B2

transport

unicellular transport

relies on diffusion

• O2/glucose in, CO2/H2O out

multicellular transport

too many cells for diffusion to supply them all in time

• exchange surfaces allow substances in/out of transport system

surface area to volume ratio

the larger an organism, the smaller a ratio

• as there isn’t enough exchange surface for diffusion, the cells in the center don’t get the resources they need in time.

SA : V ratio calculation

surface area / volume : 1

role of the alveoli

to support gas exchange between alveoli and capillaries

adaptations of the alveoli

• circular shape which allows for larger surface area for exchange

• high concentration of oxygen vs low concentration in the blood stream

• thin membrane(1 cell think) to shorten diffusion distance

• moist to dissolve gases & avoid air bubbles in blood stream

• network of capillaries around alveoli to maximize gas exchange
  

adaptations of the villi

• thin 1 cell thick walls in a single flat layer for short diffusion distance

• finger-like projections to increase surface area & allow for regular stacking

• large quantity of villi in a very long intestine

• large quantity of blood in vessels for nutrients to diffuse into

diffusion

the random movement of particles from a high concentration to a lower concentration

• moves down the concentration gradient as it is passive

concentration gradient

difference in concentration between 2 areas

• a steeper gradient means faster diffusion

concentration gradient equation

change in concentration / distance

rate of diffusion equation

Surface Area × Concentration Difference / Membrane Thickness

diffusion distance equation

factors that may affect gradient of diffusion

• concentration gradient

• temperature

• diffusion distance

active transport

the movement of molecules from an area of low concentration to an area of higher concentration

• goes up the concentration gradient(natural flow) as it goes against it

carrier proteins

required to “scoop” the particle and pushes it to the other side

• this is because energy is required to move the particles in active transport(atp)

carrier protein image

osmosis

the total movement of water molecules from an area of high water potential to an area of low water potential.

• MUST go through a partially permeable membrane

partially permeable membrane

(membrane that) allows certain substances or molecules to pass through, but not others

water potential

the ability of water to freely move, measured in Psi (Ψ)

how water potential works

as particles move from a higher concentration to a lower concentration, it eventually leads to equilibrium on both sides of the permeable membrane

water potential in practice

RBC placed in distilled water

RBC placed in concentration solution(salt/sugar)

Plant cell in distilled water

The cell becomes turgid(swollen with water) as water moves from outside at higher water potential to inside at lower water potential.

• This is because the strength of the cell wall maintains the cell’s shape

Plant cell in concentrated solution

Water moves from higher concentration inside to lower concentration outside and undergoes plasmolysis.

• vacuole shrivels up & solution fills up cell

• plasmolysis - when the cytoplasm pulls away from cell wall

double circulatory system

a system of blood circulation where blood passes through the heart twice in one complete circuit of the body.

role of the circulatory system

• the heart pumps oxygenated blood to cells deliver O2 and glucose

• the heart pumps deoxygenated blood to lungs to remove CO2 and H2O

arteries

carries blood away from the heart

• thick muscle walls to withstand high pressure of blood

• small lumen(hole) to maintain pressure(smaller area)

• high pressure from heart compressions

veins

carry blood to the heart

• thin muscle walls as blood is at low pressure

• valves to prevent backflow of blood

• large lumen to reduce resistance to flow

capillaries

connects arteries & veins

• walls are 1 cell thick(short diffusion distance)

• where gases are exchanged with cells

• pressure from heart contractions force capillary substances out

platelets

clots blood

white blood cell

fights disease by matching anti-bodies to change shape & engulf micro-organisms

red blood cell

transports o2

• small to fit through narrow capillaries

• flattened disc to increase SA:V

• no nucleus for more haemoglobin

plasma

contains dissolved substances to be transported

• amino acids, hormones, antibodies, H2O, CO2, glucose

plasma adaptations

• watery nature allows it to dissolve large amount of substance

• primarily water which many substances are soluble in 

Pulmonary

anything related to the lungs

root hair cells

adaptations of a root hair cell

• long & thin protrusions to fit between soil particles

• large surface area for uptake of minerals & water

• lots of mitochondria(atp) for active transport

• vacuole containing sap to lower water potential 

how a root hair cell works

active transport of mineral ions requires energy as it is active transport (less mineral on outside than inside)

• water potential is lowered via solutes on the inside so that water can go in through osmosis

xylem

transports water & minerals from roots to the rest of the plant

phloem

transports dissolved sugars(assimilates) from photosynthesis to the rest of the plant

• aka translocation

vascular bundle

Bundle of xylem & phloem within the plant

• different distribution in roots & system

• supports the plant in the stem

• anchors the plant in the roots

adaptations of xylem

• made of dead cells(no obstruction in osmosis)

• flows upward

• impermeable cell wall

• thick cell wall made of lignin(for structure)

• provides support

xylem how it works

water particles attracted to other water particles from transpiration moving up, all move up

Attracted to xylem wall, moving up.

adaptations of phloem

• made of living cells

• flow is up & down(constant source & sink change)

• sieve plates present at the end of cells to allow dissolved sugars to pass through

• thin cell wall made of cellulose

transport system cross section

• phloem is packed in regular shape(more dense)

• xylem is less dense, usually darker in color on test papers

key features of the heart

• atria(upper) L+R

• ventricle(lower) L+R

• valves preventing backflow

right side of the heart

receives deoxygenated blood from the body

• pumps towards the lungs

left side of the heart

receives oxygenated blood from the lungs

• pumps round the whole body

• thicker to account for higher pressure

septum

separates the two sides of the heart

diagram of the heart

vena cava

brings blood from the body

aorta

heart’s artery to the body

pulmonary

lungs

• artery = to lungs

• veins = from lungs

tricuspid valve

control blood flow from the right atrium to the right ventricle(R)

bicuspid valve

regulate blood flow from the heart's left atria to the ventrical (L)

semi lunar valve

to prevent the backflow of blood from the major arteries. Found at exits of each ventricle

order of blood flow to the heart

BODY > vena cava > right atrium > tricuspid > right ventricle > semilunar > pulmonary artery > LUNGS

order of blood flow to the body

LUNGS > pulmonary vein > left atrium > bicuspid valve > left ventricle > semilunar > aorta > BODY

translocation

transport of assimilates

• leaf is the source(where sucrose is made during photosynthesis)

• areas that need sucrose are sinks

transpiration

• water evaporates (on surface of spongy mesophyll) 

• water (vapour) passes/diffuses through the stomata/pores 

stomata

tiny holes on the surface of the cell that allows for gas exchange

guard cells

controlling stomata

• swells with water to open

• no water when closed

how water moves up the xylem

pressure gradient from high to low

• cohesion (water molecules are attracted to other molecules)

• adhesion(water molecules are attracted to the walls of the xylem)

4 main factors that affect transpiration

• Light intensity

• Temperature

• Air flow

• Humidity

light intensity

more photosynthesis > more open stomata for gas exchange = more transpiration

light intensity graph

plateau= max

temperature

water particles gain kinetic energy and evaporate faster

• more heat outside meaning less water, steepening gradient

temperature graph

concentration gradient in leaves

the inside has higher concentration than the outside as water is continuously brought in, therefore, osmosis occurs

air flow

wind blows away water particles that come out making the outside stay at lower conc.

• steepens conc gradient, higher rate

air flow graph

gradual curve

humidity

higher humidity = decreased concentration gradient

humidity graph

potometer

measures water uptake from the plant

• allows for rate of transpiration to be measured based on speed air bubble travels through tube

potometers in reality

photosynthesis occurs at the same time of transpiration meaning some water is not diffused

methods of potometer that must be met

• cut underwater + slanted = prevents air bubbles from entering xylem and disrupting flow

• dry= maintain water potential

rate of transpiration equation

air bubble movement (mm/s) = distance / time

ways to investigate each factor

humidity- plastic bag + water spray bottle

temperature- heater

light- lamp at different distances

wind- fan at different speeds

Cohesion

attraction between like (same) molecules

Adhesion

attraction between different types of molecules