Section 3 Flashcards
How do Microorganisms Obtain Nutrients & Remove Waste?
by exchange via their surface
nutrients (e.g. glucose, oxygen) move in by diffusion via their surface
waste (e.g. carbon dioxide) move out by diffusion via their surface
Why are Microorganisms able to perform exchange via their surface?
have a large surface area to volume ratio
have a short diffusion distance
have low demand
Why can’t Animals/Plants perform exchange via their surface?
have a small surface area to volume ratio
multicellular (large diffusion distance and high demand)
impermeable surface (prevent pathogens entering and reduce water loss)
therefore, require specialised Exchange & Transport systems
exchange system = increases rate of diffusion of nutrients in and wastes out
transport system = deliver nutrients and remove waste from all cells
Why do Fish have Specialised Gas Exchange Systems?
multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable
therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills
Structure of Gills in Fish?
many gill filaments and gill lamellae = large surface area
gill lamellae have a thin wall (short diffusion distance) and are permeable
ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains concentration gradient all the way along the gill lamellae
Why do Insects have Specialised Gas Exchange Systems?
multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)
therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System
Structure of Tracheal System in Insects?
starts with openings on body surface called Spiracles
spiracles contain valves, open = gas exchange, closed = prevent water loss
spiracles connect to Trachea
trachea connect to Tracheoles
tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)
How does Gas Exchange occur in Tracheal System of Insects?
at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion
when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
Function of Lungs?
site of gas exchange in mammals (oxygen into blood – used in cells for respiration,
carbon dioxide out of the blood – toxic waste product of respiration)
What is Lungs made up of?
Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)
Function of trachea, bronchi, bronchioles?
transport of air and filter air, (bronchioles also controls amount of air reaching alveoli)
Structure of trachea/bronchi?
wall made of c-shaped cartilage
cartilage is strong so trachea/bronchi do not collapse
cartilage is c-shaped to give flexibility
lining made of goblet cells and ciliated epithelial cells
goblet cells make mucus, which traps pathogens/particles
ciliated epithelial cells have cilia, which pushes mucus up and out of lungs
Structure of bronchioles?
wall made of smooth muscle
smooth muscle contracts, lumen narrows, bronchiole constricts
(occurs when surrounded by noxious gases – reduces amount reaching alveoli)
lining made of goblet cells and ciliated epithelial cells
Adaptation of alveoli?
millions of tiny alveoli that are folded (large surface area)
thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)
ventilation maintains concentration gradient (high oxygen, low carbon dioxide)
Adaptation of capillaries?
millions of tiny capillaries (large surface area)
thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
narrow lumen (increases diffusion time, decreases diffusion distance)
circulation maintains concentration gradient (low oxygen, high carbon dioxide)
How O2 moves from the alveoli to the capillaries?
by simple diffusion passing thru the alveolar epithelium and capillary epithelium
How CO2 moves from capillaries to the alveoli?
by simple diffusion passing thru the capillary epithelium and alveoli epithelium
Describe the process of Breathing/Ventilation?
Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in
Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)
Formula for Pulmonary Ventilation?
PV = tidal volume x ventilation rate
tidal volume = volume of air breathed in/out in one breath
ventilation rate = number of breaths per minute
Pulmonary Ventilation = volume of air breathed in/out per minute
Function of Intestines?
site of exchange of digested nutrients in mammals
What is Digestion?
Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)
Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase/Lactase/Sucrase (on lining of small intestine)
Proteins into Amino Acids by Endopeptidase/Exopeptidase/Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine)
Lipids into Monoglyceride and 2 Fatty Acids by Lipase (in small intestine)
What do Intestine Absorb?
Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals)
Large Intestine absorbs water
Why do Humans/Mammals require a Specialised Transport System?
multicellular organisms therefore have large diffusion distances and high demand
need a transport system to deliver nutrients and remove waste from all cells
transport system in humans/mammals called Circulatory System
Circulatory System made of heart, blood vessels, blood
(heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)
Why is the transport system in mammals called a double circulatory system?
the heart pumps twice, the blood goes through the heart twice – generates enough pressure to supply all body cells
Why is the transport system in mammals called a closed circulatory system?
blood is transported in blood vessels – helps to maintain pressure and redirect blood flow
Layout of Circulatory System?
heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart
Artery to Arterioles to Capillaries to Venules to Veins
Artery/Arterioles carry blood away from the heart
(arterioles are small arteries)
Capillaries are the site of exchange (nutrients out, waste in)
Veins/Venules return blood back to the heart
(venules are small veins)
Heart?
job is to pump blood around the body (delivers nutrients to cells and remove waste)
made of 4 muscular chambers (2 atria, 2 ventricles)
atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body)
ventricles thicker then atria (has to pump blood further)
left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can generate higher pressure and pump the blood further around the body
Blood vessels of the heart?
artery takes blood away from the heart, vein returns blood to the heart
Vena Cava supplies R atrium (with deoxygenated blood from body)
Pulmonary Vein supplies L atrium (with oxygenated blood from lungs)
R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs)
L ventricle supplies Aorta (oxygenated blood to body)
Job of valves in heart?
Ensure one way flow of blood, no backflow
(blood flows from atria to ventricles to arteries)
2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve
AV valve = between atria and ventricles
SL valve = between ventricles and arteries
When are AV valves open or closed?
Open = pressure in atria greater then pressure in ventricles, Closed = pressure in ventricles greater then pressure in atria
When are SL valves open or closed?
Open = pressure in ventricles greater then pressure in arteries, Closed = pressure in arteries greater then pressure in ventricles
Describe the processes of the cardiac cycle?
Filling Stage = atria relaxed, ventricles relaxed, AV valve open, SL valve closed
Atria Contracts = the SAN located in the R atrium initiates the heart beat and sends the impulse across both atria making them contract, this pushes all the remaining blood into the ventricles so it becomes full
Ventricles Contract = the AVN picks up the impulse, delays it (stops the atria and ventricles contracting at the same time, so the atria empties and the ventricles fill), sends the impulse down the septum in the Bundle of His, then at the apex the impulse goes up both walls of the ventricles in the purkine fibres, so the ventricles contract from the base upwards, pushing the blood up thru the arteries, when the ventricles start to contract the AV valve closes then the SL valve opens and blood leaves the heart
Ventricles Relax = the SL valve closes then the AV valve opens and filling starts again
What causes the Heart Sounds?
when the valves close
1st = AV closes
2nd = SL closes
Formula for Cardiac Output?
CO = Stroke Volume x Heart Rate
stroke volume = volume of blood pumped out of the heart in one beat
heart rate = number of beats per minuted
Cardiac Output = volume of blood pumped out of the heart in one minute
Coronary Heart Disease and Myocardial Infarction?
high blood pressure damages lining of coronary artery
fatty deposits/cholesterol builds up beneath the lining, in the wall = Atheroma
the atheroma breaks thru the lining forming a Atheromatous Plaque on the lining, in the lumen
this causes turbulent blood flow
a blood clot (thrombus) forms
this block the coronary artery
therefore less blood flow to the heart muscle
less glucose and oxygen delivered
the heart muscle cannot respire
so it dies (myocardial infarction)
Risk Factors of CHD?
Age, gender, ethnicity
Saturated fats (increases LDL, LDL deposits cholesterol in the arteries to form atheroma)
Salts (increases blood pressure – lowers water potential of the blood so it holds the water)
Smoking (nicotine = increase HR and makes platelets more sticky – blood clot, carbon monoxide = permanently blocks haemoglobin)
Obesity and Lack of Exercise
Atheroma & Aneurysm?
atheroma weakens wall of artery, blood builds up in the wall, the wall swells then bursts = aneurysm
Role of Arteries/Arterioles?
generally carry oxygenated blood away from the heart
for example, Coronary Artery to heart muscle
Hepatic Artery to liver
Renal Artery to kidneys
exception = Pulmonary Artery carries deoxygenated blood to lungs
Role of Veins/Venules?
generally carry deoxygenated blood back to the heart
for example, Coronary Vein from heart muscle
Hepatic Vein from liver
Renal Vein from kidneys
exception 1 = Pulmonary Vein carries oxygenated blood back to the heart
exception 2 = Hepatic Portal Vein carries deoxygenated blood from digestive system to liver (for filtering)
Function of Arteries/Arterioles?
carry blood away from the heart so should be able to withstand high blood pressures & maintain high blood pressures
Structure of Arteries/Arterioles?
narrow lumen = maintains pressure
lining made of squamous epithelial cells = smooth lining to reduce friction
thick wall = withstand pressure
elastic tissue in wall,
ventricles contract – elastic tissue stretches to withstand pressure ventricles relax – elastic tissue recoils to maintain pressure and smooth out flow
smooth muscle in wall (particularly in arterioles),
smooth muscle contracts – lumen narrows and arteriole constricts
smooth muscle relaxes – lumen widens and arteriole dilates
collagen in wall
prevents artery from tearing
Function of Veins/Venules?
return blood back to the heart, the blood is under low pressure
Structure of Veins/Venules?
wide lumen = ease of blood flow
lining made of squamous epithelial cells = smooth lining to reduce friction
thin wall = vein can be squashed by skeletal muscle pushing blood back to the heart
valves in lumen = prevents backflow of blood
Function of Capillaries?
site of exchange
3 locations,
With Alveoli, takes in O2 and removes CO2
With Microvilli, takes in glucose/amino acids/monoglyceride and fatty acids/vitamins/minerals
With All Cells, deliver nutrients and remove waste
Adaptation of Capillaries?
many small capillaries = large surface area
thin wall, one cell thick, squamous epithelial cells = short diffusion distance
pores between cells = allows fluid to move in and out
narrow lumen = increase diffusion time and decrease diffusion distance
Content of Blood?
main component = Plasma (fluid)
plasma carries,
Cells = red blood cells, white blood cells, platelets
Solutes = nutrients, waste, protein
How does exchange occur between Capillaries & All Cells?
by mass flow
fluid moves out of the blood in the capillaries carrying the nutrients
fluid moves back into blood in the capillaries carrying the waste
(fluid in the blood called plasma, fluid surrounding cells called tissue fluid, fluid in lymph system called lymph)
How is tissue fluid formed and returned to circulatory system?
at the start of the capillary (arterial end) there is a build up hydrostatic pressure
this pushes fluid out of the capillary via the pores
the fluid carries the nutrients with it
the fluid surrounds the cells, this is called tissue fluid
at the finish of the capillary (venous end) the fluid moves back in by osmosis
the capillary has low water potential due to the presence of proteins (too large to move out of capillaries)
any excess tissue fluid is picked up by the lymph system and deposited in the vena cava
Why does high blood pressure cause accumulation of tissue fluid?
increases hydrostatic pressure, so more tissue fluid is formed – not as much can be returned to the circulatory system
Why does diet low in protein cause accumulation of tissue fluid?
the water potential in the capillary is not as low as normal, so not as much fluid can move back into the capillary by osmosis
Blood Pressure changes along the Circulatory System?
Arteries = - highest pressure (connects directly with heart/ventricles)
- pressure fluctuates (increases when ventricles contract which causes the elastic tissue to stretch, decreases when ventricles relax which causes the elastic tissue to recoil) - overall decrease in pressure due to friction Arterioles = large decrease in pressure due to increase in total cross-sectional area (ensures pressure is not to high to damage capillaries) Capillaries = pressure here is called hydrostatic pressure (decreases due to a loss in fluid) Venules/Veins = blood under low pressure
Job of Red Blood Cells?
found in humans/mammals (animals)
carries haemoglobin
haemoglobin carries oxygen
Structure of Haemoglobin?
globular protein (soluble & specific 3d shape)
quaternary structure made of 4 polypeptide chains (2α, 2β)
each chain carries a haem group
each haem group carries Fe2+
each Fe2+ carries an O2
therefore, each haemoglobin carries 4 lots of O2
Job of Haemoglobin?
load oxygen in the lungs and deliver it to the respiring tissues
What is Affinity?
the level of attraction haemoglobin has to oxygen
(high affinity = strong attraction, low affinity = weak attraction)
Role of haemoglobin in oxygen transport?
haemoglobin has High Affinity in the lungs – due to high partial pressure of oxygen and low partial pressure of carbon dioxide, so haemoglobin loads/associates oxygen in the lungs and becomes saturated (full)
the haemoglobin is transported in the blood in the red blood cell
at the respiring tissues, haemoglobin has Low Affinity – due to low partial pressure of oxygen and high partial pressure of carbon dioxide, so oxygen is unloaded/dissociated/delivered and haemoglobin becomes unsaturated
Relationship between O2 Partial Pressure & Affinity/Saturation of Haemoglobin?
positive correlation
as O2 partial pressure increases, affinity/saturation of haemoglobin increases
the correlation is not linear but is curved (produces a s-shaped, sigmoid curve called Oxygen Dissociation Curve)
middle portion of ODC has a steep gradient so when respiring tissues change from resting to active and partial pressure of O2 falls, there is a large drop in affinity, so more O2 would be delivered to the respiring tissues
Relationship between CO2 Partial Pressure & Affinity/Saturation of Haemoglobin?
negative correlation
as CO2 partial pressure increases, affinity/saturation of haemoglobin decreases
this occurs at the site of respiring tissues = the carbon dioxide lowers the pH of the blood, makes the haemoglobin change shape, so oxygen is released, lowering affinity. this shifts the ODC to the right, called the bohr shift. benefit = more oxygen delivered to respiring cells
How does a Fetus receive oxygen?
from mother’s blood, oxygen dissociates from mother’s haemoglobin and associates with fetal haemoglobin in the placenta – fetal haemoglobin has a higher affinity compared to mother’s haemoglobin
Benefit of fetal haemoglobin having high affinity?
fetal haemoglobin’s ODC will be to the left, it has high affinity – so the oxygen will dissociate from the mother’s haemoglobin and associate with the fetal haemoglobin at the low partial pressures of oxygen in the placenta, so it has enough oxygen for its needs
Why do adults not keep with fetal haemoglobin?
the high affinity will mean less oxygen will be unloaded at the respiring tissues
Affinity of Organisms in a Low Oxygen Environment?
has a high affinity, curve to the left, therefore it can readily associate oxygen at the low oxygen partial pressures
Affinity of Active Organisms?
has a low affinity, curve to the right, therefore more oxygen can be unloaded to meet the cell’s demand for more respiration
Affinity of Small Organisms?
have a large surface area to volume ratio, lose a lot of heat, needs to respire to generate heat, therefore has a low affinity, curve to the right, so unloads enough oxygen for the cells demand of more respiration
What are the Exchange & Transport Systems in Plants?
exchange systems = leaf and root
leaf to absorb light and CO2 for photosynthesis
roots to absorb water and minerals
transport systems = xylem and phloem
xylem transports water and minerals
phloem transports glucose/sugars
xylem transports in one direction from roots to leaves, phloem transports in both directions
Job of the Roots?
absorb water and minerals
absorbs water by osmosis
absorbs minerals by active transport
plants need water for photosynthesis, cytoplasm hydration, turgidity of cells
plants need magnesium, nitrate, phosphate (magnesium to make chlorophyll, nitrate to make amino acids, phosphate to make phospholipids/ATP/DNA)
Function of the Xylem?
transport water and minerals from roots, up the plant, to the leaves
Structure of the xylem?
long continuous hollow tube (no resistance to water flow)
narrow lumen
wall made out of lignin
lignin: strong, waterproof, adhesive
wall contains pits/pores (water and minerals can leave)
How does water move up the xylem?
loss of water at the leaves (transpiration)
water moves from the top of the xylem into the leaf by osmosis (transpirational pull)
this applies TENSION to the column of water in the xylem
the column of water moves up as one as the water particles stick together, COHESION
this is is the cohesion-tension theory
it is supported by capillary action, adhesion and root pressure
(capillary action = water automatically moves up narrow lumen of xylem)
(adhesion = water particles stick to lignin in wall of xylem)
(root pressure = water absorbed at the roots pushes the column of water up slightly by hydrostatic pressure)
Why does the diameter of a tree decrease during the day?
more light and higher temperature
increase rate of transpiration
increase transpirational pull
water pulled up xylem by cohesion-tension
because the water particles stick to the wall of the xylem (adhesion)
the walls of the xylem are pulled inwards
Structure of Leaves?
upper layer called Upper Epidermis
waxy cuticle on upper epidermis (barrier to reduce water loss)
beneath the upper epidermis are Palisade Cells
palisade cells are were photosynthesis takes places
beneath palisade cells are Spongy Mesophyll Cells
are loosely packed leaving air spaces to allow ease of gas exchange
lower layer called Lower Epidermis
Adaptation of palisade cells for photosynthesis?
located near top of leaf, closer to light
large size, large surface area for light
thin cell wall, short diffusion distance for carbon dioxide
contains many chloroplasts, site of photosynthesis
large vacuole, pushes chloroplast to the edge of the cell closer to light
Structure of chloroplast?
organelle for photosynthesis has double membrane contains discs called thylakoids thylakoids contain chlorophyll stack of thylakoids called granum thylakoids surrounded by a fluid called stroma
How does Exchange occur in Leaves?
lower epidermis of leaf contains pairs of cells called Guard Cells
when turgid, guard cells form an opening called Stomata
gas exchange occurs via the stomata
In Day, plant photosynthesises and respires, CO2 moves in for photosysnthesis and O2 moves out (some is used in respiration)
At Night, plant only respires, O2 moves in for respiration and CO2 moves out
What is Transpiration?
loss of water vapour from the leaf via the stomata
How does Transpiration occur?
moist lining of spongy mesophyll cells evaporate forming water vapour
water vapour builds up in air spaces
if water vapour concentration is high enough & stomata is open, water vapour diffuses out
Factors that increase rate of transpiration?
light = more light, more stomata open, increase surface area for transpiration
temperature = more temperature, more evaporation (increase water vapour concentration) & more kinetic energy
wind = more wind, maintains concentration gradient
humidity = less humidity, less water vapour in the surrounding air, increase in water vapour concentration gradient
What is a Potometer?
apparatus used to measure rate of transpiration
Principle of potometer?
as transpiration occurs from the leaves, the plant will pull up more water from the potometer by cohesion-tension causing the bubble to move towards the plant
the more water lost by transpiration, the more water taken up, the further the bubble moves
Measuring Rate of Transpiration?
rate of transpiration = volume of transpiration divided by time
for volume of transpiration, distance bubble moved x cross-sectional area of tube (πr2)
How to set up a potometer?
choose healthy leaf and shoot
cut shoot underwater and connect to potometer underwater (prevents air bubbles entering/blocking xylem)
ensure potometer is air tight and water tight
What does a potometer actually measure?
measures rate of water uptake as a result of water loss from plant
(water loss can be due to: transpiration, photosynthesis, making cells turgid, loss from potometer)
What is a Xerophyte?
a plant adapted to reduce water loss (reduce transpiration)
Adaptations of Xerophyte?
spiky, needle like leaves = reduced surface area
thick waxy cuticle = waterproof, impermeable barrier
densely packed spongy mesophyll = less air spaces, less water vapour build up
sunken stomata/hairy leaves/rolled up leaves = traps moist layer of air,
reduces concentration gradient
Function of Phloem?
transport organic material (e.g. Sucrose) up and down a plant
Structure of phloem?
made of 2 parts (Sieve Tube with Companion Cells alongside)
How does phloem transport organic material like sucrose?
by principle of Mass Flow (mass flow of water carries the sucrose)
Sucrose loaded into Phloem at Source
Hydrogen Ions (H+) actively transported from companion cells into source
therefore, H+ diffuses back into companion cells from source
as they do, they pull in sucrose with them by co-transport
sucrose then diffuses into sieve tube
this lowers the water potential of sieve tube so water follows by osmosis
this water will carry the sucrose by hydrostatic pressure (mass flow)
Sucrose unloaded from Phloem at Sink
sucrose moves out of phloem/sieve tube into sink by diffusion
water follows by osmosis
