BIOLOGY A - (3.3.1 - 3.3.4) ORGANIMS EXCHANGE SURFACES

SURFACE AREA TO VOLUME RATIO (3.3.1)

SURFACE AREA TO VOLUME RATIO (3.3.1)

Why can very small organisms simply change substances across their surface

Because there is a big exchange surface but also a smaller distance from the outside of the organism to the middle of it

Why do smaller mammals need a high metabolic rate

Due to their high surface area to volume ratio they will lose heat quickly therefore a higher metabolic rate provides the energy required to maintain stable conditions

Why can larger mammals have a slower metabolic rate

Because they have a lower surface area to volume ratio therefore they lose heat more slowly

What are some examples of adaptations to increase surface area to volume ratio

Villi and micro villi - Absorbtion of digested food

Alveoili and bronchioles - Gas exchange

Spiracles and tracheoles - Gas exchange

Gill filaments and lamellar - Gas exchange

GAS EXCHANGE (3.2.2)

GAS EXCHANGE (3.2.2)

What is the formula for calculating rate of diffusion using FICK’S law

Rate of diffusion = (surface area x difference in concentration) / length of diffusion path

What is ventilation (breathing) controlled by

The diaphragm and the antagonistic interaction between the external and internal intercostal muscles

What is pulmonary ventilation

Pulmonary ventilation is the total volume of air that is moved into the lungs during one minute (dm3 min-1)

What is the formula for pulmonary ventilation

Pulmonary ventilation = tidal volume x ventilation rate

Why are alveoli epithelial cells very thin and surrounded by capillaries

To minimise diffusion distance and maintain a concentration gradient

What is the special adaptation that fish have to breathe called

Countercurrent flow to maintain the concentration gradient to enable diffusion to occur

How many layers of gills are there on both side of the head in a fish

4

What are gills made up of

Stacks of Gill filmanets which are covered in lamellae positioned at right angled to the filament

What does this help to achieve

A higher surface area so that when fish open their mouth water rushes in and over the gills and then out through a hole in their head

How does countercurrent exchange work

Water flows over the gills in the opposite direction to the flow of blood in the capillaries

What does counter current flow ensure

That equilibrium is not reached and that the diffusion gradient is maintained across the entire length of the Gill lamellae

How do insects respire

They have Spiracles which are little openings along the abdomen which lead to the trachea

What does the trachea branch off into

Tracheoles which help to deliver the oxygen to all respiring cells

Give 3 adaptations of tracheoles for efficient gas exchange

Thin walls for short diffusion distance (one cell thick)

Highly branched for shorter diffusion distance

Highly branched to provide large surface area for gas exchange

What is the main method of gas exchange at rest in insects

Diffusion

What method of gas exchange Is used during periods of high activity

Mass transport can occur

How does mass transport occur

The abdominal muscles contract and relax which actively moves air in and out of the tracheal system, helping to maintain the gradient for oxygen and carbon dioxide

What product is made when the insect is very active and respires anaerobically

Lactate

What effect does the production of lactate have on respiration

Lactate lowers the water potential in muscle cells which causes water at the ends of the tracheoles to move into the muscle cells via osmosis

Why is less fluid and more air in the tracheoles beneficial for respiration

Gases diffuse more quickly through air than through liquid

What two adaptations do Spiracles have to limit water loss

They can open and close to reduce water loss

They have hairs on them to trap humid air and reduce the water potential gradient, reducing evaopration

What is an insects exoskeleton made from and what property does it have

Chitin and impermeable

Why do stomata close at night

To reduce water loss by evaporation

What are xerophytic plants

Plants adapted to survive in environments with limited water

Name two adaptations to the leaves of xerohytes that helps retain water

Curled leaves trap moisture which increases local humidity

Thicker cuticles to reduce evaporation

3.3.3 DIGESTION AND ABSORPTION

3.3.3 DIGESTION AND ABSORPTION

Which two enzymes do carbohydrates require to hyrdolyse them into monosaccharides

Amylases

Membrane bound disaccharidases

Where is amylase produced and what does hydrolyses starch into

The pancreas

The salivary glands

Hydrolyses it into maltose

Why does the pancreas release more amylase into the top part of the stomach (the duodenum)

Because the enzyme amylase is denatured by the strong stomach acid

What is the name of the membrane bound disaccharidases that are bound to the membrane of the ileum cells

Sucrase - digests sucrose into its monosaccharides

Lactase - digests lactose into its monosaccharides

What is the word equation for maltose hydrolysis

Maltose + water —→ A Glucose + A Glucose

What is the word equation for sucrose hydrolysis

Sucrose + Water —→ Glucose + Fructose

What is the word equation for lactose hydrolysis

Lactose + Water —→ Glucose + Galactose

Where does protein digestion begin, continue into and finish

The stomach and continues into the duodenum and finishes in the ileum

Name the 3 enzymes that are required to digest proteins

Endopeptidases

Exopeptidases

Membrane bound dipeptidases

What do endopeptidases do

Hydrolyses the peptide bonds between amino acids in the middle of the polymer chain

What do Exopeptidases do

Hydrolyses peptide bonds between amino acids at the end of the polymer chain

What do the membrane bound dipeptidases do

Hydrolyses peptide bonds between two amino acids

Why do the endopeptidases come first

So that they break the large polypeptide chain into smaller ones to increase the surface area for Exopeptidases to work

What is the name of the enzyme that digest lipids

Lipase

What other thing are required to digest lipids (non enzyme)

Bile lats

Where is lipase produced and what does it do to lipids

In the pancreas and it can hydrolyse the ester bond in triglycerides to form monoglycerides and fatty acids

(one glycerol molecule and 3 fatty acids)

Where are bile salt produced, where are they released from and what do they do

Liver

Gallbladder

Emulsify lipids to form lipid droplets called micelles

(This increases the surface area for lipase to act on)

Do bile salts digest the lipids chemically or physically

Physically because no chemical bonds are broken

Is lipase digestion chemical or physical

Chemical because the ester bonds in the triglycerides are broken

In mammals, what cells are the products of digestion absorbed via

Ileum cells

What is the ileum wall covered in

Villi

What do ileum epithelial cells have on their membranes

Micro villi to further increase the surface area

In what 3 ways do these features maximise absorption

Increased surface area

Decreasing diffusion distance

Maintain strong concentration gradient

What are micelles

Water soluble vesicles formed by

fatty acids

glycerol

monoglycerides

bile salts

What do the bile salts do to the fatty acids and micelles

Makes them water soluble

What two ways to micelles help in lipid absorption

They make the fatty acids more soluble in water, allowing them to stay suspended in watery contents of small intestine

They carry and release fatty acids to epithelial lining of ileum, close to the cells surface.

Why is it important that the micelles carry the fatty acids close to the ileum cells

Maintains a high concentration gradient of fatty acids near the epithelial cells which allows them to be absorbed into the epithelial cells via simple diffusion

Where are the fatty acids reformed into triglycerides inside the cell and where are they sent to for transportation to lymphatic system

In the golgi apparatus where they are packaged into vesicles to be sent to the cell surface membrane where they are then transported to the lymphatic system

How are Glucose and amino acids absorbed into the epithelial cells

Co transport

3.3.4 MASS TRANSPORT

3.3.4 MASS TRANSPORT

What structure does haemoglobin have

A quaternary structure

Where is oxygen loaded

In regions of high partial pressure of oxygen (e.g alveoli)

Where is oxygen unloaded

Regions of low partial pressure (e.g respiring tissues)

What is oxyhaemoglobin dissociation show on

The oxyhaemoglobin dissociation curve

How many molecules of oxygen can haemoglobin associate with

4

What does oxygen affinity mean

Oxygen affinity refers to the strength with which haemoglobin (Hb) binds to oxygen, indicating how easily it picks up oxygen in the lungs and releases it in the tissues

What is name of the effect that allows haemoglobin's ability to bind with oxygen to change with carbon dioxide (CO2) levels and pH, allowing for efficient oxygen delivery

The Bohr effect

What is the Bohr effect

Carbon dioxide dissolves in liquid

Carbonic acid forms and decreases pH

This changes the shape of the haemoglobin slightly

Affinity for oxygen decreases in respiring tissues

Haemoglobin delivers the oxygen to the site of respiring cells so that aerobic respiration can continue

What does myoglobin do

Has a very high affinity to oxygen, even at very low partial pressures so acts as an oxygen store

What type of circulatory system do mammals have

A closed, double circulatory system

Why is it referred to as being closed

Because the blood remains within the vessels

Why is it referred to as a double circulatory system

The blood passes through the heart twice in each circuit

One circuit delivers blood to lungs and the other delivers blood to the rest of the body

Why do the aorta and venca cava both branch off

They have one branch going to the brain and body (aorta) and one branch going from the body and brain (pulmonary circuit) to the heart

Venca cava divided into superior (from brain to heart) and inferior (from body to heart)

Aorta branches with one branch going to the body and one branch going to the brain

Why do mammals require a double circulatory system

To manage the pressure of the bloodflow

Why does the blood pass through the lungs at a lower pressure

Prevents damage to the capillaries in the alveoli and also reduces blood speed, enabling more time for gas exchange

In contrast, why do we want the blood leaving the lungs to be pumped out at a high pressure

So that the blood reaches all the respiring cells in the body

Name the blood vessels attached to the kidneys

Renal artery

Renal vein

Name the blood vessels attached to the lungs

Pulmonary artery

Pulmonary vein

Name the blood vessels attached to the heart

Vena cava

Aorta

Pulmonary artery

Pulmonary vein

Coronary arteries

What do arteries do

Carry blood away from heart and into arterioles

What do arterioles do

Smaller than arteries and connect to the capillaries

What do capillaries do

Connect the arterioles to the veins

What do veins do

Carry deoxygenated blood back into the heart (have valves)

What does the aortic tissue do when the ventricles contract/relax

Contracts = stretch

Relax = Recoil

What does this help to achieve

Smooth outflow of blood and consistent pressure

What does the thick SMOOTH muscular wall and smooth endothelium (inside wall) help with

Prevents bursting due to the high pressure

Reduces friction

Why do arterioles have a Thicker layer of muscle than arteries

So tat they can vasonctrict (reduce size of lumen) and vasoldilate (increase size of lumen) to regulate the floor of blood to capillaries

Why do veins have a wide lumen and valves

Rescue bloodflow resistance

Prevent backflow of blood

How many red blood cells can fit though a capillary at once and what effect does this have on the flow of blood

One at a time which slows it down - more time for gas exchange

Why are capillaries made of flattened endothelial cells

Reduces the diffusion distance

What is tissue fluid

Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues that has been forced out of the capillaries

Why do capillaries have small gaps in the walls

So that liquid and small molecules can be forced out

As blood enters the capillaries from the arterioles, what does the smaller diameter result in

A high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out

What is this process known as

Ultrafiltration

What remains in the capillary

Large proteins

Red blood cells

Platelets

What do the large molecules that remain in the capillaries do

A lowered water potential

Why is the hydrostatic pressure lowered towards the venue end of the capillaries

Loss of liquid

Why is not all of the liquid that went into the tissue fluid reabsorbed

Because osmosis means that once equilibrium is reached, no more liquid can be absorbed