unit 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
Name three
structures in
tracheal system
Involves trachea, tracheoles,
spiracles
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
How tracheal
system provides
large surface area
Highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles
moves into tissues during
exercise
so larger surface area for
gas exchange
How do insects
limit water loss
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
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 tracholes
to cells by osmosis
gases diffuse faster in air
Dicotyledonous
plants leaf
tissues
Key structures involved are
mesophyll layers
(palisade and spongy
mesophyll)
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
Locations of
carbohydrate
digestion
outh -> duodenum -> ileum
Role of guard
cells
swell - open stomata
shrink - closed stomata
at night they shrink, reducing
water loss by evaporation
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
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
Digestion
Process where large insoluble
biological molecules are
hydrolysed into smaller soluble
molecules
so they can be absorbed across
cell membranes
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
Membranebound
dipeptidases
Break peptide bond between
two amino acids
Digestion of
lipids
Digestion by lipase (chemical)
emulsified by bile salts
(physical)
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 and micelles
increases surface area for
lipase action - faster hydrolysis
Micelles
Water soluble vesicles formed
from fatty acids, glycerol,
monoglycerides and bile salts
Lipid
modification
Smooth ER reforms
monoglycerides / fatty acids
into tryglycerides
golgi apparatus combines
tryglycerides with proteins to
form vesicles called
chylomicrons
Lipid
absorption
Micelles deliver fatty acids,
glycerol and monoglycerides to
epithelial cells of ileum for
absorption
cross via simple diffusion as
lipid-soluble and non-polar
How lipids enter
blood after
modification
Via co-transport in the ileum
Haemoglobin
(Hb)
Quaternary structure protein
2 alpha chains
2 beta chains
4 associated haem
groups in each chain
containing Fe2+
transports 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)
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 changes
shape meaning others bind
more easily
explaining S shape of curve
Closed
circulatory
system
Blood remains within blood
vessels
How carbon
dioxide affects
haemoglobin
When carbon dioxide dissolves
in liquid, carbonic acid forms
decreases pH causing Hb to
change shape
affinity decreases at respiring
tissues
more oxygen is unloaded
Bohr effect
High carbon dioxide partial
pressure
causes oxyhaemoglobin curve
to shift to the right
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
Structure of
arteries
Thick muscular layer
thick elastic layer
thick outer layer
small luman
no valves
Name different
types of blood
vessels
Arteries, arterioles, capillaries,
venules and veins
Reabsorption
of tissue fluid
Large molecules remaining in
capillary lower its water
potential
towards venule end there is
lower hydrostatic pressure due
to loss of liquid
water reabsorbed back into
capillaries by osmosis
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
Capillary
endothelium
Extremely thin
one cell thick
contains small gaps for small
molecules to pass through (e.g.
glucose, oxygen)
Arterioles
Branch off arteries
thickest muscle layer to restrict
blood flow
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 arteriole end, the smaller
diameter results in high
hydrostatic pressure
small molecules forced out
(ultrafiltration)
red blood cells / large proteins
too big to fit through capillary
gaps so remain
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
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)
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
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
Veins
connect to
the heart
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
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
Stroke volume
Volume of blood that leaves the
heart each beat
measured in dm^3
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 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
Cardiac output
Volume of blood which leaves one
ventricle in one minute.
cardiac output = heart rate x stroke vol
Atrial systole
Atria muscular walls contract,
increasing pressure further.
pressure atria > pressure
ventricles
atrioventricular valves open and
blood flows into ventricles
ventricular muscle relaxed
Ventricular
systole
After a short delay (so ventricles
fill), ventricular muscular walls
contract
pressure ventricle > atria
pressure and artery pressure
atrioventricular valves close
and semi-lunar valves open
blood pushed into artery
How light
intensity affects
transpiration
As light intensity increases, rate
of transpiration increases
more light means more stomata
open
larger surface area for
evaporation
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 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 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 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
Translocation
Occurs in phloem
explained by mass flow
hypothesis
transport of organic substances
through plant
Adhesion in
plant transport
Water can stick
to other
molecules (xylem
walls) by forming
H-bonds
helps hold water
column up
against gravity
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
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
Cohesiontension theory
As water evaporates out the
stomata, this lowers pressure
water is pulled up xylem (due to
negative pressure)
cohesive water molecules
creates a column of water
water molecules adhere to walls
of xylem pulling it upwards
this column creates tension,
pulling xylem inwards
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
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
Why don’t small
organisms need
breathing systems
They have a large surface area
to volume ratio
no cells far from the surface
Investigating
translocation
Can be investigated using
tracer and ringing experiments
proves phloem transports
sugars not xylem
How is pressure
generated for
translocation
Photosynthesising cells
produce glucose which diffuses
into companion cell
companion cell actively
transports glucose into phloem
this lowers water potential of
phloem so water moves in from
xylem via osmosis
hydrostatic pressure gradient
generated
What happens to
sucrose after
translocation?
Used in respiration at the sink
stored as insoluble starch
How do small
organisms
exchange gases
Simple diffusion
across their surface
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
How alveoli
structure relates
to its function
Round shape & large number in
- large surface area for gas
exchange (diffusion)
epithelial cells are flat and very
thin to minimise diffusion
distance
capillary network maintains
concentration gradient
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
circulation replaces blood
saturated with oxygen
Ventilation replaces water with
oxygen removed
Name of gas
exchange system in
terrestrial insects
Tracheal system
How tracheal
system provides
short diffusion
distance
Tracheoles have thin walls so
short diffusion distance to cells
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
Describe
structure of
spiracles
Round, valve-like openings
running along the length of the
abdomen
How tracheal
system maintains
concentration
gradient
Body can be moved by muscles
to move air - ventilation
Use of oxygen in respiration and
production of CO2 sets up steep
concentration gradient
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
thin elastic layer
thin walls
valves
Describe the
elastic layer in
veins
Thin elastic layer as pressure
lower
cannot control the flow of bloods
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
Explain role of
elastic layer in
arteries
Thick elastic layer
to help maintain blood pressure
by stretching and recoiling
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 arterioles
