Biology AS Module 2 of Module 2

EXCHANGE SURFACES

speciallised area that is adapted to make it easier to cross from one side to the other.

such as...

• small intestine- absorbs nutrients
• liver- adjusts blood sugar levels
• root hairs- absorb water and minerals
• hyphae- absorb nutrients

GASEOUS EXCHANGE

the movement of gases by diffusion between and organism and its environment across a barrier.

Oxygen passes from the alveoli to the blood in the capillaries

Carbon Dioxide passes from the blood in the capillaries into the alveoli.

LUNG ADAPTATIONS

• large surface area- individual alveioli are 100- 300 um across.  this gives more space for gases to pass through.
• 1 cell thick
• squamous cell which are thin
• capillaries are close to the alveoli wall
• capillaries are narrow- squeezing red blood cells so the are closer to the air.

MAINTAINING THE DIFFUSION GRADIENT

blood brings carbon dioxide from the tissue back to the lungs so the concentration of carbon in the blood is greater.

Oxygen is carried away from the lungs so the concentration of oxgen in the blood is lower

BREATHING IN

diaphram contracts and moves down

intercoastal muscles contract and the ribcage moves up and out

volume of chest cavity increase

the pressure inside the lung cavity is less than atmospheric pressure.

air rushes in

EXHALING

diaphram relaxes intercoastal muscles relax. Rib cage moves in and down

volume of chest cavity decreases, pressure is greater inside the chest cavity so air rushes out

Tidal Volume

the air moved in and out of the lungs with each breath at rest (0.5dm)

vital capacity

the largest volume of air that can be moved in and out of the lungs in one breath (5dm)

residual volume

volume of air which remains in the lungs after exhilation (1.5dm)

Dead space

air held in the broncus, bronchi and trachea

Inspiratory reserve

the volume of air which can be breathed in above the tidal volume

Expiratory reserve

the volume of air which can be breathed out over the normal tidal volume

SPIROMETERS

Inhalation takes air from the oxygen chamber causing it to sink down. This pulls the pen trace down

Exhaulation put air back into the tank causing it to rise, this pushes the pen trace up.

Small animals dont need separate transport systems because diffusion will reach all of their cells

Good transport systems

• a pump- creates pressure
• good exchange sufaces- efficient transport
• vessels-to carry blood
• double circuit

Single Circulatory System

passes through the heart only once in each circulation

heart-> gills-> body-> heart

Double Circulation

passes through the heart twice in each circulation

Body-> heart -> luungs -> heart-> body-> heart

Advantages

• heart can increase the blood pressure after it has been through the lungs
• systemic circulation can carry blood at a higher pressure than the systemic.

HEART

a muscular pump which creates pressure to propel blood through the arteries

DIASTOLE

atria and ventricals are relaxing

pressure in the ventricals is lower than in the atria

semilunar valves are closed  because the pressure in the arteries are high.

AV valves are open

ATRIAL SYSTOLE

atra contract increasing the pressure so blood is pumped into the ventricalsl

when pressure in the ventricals is greater than the pressure in the atria the av valves shute

VENTRICULAR SYSTOLE

when all 4 valves are shut the ventricals contract. Blood is pushed onto the arteries, semi lunar valves open.

SEMILUNAR VALVES

clsoed- when pressure in the arteries is greater than the pressure in the ventricalsOpen- when pressure in the ventricals is greater.

LUB-  av valves closing

Dup-  semilunar valves opening.

SAN- hearts pacemaker

PURKYNE TISSUE

adapted muscle fibres taht conduct a wave of depolarisation from the AVN dow nthe septum to the ventricals

P- depolarisation of the atria

QRS- depolarisation of the venricals

P-R interval- the time for the wave to travel from the SAN to the perkyne fibres

T- diastole

OPEN CIRCULATORY SYSTEM

blood isnt always contained in vessels

IN INSECTS-cells are bathed directly in the bloood. It enters the heart through ostia. the heart pumps it toward the head.

CLOSED CIRCULATORY SYSTEM

blood remains inside vessels. Tissue fluid bathes cells so blood can be pumped at higher pressure.

ARTERIES

• small lumen to maintain pressure
• thick wall containing collagen to provide strength
• elastic tissue to stretch and recoil when heart pumps
• endothelium is folded so it can unfold when artery stretches

VEINS

• large lumen
• thinner walls with less collagen
• they dont need to stretch and recoil
• contain valves to prevent backflow.

CAPPILARIES

• 1 single layer of endothelium cells
• narrow lumen the same size as a red blood cell squeezing it so oxygen is easily removed

BLOOD
oxygen, carbon dioxide, salts, glucose, fatty acids, amino acids, hormones, and plasma proteins.

TISSUE FLUID

transports oxygen and nutrients from the blood to cells. Carries carbon dioxide and other wastes back to the clood

FORMATION

Arteries branch of into arterioles at the tissues and then into cappilaries.

There is higher hydrostatic pressure at the arterioles pushing fluid out through tiny gaps in the capillary  wall. Thid fluid is tissue fluid.  At the venuole end the osmotic pressure is greater so the tissue fluid moves back in.

Some tissue fluid is drained into the lymphatic system which consists of many vessels. These drain excess fluid into larger vessels which rejoin the blood system in the chest cavity.

Haemoglobins ability to take up oxygen depends on how much is in the surrounding tissue.

OXYHAEMOGLOBIN DISSOCIATION CURVE

at low oxygen tension the haemoglobin doesnt readily take up oxygen. This is because the haem groups are in the centre of the molecule so it is difficult for the first oxygen to bind.  as the oxygen tension increases the diffusion gradient increases until one oxygen molecule associates with the haem group.  This causes a confimational change allowing oxygen molecules to associate with the other haem groups. The 4th molecule is more difficult which is why 100% saturation is difficult.

Mamalian Haemoglobin

oxygen tetions in the lungs can almost achieve 100% saturation

oxygen tension in respiring tissues is very low so oxygen can readily dissociate

FETAL HAEMOGLOBIN

high oxygen affinity

get fluid from the mothers blood through the placenta which reduces the oxygen tension

BOHR EFFECT

change in shape of and oxyhaemoglobin curve in the pressence of carbon dioxide

• carbon dioxide diffuses from body cells into red blood cells
• carbonic anhydrase combine water and carbon dioxide to form carbonic acid CO2+H20->H2CO3
• Carbonic acid dissociates to form H+ and HCO3- ions
• hydrogen carbonate diffuses out of the cell
• oxyhaemoglobin dissociates under the influence of H+
• Hb08-> Hb+ 4O2
• Haemoglobinic acid is formed
• chlorine shift maintains the charge

the endodermis surrounds the vascular bundle

the pericycle (layer of meristem cells) is just inside the endodermis

XYLEM

• dead cells lined end to end
• narrow tubes so the water column doesnt break easily
• pits in the lignified walls allowing water to move from one vessel to another
• coiled lignin allows the xylem to stretch and flex as the plants grows and bends.

water isnt impended because...

• no end walls
• no cells contents (nucleus or cytoplasm)
• lignin prevents the xylem from collapsing

SIEVE TUBES

• lined end to end
• no nucleus and little cytoplasm
• sucrose is transported in the form of sap
• perforated cross-walls at intervals allowing sap to flow

COMPANION CELLS

• inbetween sieve tubes
• large nucleus
• dense cytoplasm
• many mitichondria to produce ATP neede for the active process.
• they carry out the metabolic processes needed for the sieve plate elements.

WATER POTENTIAL

potential energy of water molecules in a system.  Its a measure of how likely water will be lost by a system via diffusion down a water potential gradient.

SYMPLAST PATHWAY

travels through the plasma membrane into the cytoplasm it travels inbetween cells via plasmodesma.

PLASMODESMA

fine strand of cytoplasm that links the contents of adjacent cells.

water enters the root hairs by osmosis.

Endodermis cells move minerals by active transport from the cortex to the xylem

Casparian *****

• blocks the appoplast pathway
• ensures water passes through the cytoplasm
• there are transporter proteins in the cell membrane

ROOT PRESSURE

action of the endodermis moving minerals into the xylem by active transport

TRANSPIRATION PULL

loss of water by evaporation from the leaves, coheison adn trnapiration stream.

Cappilary Action

narrow xylem

adheision

TRANSPIRATION

loss of water by evaporation from airial parts of the plants.

POTOMETER

estimates the water lost from a plant

translocation

the transportation of assimulates through the plant in the phloem

source- releases sucrose into the phloem

sinks- removes sucrose from the phloem

• sucrose is activly loaded into sieve tube elements reducing water potential
• water follows by osmosis increasing hydrostatic pressure in the sieve tube elements.
• water moves down sieve tube along hydrostatic pressure gradient to the sink
• sucrose is removed from the sieve tube by surrounding cells increasing thier water potential
• water moves out reducing hydrostatic pressure.

RINGING

phloem is in the bark of woody plants

when a ring of bark is cutaway the sugars collect above the cut creating a buldge

below this there will be no further growth.

APHIDS

where stem is sectioned the stylet is found in the phloem where fluid is easily collected. fluid collected from the aphids will have high concentration of sugars