B6 Exchange Flashcards
What’s the SA :V
The relationship between the size of an organism or structure and its surface area to volume ratio plays a significant role in the types of adaptations an organism will have.
Small organisms & SA:V
Small organisms e.g amoeba, very large surface area in comparison to volume.
big surface for exchange of substances, but also there is a smaller distance from the outside of the organisms to the middle of it.
As a result, very small organism can simply exchange substances across their surface.
Larger organisms and SA:V
larger an organism, smaller its SA compared to vol and larger the distance from middle to outside.
typically have higher metabolic rate, which demands efficient transport of waste out of cells and reactants into cells.
have adaptations help make exchange across surfaces more efficient.
Adaptations of larger organisms to increase SA:V
Villi and microvilli - Absorption of digested food
Alveoli and bronchioles - Gas exchange
Spiracles and tracheoles - Gas exchange
Gill filaments and lamellae - Gas exchange
Thin wide leaves - Gas exchange
Many capillaries -capillary network
What happens during digestion
large biological molecules hydrolysed to smaller molecules that can be absorbed across cell membranes.
What enzymes do carbohydrates require to hydrolyse them into monosaccharides
Amylases
Membrane-bound disaccharidases
Where is amylase produced
Pancreas and salivary glands
What does amylase do
It hydrolyses polysaccharides into disaccharide maltose by hydrolysing glycosidic bonds.
What are examples of membrane-bound enzymes
Sucrose and lactase
What do membrane-bound enzymes(sucrase and lactase) do
hydrolyse sucrose and lactose into monosaccharides.
How many enzymes can protein be hydrolysed by
3
What are the 3 enzymes proteins can be broken down by
Endopeptidases
Exopeptidases
Membrane-bound dipeptidases
What d Endopeptidases do
hydrolyse peptide bonds between amino acids in middle of polymer chain
What do Exopeptidases do
hydrolyse peptide bonds between amino acids at end of polymer chain
What do Membrane-bound dipeptidases
hydrolyse peptide bonds between 2 amino acids
Where are proteins digested
Protein digestion starts in stomach, continues in the duodenum and is fully digested in ileum.
Where are lipids digested
Lipids are digested by lipase and the action of bile salts.
Where is lipase produced and what does it do
Lipase is produced in the pancreas and it can hydrolyse the ester bond in triglycerides to form the monoglycerides and fatty acids.
Where are bile salts produced and what do they do
Bile salts are produced in the liver and can emulsify lipids to form tiny droplets, micelles. This increases the surface area for lipase to act on.
What are the 2 stages in lipid digestion
Physical (emulsification & micelle formation)
Chemical (Lipase)
What happens in the 1st stage of lipid digestion
Physical (emulsification & micelle formation)
Lipids are coated in bile salts to create an emulsion.
Many small droplets of lipids provides a larger surface area to enable the faster hydrolysis action by lipase.
What happens in the 2nd stage of lipid digestion
Chemical (Lipase)
Lipase hydrolyses lipids into glycerol and fatty acids (some monoglycerides) .
What are micelles
Micelles are water soluble vesicles formed of the fatty acids, glycerol, monoglycerides and bile salts.
What do micelles do
Micelles deliver the fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum for absorption.
How does micro villi maximise absorption
by increasing SA, decreasing diffusion distance and maintaining concentration gradient.
What is the ileum covered in
The ileum wall is covered in villi, which have thin walls surrounded by a network of capillaries and epithelial cells have even smaller microvilli
In mammals the products of digestion are absorbed where
Across the cells lining the ileum
What are lipids digested into and by what
monoglycerides and fatty acids by the action of lipase and bile salts.
Describe process of lipid absorption
Lipids digested into monoglycerides and fatty acids by action of lipase and bile salts.
These form tiny structures called micelles
When micelles encounter ileum epithelial cells, due to non-polar nature of fatty acids and monoglycerides, they can simply diffuse across cell surface membrane to enter cells of epithelial cells.
Once in cell, these will be modified back into triglycerides inside of endoplasmic reticulum and Golgi body.
Describe how digested lipids are absorbed and then transport to the ileum and lymphatic system. [5]
- Micelles are made of bile salts, fatty acids and monoglycerides
- Micelles carry the fatty acids to the epithelial cells of the ileum
- Fatty acids are absorbed into the cells of the ileum by simple diffusion
- Triglycerides or chylomicrons are formed
- Vesicles are removed by exocytosis
Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum. [3]
- Micelles are made of bile salts, fatty acids and monoglycerides/glycerol
- Micelles make fatty acids more soluble in water
- Micelles carry fatty acids to the epithelial cells of the ileum
- The fatty acids are released from the micelle and are absorbed into the cell by simple diffusion
When lipids are digested, they first form smaller droplets and then micelles are formed.
Explain the advantages of these two stages. [3]
- Lipid droplets the increase surface areas for lipase
- This speeds up hydrolysis / digestion
- The micelles bring the fatty acids, monoglycerides and glycerol to the epithelial cell
How are Golgi apparatus involved in the absorption of lipids? [3]
- They modify triglycerides
- They combine proteins with triglycerides to form chylomicrons
- These are packaged into vesicles
How do micelles help with lipid absorption?
They make the fatty acids more soluble in water
They carry the fatty acids to epithelial cells of the ileum
They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum
The fatty acids are then released from the micelle and enter the epithelial cell by simple diffusion
Why do fatty acids enter by simple diffusion?
They are non-polar (lipid soluble)
So they can dissolve and diffuse through the phospholipid bilayer.
What happens once fatty acids are in the cell?
The fatty acids.and monoglycerides are modified back into triglycerides inside of the endoplasmic reticulum and Golgi body.
Sometimes a protein is added to the lipid, making it a chylomicron.
How do modified lipids leave the epithelial cell?
Vesicles containing the triglyceride/chylomicron are released and move towards the cell membrane.
• They are released by exocytosis
• Then the triglycerides/chylomicrons enter the lacteal.
Why is active transport and co-transport required to absorb glucose and amino acids from the lumen to the gut.
To absorb glucose and amino acids from the lumen to the gut there must be a higher concentration in the lumen compared to the epithelial cell (for facilitated diffusion).
BUT
There is usually more in the epithelial cells.
What’s Tissue fluid
Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues.
How is tissue fluid formed
Capillaries have small gaps in the walls so that liquid and small molecules can be forced out.
As blood enters the capillaries from arterioles, the smaller diameter results in a high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out. This is known as ultrafiltration.
Large molecules remain in the capillaries and therefore create a lowered water potential.
Towards the venule end of the capillaries, hydrostatic pressure is lowered due to loss of liquid, but water potential is very low.
Water re-enters capillaries by osmosis.
What is forced out when forming tissue fluid
Water molecules
Dissolved minerals and salts
Glucose
Small proteins and amino acids
Fatty acids oxygen
What remains in the capillary when forming tissue fluid
Red blood cells
Platelets
Large proteins
The lymph
Not all the liquid will be reabsorbed by osmosis, as equilibrium will be absorbed.
The rest of the tissue fluid is absorbed into the lymphatic system and eventually drains back into the bloodstream near the heart.
What is breathing
movement of air into and out of the lungs.
What is respiration
chemical reaction to release energy the form of ATP.
What is ventilation
the scientific word for breathing.
What is gaseous exchange
diffusion of oxygen from the air in the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli.
Why is Breathing an active process
It uses energy
Describe the process of inspiration
external intercostal muscles contract, internal intercostal muscles relax.
ribs pulled upwards and outwards, increasing volume of thorax.
diaphragm muscles contract, causing it to flatten, which also increases volume of thorax.
• increased volume of thorax results in reduction of pressure in lungs.
• Atmospheric pressure now greater than pulmonary pressure, and so air is forced into lungs.
Describe the process of expiration
internal intercostal muscles contract, external intercostal muscles relax.
ribs move downwards and inwards, decreasing volume of thorax.
diaphragm muscles relax and so it’s pushed up again by contents of abdomen that were compressed during inspiration.
volume of thorax is therefore further decreased.
decreased volume of thorax increases pressure in lungs.
pulmonary pressure is now greater than that of atmosphere, and so air forced out of lungs.
What is tidal volume
Volume of air that enters and leaves the lungs at normal resting breath (0.5dm3)
What is Vital capacity
Max volume of air we can inhale and exhale
What is Residual volume
Volume of air left in lungs after the strongest exhalation
What’s total lung capacity
Vital capacity + residual capacity (normally 5-6dm3)
What’s pulmonary ventilation
the total volume of air that is moved into the lungs during one minute (dm min-‘).
Pulmonary ventilation equation
Pulmonary ventilation = tidal volume x ventilation rate
(dm min-1). (dm3). (min-1)
What are examples of lung diseases
Pulmonary fibrosis
Asthma
Emphysema
Bronchitis
Example exam question style
A student concluded the data shows more cigarettes smoked per day will increase deaths.
Do you agree?
There is a positive correlation between lung cancer deaths and cigarettes smoked
However:
The data overlaps
Correlation does not prove causation - other factors, such as genetics or pollution could cause the deaths
There is no correlation coefficient statistic to know if the correlation is significant.
Why do fish require a gas exchange surface
Fish are waterproof and the have a small surface area to volume ratio.
What’s the gas exchange surface in fish
Gills
Why do fish have a special adaptation to maintain conc gradient to enable diffusion to occur.
As Fish obtain oxygen from water, but there’s 30 time less oxygen in water than air,
Features of gas exchange surfaces
Large surface area to volume ratio
Short diffusion distance
Maintained a concentration gradient
What law can be used to calculate the rate of diffusion
Diffusion (alpha sign)
(surface area x difference in concentration) /length of diffusion path
How many layers of gills are on both sides of the head
4
What are the gills made up of
Stacks of gill filaments
What is each gill filament covered in
Each gill filament is covered in gill lamellae, position at right angles to the filament.
What do gill lamellae do
Create a large SA
What happens when fish open their mouth
When fish open their mouth
water rushes in and over the gills
and then out through a hole in the sides of their head.
Terrestrial insects features
• Insects have an exoskeleton made of hard fibrous material for protection and a lipid layer to prevent water loss.
• Insects do not have lungs, and instead have a tracheal system.
What gas exchange system do insects have
Tracheal system (trachea, tracheoles and spiracles
What are spiracles and what do they do
Spiracles are round, valve like openings, running along the length of the abdomen. Oxygen and carbon dioxide enter and leave via the spiracles. The trachea attach to these openings.
What are trachea
The trachea is a network of internal tubes.
The trachea tubes have rings within them to strengthen the tubes and to keep them open.
What do the trachea do
The trachea branch into smaller tubes, deeper into the abdomen of the insect called tracheoles.
These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.
How many methods of moving gases in the tracheal system are there
3
What’s the 1st method of moving gases in the tracheal system
Gas can exchange by diffusion, as when cells respire, they use up oxygen and produce carbon dioxide, creating a concertation gradient from the tracheoles to the atmosphere.
What’s the 2nd method of moving gases in the tracheal system
The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abdominal muscles to move gases on mass.
What’s the 3rd method of moving gases in the tracheal system
When the insect is in flight the muscle cells start to respire anaerobically to produce lactate. This lowers the water potential of the cells, and therefore water moves from the tracheoles into the cells by osmosis. This decreases the volume in the tracheoles and as a result more air from the atmosphere is draw in.
What happens once the gases are in the alveoli
gas exchanges between the epithelium and the blood.
Features of alveolar epithelium for efficient gas exchange
Alveoli are tiny air sacks, and there are 300 million in each human lung - creates very large SA for gas exchange.
alveoli epithelium cells very thin, to minimise diffusion distance.
Each alveolus is surrounded by network of capillaries to remove exchanged gases, and therefore maintains conc gradient.
5 features of the human gas exchange system
alveoli
bronchioles
bronchi
trachea
lungs
Which enzyme are proteins broken down to aminonacids
Proteases
Insect adaptations to limit water loss
Insects have a small surface area to volume ratio where water can evaporate from
Insects have a waterproof exoskeleton
Spiracles, where gases enter and water can evaporate from, can open and close to reduce water loss.
Adaptations for efficient diffusion in insects
Large number of fine tracheoles - large surface area
Walls of tracheoles are thin and short distance between spiracles and tracheoles - short diffusion pathway
Use of oxygen and production of carbon dioxide sets up steep diffusion gradients
Adaptations for efficient gas exchange in fish
Large surface to volume ratio created by many gill filaments covered in many gilli lamellae
Short diffusion distance due to a capillary network in every lamellae and very thin gill lamellae
Maintaining concentration gradient
countercurrent flow mechanism.
What is the countercurrent exchange principle
This is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.
What does countercurrent flow ensure
Countercurrent flow ensures that equilibrium is not reached
This ensures that a diffusion gradient is maintained across the entire length of the gill lamellae.
