Gas exchange Flashcards
Why do organisms need to exchange substances?
To take in raw materials
To dispose of waste products
What is metabolic rate?
The speed of all chemical reactions in an organism e.g. respiration
What is the best feature to improve efficiency of an exchange surface?
The exchange surface must be large compared to the organisms volume
What are features of a good exchange surface?
- Good blood supply
- Short diffusion distance
- Increased surface area
- Selective / partially permeable membrane
- Steep concentration gradient
What are the consequences of a thin exchange surface?
It can be easily damaged
It’s often located inside the organism
How do you calculate the rate of diffusion?
surface area × steepness of concentration gradient / length of diffusion pathway
What do mammals have to maintain a high core body temperature?
A high metabolic and respitory rate
What is the pharynx?
A common passage for food and air
What two tubes extend down from the pharynx?
The oesophagus and the trachea
What is the larynx
The voice box
How is an open passageway for air maintained in the trachea?
By a series of cartilage rings that prevent the trachea wall from collapsing
What is the inner surface of the trachea lined with?
Cilia
What does cilia in the trachea do?
It prevents the entry of small foreign bodies and moves them to the pharynx to be swallowed
What is ventilation?
The constant movement of air in and out of the lungs
What is the process of inspiration?
-The external intercostal muscles contract and the internal intercostal muscles relax
- The ribs expand and the diaphragm contracts and flattens
- The pressure in the lungs decreases as the thorax volume increases and air is forced in
What is the process of expiration?
- The internal intercostal muscles contract and the external intercostal muscles relax
- The rib cage moves downwards and inwards and the diaphragm relaxes and rises
- The pressure in the lungs increases, as the thorax volume decreases and air is forced out
What is the main cause of air being forced out during regular breathing?
The recoil of elastic tissues in the lungs
When do various muscles in the lungs play a part in breathing?
Under much more strenuous conditions
What is the pulmonary ventilation rate?
The total volume of air that is moved into your lungs in a one minute period
How do you calculate the pulmonary ventilation rate?
tidal volume × ventilation
What is tidal volume?
The volume of air normally taken in at each breath when at rest
What is ventilation?
The number of breaths taken in a one minute period
What are some examples of single celled organisms?
- Bacteria
- Diatom
- Paramecium
- Yeast
Why don’t single celled organisms need a gas exchange system?
They have a very large SA:V and all gases are absorbed and released by diffusion through their cell membrane
What is a problem with gas exchange in insects?
Their high SA:V increases evaporation of water, creating issues conserving water
How do insects reduce water loss?
They have a hard, waterproof exoskeleton
Why do insects need an internal gaseous exchange system?
Because of their hard, waterproof exoskeleton, gas exchange can’t happen across the skeletal surface
What is the structure of insects’ internal gad exchange system?
An internal network of tubes called tracheae divide into smaller tubes known as tracheoles that end in spiracles - pores for gases to exchange in and out. The tracheae are supported by strengthened rings made of chitin to prevent them from collapsing and the spiracles are able to open and close to increase / decrease gas exchange (they open to allow gas exchange and close to decrease water loss)
What are the three ways that gases move in and out of insects?
Along a diffusion gradient
Mass transport
Ends of tracheoles filled with water
What is the process of anaerobic respiration in insects?
- Soluble lactate is produced during anaerobic respiration which lowers the water potential of the muscle cells
- Water will move into the cells via osmosis from the tracheoles
- This decrease of water in the tracheoles draws air into the end of the tracheoles, allowing gaseous diffusion rather than liquid diffusion as it’s faster
- However, this does cause the insect to lose a lot of water
What happens in an insects’ respitory system when the concentration of oxygen becomes too low?
- The spiracle open and this causes oxygen to enter as it’s moving down a concentration gradient
- The concentration of carbon dioxide decreases when the spiracles open, moving down a concentration gradient and diffusing out of the insect
What is the process of mass transport / ventilation in an insect?
- Insects beat their abdomen in and out by squeezing the muscles around it
- This squeezes the trachea, enabling the mass movement of air in and out
- This speeds up the exchange of gases by maintaining a steep concentration gradient
What is the process of ventilation in a fish?
- The fish opens its mouth and lowers its buccal floor, increasing the volume in the mouth and so decreasing the pressure
- Water rushes in and the fish closes its mouth and raises its buccal floor
- This decreases the volume and so increases the pressure in the mouth
- Water is forced over the gills and out of the operculum so gas exchange can happen in the gills
What is the operculum?
The part of a fish that covers the gills
What is the counter current flow in a fish?
- Blood thay already has some oxygen in it meets water, which has its maximum concentration of oxygen and diffusion of oxygen from the water to the blood takes place
- Blood with little oxygen in it meets water which has had most, but not all, of its oxygen removed so again, diffusion of oxygen from water to the blood can take place
Compare parallel and counter flow
Parallel - a diffusion gradient is maintained for only half the distance across the gill lamellae. Only 50% of the oxygen from the water diffuses into the blood
Counter current - a diffusion gradient is maintained all the way across the gill lamellae. Almost all of the oxygen from the water diffuses into the blood
What is a dicotyledonous?
Any member of the flowering plants thay has a pair of leaves, or cotyledons, in the embryo of the seed
How does the stomata open?
When water moves into the guard cell by osmosis, the cell becomes turgid, causing the thin outer walls to expand and pulls the thick inner walls, causing them to bend, opening the stomata
What is a xerophlyte?
A plant that has a restricted supply of water e.g. if it lives in a desert region
What are adaptations of plants to conserve as much water as possible?
- A thick cuticle
- Rolling up their leaves
- Having hairy leaves
- Having the stomata in pits or grooves
- Leaves having a small SA:V
- Storing water in stems / leaves
What is digestion?
The hydrolysis of large biological molecules into smaller molecules that can be absorbed across cell membranes
What is the alimentary canal?
The passage from the mouth to the anus
What is the cardiac sphincter?
The muscle between oesophagus and stomach that prevents backflow
What is the duodenum?
The first part of your small intestine that food passes through
What does amylase break down, what bonds are broken and what is the product?
- Starch
- Glycosidic bonds
- Glucose
Where is amylase produced?
Salivary glands
The pancreas
What does disaccharidase break down, what bonds are broken and what are the products?
- Maltose
- Glycosidic bonds
- Glucose
Where are disaccharidase produced?
In the ileum
What does lipase breakdown, what bonds are broken and what are the products?
- Triglycerides
- Ester bonds
- Fatty acids and monoglycerides
Where are lipase produced?
In the pancreas
What do peptidase break down, what bonds are broken and what are the products?
- Protein
- Peptide bonds
- Dipeptides and amino acids
Where are peptidase produced?
In the ileum
What do dipeptidase break down, what bonds are broken and what are the products?
- Dipeptides
- Peptide bonds
- Amino acids
Where are dipeptidase produced?
In the ileum
What is the process of cotransport with a sodium potassium pump?
- The sodium potassium pump moves sodium out of the cell and potassium into the cell
- There is therefore a high concentration of sodium ions outside the cell which will diffuse back in
- At the same time that the sodium diffuses back into the cell, it couples with glucose which is carried with the sodium
- This is an indirect form of active transport as glucose is being transported against its concentration gradient
What is the process of lipid absorption?
- Bile salts, produced by the liver, emulsify lipids into small droplets
- This increases the surface area and makes it easier for lipase to hydrolyse it, producing monoglycerides and fatty acids
- These monoglycerides and fatty acids stick with the bile salts to form micelles
- Micelles help the products of lipid digestion to be absorbed
What are chylomiorons?
Large lipoprotein particles that transport dietary fat and cholesterol to the liver and peripheral tissues
