Topic 4: requirements for life

gills

• site of gas exchange in fish

• 4 on each side of the head

• only flows 1 way

• supported by the gill arch

filaments

gills have 2 rows of them to increase the surface area

lamellae adaptations for gas exchange

• plate like projections covering each filament

• increases surface area for diffusion

• surface of gas exchange so has lots of capillaries

• large blood supply

• short diffusion pathway

bony fish

most fish, have internal skeleton of bone, have counter current flow, opererculum, live in fresh and salt water

counter current flow in bony fish

• water flows over the gill lamellae in the opposite direction of blood flowing into capillaries

• levels of o2 in blood increase due to diffusion of oxygen from water to blood when o2 conc in water increases

operculum

flap covering the gills in bony fish instead of gills opening directly

why does water flows over lamellae in the opposite direction of blood

to maintain a concentration gradient gradient along the whole gill lamellae

ventilation in bony fish

• to maintain continuous flow, h2o forced over gill fillaments by pressure differences

• water pressure in the mouth cavtiy is higher than in the opercular cavity

• operculum acts as a valve letting water out and pumps moving water past gill fillament

• mouth also acts as a pump

ventilation mechanism to take in water in bony fish

1. mouth opens

2. operculum closes

3. floor of the mouth lowers

4. volume inside operculum cavity increases

5. pressure inside operculum cavity decreases

6. water flows in as the external pressure is higher than the pressure inside the mouth

ventilation mechanism, to force water out over the gills in bony fish

1. mouth closes

2. operculum open

3. floor of the mouth raises

4. volume inside operculum cavity decreases

5. pressure inside operculum cavity increases

6. water flows out over the gills because pressure in the mouth cavity is higher than in the opercular cavity and outside

co2 exchange in bony fish

• co2 diffuse out of blood into water like cartilaginous fish

• but because of counter current system co2 diffuses out of the blood along the whole length of gill lamellae

• more efficient

cartilaginous fish

• gills in 5 spaces on each side

• gill pouches open to outside at gill slits

• less efficient at ventilation

why are cartilaginous fish less efficient at ventilation

don’t have special mechanism to force water over the gills but must keep swimming for ventilation to happen

parallel flow

• blood travels through gill capillaries in the same direction as water

• o2 diffuses from most concentrated (h2o) to less in the blood

• continues until both conics are equal so limited to 50% max

• doesn’t occur across whole gill lamellae

why do trachea have rings of protective cartilage

it is flexible allowing trachea to accommodate movement

why is lung’s tissue advantageous to gas exchange

elastic so can recoil pushing air out the lungs

pleural cavity and membrane

keeps lungs lubricated preventing friction as air moves in and out of the lungs

alveoli

site of gas exchange made of layer of squamous epithelial tissue, coated with surfactants for anti sticking

why is alveoli coated with surfactants and what are they

• moist secretions with phospholipids to decrease surface tension

• proteins to prevent collapse when air pressure decreases

• let’s gasses dissolve

inhalation/ inspiration definition

active process of breathing as muscle contraction requires energy

inhalation process

1. external intercostal muscles contract

2. ribs pulled upwards and outwards

3. diaphragm muscles contract so flattened

4. increases thorax volume

5. reduces air pressure in lungs

6. atmospheric air pressure greater than pressure in lungs so air is forced into lungs

exhalation process

1. external intercostal muscles relax

2. ribs pulled downwards and inwards

3. diaphragm muscles relax so domes upwards

4. decreases thorax volume

5. increases air pressure in lungs

6. atmospheric air pressure less than pressure in lungs so air is forced out lungs

alveoli adaptations for gas exchange

• larger SA:VOL

• surfactant moisture lining let’s gasses dissolve in

• squamous epithelial walls 1 cell thick so short diffusion pathway

• extensive capillary network surround it and maintains diffusion gradient

• capillary walls also 1 cell thick

• large blood supply

operculum

flap like structure that covers and protects the buccal cavity

gill arch

bony structure that serves as support and attachment points for gill filaments

gill rakers

projections on the side of the gill arch that help to filter food particles out of the water

lamellae

microscopic projections on the filament surface that further increase its area and are the site of gas exchange

buccal cavity

interior mouth compartment of fish

gill filament

fleshy projections that occur in pairs along gill filaments creating larger surface area for gas exchange

how is direction of water in the fish maintained

by the mouth opening and closing which changes pressure

how is pressure in fishes mouth in gas exchange changed

by raising and lowering the buccal cavity

surface area of gill filaments in water

large as they fan out like feathers

surface area of gill filaments out of water

filaments clump together decreasing SA

doffusion for gas exchange depends on

difference in conc of gases on either side of the respiratory surface

volume of gas that must be exchanged depends on

volume of the animal akd it’s activity level

why have most multicellular organisms evolved to have specialised respiratory surface organs

surface area too small to meet gas exchange demand

ficks law

rate of diffusion= SA x difference in conc/ length of diffusion path

conditions for fastest diffusion

• large SA

• short diffusion pathway

• permeable and moist surface

• steep concentration gradient

gas exchange in unicellular organisms with carbon dioxide

they can remove co2 fast enough to prevent building up a high conc and making the cytoplasm too acid for enzymes to function

amoeba in gas exchange

• unicellular aquatic

• uses cell membrane as gas exchange surgace

• this is possible due to: high sa:vol, short diffusion pathways, moist and permeable membrane

• conc gradient maintained by amoeba using oxygen that enters in aerobic respiration

how high blood pressure helps maximise gas exchange in fish

increased flow rate to maintain conc gradient

flatworms in gas exchange

• multicellular

• flattened body to increase SA, larger SA:VOL, short diffusion pathways

• gas exchange surface is outer layer, moist due to to aquatic habitat

• conc gradient maintained by flatworms using O2 that enters in aerobic respiration

earthworms in gas exchange

• multicellular

• cylindrical so sa:vol less than flatworm

• gas exchange over body surface due to large SA, damp environment, mucus secretions

• closed circulatory system

advantage of earthworms living in damp environment

surface is always moist

advantage of closed circular tory system with blood pigment for earthworms

• carriers nutrients and gasses around body

• maintains conc gradient over respiratory surface

• low oxygen requirements as low metabolic rate

multicellular animals with gas exchange

• active lifestyle

• higher metabolic rate

• large volume

• tissues and organs more interdependent

• specialised respiratory surfaces to meet gas exchange needs

why do multicellular animals have specialised respiratory surfaces to meet gas exchange needs

sa:vol too small to allow rapid enough diffusion of o2 to meet respiratory requirements if gas exchanged over the outer body surface

problems for terrestrial organisms in gas exchange

• water evaporates from body’s surface leading to dehydration

• gas exchange surface thin and permeable with large sa, water molecules very small and pass through exchange surface so always moist meaning loss of water

BUT lungs internal to minimise loss of water akd heat

amphibians in gas exchange

• moist permeable skin with well developed capillary network just below the surface

• gas exchange takes place through the skin

• as well as when animal is active in the lungs

how has exchange develops in amphibians from tadpoles

• as tadpoles they have gills for gas exchange surface

• when adult they loose gills and evelio lungs

• adults use skin when in active or underwater as gas exchange surface kept moist via mucus secretions

• lungs for gas exchange when active

• lungs are thing walled sacs inflated by frog filling mouth with air and the.

• with mouth and nostrils closed it raises floor of the mouth to force air into the lungs

why are trachea walls in insects lined with chitin

strong to hold tubes open, impermeable to gasses so no gas exchange there

gas exchange in plants at night

• plants only respire so need o2 from the atmosphere

• some o2 enters the stem and roots via diffusion

• but most gas exchange happens in leaves

gas exchange in plants during the day

• rate of photosynthesis is faster then diffusion

• as more o2 made in photosynthesis than used in diffusion

veins in the leaf

transport water and other nutrients made of xylem and phloem

mechanism of opening and closing the stomata in the day

• water enters guard cells

• goes turgid and swells so the pore opens

• water leaves, swells and the pore closes

how structure of the stomata enables guard cells to open and close at daylight

• guard cells open by inflating with extra water

• via active transport if K+ ions into guard cell (using ATP made by chloroplasts from photosynthesis)

• starch→malate

• K+ and malate lower the water potential of guard cells so water enters via osmosis

• pore appears between thicker and thinner cell walls

why guard cells might close at daytime too

• bright and intense lights increase the heat

• this means more evaporation of wayer

• causing excessive water loss

enzymes

• globular proteins

• biological catalysts (speed up reactions without being used up)

• high turn over number

enzymes as gobular proteins

small area with specific 3D shape in the active site

sites of enzyme action

• extracellular

• intracellular in solution

• intracellular membrane bound

extracellular site of enzyme action

some enzymes secreted from cells by exocytosis and catalyse extracellular reactions e.g amylase

intracellular in solution site of enzyme action

acts in solutions inside of cells e.g enzyme that catalyses glucose break down in glycolysis

intracellular membrane bound site of enzyme action

attach to membranes on cristae of mitochondria

lock and key model

shows how enzyme can only catalyse 1 type of reaction

enzyme is specific to its substrate creating enzyme substrate complex

how do enzymes catalyse reactions

• molecules need KE so more frequent successful collisions breaking bonds

• enzymes lower activation energy as the shape alters allowing reactions to occur at lower temps than without

• less energy required means it’s more likely to happen spontaneously

why are enzymes described as biological catalysts

metabolic pathways are controlled by enzymes

they reduce the required activation energy and therefore increase the rate of chemical reactions in living organisms

this is essential for maintaining processes such as DNA replication and protein synthesis

metabolism

all chemical reactions occur inside living cells

reactions occur in sequences called metabolic pathways where products of one reaction become reactants in the next

catabolism

energy is released from large molecules being broken down (exergonic)

e.g digestive enzymes catalyse break down of large complex substrate molecules into smaller less complex molecules

anabolism

energy is taken in to combine smaller substrate molecules into bigger product molecules (endergonic)

e.g protein synthesis, DNA synthesis

induced fit model of a lysosome

enzyme shape is altered by binding it’s substrate suggesting it was flexible not rigid

course of an enzyme controlled reaction

• substrate molecules bind to active site and in successful collisions breaking bonds substrate broken down and products released

• more active sites become filled with substrate molecules

• rate depends on number of free active sites if other conditions optimal

• all substrate used up eventually and no more product formed so line plateaus

• line goes through origin as 0 time no reaction

factors affecting enzyme action

• temperature

• pH

• substrate conc

• enzyme conc

effect of high temps on enzyme action

• increases temp increased KE of enzyme and substrate molecules

• so more frequent successful collision increasing rate

• rate doubles for each 10• rise up to 40•

• but if too hot, increasing KE increases vibrations breaking H bonds akd changing tertiary structure

• changes shape of active site denaturing it

effects of low temps on enzyme action

• enzyme inactivated as molecules have low KE

• but shape is unchanged so can work if temp is increased

effect of extreme pH changes on enzyme action

• lead to hydrogen bonds and ionic bonds holding the tertiary structure of an enzyme together to break

• this is due to presence of H+ and OH- ions

• this changes the shape of the active site so the substrate can no longer bond forming enzyme substrate complex

• denaturing the enzyme

effect of small pH changes on enzyme activity

small changes around the optimum cause small reversible changes in enzyme structure decreasing activity

effect of substrate concentration on enzyme activity

• in enzyme conc is constant the rate increases as substrate conc increases

• substrate conc decreases when enzyme molecules have only a few sub to collide with so active site doesn’t work at full capacity so less are filled

• it is the limiting factor until all active sites are filled and rate is at max

• enzyme is saturated and the line plateaus

• no longer limiting factor as doesn’t control the rate anymore

effect of enzyme concentration on enzyme action

• once product leaves the enzyme molecule can be reused

• only a low enzyme conc needed to catalyse large number of reaction

• increasing enzyme conc increases active sites available so higher rate

enzyme inhibitor

molecule that reduces the rate of an enzyme controlled reaction

competitive inhibitors

reduction of the rate of an enzyme controlled reaction by a molecule that has a complementary shape to active site

similar to active site and prevents substrate from binding

how rate of enzyme is affected by competitive inhibitor

• increasing conc of substrate decreases effect of inhibitor as higher chance of them binding to active site

• increases rate as less active sites available for inhibitor

non competitive inhibitors

reduces rate by molecule binding to enzyme somewhere other than active site altering the shape so substrate can’t bind

can be reversible or not

effect of non competitive inhibitor

as it’s conc increases more denatured enzymes decreasing the rate and mass

immobilised enzymes

enzyme molecules bound to inert material over which the substrate moves

how immobilised enzymes work

• substrate added to top of column of inert matrix

• as it flows down molecules bind to enzyme active site on both the surface and inside the matrix as substrate molecules diffuse in

advantages of immobilised enzymes

• increases stability and function over wider range of temps and pH

• products not easily contaminated with enzyme

• enzymes recover easily for reuse

• sequences of columns can be used so several enzymes with differing pH or temp optímala can be used in 1 process

• can be easily added or removed so more control

uses of immobilised enzymes

• lactose free milk

• biosensors

• high fructose corn syrup (HFCS)

how biosensors use immobilised enzymes

• device that combines bio molecule to produce an electrical signal which measures the conc of a chemical

• can also be immobilised onto test strips to detect a variety of molecules

how lacto free milk use immobilised enzymes

milk passed down column with immobilised lactase

lactase binds to its active sites and is hydrolysed into glucose and lactose

how high fructose corn syrup use immobilised enzymes

manufactured multi step process from starch using several immobilised enzymes required different physical conditions

why is water described as a universal solvent

polar so substances like CO2 can dissolve into it

function of the cuticle

waxy, waterproof to reduce water loss and transparent to enable light to penetrate to mesophyll cells

breathing

action performed by diaphragm and intercostal muscles

respiration

process in living organisms involving release of energy from within cells

ventilation

refreshing of air in lungs so higher concern of oxygen in the lungs than the blood and lower concentration of CO2

why isn’t the cartilage in trachea in complete rings around it

to allow trachea to expand allowing food down

flap epiglotus

closes so food doesn’t go into the wear way

angiosperm

flowering plant that can either be monocot (stomata on upper and lower surface as thin) or dicot

why do stomata close

to prevent EXCESS water loss at night

collenchyma

tissue that gives support to short lived structures