1
Q
What is meant by the term ‘passive exchange’?
A
No metabolic energy required for exchange, by diffusion or osmosis.
2
Q
What is meant by the term ‘active exchange’?
A
Metabolic energy required for exchange, by active transport.
3
Q
Name features of specialised exchange surfaces for effective transfer of materials
A
- A large surface area to volume ratio of the organism increases the rate of exchange.
- Very thin so that the diffusion distance is short and therefore materials cross the exchange surface rapidly.
- Selectively permeable membrane to allow selected materials across.
- Movement of the environmental medium
- A transport system to ensure movement of the internal medium, eg blood, in order to maintain a concentration gradient.
4
Q
Define ‘tissue fluid’
A
Fluid that surrounds the cells of the body. Its composition is similar to that of blood plasma, except it lacks proteins. It supplies nutrients to the cells and removes waste products.
5
Q
Name 4 general things that need to be exchanged between organisms and their environment.
A
- respiratory gases
- nutrients
- excretory products
- heat
6
Q
Name the process by which carbon dioxide is removed from a single celled organism
A
Diffusion over the body surface
7
Q
Explain why there is a conflict between gas exchange and conserving water in terrestrial insects.
A
Gas exchange requires a thin permeable surface with a large area.
Conserving water requires thick, waterproof surfaces with a small area.
8
Q
Explain how the tracheal system effects the size of insects
A
because it relies on diffusion to bring oxygen to the respiring tissues.
9
Q
Name the system of gas exchange in insects.
A
Tracheal system
10
Q
Describe the features of the tracheal system.
A
Insects have evolved an internal network of tubes called tracheae. The tracheae are supported by strengthened rings to prevent them collapsing. The trachea divide into smaller, dead-end tubes called tracheoles. The tracheoles extend throughout the body tissues of the insect. Atmospheric air, containing oxygen, is brought directly to the respiring tissues, as there’s a short diffusion pathway from tracheole to any body cell.
11
Q
How do respiratory gases move in and out the tracheal system?
A
- Along a diffusion gradient
- Mass transport
- The ends of the tracheoles are filled with water.
12
Q
In relation to fish gills, describe what is meant by countercurrent flow
A
The movement of water and blood in opposite directions across the gill lamellae.
13
Q
Outline why countercurrent flow is an efficient means of exchanging gases along gills of fish
A
Because a steady diffusion gradient is maintained over the whole length of the gill lamellae. Therefore more oxygen diffuses from the water into the blood.
14
Q
Mackerel are active, fast-swimming fish, while plaice move slowly along the seabed. Suggest the differences in the gills of these two types of fish.
A
Mackerel have more gill lamellae, filaments, larger surface area compared to plaice.
15
Q
Water flow over fish gills is one-way, whereas the flow of air in and out of the lungs is two-way. Suggest why one-way flow is an advantage to fish.
A
Less energy is required because the flow
doesn’t have to be reversed (water is dense and difficult to move).
16
Q
Describe the structure of the gills.
A
The gills are located within the body, behind the fish’s head. They’re made up of gill filaments, which stack up in a pile. At right angles to the filaments are gill lamellae, which increase the surface area of the gills. Water is taken in through the mouth and forced over the gills and out through an opening on each side of the body.
17
Q
Name the process of gas exchange in plants
A
Gases move in and out of plants by diffusion.
18
Q
Name three adaptations of the leaves for rapid diffusion of gases
A
- many small pores, stomata, no cell is far from a stoma so diffusion distance is short
- numerous interconnecting air spaces occurring throughout the mesophyll so gases can readily come into contact with mesophyll cells.
- large surface area of mesophyll cells for rapid diffusion.
19
Q
Explain the advantage to a plant being able to open and close the stomata via guard cells.
A
Helps control water loss by evaporation
20
Q
State two similarities between gas exchange in a plant leaf and gas exchange in a terrestrial insect.
A
- No living cell is far from the external air
- Diffusion occurs in the gas phase
- Need to avoid excessive water loss
- Diffuse air through pores in their outer covering
21
Q
State two differences between gas exchange in a plant leaf and gas exchange in a terrestrial insect.
A
- Insects may create mass air flow; plants never do
- Insects have a smaller surface area to volume ratio than plants.
- Insects have special structures (trachea) which gases diffuse along; plants don’t
- Insects do not interchange gases between respiration and photosynthesis; plants do
22
Q
Name adaptations developed by insects to limit water loss
A
- Small surface area to volume ratio (minimises area of water loss)
- Waterproof coverings over body surfaces
- Spiracles at tracheae and body surface openings, closed to limit water loss.
23
Q
What are xerophytes?
A
Plants with a restricted supply of water, that have evolved a range of adaptations to limit water loss through transpiration
24
Q
Name adaptations developed by xerophytes to limit water loss
A
- Thick cuticle (waxy cuticle forms a waterproof barrier, but the thicker the less water lost)
- Rolling up leaves (protects stomata on lower epidermis by trapping a region of still air within the rolled leaf. This region becomes saturated with water vapor so has a very high water potential- no water potential gradient- no water loss).
- Hairy leaves (traps still, moist air next to leaf surface, reducing water potential gradient and heat loss)
- Stomata in pits/grooves (traps still, moist air next to leaf surface, reducing water potential gradient and heat loss)
- Reduced surface area to volume ratio (smaller sa:vol, slower rate of diffusion, reducing water loss, balanced with need for sufficient area for photosynthesis.
25
What is the main problem both insects and plants share when it comes to living on land?
Conflict of conserving water and gas exchange.
Efficient gas exchange requires a thin, permeable surface with a large area. On land these features can lead to a considerable amount of water loss by evaporation.
26
State one modification to prevent water loss shared by plants and insects
Waterproof covering to the body.
27
Insects limit water loss by having a small surface area too volume ratio- why is this not a feasible way of limiting water loss in plants?
Plants photosynthesise and therefore need a large surface area to capture light.
28
Why would rolling leaves with the upper epidermis on the inside not be effective in reducing water loss?
Almost all stomata are on the lower epidermis. This would be exposed to air currents that would reduce the water potential immediately outside the leaf. The water potential gradient would be increased and a lot of water vapor would be lost.
29
State two reasons why humans need to absorb large volumes of oxygen from the lungs.
- Humans are relatively large organisms with a large volume of living cells.
- They maintain a high body temperature which is related to them having high metabolic and respiratory rates.
30
Explain how the cells lining the trachea and the bronchus protect the alveoli from damage.
The cells produce mucus that traps particles of dirt and bacteria breathed in. The cilia on these cells move this debris up the trachea and into the stomach. The dirt/bacteria could cause infection in the alveoli.
31
Why are the lungs located inside the body.
- Air isn't dense enough to support and protect these delicate structures
- The body as whole would otherwise lose a great deal of water and dry out.
32
Describe the structure of the lungs
The lungs are a pair of lobed structures made up of a series of highly branched tubules, called bronchioles, which end in tiny air sacs called alveoli.
33
Describe the structure and function of the trachea
The trachea is a flexible airway that is supported by rings of cartilage. The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing in. The tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells.
34
Describe the structure and function of the bronchi
The bronchi are two divisions of the trachea, each leading to one lung. Similar structure to trachea, and like trachea, produce mucus to trap dirt particles and have cilia to move dirt-laden mucus towards the throat. The larger bronchi are supported by cartilage, the amount if cartilage reduced as the bronchi gets smaller.
35
Describe the structure and function of the bronchioles
The bronchioles are a series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cells. The muscle allows them to constrict so they can control the airflow in and out of the alveoli.
36
Describe the structure and function of the alveoli
The alveoli are minute air sacs, with a diameter of between 100μm-300μm, at the end of the bronchioles. Between the alveoli there are collagen and elastic fibres. The alveoli are lined with epithelium. The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They then spring back during breathing out in order to expel the carbon dioxide-rich air. The alveolar membrane is the gas exchange surface.
37
Which muscles are involved in the pressure changes in the lungs?
- the diaphragm: a sheet of muscle separating the thorax from the abdomen.
- the internal intercostal muscles: contract to expire
- the external intercostal muscles: contract to inspire.
38
Is inspiration (breathing in) an active or passive process?
An active process, it requires energy.
39
Is expiration (breathing out) an active or passive process?
A largely passive process, doesn't require much energy.
40
Describe the process of inspiration
- The external intercostal muscles contract, whilst 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, also increasing the volume of the thorax.
- The increased volume of the thorax results in reduced pressure in the lungs.
- Atmospheric pressure is now greater than pulmonary pressure, so air is forced into the lungs.
41
Describe the process of expiration
- The internal intercostal muscles contract, whilst the external intercostal muscles relax
- The ribs are pulled downwards and inwards, decreasing the volume of the thorax.
- The diaphragm muscles relax, so it's pushed up again by the contents of the abdomen that were compressed during inspiration, decreasing the volume of the thorax.
- The decreased volume of the thorax results in increased pressure in the lungs.
- Pulmonary pressure is now greater than atmospheric pressure, so air is forced out of the lungs.
42
How is efficiency of gas exchange increased due to the wall of each alveolus not being more than 0.3μm thick?
The rate of diffusion is more rapid the shorter the distance across which the gases diffuse.
43
How is efficiency of gas exchange increased because there are 300 million alveoli in each lung.
There is a very large surface area in around 600 million alveoli, making diffusion rapid.
44
How is efficiency of gas exchange increased by each alveolus being covered by a dense network of pulmonary blood capillaries?
Diffusion is more rapid the greater the concentration gradient. Pumping of blood through capillaries removes oxygen as it diffuses from the alveoli into the blood. The supply of new carbon dioxide as it diffuses out of the blood into the alveoli helps to maintain a concentration gradient that would otherwise disappear as the concentrations are equalised.
45
How is efficiency of gas exchange increased due to pulmonary capillaries being very narrow.
Red blood cells are flattened against the walls of the capillaries to enable them to pass through. This slows them down, increasing the time for gas exchange and reducing the diffusion pathway, thereby increasing the rate of diffusion.
46
Why is diffusion of gases between the alveoli and the blood rapid?
- Red blood cells are 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 surface area.
- Breathing constantly ventilates the lungs, and the action of the heart constantly circulates blood around the alveoli, maintaining a steep concentration gradient of gases.
47
What are some risk factors of lung disease (chronic obstructive pulmonary disease)?
- Smoking: 90% of sufferers of COPD are heavy smokers
- Air pollution: Pollutant particles and gases eg sulfur dioxide
- Genetic make-up
- Infections: People who frequently get other chest infections
- Occupation: People working with harmful chemicals, gases and dusts that can be inhaled increased risk
48
What is the role of the oesophagus in digestion?
Carries food from the mouth to the stomach
49
What is the role of the stomach in digestion?
Stores and digests food-especially proteins. It has glands that produce enzymes to digest protein.
50
What is the role of the ileum in digestion?
Produces enzymes by its walls and glands that pour their secretions into it. The inner walls of the ileum are folded into villi and microvilli, giving a large surface area. This adapts the ileum for its purpose if absorbing the products of digestion into the bloodstream.
51
What is the role of the large intestine in digestion?
Absorbs water- most of the water that's absorbed is water from secretions of the many digestive glands.
52
What is the role of the rectum in digestion?
Stores faeces, before they're egested via the anus.
53
What is the role of the salivary glands in digestion?
They pass their secretions via a duct into the mouth. Contain the enzyme amylase, which hydrolyses starch to maltose.
54
What is the role of the pancreas in digestion?
It produces a secretion called pancreatic juice, which contains proteases to hydrolyse proteins, lipase too hydrolyse lipids, and amylase to hydrolyse starch.
55
Define physical breakdown of food / molecules
Breaks down large molecules of food by means of structures, such as teeth. Food can be ingested and provides a large surface area. Food is also churned by muscles in stomach.
56
Define chemical breakdown of food / molecules
Chemical digestion hydrolyses large, insoluble molecules into smaller, soluble ones. Carried out by specific enzymes. More than one enzyme is usually needed to hydrolyse a large molecule.
57
Name the 3 main digestive enzymes and their functions
- Carbohydrases- hydrolyse carbohydrates to monosaccharides
- Lipases- hydrolyse lipids into glycerol and fatty acids
- Proteases- hydrolyse proteins into amino acids
58
Describe the process of human digestion of carbohydrates (Starch / maltose)
- Saliva enters mouth from salivary glands and mixes with food during chewing. Saliva contains salivary amylase, which hydrolyses any starch in the food to maltose. Contains mineral salts to keep pH neutral (optimum for salivary amylase).
- Food swallowed and enters acidic stomach- denaturing amylase, preventing further hydrolysis of starch.
- Food passed into small intestine, mixes with pancreatic juice (from pancreas).
- Pancreatic juice contains pancreatic amylase- which hydrolyses remaining starch to maltose. Alkaline salts produced by both pancreas and intestinal wall to maintain neutral pH for amylase.
- Muscles in the intestine wall push the food along the ileum. Its epithelial lining produces a second enzyme, maltase (membrane-bound disaccharidase). The maltase hydrolyses the maltose into alpha-glucose.
59
How are sucrose molecules digested?
Sucrase hydrolyses the single glycosidic bond in the sucrose molecule. Produces the two monosaccharides glucose and fructose.
60
How are lactose molecules digested?
Lactase hydrolyses the single glycosidic bond in the lactose molecule. Produces the two monosaccharides glucose and galactose.
61
How are lipids digested?
Lipids are hydrolysed by lipase enzymes. Lipases are produced in the pancreas and hydrolyse the ester bond in triglycerides. Lipids are firstly split into droplets called micelles by bile salts, produced by liver. Process called emulsification- increases surface area of the lipids so that action of the lipases is sped up.
62
Name and give the functions of the three different enzymes used to hydrolyse proteins
- Endopeptidases- hydrolyses the peptide bonds between amino acids in the central region of a protein molecule, forming a series of peptide molecules.
- Exopeptidases- hydrolyses 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.
- Dipeptidases- hydrolyses the bond between the two amino acids of a dipeptide. Dipeptidases are membrane-bound, being part of the cell-surface membrane of epithelial cells lining the ileum.
63
Define hydrolysis
The breakdown of molecules by the addition of water to the bonds that hold these molecules together.
64
List two structures that produce amylase
Salivary glands
| Pancreas
65
Suggest why the stomach does not have villi or microvilli
Villi and microvilli increase surface area to speed up absorption of soluble materials. As food in the stomach has not yet been hydrolysed into soluble materials they cannot be absorbed and so villi and microvilli are unnecessary.
66
List three enzymes produced by the epithelium of the ileum
Maltase, sucrase, lactase
67
The wall of the ileum posses villi. How do villi increase the efficiency of diffusion?
- Increase surface area for diffusion
- Very thin walled, reducing distance.
- Contain muscle for movement- mixes contents of ileum, so material rich in digestive products replaces products absorbed: maintains diffusion gradient.
- Well supplied with blood vessels, blood carries away absorbed molecules: maintains diffusion gradient.
- Epithelial cells possess microvilli, providing even more surface area.
68
Name two processes that absorb amino acids and monosaccharids
- Diffusion
| - Co-transport
69
Describe the absorption of triglycerides
Monoglycerides and fatty acids remain associated with bile salts, which emulsified lipids to micelles. The micelles come into contact with the epithelial cells lining the villi of the ileum. The micelles break down, releasing monoglycerides and fatty acids, which easily diffuse along the cell surface membrane into epithelial cells. Inside epithelial cells, the monoglycerides and fatty acids are transported to the endoplasmic reticulum, and recombined to form triglycerides. They then continue to the Golgi and associate with cholesterol an lipoproteins to form chylomicrons. Chylomicrons move out of epithelial cells by exocytosis. They enter lacteals found at the centre of each villus. There, the chylomicrons pass into the blood stream. Triglycerides in chylomicrons are hydrolysed and diffuse into cells.
70
List three organelles you would expect to be numerous in an epithelial cell of the ileum and why?
Endoplasmic reticulum to resynthesise triglycerides from monoglycerides and fatty acids.
Golgi apparatus to form chylomicrons from triglycerides, cholesterol and lipoproteins.
Mitochondria to provide ATP required for co-transport of glucose and amino acid molecules.
71
Name the other chemical that moves across epithelial cells with glucose molecules during co-transport.
Sodium ions
72
In addition to microvilli, state one other feature of the epithelial cells of the ileum that would increase the rate of absorption of amino acids.
An increase in the number of protein channels and carrier proteins.
Biology
flashcards
Decks in class (21)
# Cards
-
1. Biological Molecules80
-
2. Nucleic Acids41
-
3. Cell Structure54
-
4. Transport Across Cell Membranes38
-
5. Cell Recognition and the Immune System49
-
6. Exchange72
-
7. Mass Transport87
-
8. DNA, Genes and Protein Synthesis31
-
9. Genetic Diversity and Adaptation.25
-
10. Biodiversity43
-
11. Photosynthesis25
-
12. Respiration30
-
13. Energy and Ecosystems47
-
14. Response to Stimuli66
-
15. Nervous coordination and muscles85
-
16. Homeostasis63
-
17. Inherited Change61
-
18. Populations and Evolution40
-
19. Populations in ecosystems73
-
20. Gene expression76
-
21. Recombinant DNA Technology64
