

43
Q

what are the rings of cartilage

A

incomplete c - shaped
help keep trachea open when pressure change would cause it to collapse and stick

44
Q

what are the bronchi

A

L + R bronchus branch off the trachea one entering each lung
-lined with epithelial cells and have rings of cartilage

45
Q

what is the pleural mebrane

A

surround lungs and contains pleural fluid
-fluid acts as a lubricant - cushion and protects the lungs from damage by the ribs

46
Q

what are the bronchioles

A

bronchi divide into smaller bronchioles
large numbers in the lungs
larger supported by cartilage and lines with epithelial cells + mucus

get smaller as get close to the alveoli
-epithelial cells change int cuboidal cells-reduce distance for diffusion and increasing gas exchange
smaller can contract and expand during ventialtion

47
Q

what are the alveoli

A

air sacs- alveolar air sacs
increase SA for diffusion
each cavity = alveolus and provide vast SA
bwt alveoli are collagen and elastic fibres which allow stretch and recoil during gas exchange
-moist and permeable - deep in body so limited water loss

48
Q

what is the ventilation in the lungs described as

A

tidal flow - in and out same way - due to difference in pressure

49
Q

how do humans achieve inspiration

A

active process
-external intercoastal contract and internal ‘’ relax which pulls ribcage up and out
-diaphragm contacts and flattens
-both increase vol in thorax
-decrease pressure
-atmospheric pressure greater than pulmonary so air forced in

50
Q

how do humans achieve expiration

A

passive
-internal contract and external relax ribcage down and in
-diaphragm muscles relax and becomes dome-shaped
-decrease vol
-increase pressure
-pulmonary pressure greater than atmos so air forced out

51
Q

how does gas exchange occur in the lungs

A

one cell thick- squamous epithelia- rapid diffusion as reduced distance
thin layer of water covers the CSM as it is permeable to water - this increases the distance - as lower in water than air
-so slightly lower rate

-capillary walls very thin - curved into narrow tubes - red blood cells have to squeeze through so slow down

52
Q

how is diffusion rapid in the Alevoli

A

red blood cells slowed as pass capillaries - more time for diffusion
distance bwt alveolar and RBC is reduced as RBC flattened against the walls
walls are thin so short diffusion path
-breathing movements ventilate the lungs and heart circulate the blood to ensure steep conc gradient
alveoli and p capillary have large SA
blood flow in capillaries maintain conc grad

53
Q

name the organ that drives the operation of the human breathing system

A

diaphragm

54
Q

what must happen to the oxygen before it can diffuse into the blood

A

dissolve

55
Q

explain how th elastic fibres in the walls of the alveoli assist in exhalation

A

-provide elastic recoil
-helps to force air out of lungs

56
Q

how do u calculate PVR

A

tidal vol x breathing rate

57
Q
A

Biology - AS Level (17 decks)

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