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mass transport Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is transported in the xylem and phloem?

A

xylem: water and mineral ions
phloem: organic substances eg sucrose/sugars

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2
Q

adaptations of xylem

A

end walls broken = continuous column
strengthened with lignin = support
no cytoplasm/organelles = doesn’t obstruct continuous flow

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3
Q

cohesion tension theory

A

water evaporates from mesophyll cels in leaf
water vapour diffuses out of leaf through stomata
down concentration gradient between leaf and air

creates tension which pulls more water into the leaf
water moves out of xylem into leaf cells

creates tension on column of water in xylem
water molecules cohesive, joined by hydrogen bonds
moves upwards

water enters root hair cells by osmosis
as water pulled upwards

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4
Q

evidence for cohesion tension

A

change in trunk diameter
- increased transpiration = narrower trunk as xylem pulled in by cohesion

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5
Q

translocation (mass flow)

A

at source
Sucrose actively transported into phloem
By companion cells

decreases water potential in phloem
so water moves in by osmosis from xylem
creates high hydrostatic pressure

at source
sugars used in respiration or stored

lower water potenial
so water moves out by osmosis into xylem
low hydrostatic pressure

creates pressure gradient
= mass transport from source to sink

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6
Q

evidence for mass flow

A

higher concentration of sucrose in sap nearer source than sink
- suggests osmosis would occur to move sugars

radioactive tracers to track movement of sugars

puncture phloem
sap flows out fast (faster nearer leaves then stem)
suggests there’s a pressure (gradient)

metabolic inhibitor (stops ATP production) stops translocation
suggests active transport involved

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7
Q

evidence against mass flow

A

sugar moves to many sinks
not just ones with lower water potential

sieve plates create a barrier
its of pressure needed to get solutes through fast enough

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8
Q

what is transpiration?

A

loss of water vapour from stomata by diffusion

due to water potential gradient between leaf and air

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9
Q

factors affecting transpiration

A

light - positive correlation
- stomata open when light for photosynthesis, allow transpiration

temperature - higher = faster
- warmer water molecules have more kinetic energy so evaporate faster, creates gradient so water diffuses out leaf faster

humidity - lower = faster
- air dry, concentration gradient between leaf and air increased, faster

wind - windier = faster
- blows water molecules from around stomata, increases concentration gradient

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10
Q

potometer

A

measures water uptake (assumes same as transpiration)

cut the shoot underwater
(stops air entering xylem)
cut at slant
(increase surface area)

assemble underwater so no air can enter
remove but keep end of capillary tube submerged in beaker

make sure water and air tight
shut tap (attached to resevoir, used to reset water bubble if needed)

remove end of capillary tube from beaker until air bubble formed before replacing it

record starting position and time
distance moved per unit time

rate of movement is estimate of rate of transpiration

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11
Q

how are radioactive tracers used to investigate translocation?

A

supply plant with organic substance that has a radioactive label
eg carbon dioxide (with radioactive isotope)

will be incorporated with organic substances in leaf and move around by translocation

movement tracked using autoradiography
- placed on photographic film
- turns black where radioactivity is

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12
Q

gas exchange in single celled organisms

A

absorb and release gas by diffusion through outer surface
large surface area to volume ratio
thin surface and short diffusion distance

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13
Q

gas exchange in fish

A

water enters fish through mouth
passes out through gills

each gill made of thin plates called gill filaments
- give large surface area for exchange
gill filaments covered in lamellae
- increase surface area more
lamellae have thin surface layer of cells and many blood capillaries to aid diffusion
by the counter current system

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14
Q

outline the counter current system

A

blood flows through lamellae in one direction and water flows in the opposite direction
maintains large concentration gradient between water and blood along whole lamellae
allows as much oxygen as possible to diffuse into blood

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15
Q

gas exchange in insects

A

air moves into tracheae through spiracles (pores)
oxygen travels down concentration gradient to cells
branch into tracheoles - have thin permeable walls straight to cells

carbon dioxide from cells move down its own concentration gradient to be released
gases not carried in blood

use rhythmic abdominal pumping to move air in and out of spiracles

gradient created as oxygen used by respiring cells

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16
Q

adaptations of insects gas exchange system

A

tracheoles have thin walls = short diffusion distance

highly branched and have many tracheoles = large surface area
and short diffusion distance

abdominal pumping moves air in and out to maintain concentration gradient

spiracles controlled by muscles, can close to reduce water loss

17
Q

gas exchange in dicotyledonous plants

A

needs CO2 for photosynthesis and O2 for respiration, release

surface of mesophyll cells in leaf
- main gas exchange surface
- large surface area
- inside leaf
- contains many air spaces so co2 diffuses in
- used in photosynthesis by nearby chloroplasts = maintains concentration gradient

gases move in and out through stomata in epidermis
- open to allow gas exchange
- close to reduce water loss
- controlled by guard cells

18
Q

adaptation of plants

A

large surface area - maintained by air spaces in leaf

short diffusion distance - thin tissues

large concentration gradient - gases used quickly in photosynthesis

19
Q

how do insects reduce water loss?

A

close spiracles using muscles

reduce evaporation (less water lost)
- waterproof waxy exoskeleton
- hairs around spiracles, traps moist air

20
Q

how do plants reduce water loss?

A

open stomata during the day

water enters guard cells making them turgid, stomata kept open
if dehydrated, guard cells lose water and become flaccid, closes stomata

21
Q

xerophytes and their adaptations (5)

A

plants adapted to warm, dry or windy conditions, where water loss is an issue

stomata sucks in pits, trap moist air
- reduces concentration gradient of water so less water moves out of leaf

hairs on epidermis - trap moist air around stomata

curled leaves with stomata inside - protect them from wind (wind moves moist air, increasing concentration gradient and therefore evaporation)

reduce stomata, less to escape from

waxy cuticles, reduce evaporation

22
Q

gas exchange in humans

A

air enters trachea
splits into 2 bronchi (one to each lung)
branches into bronchioles
end in alveoli (where exchange happens)

ribcage, intercostal muscles and diaphragm work to move air in and out

23
Q

inspiration

A

external intercostal muscles contract
(internal relax)
diaphragm contracts

ribcage moves up and out
diaphragm flattens
increases volume of thoracic cavity

so decreases pressure (below atmospheric)
air flows down pressure gradients into lungs

inspiration active - requires energy

24
Q

expiration

A

external intercostal muscles relax
(internal contract)
diaphragm relaxes

ribcage moves down and in
diaphragm domes again
decreases volume in thoracic cavity

so increases pressure (above atmospheric)
air flows down pressure gradient out of lungs

normal expiration passive - no energy

forced expiration active - internal and external intercostal muscles work together, decrease volume further, muscles antagonistic

25
Q

gas exchange in the alveoli

A

alveoli surrounded by network of capillaries
- oxygen moves down concentration gradient into blood (in haemoglobin)
- carbon dioxide diffuses into alveoli and in breathed out

flow of blood in capillaries maintain concentration gradient
arrives as deoxygenated from heart and then carries oxygenation back to the heart

26
Q

adaptations of alveoli

A

thin exchange surface
- epithelium one cell thick, creates short diffusion pathway

large surface area
- millions of them

steep concentration gradient
- maintain by blood flow
- allows quicker diffusion

27
Q

how do you calculate pulmonary ventilation rate?

A

tidal volume x breathing rate

28
Q

what is tidal volume?

A

volume of air in each breath

29
Q

ventilation rate

A

number of breaths per minutes

30
Q

forced expiratory volume

A

max volume of air breathed out in 1 second

31
Q

forced vital capacity

A

max volume of air to be forcefully breathed out

32
Q

TB

A

infection with bacteria

causes damage to gas exchange surface
= decreased tidal volume
smaller efficient surface area

33
Q

fibrosis

A

formation of scar tissue in lungs
thicker and less elastic than normal

less able to expand
= reduced tidal volume
larger diffusion distance

reduced rate of gas exchange
= slower diffusion rate

34
Q

asthma

A

airways become inflamed
muscle lining bronchioles contracts and lots of mucus produced

constriction so harder to breathe
= air flow restricted, less o2 in blood

35
Q

emphysema

A

particles trapped in alveoli
causes inflammation, attracts phagocytes
produce enzyme that breaks down elastin
- makes alveoli elastic so loss means they cant recoil to expel air
- also damages walls so reduces surface area
= decreased rate of gas exchange

36
Q

what do organism exchange with their environment?

A

take in oxygen and nutrients

excrete waste products such as CO2 and urea

exchange heat to maintain temperature

37
Q

SA : V

A

smaller animals =
larger SA:V ratio

larger animals =
smaller SA:V ratio

38
Q

affect of SA:V on heat and water loss

A

larger SA compared to V = increased heat loss

smaller animals
larger SA:V ratio
= lose heat and water more easily

therefore need higher metabolic rate to remain warm
- need adaptations if living in cool, eg eat high energy foods
- have kidney adaptations to produce small volumes of urine to retain water

larger animals
smaller SA:V ratio
= harder to lose heat and water
- need adaptation if living in heat eg large ears or in water to cool

Biology 🌿 (23 decks)

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