Topic 3 Flashcards
Surface area to volume ratio
The surface area of an organism divided by its volume
the larger the organism, the smaller the ratio
Factors affecting gas exchange
diffusion distance
surface area
concentration gradient
temperature
Ventilation
Inhaling and exhaling in humans
controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
Inspiration
External intercostal muscles contract and internal relax
Pushing ribs up and out
Diaphragm contracts and flattens
Air pressure in lungs drops below atmospheric pressure as lung volume increases
Air moves in down pressure gradient
Expiration
External intercostal muscles relax and internal contract
Pulling ribs down and in
Diaphragm relaxes and domes
Air pressure in lungs increases above atmospheric pressure as lung volume decreases
Air forced out down pressure gradient
Passage of gas exchange
Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli
crosses alveolar epithelium into capillary endothelium
Alveoli structure
Tiny air sacs
highly abundant in each lung - 300 million
surrounded by the capillary network
epithelium 1 cell thick
Why large organisms need specialised exchange surface
They have a small surface area to volume ratio
higher metabolic rate - demands efficient gas exchange
specialised organs e.g. lungs / gills designed for exchange
Fish gill anatomy
Fish gills are stacks of gill filaments
Each filament is covered with gill lamellae at right angles
How fish gas exchange surface provides large surface area
Many gill filaments covered in many gill lamellae are positioned at right angles creates a large surface area for efficient diffusion
Countercurrent flow
When water flows over gills in opposite direction to flow of blood in capillaries
equilibrium not reached
diffusion gradient maintained across entire length of gill lamellae
Name three structures in tracheal system
Involves trachea, tracheoles, spiracles
How tracheal system provides large surface area
Highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles moves into tissues during high metabolic activity
so larger surface area for gas exchange
Fluid-filled tracheole ends
Adaptation to increase movement of gases
When insect flies and muscles respire anaerobically - lactate produced
Water potential of cells lowered, so water moves from tracheoles to cells by osmosis
Gases diffuse faster in air
How do insects limit water loss(4)
Small surface area to volume ratio
Waterproof exoskeleton
Spiracles can open and close to reduce water loss
Thick waxy cuticle - increases diffusion distance so less evaporation
Dicotyledonous plants leaf tissues
Key structures involved are
mesophyll layers with many interconnecting air spaces
Palisade and spongy mesophyll - lots of air spaces and chlorophyll.
Stomata created by guard cells
Gas exchange in plants
Palisade mesophyll is site of photosynthesis
Oxygen produced and carbon dioxide used creates a concentration gradient
Oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
Role of guard cells
Swell - open stomata
Shrink - closed stomata
At night they shrink, reducing water loss by evaporation
Xerophytic plants
Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
Structural features for efficient gas exchange but limiting water loss like:
Stomata in sunken pits and small hairs reduce conc extraction gradient as water vapour is trapped
Thick waxy cuticle
Leaves modified to spines which reduces surface area
Roots seep deep down to reach water
Rolling up of leaves as majority of stomata in lower epidermis this traps layer of still air reducing concentration gradient
Adaptations of xerophyte
Adaptations to trap moisture to increase humidity -> lowers water potential inside plant so less water lost via osmosis
-sunken stomata
-curled leaves
-hairs
Thick cuticle reduces loss by evaporation
longer root network
Digestion
Process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
So they can be absorbed across cell membranes
Locations of carbohydrate
digestion
Mouth -> duodenum -> ileum
Locations of protein digestion
Stomach -> duodenum -> ileum
Endopeptidases
Break peptide bonds between amino acids in the middle of the chain
Creates more ends for exopeptidases for efficient hydrolysis
Exopeptidases
Break peptide bonds between amino acids at the ends of polymer chain
Membrane- bound dipeptidases
Break peptide bond between two amino acids
Digestion of lipids
Bile salts combine with lipids which causes them two split and form tiny droplets called micelles and this increases the S.A for the action of lipase - this is called emulsification
Lipase hydrolyses the ester bonds and forms monoglycerides and fatty acids (non polar and lipid soluble)
Lipase produced in pancreas
Bile salts produced in liver and stored in gall bladder
Lipase
Produced in pancreas
Breaks ester bonds in triglycerides to form :
monoglycerides
glycerol
fatty acids
Role of bile salts
Emulsify lipids to form tiny droplets called micelles
Increases surface area for lipase action - faster hydrolysis
Micelles
Water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts
Lipid absorption
Micelles after emulsification and digestion delivers fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
Cross via simple diffusion as these are lipid-soluble and non-polar
Lipid modification
Smooth ER reforms monoglycerides / fatty acids into tryglycerides
Golgi apparatus combines tryglycerides with proteins to form vesicles called chylomicrons
How lipids enter blood after modification
Chylomicrons move out of cell via exocytosis and enter lacteal
lymphatic vessels carry chylomicrons and deposit them in bloodstream
How are glucose and amino acids absorbed
Via co-transport in the ileum
1-Na+ actively transported out of epithelial cells by sodium potassium pump. Takes place in a different type of carrier protein.
2-Thus maintains concentration gradient between lumen and epithelial cells as there is high concentration of Na+ in the ileum compared to epithelial cells
3-So Na+ moves down the concentration gradient into epithelial cells using co transport protein as it carries either amino acids or glucose into the epithelial cells.
4- the glucose or amino acid moves into blood plasma by facilitated diffusion using different type of carrier protein
5-Na+ is down the concentration gradient while glucose/amino acid is against. It’s the movement of Na+ down the concentration gradient rather than ATP which drives this process
Haemoglobin (Hb)
Quaternary structure protein - globular protein
2 alpha chains
2 beta chains
4 associated haem groups in each chain containing Fe2+
transports oxygen
Primary structure, secondary structure and
tertiary structure decides the further folding which is an important factor in its ability to carry oxygen
Affinity of haemoglobin
The ability of haemoglobin to attract / bind to oxygen
Saturation of haemoglobin
When haemoglobin is holding the maximum amount of oxygen it can hold
Loading / unloading of haemoglobin
Binding/detachment of oxygen to haemoglobin
also known as association and disassociation
Oxyhaemoglobin dissociation curve
Oxygen is loaded in regions with high partial pressures (alveoli)
Unloaded in regions of low partial pressure (respiring tissue)
S shaped
Oxyhaemoglobin dissociation curve shifting left
Hb would have a higher affinity for oxygen
Load more at the same partial pressure
Becomes more saturated
Adaptation in low-oxygen environments
e.g. llamas/ in foetuses
Cooperative binding
Hb’s affinity for oxygen increases as more oxygen molecules are associated with it
When one binds, Hb’s quaternary structure changes meaning others bind more easily
explaining S shape of curve
Positive cooperativity
How carbon dioxide affects haemoglobin
When carbon dioxide dissolves in liquid, carbonic acid forms
decreases pH causing Hb to change shape into one that has lower affinity for O2
at respiring tissues
more oxygen is unloaded
Bohr shift
Bohr effect
High carbon dioxide partial pressure- respiring tissues -pH decreases
causes oxyhaemoglobin curve to shift to the right
Low CO2 partial pressure - pH is high eg lungs-alveoli
Causes oxyhemoglobin curve to shift to the left
Oxyhaemoglobin dissociation curve shifting right
Hb has lower affinity for oxygen
unloads more at the same partial pressures
less saturated
present in animals with faster metabolisms that need more oxygen for respiration
e.g. birds/rodents
Closed circulatory system
Blood remains within blood vessels
Name different types of blood vessels
Arteries, arterioles, capillaries, venules and veins
Structure of arteries
Thick muscular layer compared to veins- smaller arteries control the flow of blood by constricting and dilating
thick elastic layer compared to veins - important to maintain high pressure of blood by stretching and recoiling
thick outer layer - resists the vessel bursting under pressure
small lumen
no valves except in the ones leaving the heart, due to constant high pressure
Capillary endothelium
Extremely thin
one cell thick
contains small gaps for small molecules to pass through (e.g. glucose, oxygen)
Numerous as they’re highly branched providing larger SA for exchange
Very narrow diameter and can permeate tissues and therefore no cell which is far from capillary
Capillaries
Form capillary beds
narrow diameter (1 cell thick) to slow blood flow
red blood cells squashed against walls shortens diffusion pathway
small gaps for liquid / small molecules to be forced out
Arterioles
Branch off arteries
Relatively thicker muscle layer(smooth endothelium) compared to arteries - contraction of this layer constricts the lumen and this restricts blood flow
Helps control movement of blood into capillaries
Thinner elastic layer and outer layer than arteries as pressure lower
Tissue fluid
Liquid bathing all cells
contains water, glucose, amino acids, fatty acids, ions and oxygen
enables delivery of useful molecules to cells and removal of waste
Tissue fluid formation
-At arterial end of capillary, high hydrostatic pressure due to pumping of heart and also the smaller diameter
-Hydrostatic pressure is high inside capillaries than outside which causes small molecules forced out (ultrafiltration) through the small gaps in the capillary endothelium, red blood cells / large proteins too big to fit through capillary gaps so remain inside.
-However the osmotic pressure or the water potential is lower inside capillary than outside causing fluid to move back in
-But HP is stronger than osmotic pressure which means the combined effect causes the fluid to move out of capillary
Reabsorption of tissue fluid
Large molecules remaining in capillary lower its water potential
towards venule end of capillary bed there is lower hydrostatic pressure due to loss of liquid
water reabsorbed back into capillaries by osmosis down the water potential gradient
Not all tissue fluid is reabsorbed by capillaries, the remaining unabsorbed ones are carried back via the lymphatic system which drains their contents back into bloodstream via ducts that joins veins to the heart.
Role of the lymph in tissue fluid reabsorption
Not all liquid will be reabsorbed by osmosis as equilibrium will be reached
Excess tissue fluid (lymph) is absorbed into lymphatic system and drains back into bloodstream and deposited near heart
Cardiac muscle
Walls of heart having thick muscular layer
unique because it is:
myogenic - can contract and relax without nervous or hormonal stimulation
never fatigues so long as adequate oxygen supply
Coronary arteries present all through the cardiac muscle which provides oxygenated blood
Coronary arteries
Blood vessels supplying cardiac muscle with oxygenated blood
branch off from aorta
if blocked, cardiac muscle will not be able to respire, leading to myocardial infarction (heart attack)
Structure of heart
Labels:
Aorta
Right atrium and ventricle
Left atrium and ventricle
Superior vena cava
Pulmonary artery and vein
Tricuspid valve and mitral or bicuspid
Aortic valve
Inferior vena cava
Pericardium
Semilunar valve
Adaptation of left ventricle
Has a thick muscular wall in comparison to right ventricle
enables larger contractions of muscle to create higher pressure
ensures blood reaches all body cells
Veins connected to the heart(2)
Vena cava - carries deoxygenated blood from body to right atrium
Pulmonary vein - carries oxygenated blood from lungs to left atrium
Arteries connected to the heart
Pulmonary artery - carries deoxygenated blood from right ventricle to lungs
Aorta - carries oxygenated blood from left ventricle to rest of the body
Valves within the heart
Ensure unidirectional blood flow
Semilunar valves are located in aorta and pulmonary artery near the ventricles
Atrioventricular valves between atria and ventricles
Opening and closing of valves
Flaps made of fibrous, elastic but strong fibre which forms a cusp like shape
If blood builds in the convex side it is allowed to pass across
If blood collects in the concave side it’s collected and not let through and it passes in one direction
Valves open if the pressure is higher behind them compared to in front of them.
AV valves open when pressure in atria > pressure in ventricles
SL valves open when pressure in ventricles > pressure in arteries
The Septum
Muscle that runs down the middle of the heart
Separates oxygenated and deoxygenated blood
Maintains high concentration of oxygen in oxygenated blood
Maintaining concentration gradient to enable diffusion to respiring cells
Cardiac output
Volume of blood which leaves one ventricle in one minute.
Cardiac output = heart rate * stroke volume
heart rate = beats per minute
Stroke volume - amount of blood in one contraction that is pumped from left ventricle of the heart
Stroke volume
Volume of blood that leaves the heart each beat
measured in dm^3
Cardiac cycle
Consists of diastole, atrial systole and ventricular systole
Diastole
Atria and ventricular muscles are relaxed
When blood enters atria via vena cava and pulmonary vein
Increasing pressure in atria
Atrioventricular valves open
Blood flows into the ventricles and this is aided by gravity, relaxation of the ventricle walls causes them to recoil which reduces the pressure of ventricles below that of aorta and pulmonary artery causing semilunar valves to close
This is accompanied by the characteristic dub sound of heart beat
Atrial systole
Contraction of the atrial walls along with the recoiling of the relaxed ventricle’s walls forces the remaining blood into ventricles from atria
Throughout this stage ventricle relaxed.
Ventricular systole
After a short delay (so ventricles fill), ventricle walls contract simultaneously which increases the pressure in ventricle
Pressure ventricle > atria causes atrioventricular valve to shut
This increases the pressure further in ventricles
When pressure in ventricles > pressure in pulmonary artery and aorta semilunar valves open and blood moves to those
Left ventricle more thicker than right as left has to pump blood to the whole body including extremities so contraction of LV has higher pressure
Right ventricle pumps blood to lungs
Transpiration
Loss of water vapour from stomata by evaporation affected by:
light intensity
temperature
humidity
wind
can be measured in a lab using a potometer
How light intensity affects transpiration
As light intensity increases, rate of transpiration increases
more light means more stomata open
larger surface area for evaporation
How temperature affects transpiration
As temperature increases, rate of transpiration increases
the more heat there is, the more kinetic energy molecules have
faster moving molecules increases evaporation
How humidity affects transpiration
As humidity increases, transpiration decreases
the more water vapour in the air, the greater the water potential outside the leaf
reduces water potential gradient and evaporation
How wind affects transpiration
As wind increases, rate of transpiration increases
the more air movement, the more humid areas are blown away
maintains water potential gradient, increasing evaporation
Cohesion in plant transport
Because of the dipolar nature of water, hydrogen bonds can form - cohesion
water can travel up xylem as a continuous column
Adhesion in plant transport
Water can stick to other molecules (xylem walls) by forming H-bonds
helps hold water column up against gravity
Root pressure in plant transport
As water moves into roots by osmosis, the volume of liquid inside the root increases therefore the pressure inside the root increases
this forces water upwards down the water potential gradient
Cohesion- tension theory
Water forms continuous, unbroken column across the mesophyll cells and xylem
As water evaporates out the stomata or mesophyll cells due to heat from sun, this lowers water potential
Causes water molecules to be pulled from behind i.e xylem due to this cohesion.
Column of water is therefore pulled up xylem due to transpiration- transpirational pull
Along with cohesion, water molecules also adhere to walls of xylem
The transpirational pull creates tension in xylem pulling xylem inwards
Negative pressure in xylem
Translocation
Occurs in phloem
explained by mass flow hypothesis
transport of organic substances through plant
Sieve tube elements
Living cells
contain no nucleus
few organelles
this makes cell hollow
allowing reduced resistance to flow of sugars
Companion cell
Provide ATP required for active transport of organic substances
contains many mitochondria
Mass flow hypothesis
Organic substances, sucrose, move in solution from leaves (after photosynthesis) to respiring cells
source -> sink direction
How is pressure generated for translocation
Photosynthesising cells produce glucose which diffuses into companion cell by facilitated diffusion
Companion cells actively transports H+ ions into spaces within cell wall of companion cells
The H+ ions move down the concentration gradient via co transport protein into seive tube elements as it also transports sucrose molecules along with it.
This lowers water potential of phloem so water moves in from xylem via osmosis as xylem has higher water potential
Hydrostatic pressure gradient generated
What happens to sucrose after translocation?
Used in respiration at the sink
stored as insoluble starch
Investigating translocation
Can be investigated using tracer and ringing experiments
proves phloem transports sugars not xylem
Tracing
Involves radioactively labelling carbon - used in photosynthesis
create sugars with this carbon
thin slices from stems are cut and placed on X-ray film which turns black when exposed to radioactive material
stems will turn black as that is where phloem are
Ringing experiments
Ring of bark (and phloem) is peeled and removed off a trunk
consequently, the trunk swells above the removed section
analysis will show it contains sugar
when phloem removed, sugar cannot be transported
How do small organisms exchange gases
Simple diffusion
across their surface
Why don’t small organisms need breathing systems
They have a large surface area to volume ratio
no cells far from the surface
How alveoli structure relates to its function
Round shape & large number in - large surface area for gas exchange (diffusion)
Lined with epithelium and epithelial cells are flat and very thin to minimise diffusion distance
Capillary network maintains concentration gradient
Contains collagen and elastic fibres between alveoli allows it to stretch and recoil during inspiration and exhalation
How fish gas exchange surface provides a short diffusion distance
Thin lamellae epithelium means short distance between water and blood
capillary network in every lamella
How fish gas exchange surface maintains diffusion gradient
Counter-current flow mechanism - water and blood flows in opposite direction which means equilibrium is never reached
Circulation replaces blood saturated with oxygen
Ventilation replaces water with oxygen removed
Name of gas exchange system in terrestrial insects
Tracheal system
Describe structure of spiracles
Round, valve-like openings
running along the length of the abdomen
Describe trachea & tracheoles structure
Network of internal tubes
Have rings of cartilage adding strength and keeping them open
Trachea branch into smaller tubes - tracheoles
Tracheoles extend through all tissues delivering oxygen to insects
How tracheal system provides short diffusion distance
Tracheoles have thin walls so short diffusion distance to cells
How tracheal system maintains concentration gradient
Mass transport - muscle contraction squeezes trachea which enables mass movement of air in and out and this speeds up exchange.
Use of oxygen in respiration and production of CO2 sets up steep concentration gradients
Amylase
Produced in pancreas & salivary gland
hydrolyses starch into maltose
Membrane-bound disaccharidases
Maltase / sucrase / lactase
hydrolyse disaccharides into monosaccharides
Enzymes involved in protein digestion
endopeptidases
exopeptidases
membrane-bound dipeptidases
Products of protein digestion
Large polymer proteins are hydrolysed to amino acids
Double circulatory system
Blood passes through heart twice
pulmonary circuit delivers blood to/from lungs
systemic circuit delivers blood to the rest of the body
Coronary arteries
Supply cardiac muscle with oxygenated blood
for continued respiration and energy production for contraction
Blood vessels entering / exiting the kidney
Renal artery carries oxygenated blood to kidney
Renal vein carries deoxygenated blood to heart
Blood vessels entering / exiting the lung
Pulmonary artery carries deoxygenated blood to lung
pulmonary vein carries oxygenated blood to heart
Blood vessels entering / exiting the heart
Vena cava carries deoxygenated blood to heart (right atrium)
aorta carries oxygenated blood to body
pulmonary artery - carries blood from the heart to the lungs
pulmonary vein - carries blood from the lungs into the heart
Describe then structure of veins
Thin muscular layer compared to arteries as they carry blood away from the body so constriction and dilation cannot control the flow of blood
thin elastic layer - as low pressure it’s too low to create a recoil action
thin walls- very low pressure so no risk of bursting
valves - due to low pressure makes sure blood flows in one direction, prevents back flow.
Explain role of elastic layer in arteries
Thick elastic layer
to help maintain blood pressure
by stretching and recoiling
Describe the elastic layer in veins
Thin elastic layer as pressure lower
cannot control the flow of blood
Explain the role of valves in veins
Due to low pressure in veins
skeletal muscle usually used to flatten walls of veins for blood flow
valves prevent the backflow of blood
unidirectional flow
What causes the AV valves to open
Higher pressure in the atria than in the ventricles
What causes the semi-lunar valves to open
Higher pressure in the ventricles than in the arteries
Tell me about the lymphatic system
System of vessels that begin in the tissues
Carry lymph which are the excess fluid which wasn’t reabsorbed by capillaries as equilibrium reached
Initially they resemble capillaries except they have a dead ends
Gradually merges into lager vessels that forms a network around the body
These vessels drain their content back into the bloodstream via ducts that joins veins to the heart
