Topic 3 - Exchange + Mass Transport Flashcards
1
Q
what is formula for diffusion?
A
diffusion ∝ (surface area x difference in concentration) / length of diffusion path
2
Q
how do gases enter and leave the tracheae of an insect?
A
through spiracles on the body surface
3
Q
how are spiracles opened and closed?
A
By a valve
4
Q
what happens when the spiracles are opened?
A
water vapour can evaporate from the insect
5
Q
what are the limitations of the tracheal system?
A
relies mostly on diffusion for diffusion to be effective, the diffusion pathway needs to be short, which is why insects are of a small size so the length of the diffusion pathway limits the size that insects can attain
6
Q
How does gas exchange in insects work?
A
Air enters via spiracles, travels through trachea and tracheoles, delivering
oxygen directly to every tissue.
7
Q
what is the outside of a fish like?
A
waterproof → gas-tight
8
Q
what is the structure of the gills?
A
- made up of gill filaments
- they’re stacked up in a pile
- gill lamellae are at right angles to the filaments
- increases surface area
9
Q
how is water passed through in fish?
A
- water is taken through the mouth and forced over the gills and out through an opening on each side of the body
- flow of water over the gill lamellae is opposite to the direction of the flow of blood
10
Q
what does the countercurrent flow mean for gas exchange?
A
- Blood that is already well loaded with oxygen meets water, which has its maximum concentration of oxygen. Therefore diffusion of oxygen from the water to the blood takes place.
- Blood with little oxygen in it meets water which has had most of its oxygen removed. diffusion or oxygen from the water to blood takes place.
- as a result a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae
11
Q
what are the adaptations for rapid diffusion in leaves?
A
- many stomata, no cell is far from a stoma and therefore the diffusion pathway is short
- numerous interconnecting air-spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
- large surface area of mesophyll cells for rapid diffusion.
12
Q
how have insects adapted to reduce water loss?
A
- Small surface area to volume ratio
- to minimise the area over which water is lost.
- Waterproof coverings over their body surfaces.
- in the case of insects this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle.
- Spiracles
- the openings of the tracheae at the body surface and these can be closed to reduce water loss
- tracheae
- carry air containing oxygen directly to the tissues
13
Q
How do plants reduce water loss?
A
waterproof covering over parts of the leaves and the ability to close stomata when necessary
14
Q
what are xerophytes?
A
plants that are adapted to living in areas where water is in short supply
15
Q
what are examples of adaptations in xerophytes?
A
a reduced surface area to volume ratio of the leaves
stomata in pits or grooves
hairy leaves
rolling up of leaves
a thick cuticle
16
Q
what do all aerobic organisms require in respiration?
A
a constant supply of oxygen to release energy in the form of ATP
17
Q
What is the order of movement in human gas exchange?
A
Lungs -> trachea -> bronchi -> bronchioles -> alveoli
18
Q
What 3 muscles change pressure?
A
- diaphram
- internal intercostal muscles
- external intercostal muscles
19
Q
What do internal intercostal muscle do?
A
Contract for expiration
20
Q
what do external intercostal muscles do?
A
contract for inspiration
21
Q
what is the process of breathing?
A
- The external intercostal muscles contract, while the internal
intercostal muscles relax. - The ribs are pulled upwards and outwards, increasing the volume of the thorax.
- The diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax.
- The increased volume of the thorax results in reduction of pressure in the lungs.
- Atmospheric pressure is now greater than pulmonary pressure, and so air is forced into the lungs
22
Q
what is the process of expiration?
A
- The internal intercostal muscle contract, while the external
intercostal muscles relax. - The ribs move downwards and inwards, decreasing the volume of the thorax.
- The diaphragm muscles relax and so it is pushed up again by the contents of the abdomen that were compressed during inspiration. The volume of the thorax is therefore further decreased.
- The decreased volume of the thorax increases the pressure in the lungs.
- The pulmonary pressure is now greater than that of the
atmosphere, and so air is forced out of the lungs
23
Q
what makes diffusion of gases between alveoli and the blood fast?
A
- red blood cells arc slowed as they pass through pulmonary capillaries, allowing more time for diffusion
- the distance between the alveolar air and red blood cells is reduced as the red blood cells are flattened against the capillary walls
- the walls of both alveoli and capillaries are very thin and therefore the distance over which diffusion takes place is very short
- alveoli and pulmonary capillaries have a very large total surface area
- breathing movements constantly ventilate the lungs. and the action of the heart constantly circulates blood around the alveoli. Together. these ensure that a steep concentration gradient of the gases to be exchanged is maintained
- blood flow through the pulmonary capillaries maintains a concentration gradient
24
Q
What do glands do?
A
produce enzymes that hydrolase large molecules into small ones ready for absorption
25
What are the parts of the digestive system? What do they do?
- oesophagus
- carries food from the mouth to the stomach.
- stomach
- a muscular sac with an inner layer that produces enzymes. Its role is to store and digest food, has glands that produce enzymes which digest protein.
- ileum
- long muscular tube. Food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into it. The inner walls of the ileum are folded into villi = large surface area. The surface area of these villi is further increased by microvilli, on the epithelial cells of each villus. This adapts the ileum for its purpose of absorbing the products of digestion into the bloodstream.
- large intestine
- absorbs water. Most of the water that is absorbed is water from the secretions of the many digestive glands.
- rectum
- faeces are stored here before periodically being removed via the anus
- salivary glands
- situated near the mouth. They pass their secretions via a duct into the mouth. These secretions contain the enzyme amylase, which hydrolyses starch into maltose.
- pancreas
- a large gland situated below the stomach. Il produces a secretion called pancreatic juice. This secretion contains proteases co hydrolyse proteins, lipase to hydrolyse lipids and amylase co hydrolyse starch.
26
What is chemical digestion?
Chemical digestion hydrolyses large, insoluble molecules into smaller, soluble ones. It is carried out by enzymes. All digestive enzymes function by hydrolysis.
27
Where is amylase produced?
| What is its function?
- mouth + pancreas
| - hydrolyses the alternate glycosidic bonds of the starch molecule to produce the disaccharide maltose
28
Where is Maltase produced?
| What is its function?
- lining of the ileum
| - hydrolyses maltose into alpha-glucose
29
what is the process of carbohydrate digestion?
- Saliva enters the mouth from the salivary glands and is thoroughly mixed with the food during chewing.
- Saliva contains salivary amylase. This starts hydrolysing any starch in the food to maltose. It also contains mineral salts that help to maintain the pH at around neutral. This is the optimum pH for salivary amylase to work.
- The food is swallowed and enters the stomach, where the conditions arc acidic. This acid denatures the amylase and prevents further hydrolysis of the starch.
- After a time the food is passed into the small intestine, where it mixes with the secretion from the pancreas called pancreatic juice.
- The pancreatic juice contains pancreatic amylase. This continues the hydrolysis of any remaining starch to maltose. Alkaline salts are produced by both the pancreas and the intestinal wall to maintain the pH at around neutral so that the amylase can function.
- Muscles in the intestine wall push the food along the ileum. Its epithelial lining produces the disaccharide maltase. Maltase is not released into the lumen of the ileum but is part of to the cell-surface membranes of the epithelial cells that line the ileum. The maltase hydrolyses the maltose from starch breakdown into alpha-glucose
30
what does sucrase do?
hydrolyses the single glycosidic bond in the sucrose molecule. This hydrolysis produces the two monosaccharides glucose and fructose.
31
What does lactase do?
hydrolyses the single glycosidic bond in the lactose molecule. This hydrolysis produces the two monosaccharides glucose and galactose
32
where are lipases produced?
in the pancreas that hydrolyse the ester bond found in triglycerides to form fatly acids and monoglycerides.
33
What is a monoglyceride?
glycerol molecule with a single fatly acid molecule attached
34
what is emulsification?
Lipids are split up into micellles by bile salts (produced in the liver), it increases the S.A of the lipids so that action of lipases is speed up
35
what do endopeptidase do?
hydrolyse the peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules.
36
what do exopeptidase do?
hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. In this way they progressively release dipeptides and single amino acids.
37
what do dipeptidases do?
hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane-bound, being part of the cell-surface membrane of the epithelial cells lining the ileum.
38
how are triglycerides absorbed?
- Once formed during digestion, monoglyccrides and fatty acids remain in association with the bile salts that initially emulsified the lipid droplets formed = micelles.
- Through the movement of material within the lumen of the ileum, the micelles come into contact with the epithelial cells lining the villi or the ileum. Here the micelles break down, releasing the monoglycerides and fatty acids. As these are non-polar molecules, they easily diffuse across the cell-surface membrane into the epithelial cells.
- Once inside the epithelial cells, monoglycerides and fatty acids are transported to the endoplasmic reticulum where they are recombined to form triglycerides. Starting in the endoplasmic reticulum and continuing in the Golgi apparatus, the triglycerides associate with cholesterol and lipoproteins to form structures called chylomicrons.
- Chylomicrons move out of the epithelial cells by exocytosis. They enter lymphatic capillaries called lacteals that are found at the centre of each villus.
- the chylomicrons pass, via lymphatic vessels, into the blood system. The triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of blood capillaries from where they diffuse into cells.
