Chapter 3.3 Exchanging Substances Flashcards
Def do exchange?
Transfer of materials between organisms and their environment
Def of transport?
Distribution of absorbed material round organism’s body
Link the size of organism with the SA:V ratio
Smaller organism have higher SA:V ratios than larger organism
This means that substances are exchanged more quickly (can be + or - for the organism)
Calculation of SA: V ratio
Of cube/cuboid
SA ( 6x Hx L) : V ( Hx Lx W)
Calculation; volume of cylinder
(SA:V ratios)
π x radius^2 x height
Examples of exchanged substance?
O2, CO2, nutrients, excretory products (urea, ammonia, water), heat
{def of }
1) excrete
2) secrete
3) egest
1) excrete -metabolic water removal
2) secrete- useful molecules move out of cells
2) egest - removal of undigested food
Examples of passive and active processes of exchange?
passive Active
- diffusion. - active transport
- osmosis. - co transport
- conduction - bulk transport (exo/endo cytosis)
- convection
-radiation
Substance exchange in single celled organism? + why this method
Simple diffusion occurs fast enough to be sufficient (takes place across membrane)
E.g gas exchange happens this way
+ large SA:V so efficient diffusion
+ steep concentration gradient maintained by substances used/ produced/ stored quickly
Reasons multicellular organism need adaptions for substance exchange ?
Diffusion across outer membrane is too slow
1) some cells are deep within the body - large distance between them and environment
2) decreased SA:V ratio - exchange is less efficient
Process of gas exchange in INSECTS?
Insects have a tracheal system:
- air entres exoskeleton via spiracles - pores on insects skin
- oxygen moves down conc. gradient (diffusion) & travels along tracheae - air filled pipes
- tracheae branches off into smaller tracheoles
- trancheoles terminate in respiring tissues and oxygen diffuses into cells CO2 diffuses out and travels out of spiracles
Adaptions gases exchange organs in insects
TRACHEOLES
- thin permeable walls
- gas exchange with tissue fluids by diffusion down conc. gradient
- terminate within body tissues (short diffusion pathway)
- tracheal fluid/ moisture allows O2 to diffuse into liquid before cells
SPIRACLES
-
TRACHEA
- muscles in trachea can squeeze trachea leading to mass movement of air
Insects can increase/control air flow;
> rhythmic abdominal movements either 🔼or 🔽 abdominal pressure moving air in & out of spiracles
Problems of water loss through spiracles for insects? + how is it prevents
-
+ close their spiracles using muscles (sphincters)
+ waterproof, waxy cuticle all over body & tiny hairs around spiracles both to reduce evaporation
How are fish adapted for gas exchange?
-have gills with pairs of lamella on them
- short diffusion pathway (lamellea)
- excellent blood supply to gills
- counter current exchange system
- one way flow of water over gills
Explain gas exchange system in fish
Counter-current exchange system
1) blood flows through lamella in 1 direction
2) water (entre through mouth) flows in opposite direction over lamella
This means that O2 concentration of the water flowing towards the blood is always higher than the blood flowing towards the water.
Benefits of fish using counter current system
Counter current system ensures a concentration gradient is maintained across the membrane thus maximising uptake of O2.
This is important because lower levels of O2 in water that the air therefore maximising its uptake is critical for a fish to survive
Describe the structure of the gills?
Each gill is made of lots of thin plates gill filaments attached onto a gill arch.
Each of these gill filaments is then covered in tiny structures called lamellae
[singular= lamella, plural = lamellae]
Role of salivary gland
+mouth
- situated near mouth, pass secretion via ducts in mouth
Secretion contains amylase to hydrolyse starch into maltose
+mouth = mechanical digestion to increase SA of particles
And starch digestion due to saliva
Role of stomach
- muscular sac w. inner enzyme producing layer
It stores and digests foods (chemically and mechanically)
mechanical digestion - muscles break down food
chemical digestion - protase in stomach juices
Role of pancreas
-gland situated below stomach, produces secretions (pancreatic juices)
secretes enzymes
Pancreatic juices contain protease, lipase, amylase
Role of ileum
-long muscular tube, food digested here via enzymes produced by its walls & glands.
- inner walls folded into villi- ^SA also microvilli on epithelial cells
Role of large intestine
Absorb water
(Water has come from secretion of digestive glands)
Role of rectum
Store faeces before removed by anus in process called egestion
Def of Micelles
Tiny droplets of broken up lipids
Process of carb digestion in humans
1) saliva contains amylase that hydrolyses starch > maltose
2) food swallowed and enters stomach which acidic conditions denature amylase preventing further hydrolysis
3) in small intestines mixed with pancreatic juices that contain amylase and maintain optimum conditions
4) muscles in intestine push food along ileum. epithelial lining produces maltase on cell surface hydrolysing maltose > glucose
(lactose and sucrose also hydrolysed in this way by membrane bound enzymes)
5) Glucose absorbed by epithelial cell (see transport topic)
Process of lipid digestion in human
1) lipids broken up in tiny droplets (micelles) by bile salts from liver.
This process called emulsification and ^ SA to speed up action of lipase.
2) micelles travel to ileum on contact to lipase on surface they are hydrolysed-> monoglyceride and fatty acids.
3) monoglyceride and fatty acids diffuse into epithelial cell
4) then transported to ER where recombine -> triglycerides
5) move to Golgi -triglycerides associated with cholesterol & lipoproteins to form chylomicrons (special partial adapted for lipid transport)
6) chylomicron moves out of epithelial cell by exocytosis
7) then enter lymphatic capillary found in each villus
8) lymph then passes them to blood stream
Process of protein digestion in humans.
Digestion of proteins takes place in stomach and duodenum of small intestine.
▸ *the stomach contains enzyme of protease which begins to break down peptide bonds in polypeptide chains into smaller chains
In small intestine on the membrane
▸ Endopeptidases break the peptide bond in the middle of the peptide chain.
▸ Exopeptidases acts at the end of the peptide chain and helps in releasing the last
amino acid.
Def of absorption
Transport of products of digestion across epithelial cells into the bloodstream
Def of assimilation
To become part of an organism
(When Soluble food molecules are used to build new parts of cells)
Role of oesophagus
Move food to stomach
Peristalsis- contraction of muscles
Role of the liver
To produce bile that neutralises stomach acid and emulsifies lipids
Adaptions of small intestine for absorption
1) long, folded to increase surface area
2) villi (finger like projections on inner layer) ^ SA and is lined with single layer of epithelial cells =short diffusion pathway
3) microvilli (smaller projections on villi) ^ SA and is site of some enzymes like maltase are found
Describe the structure of an intrinsic transmembrane protein that acts as an aquaporin?
(9 marks)
- primary structure specific sequence of amino acids
- amino acids are joined together by peptide bonds
- secondary structure of alpha coil helix
- H bonds between Amine and carboxyl group
- tertiary/quaternary structure create 3D shape
- bonds between R groups e.g ionic, hydrophilic, disulfate, H
- hydrophobic amino acids embedded in section that interact with fatty acid in bilayer
- hydrophilic amino acids in the inner and outer phosphate groups of bilayer
Def of digestion
The process of breaking down large insoluble molecules by enzymes during hydrolysis with the addition of a water molecule into smaller soluble molecules that can be absorbed and assimilated.
Where do endopeptidases work?
+ what are the products of hydrolysis
Hydrolyse peptide bonds in the middle region of proteins
+ smaller polypeptide chains
Where do exopeptidases work?
+what are products from hydrolysis reaction
Hydrolyse peptide bonds on terminal amino acids
+ single amino acid + dipeptides
Substrate and products of membrane bound dipeptidases in small intestine?
Hydrolyse dipeptides into single amino acids
Structure of human gas exchange system
See diagram
- trachea (windpipe held open by rings of cartilage)
- bronchus (smaller pipes that lead to right/left lung)
- bronchioles (smaller tubes in the lungs)
- alveoli (air sacs)
Adaptions of trachea and bronchus
tranchea
- supported by C-shape cartilage rings to prevent collapsing during breathing
bronchus
- lined with ciliates epithelial cells and goblet cells.
goblet cells= secrete mucus to trap dust/microorganism, cilia then waft mucus out
alveolus
- adaptions folllow fick’s law
Process of ventilation in humans gas exchange
INSPIRATION
1) external intercostal and diaphragm muscles contract - ribcage moves 🔼 ,out and diaphragm flatterns
2) 🔼 volume in thoracic cavity causes 🔽 pressure in thorax cavity so that it is below atmopsheric pressure
3) air flows down pressure gradient so air moves into lung
(this process is an active process requiring energy)
EXPIRATION
1) external intercostal and diaphram muscles relax, ribs move 🔽 and in, diaphram curves upwards again.
2) 🔽 volume in thorax cavity means pressure 🔼 above atmospheric
3) air moves down pressure gradient out of the lungs
(normal expiration is a passive process however duing forced expiration or heavy exercise internal intercostal muscles contract antagonisticly to external pulling ribcage further Down and in.
Adaptions of lungs for efficient gas exchange
- thin wall of alveoli (single layer of thin, flat alveolar epithelium)
Short diffusion pathway - lots of alveoli
Increase surface area - alveoli have good capillary network and blood supply
Maintains concentration gradient - ventilation process
*maintains concentration gradient - moist surfaces of alveoli walls
dissolve gases increasing diffusion
What is spirometer for?
A device that measures volume and speed of inhalation/exhalation
See notes for example
Adaptions for gas exchange in dicotyledon plant?
- large SA of leaf = increasing rate of diffusion
- leaves are thin = shortening diffusion pathway
- permeable through stomata
Internally spongy mesophyll
- creates Larger SA
-air spaces allow lateral diffusion of gases
- allows most cells to have direct contact with air
- moist allowing gas to move between gas + lipid phase
Def of xerophytes
+ adaptions of marram grass
Xerophyte- plant that is adapted for life in area of little to no liquid water
Adaption to prevent water loss in marram gras:
- sunken stomata trap moist air (reducing conc gradient of water preventing evaporation)
- layer of ‘hairs’ on epidermis trap water vapour around stomata
- curled leaves protect stomata from wind and trap moist air
- reduced number of stomata
- thick waxy waterproof cuticle
[def of]
1) tidal volume
2) ventilation rate
3) Forced Expiration volume (FEV1)
4) Forced Vital capacity (FVC)
1) the volume of air in each breath - usually 0.4 - 0.5 dm3
2) the number of breaths per minute - usually 15 breaths
3) the maximum volume of air that can be breathed out in 1 sec
4) maximum volume of air it is possible to breath forcefully out of the lungs after a really deep breath in
Info for tuberculosis
+ effect on gas exchange
Lung disease caused by bacteria, immune system build a wall around the bacteria in the lungs.
This forms small hard lumps (tubercules).
Infected tissue with tubercles dies damaging exchange surface so tidal volume is 🔽.
TB also causes fibrosis.
Tidal volume 🔽 so less air inhaled in so patients must breath faster
Common symptoms of turberculosis= cough (with blood), mucus, chest pain, shortness of breath
Info of Fibrosis
+ effect on gas exchange surfaces
Fibrosis= formation of scar tissue in lungs
(Can be result of infection, or substances exposure e.g asbestos)
Scar tissue= thicker &less elastic so lungs cannot expand as much so hold less air- tital volume 🔽 and FVC 🔽.
diffusion is slower due to thickened tissue - loonger pathway
symptoms = shortness of breath, dry cough, chest pain, fatigue, weakness
Info of asthma
+ effect on gas exchange
Asthma = airway becomes inflamed and irritated
During asthma attack- smooth muscle lining bronchioles contract and mucus is produced this constricts airway, making it difficult to breath.
Air flow severely reduced
Symptoms include= wheezing, tight chest. Shortness of breath.
Info of emphysema
+effect on gas exchange
Emphysema= caused by smoking or long exposure to air pollution
Trapped substances cause inflammation, attracting phagocytes to area. Phagocytes produce an enzyme that breaks down protein elastin in alveoli walls.
This prevents alveoli recoiling expelling air well. Also damage to alveoli wall reduces surface area.
Symptoms= shortness of breath, wheezing
describe the processes involved in absroption and transport of digested lipid molecules from the ileum into lymph vessels
[5 marks]
- Micelles constrain bile salts and fatty acids/monoglyceride
- Make fatty acids/monoglyceride more soluble in water
Or - release fatty acids/monoglyceride at lining of ileum - Fatty acids/ monoglycerides absorbed by diffusion
- Triglycerides reformed in cells
- Vesicles move to cell membrane and release via exocytosis
Summary of tissue fluid formation
At the ateriole end of capillary, the outward hydrostatic pressure is greater than the inward osmotic pull. Water, ions and small molecules are filtered out of the blood into the spaces between the cells- this is tissue fluid.
The loss of fluid from the hood leads to a fall in hydrostatic pressure as the blood approaches the venule end of capillary. At the venule end of capillary, the inward osmotic pull now exceeds the outward hydrostatic pressure and some of the water re-enters the capillary by osmosis.
Tissue fluid is drained away from the cells by the lymphatic system and returned to the circulation near the heart.
Annotate formation of tissue fluid
Use premade diagrams /see notes
Blood vessels
Different types of blood vessels?
Flow chart of them to show movement of oxygenated blood
Arteries
Arterioles
Capillaries
Venules
Veins
Inner Structure of artery/vein
From inside out
Lumen
Tunica intima (Inner layer)
Tunica media (elastic layer & smooth muscle)
Tunica adventitia (tough outer wall made of connective tissue)
structure and adaptions for function of TUNICA INTIMA in arteries/veins
- single layer - flattened epithelial cells
Smooth surface to🔽 friction allow quick blood flow
(In arteries this is folded to allow it to expand under 🔼 pressure)
structure and adaptions for function of TUNICA MEDIA in arteries/veins
-smooth muscle & elastic fibres
- smooth muscles contract > narrowing lumen 🔼BP & 🔽flow to capillary bed
- elatic fibres stretch &recoil > maintain blood pressure (BP) diastolic
structure and adaptions for function of TUNICA ADVENTITIA in arteries/veins
-elastic fibres & collagen layer
*collagen = tough, fibrous protein > strengthen walls
(In large arteries/veins this layer also has small blood vessels
Structure and adaptions of CAPILLARIES
-walls made from flattered endothelial cells
>ensures 🔽 diffusiob distance so substances can be exchanged
Artery structure related to its function:
withstand high pressure
thick walls - tunica media very thick
lots of collagen fibres - give strength (All of these prevent damage to walls as a
folded endothelium - allows expansion result of high pressure)
elastic fibres - allow expansion
maintain pressure
elastic fibres recoil/stretch - puts pressure on blood inside artery
contraction of smooth muscle - narrows lumen 🔼 pressure
control volume of blood flowing to capillary bed
contraction of smooth muscle - narrow lumen (vasoconstriction) 🔽 blood flow
relaxtion of smooth muscle - widening lumen (vasodilation) 🔼 blood flow
Veins structure related to its function:
thin muscle layer (compared to arteries)
- constriction/ dilation cannot control flow of blood to tissue
thin elastic layer
- at low pressure so cannot create recoil action or expand as much
small thickness of walls
- pressure within veins is too 🔽 to risk bursting, this also flattens easily to aid blood flow within
valves at intervals throughout
- ensures blood doesn’t flow backwards (pressure too 🔽)
When skeletal muscles contract, veins = compressed
Pressuring blood within. Valves ensure that this pressure directs blood in only 1 direction > ❤️
Steps in the Cardiac cycles
(No explanation)
-diastole (no contraction of cardiac muscles)
- atrial systole (atria contracts)
- ventricular systole (ventricle contracts)
- diastole again ..
What happens during atrial systole ?
- atria contracts due to pacemaker cells
- pressure in Arita is higher than ventricles
So … cuspid valves open and blood move from Arita -> ventricles
What happens during ventricular systole?
-atria relaxes
-ventricles contract
- pressure in ventricles 🔼 above atrial pressure = cuspid valves close
- pressure 🔼 above arterial pressure = semi lunar valves open blood forces into arteries (via aorta)
What happens during diastole? (cardiac cycle)
AT END OF CYCLE
-ventricles relax
- pressure drops below artery pressure, semi-lunar valves close
Then AT BEGINNING OF CYCLE
- atrial filling
- blood moves from veins into atria down pressure gradient
What does it mean if heart is myogenic?
The contraction of heart muscles can be controlled by itself (not nervous system)
Summary of Conndution pathway of the heart?
-all stimulus for contraction of heart originate from within cardiac muscles
- sino-atrial node emits electrical impulses that spread rapidly across both atria which stimulates wave of contraction (atrial systole)
- border between atria & ventricular made of non conducting fibrous tissue to prevent impulses leading to ventricles contracting
- impulses can only pass through AV node - slows spread of electrical transmitting
(Atria can complete contractions + empty before ventricle contraction)
- as AV node depolarises impulses quickly spread down bundle of his + purkinji fibres to ventricules (ventrical systole occurs from apex up ventricules.
Label heart diagram
See notes
Calculation of cardiac output?
Cardiac output = heart rate X stroke volume
Factors that heart rate
- autonomic innervation
- hormones (e.g. adrenaline)
- fitness level
- age
Factors that effect stroke volume
- heart size
- fitness level
- gender
- duration of contraction
Part of the brain that affects heart rate
Medulla Oblongata
2 parts to it
- cardioacceleratory centre
- cardioinhibitory centre
What stimuli are detected by receptors that lead to nervous system altering heart rate?
- blood pressure. (Detected by baroreceptors)
- carbon dioxide concentration ( detected by Chemorecpetors)
- oxygen concentration
-pH of blood
Summary of response of body if low blood pressure is detected to increase it
- blood pressure is detected by baroreceptors in aorta + cardio artery
- If Bp too low nerve impulses sent along sensory nerves
-Bp too low = cardioaccelerator centre in Medulla (brain) sends impulse down sympathetic acceleratory neurone - at synapse between sympathetic neurone & SAN noradrenaline (neurotransmitter) is released increasing heart rate
Summary of response of body if high blood pressure is detected to reduce it
- Bp is detected by chemoreceptors in aorta + cardio artery
- If Bp too high nerve impulses sent along sensory nerves
-BP too high = cardioinhibitory centre in Medulla (brain) sends impulse down parasympathetic neurone (vagus nerve) - at synapse between parasympathetic neurone & SAN acetylcholine (neurotransmitter) is released reduce heart rate
Different parts of automomic nervous system?
+ what are they?
- sympathetic
Fight or flight like response
-parasympathetic
Feed and breed (normal reaction)
Def of translocation?
The movement of assimilates (organic molecules made by plants) around the plant
Two vascular bundle organs in plants?
+ what do they transport?
Xylem - water & dissolved minerals
Phloem - sucrose, amino acids, other assimilates
Describe the movement of substances in the phloem?
From where to where?
From source (leaf cell) which has high hydrostatic pressure to sink (root cell) which has low hydrostatic pressure
Annotate the phloem diagram
See notes
Describe how sucrose is loaded into the phloem at the source
1) in leaf (source) active transport pumps H+ ions out of cell. Facilitated diffusion va co-transport proteins carries sucrose against gradient out of cell into companion
2) sucrose concentration in companion cell ^
3) sucrose diffuses (simply) through plasmodesmate (gaps in sieve tube elements- STE and companion cell)
4) conc. of sucrose in STE ^ which decreases water potential in STE
5) water moves into STE from xylem by osmosis
6) water moving into phloem increases hydrostatic pressure at the source.
Describe how assimilates leave the phloem at the sink?
Opposite process to before (loading)
1) sucrose actively unloaded from the phloem at the sink
2) sucrose then diffuses out of STE (sieve tube element) into companion cells down conc. gradient though plasmodesmate
3) water potential in phloem ^ as it looses solute
4) water moves from phloem to xylem via osmosis
5) hydrostatic pressure in phloem decreases
Adaption of sieve tube elements for their function?
+ what is the role of companion cells?
-Thin peripheral cytoplasm
- specialised with few organelles
+ companion cells carry out all metabolic functions needed for the sieve tube elements
Def of translocation
The movement of assimilates (made in the plant) around the plant
E.G amino acids, sucrose, etc
Def of source (in translocation)?
Tissues that synthesis organic molecules (assimilates) such as glucose
-these can be leaves or roots depending on the season
Def of sink (in translocation)?
Tissue that utilises organic molecules such as leaves, fruits, flowers, roots
Def of transpiration?
Loss of water vapour from the leaf
Types of ions that plant takes in via active transport and what they are used for
1> Magnesium - for the formation of chloroplast
2> Nitrates - for formation of amino acids
3> phosphates - cell membranes and DNA
Simplified movement of water during transpiration
Root hair cell absorbs water and mineral ions from soil .
Moves through cortex cells
Then into xylem tube via osmosis
Moves into spongy mesophyll via osmosis
The diffuses into air as vapour through stomata
Structure of xylem tissue?
- narrow hollow vessel with walls strengthened with lignin and tracheids
(* xylem parenchyma cells act as packing and provide support )
What is the role of lignin in xylem tissue?
+ other adaptions for xylem function
Lignin
- waterproofs to reduce water loss from xylem
- acts to keep fibres together
- vey strong to provide mechanical strength agains tension
- allows adhesion of water to side helping water rise by capillary action
Narrowness of vessel increases capillary action
Describe the movement of water in the xylem vessel?
1) hydrostatic pressure decreases by water leaving vessels
2) water moves up from roots where higher hydrostatic pressure due to active loading of ions
3) osmosis of water though cells from xylem
4) water vapour diffuses through leaf air spaces
5) if water vapour conc in leaf is higher than outside, wate vapour diffuses out of leaf via stomata
Describe the cohesion -tension theory
Due to pressure gradients water column is under tension
- water molecules have dipoles causes an attraction between them (cohesion)
- water is ‘pulled’ up the xylem by transpiration when this happens the pull is transmitted all the way down the water column, pulling all water molecules up vessel (applying tension)
-for this to work the xylem vessel must be a continuous column of water (no air bubbles)
Factors that affect transpiration rates?
1) light intensity - ⬆️light ⬆️ rate
stomata open to allow gas exchange for photosynthesis. large number of stomata open means increased diffusion of water vapour
2) Temperature - ⬆️ temp ⬆️rate
increased evaportation rate & increases diffusion as moleucles have more kinetic energy.
3) Humidity - ⬆️ hunidity ⬆️rate
increased humidity decreases water potential gradient between air space in leaf& air
4) Wind - ⬆️ wind ⬆️rate
air removes water vapour from stomata opening, increases water potential gradient steepness.
Precautions when setting up potometer?
1) cut shoot underwater to prevent air from entering the xylem.
2) make slanted cut to increase the surface area for water uptake and minimise chance of air bubbles
3) assembly the potometer under the water with shoot under water too. This prevents air entering and maintains continuous column with water in potometer
4) dry the leaves
5) apparatus must be watertight and airtight (with Vaseline)
Precautions when setting up potometer?
What is a Haemglobin molecule?
Haemoglobin is a polypeptide with a quaternary structure that has been evolved to make it efficient at loading oxygen in one set of condition and then unload in other set of conditions.
Describe the protein structure of haemoglobin
Primary structure
- sequence of amino acid in 4 polypeptide chain
Secondary structure
- each of the polypeptide chains is coiled into a helix
Tertiary structure
- each polypeptide chains is folded into a precise shape to carry O2 molecule
Quaternary structure
- all 4 polypeptide chains are linked together to form an almost spherical molecule.
What group on the haemoglobin molecule attaches to the oxygen
Harem group which contains Fe2+ ion.
Each Fe2+ ion can combine with a single o2 molecule
Where does loading of haemoglobin occur
In the lungs haemoglobin binds with oxygen
(This is called Loading or associating)
Where does dissociating occur
In respiring tissue haemoglobin releases its oxygen which is called unloading or dissociating
When Haemoglobin has higher affinity for oxygen what does that mean for
Loading
Unloading
Haemoglobin with high affinity for O2
Oxygen is taken up more easily
But oxygen is releases less easily
When Haemoglobin has lower affinity for oxygen what does that mean for
Loading
Unloading
Haemoglobin with low affinity for O2
Oxygen is taken up less easily
But oxygen is releases more easily
For haemoglobin to be efficient at transporting oxygen what must happen
- readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate from oxygen at those tissues requiring it
Why does haemoglobin have different affinities for oxygen
Each species produces a Hb with different amino acid sequences. The Hb of each species therefore has slightly different tertiary and quaternary structure and hence different oxygen binding properties. Depending on the structure of Hb ranged from those that have high affinity for O2 to those that have lower affinity for O2
What does oxygen dissociation curve show?
The graph of the relationship between the saturation of Hb with oxygen and the partial pressure of oxygen
Draw and explain the shape of the oxygen dissociation curve
See notes but it is an S- shaped curve
- Hb molecules make difficult for the first O2 molecule to bind to one of the sites
at low conc O2, little O2 bind to Hb. Gradient is shallow initially - binding of the first O2 molecule changes the quaternary structure causing it to change shape and make it easier for other molecules to bind
- there small increase in the partial pressure of O2 to bind the 2nd O2.
positive cooperatively because biding of 1st makes it easier and so on- the gradient steepens - after binding the 3rd molecule it is difficult to bind the 4th and final O2. This is due to most biding sites being occupied and therefore less likely that a single o2 molecule will find an empty site to bind to
gradient of the curve reduces and the graph flattens off
If the oxygen dissociation curve moves to the left what happens
The further to the left the curve
- the greater the affinity of Haemoglobin for O2
so it loads O2 readily but unloads it less easily
If the dissociation curve moves to the right what happens
The further to the right the curve
- the lower is the affinity for Hb
so it loads O2 less readily but unloads it more easily
What is the effect of increasing the Carbon Dioxide concentration in the blood on the oxygen dissociation curve
In greater concentrations of CO2, the curve shifts to the right (the Bohr effect)
- for example in rapidly respiring tissues conc of CO2 is high. The affinity of Hb for oxygen is reduced with coupled with low conc of O2 in muscles means oxygen unloads readily causing oxygen dissociation curve to shift to the right
How does partial pressure of Carbon dioxide affect Oxygen-haemoglobin binding?
As partial presssure of Carbon Dioxide increases, the conditions become acidic causing Hb to change shape.
The affinity of Hb for O2 therefore decreases, so O2 is released from Haemoglobin.
This is known as the Bohr Effect
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
As partial pressure of O2 increases, the affinity of Hb for O2 also increases, so oxygen binds tightly to Hb. When partial pressure is low, oxygen is released from haemoglobin
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding?
It is hard for the first oxygen molecule to bind. Once it does, it changes the shape to make it easier for the second and third molecules to bind, known as positive cooperativity. It is then slightly harder for the fourth oxygen molecule to bind because there is a low change of finding a binding site.
Explain why oxygen binds to haemoglobin in the lungs
- partial pressure of oxygen is high
- low concentration of carbon dioxide increases the lungs, so affinity is high
- positive cooperativity (after the first oxygen molecule binds, binding of subsequent molecules is easier)
Explain why oxygen is released from Haemoglobin in respiring tissues
- partial pressure of oxygen is low
- high concentration of Carbon dioxide in respiring tissues, so affinity decreases
What is the effect of low carbon dioxide (for example in lungs) concentration of the oxygen dissociation curve of Hb
Low Conc of CO2 causes
- affinity of Hb for oxygen to increase
- oxygen is readily loaded by Hb
-oxygen dissociation curve is shifted to the left
Why does changes in the CO2 concentration lead to different affinities for oxygen by Hb
The pH of blood is slightly lowered due as more carbon dioxide dissolved into it
This lower pH changes the shape of Hb into one that enables oxygen to unload readily
(Lower affinity for oxygen)
Hb releases oxygen into the respiring tissues
the opposite effect is seen in areas of low carbon dioxide concentration
Do all species have the same type of Hb?
No different species have different types of Hb, each with their own oxygen dissociation curve.
(Each one is evolved to adapt to different environments and conditions)
