How does size of an organism correlate to rate of diffusion? The larger the surface area to
volume ratio the easier the exchange of substances is
What is special about single-celled organisms? Do not need adaptation for diffusion due
to their larger surface area to volume ratio
Why is diffusion rate slow in multicellular organisms? - large diffusion distance
- low surface area to volume ratio
What do multicellular organism need to carry out diffusion? Specialised exchange
organs
Efficient systems - mass transport
What does the rate of heat loss depend on? How? Depends on the surface area
Larger the surface area to volume ration the more heat is lost
so smaller animals need a high metabolic rate to produce enough heat to stay warm
How does shape relate to surface area to volume ratio? The more compact their shape the
smaller the surface area to volume ratio is so they are minimising heat loss
Describe how fish are adapted for gas exchange? - Lots of gill filaments which have lots of
gill lamellae for a larger surface area
- Lamella have lots of blood capillaries to maintain a conc gradient
- Lamellae have thin epithelium so short diffusion distance
- Counter current system:
- Blood and water flow in opposite directions in the lamellae to maintain conc gradient
- Conc of oxygen is always higher in water than blood so as much oxygen as possible can
diffuse in
Describe how insects are adapted for gas exchange? - Use trachea
- Air moves into the trachea through spiracles
- Oxygen travels down the conc grad towards the cells
- Trachea branches off into tracheoles which have thin permeable walls for a short diffusion
distance
- So oxygen diffuses directly into respiring cells not through a circulatory system
- Carbon dioxide moves from the cells down its own conc grad to the spiracles to be released
- Use rhythmic abdominal movements to move air in and out
What do insects do if they're loosing too much water through respiration? - Close their
spiracles
- Waterproof waxy cuticle all over the body
- Tiny hairs around spiracles
- Reduce evaporation
When do guard cells become flaccid? Flaccid ; closing stomata
When do guard cells become turgid? Turgid; opens stomata
Name xerophytic adaptations - Sunken stomata to trap moist air and reduce conc grad of
water therefore reducing amount of water diffusing out of the leaf and evaporating away
- Layer of hairs on the epidermis - trap moist air
- Curled leaves with stomata inside - protecting them from windy conditions which increases
rate of diffusion
- Reduced number of stomata - fewer places for water to escape
- Waxy waterproof cuticle - reduces evaporation
Describe inspiration - External intercostal muscles contract, pulling the ribcage up and out
- Diaphragm contracts, making it flatten
- Volume of thorax
- So pressure is reduced to below atm
- Air enters and goes down the pressure gradient
Describe expiration - External intercostal relax
,- Ribcage moves down and in
- Diaphragm relaxes and curves
- Volume of thorax decreases
- So pressure increases to above atm
- Air moves out through a pressure gradient
Which one is active and requires energy? Inspiration or expiration? Inspiration
Which one is passive? Inspiration or expiration? Expiration
Describe forced expiration - Eternal intercostal muscles relax.
- Internal intercostal muscles contract.
- Causing ribcage to move down and in more.
- Movement of intercostal muscles is antogonistic
How are alveoli adapted for gas exchange? - Many of them : large surface area
- Alveoli has a thin epithelium : short diffusion distance
- Surrounded by a large network of capillaries ; flow of blood + ventilation : maintains a
steep conc grad
What does lung disease affect? Affects both ventilation and gas exchange
What is tidal volume? Volume of air in each breath - usually between 0.4 dm³ and 0.5dm³ for
adults
What is breathing rate? The number of breaths per minute - for a healthy person its 15
How can you measure tidal volume etc.. Using a spirometer
What is pulmonary ventilation? Movement of air into and out of the lungs (breathing)
What is the calculation for pulmonary ventilation ( dm³ min⁻¹ ) Tidal volume ( dm³ ) x
breathing rate ( min⁻¹ )
What is a correlation? A link between two variables
Does correlation mean causation? NO
What are the ethical issues concerning dissection of animals? - morally wrong to kill
just for dissections
- use animals that have been killed already for their meat
- animals may not be raised in a humane way ( i.e overcrowding , lack of food , extremes of
temperatures )
- may not be killed humanely
What happens during digestion? Large biological molecules are hydrolysed to smaller
molecules that can be absorbed across cell membranes.
Describe how carbohydrates are digested and absorbed. - Amylase hydrolyses starch to
maltose by breaking glycosidic bonds
- Membrane bound disaccharidases break down the disaccharides into monosaccharides
- Breaking glycosidic bonds
Describe the absorption of carbs Glucose and galactose is absorbed by active transport
with sodium ions via the co-transporter protein
Where is amylase produced and released? Produced by the salivary glands
Released in the mouth and small intestine
Where are membrane bound disaccharidases found? Attached to the cell membranes of
epithelial cells lining the ileum
Describe the digestion and absorption of lipids. - Lipase breakdown lipids into
monoglycerides and fatty acids by breaking ester bonds
- Bile salts emulsify lipids increasing their surface area
- Micelles are formed
- Micelles move monoglycerides and fatty acids towards epithelium reducing diffusion
distance
, - Micelles release monoglycerides and fatty acids allowing them to be absorbed down a conc
grad
- Diffuse directly as they are lipid soluble
- SER reforms triglycerides
- Golgi apparatus modifies the lipids
- By adding cholesterol + lipoproteins making a chylomicron
- Chylomicron leaves cell via exocytosis and enters lacteal
Where are lipases made and released? Made in the pancreas
Released in the small intestine
Where are bile salts made? Made in the liver
Describe the digestion of proteins. - Endopeptidase hydrolyses central bonds of a protein
- Exopeptidase hydrolyses terminal bonds of a protein
- Membrane bound dipeptidases hydrolyse peptide bond of a dipeptide
Describe the absorption of proteins Via co-transport:
- Sodium ions actively transport out of ileum epithelial cells into blood
- Creates a sodium ion conc grad
- So sodium ion can diffuse back from lumen to ileum through sodium dependant tansporter
proteins carrying amino acids with them
Where are membrane bound dipeptidases found? Epithelial cells of the small intestine
What is haemoglobin?A globular protein with a quaternary structure
What do all haemoglobins have in common? A group of chemically similar molecules found
in many different organisms
What is in the haem group? Iron ion which gives the red color
Does haemoglobin have a high affinity for oxygen? Yes it can carry four oxygen molecules
Describe the reaction between oxygen and haemoglobin to make oxyhaemoglobin.
Reversible
What does haemoglobin depend on? Partial pressure of oxygen
What is the partial pressure of oxygen? A measure of oxygen concentration
Describe the relationship between haemoglobin affinity and partial pressure of
oxyhaemoglobin Oxygen loads onto haemoglobin to form oxyhaemoglobin where theres
a high pO₂.
Oxyhaemoglobin unloads its oxygen where theres a lower pO₂
What does a dissociation curve show? How saturated the haemoglobin is with oxygen
at any given partial pressure
What does it mean when partial pressure of oxygen is high? - Haemoglobin has a high affinity
for oxygen
- It will readily combine with oxygen ( high saturation )
What does it mean when partial pressure of oxygen is low? - Haemoglobin has a low affinity
for oxygen
- It releases it
When will haemoglobin have a low affinity for oxygen? in respiring cells
When will haemoglobin have a high affinity for oxygen? in the lungs
Why is the dissociation curve 'S' shaped? - When haemoglobin combines with the first
oxygen molecule, another binding site is uncovered for the binding of a second oxygen
molecule
-As haemoglobin starts to become saturated it gets harder from more oxygen molecules to
join.
-The curve has a steep bit in the middle where it's really easy for oxygen molecules to join
- Shallow bits on the end where its really hard
volume ratio the easier the exchange of substances is
What is special about single-celled organisms? Do not need adaptation for diffusion due
to their larger surface area to volume ratio
Why is diffusion rate slow in multicellular organisms? - large diffusion distance
- low surface area to volume ratio
What do multicellular organism need to carry out diffusion? Specialised exchange
organs
Efficient systems - mass transport
What does the rate of heat loss depend on? How? Depends on the surface area
Larger the surface area to volume ration the more heat is lost
so smaller animals need a high metabolic rate to produce enough heat to stay warm
How does shape relate to surface area to volume ratio? The more compact their shape the
smaller the surface area to volume ratio is so they are minimising heat loss
Describe how fish are adapted for gas exchange? - Lots of gill filaments which have lots of
gill lamellae for a larger surface area
- Lamella have lots of blood capillaries to maintain a conc gradient
- Lamellae have thin epithelium so short diffusion distance
- Counter current system:
- Blood and water flow in opposite directions in the lamellae to maintain conc gradient
- Conc of oxygen is always higher in water than blood so as much oxygen as possible can
diffuse in
Describe how insects are adapted for gas exchange? - Use trachea
- Air moves into the trachea through spiracles
- Oxygen travels down the conc grad towards the cells
- Trachea branches off into tracheoles which have thin permeable walls for a short diffusion
distance
- So oxygen diffuses directly into respiring cells not through a circulatory system
- Carbon dioxide moves from the cells down its own conc grad to the spiracles to be released
- Use rhythmic abdominal movements to move air in and out
What do insects do if they're loosing too much water through respiration? - Close their
spiracles
- Waterproof waxy cuticle all over the body
- Tiny hairs around spiracles
- Reduce evaporation
When do guard cells become flaccid? Flaccid ; closing stomata
When do guard cells become turgid? Turgid; opens stomata
Name xerophytic adaptations - Sunken stomata to trap moist air and reduce conc grad of
water therefore reducing amount of water diffusing out of the leaf and evaporating away
- Layer of hairs on the epidermis - trap moist air
- Curled leaves with stomata inside - protecting them from windy conditions which increases
rate of diffusion
- Reduced number of stomata - fewer places for water to escape
- Waxy waterproof cuticle - reduces evaporation
Describe inspiration - External intercostal muscles contract, pulling the ribcage up and out
- Diaphragm contracts, making it flatten
- Volume of thorax
- So pressure is reduced to below atm
- Air enters and goes down the pressure gradient
Describe expiration - External intercostal relax
,- Ribcage moves down and in
- Diaphragm relaxes and curves
- Volume of thorax decreases
- So pressure increases to above atm
- Air moves out through a pressure gradient
Which one is active and requires energy? Inspiration or expiration? Inspiration
Which one is passive? Inspiration or expiration? Expiration
Describe forced expiration - Eternal intercostal muscles relax.
- Internal intercostal muscles contract.
- Causing ribcage to move down and in more.
- Movement of intercostal muscles is antogonistic
How are alveoli adapted for gas exchange? - Many of them : large surface area
- Alveoli has a thin epithelium : short diffusion distance
- Surrounded by a large network of capillaries ; flow of blood + ventilation : maintains a
steep conc grad
What does lung disease affect? Affects both ventilation and gas exchange
What is tidal volume? Volume of air in each breath - usually between 0.4 dm³ and 0.5dm³ for
adults
What is breathing rate? The number of breaths per minute - for a healthy person its 15
How can you measure tidal volume etc.. Using a spirometer
What is pulmonary ventilation? Movement of air into and out of the lungs (breathing)
What is the calculation for pulmonary ventilation ( dm³ min⁻¹ ) Tidal volume ( dm³ ) x
breathing rate ( min⁻¹ )
What is a correlation? A link between two variables
Does correlation mean causation? NO
What are the ethical issues concerning dissection of animals? - morally wrong to kill
just for dissections
- use animals that have been killed already for their meat
- animals may not be raised in a humane way ( i.e overcrowding , lack of food , extremes of
temperatures )
- may not be killed humanely
What happens during digestion? Large biological molecules are hydrolysed to smaller
molecules that can be absorbed across cell membranes.
Describe how carbohydrates are digested and absorbed. - Amylase hydrolyses starch to
maltose by breaking glycosidic bonds
- Membrane bound disaccharidases break down the disaccharides into monosaccharides
- Breaking glycosidic bonds
Describe the absorption of carbs Glucose and galactose is absorbed by active transport
with sodium ions via the co-transporter protein
Where is amylase produced and released? Produced by the salivary glands
Released in the mouth and small intestine
Where are membrane bound disaccharidases found? Attached to the cell membranes of
epithelial cells lining the ileum
Describe the digestion and absorption of lipids. - Lipase breakdown lipids into
monoglycerides and fatty acids by breaking ester bonds
- Bile salts emulsify lipids increasing their surface area
- Micelles are formed
- Micelles move monoglycerides and fatty acids towards epithelium reducing diffusion
distance
, - Micelles release monoglycerides and fatty acids allowing them to be absorbed down a conc
grad
- Diffuse directly as they are lipid soluble
- SER reforms triglycerides
- Golgi apparatus modifies the lipids
- By adding cholesterol + lipoproteins making a chylomicron
- Chylomicron leaves cell via exocytosis and enters lacteal
Where are lipases made and released? Made in the pancreas
Released in the small intestine
Where are bile salts made? Made in the liver
Describe the digestion of proteins. - Endopeptidase hydrolyses central bonds of a protein
- Exopeptidase hydrolyses terminal bonds of a protein
- Membrane bound dipeptidases hydrolyse peptide bond of a dipeptide
Describe the absorption of proteins Via co-transport:
- Sodium ions actively transport out of ileum epithelial cells into blood
- Creates a sodium ion conc grad
- So sodium ion can diffuse back from lumen to ileum through sodium dependant tansporter
proteins carrying amino acids with them
Where are membrane bound dipeptidases found? Epithelial cells of the small intestine
What is haemoglobin?A globular protein with a quaternary structure
What do all haemoglobins have in common? A group of chemically similar molecules found
in many different organisms
What is in the haem group? Iron ion which gives the red color
Does haemoglobin have a high affinity for oxygen? Yes it can carry four oxygen molecules
Describe the reaction between oxygen and haemoglobin to make oxyhaemoglobin.
Reversible
What does haemoglobin depend on? Partial pressure of oxygen
What is the partial pressure of oxygen? A measure of oxygen concentration
Describe the relationship between haemoglobin affinity and partial pressure of
oxyhaemoglobin Oxygen loads onto haemoglobin to form oxyhaemoglobin where theres
a high pO₂.
Oxyhaemoglobin unloads its oxygen where theres a lower pO₂
What does a dissociation curve show? How saturated the haemoglobin is with oxygen
at any given partial pressure
What does it mean when partial pressure of oxygen is high? - Haemoglobin has a high affinity
for oxygen
- It will readily combine with oxygen ( high saturation )
What does it mean when partial pressure of oxygen is low? - Haemoglobin has a low affinity
for oxygen
- It releases it
When will haemoglobin have a low affinity for oxygen? in respiring cells
When will haemoglobin have a high affinity for oxygen? in the lungs
Why is the dissociation curve 'S' shaped? - When haemoglobin combines with the first
oxygen molecule, another binding site is uncovered for the binding of a second oxygen
molecule
-As haemoglobin starts to become saturated it gets harder from more oxygen molecules to
join.
-The curve has a steep bit in the middle where it's really easy for oxygen molecules to join
- Shallow bits on the end where its really hard
