chapter 6 -exchange Flashcards
(45 cards)
1
Q
Which animals have high/ low SA:V
A
- unicellular = high. SA:V
- multicellular = low SA:V
2
Q
Why do multicellular organism have specialise exchange surfaces ?
A
- the cells are not in direct contact with their external environment
- so the diffusion distance between the cells and the environment is large
- and larger molecules have higher metabolic rates and so need more oxygen and glucose
3
Q
What are features of specialises exchange surfaces ?
A
- a large surface area so there is a larger sour face area for cell to cross
- thin wall to minimise diffusion distance
- extensive blood supply/ ventilation =to maintain steep concentration gradient
- selectively permeable plasma membranes = controls what substances are being exchanged
4
Q
What are the features on the insect gas exchange system ?
A
- spiracles
- tracheae
- tracheoles with tracheal fluid
5
Q
How does the gas exchange system in insects work ?
A
- air enters the open spiracles
- air then moves through the tracheae
- then diffuses into the tracheoles which are directly next to cells
- oxygen dissuades into the tracheal fluid and will diffuse down its concentration gradient into the body cells
- carbon dioxide diffuses down ins concentration gradient out of the cells and into the atmosphere
6
Q
What are the adaptations of the structure in the insect gas exchange system ?
A
- spiracle can open and close to control gas exchange and minimise water loss
- tracheae are reinforced with spirals of chitin to prevent it from collapsing and have multiple tracheae to increase surface area
- tracheoles : penetrate direct input tissues and have thin walls to reduce diffusion distance
- are highly branches to increase surface area
- no reinforced chitin so gas exchange can occur
- tracheoles fluid allows oxygen dissolve into it it to help diffusion and reduce water loss
7
Q
What is abdominal pumping ?
A
- when the insect contract and relax their abdomen to change the pressure and volume and allow air to be moved in or out
8
Q
What are other ventilation mechanisms that insects have ?
A
- tracheal fluid moves into tissue during exercise to increase the diffusion rate and surface area
- accessory sacs/air reservoirs/ enlarged collapsible tracheae can deflate or inflate to increase the volume of air moved into the system
- wing muscles are connected to sacs wind pump air to ventilate the tracheal system
- thoracic muscles vibrate to also pump air to ventilate the tracheal system
9
Q
What is lactate ?
A
- a substance that accumulates in tissues during activity
- like lactic acid ?
10
Q
How can lactate affect the rate of gas exchange ?
A
- when it builds up in the tracheal fluid it reduces the water potential there
- so water leaves the tracheoles via osmosis
- and so higher surface area is exposed for gas exchange
11
Q
Why do fish need a specialised exchange system ?
A
- water is more dense and viscous than air so there is slower diffusion of oxygen
- water has less oxygen than air
- fish are very active so have high oxygen demands
12
Q
What are the structure of the gills in fish ?
A
- they are covered by an operculum flap
- they have filaments which stem from a gill bar
- on the filaments there are lamellae
- lamellae are surrounded by a lot of blood vessels
13
Q
How are the gills adapted for efficient gas exchange ?
A
- the lamellae provide a large surface area
- the membrane of the lamellae are thin to minimise diffusion distance
- there is a rich blood supply to maintain a steep concentration gradient
- the countercurrent flow creates a very steep concentration gradient
- overlapping filaments increase resistance which slows the flowing of water over the gills which gives more time for gas exchange
14
Q
Explain how counter current exchange works ?
A
- blood and water flow over the lamellae in opposite directions
- so oxygen rich blood meat water that is at its maximum oxygen capacity
- and oxygen poor blood coming in wants oxygen reduced water
- but the concentration of oxygen in the water os always greater than that in the blood
- so a steep concentration gradient is maintained across the entire gill
15
Q
Explain why a parallel flow system in fish is not efficient ?
A
- oxygen poor blood will meet oxygen rich water
- at first oxygen will diffuse into the blood
- but eventually the concentrations in both the water in the blood will reach an equilibrium so no more oxygen will be absorbed
16
Q
What is the structure of a leaf ?
A
- a waxy cuticle on top the upper epidermis which reduces water loss
- palisade mesophyll cells have a lot of chloroplasts for photosynthesis and they are all over the leaf to provide a large surface area for gases exchange
- the spongey mesophyll has spaces which provide an network for gases to quickly move in and out and access cells
- lower epidermis which have stomata and guard cells
- stomata are pore which gases diffuse through, open when conditions are suitable for photosynthesis
- guard cells control the opening and closing of the stomata
- there are also xylem and phloem which transport water and sugar respectively
17
Q
How are plants adapted to limit water loss ?
A
- a waterproof waxy cuticle on the leaves prevents water from leaving
- guard cells close and open stomata when needed
18
Q
What are xerophytic plants ?
A
- plants that are adapted to living in very dry conditions and limit their water loss
19
Q
What adaptations do xerophytes have ?
A
- thick waxy cuticle reduces water loss through evaporation
- rolling up leaves, hairy leaves stomata in pits/ grooves - these all trap moisture air and reduce air flow so water there is a reduced water potential gradient between leaves and air so less transpiration
- small needle like leave reduce the surface area so less transpiration can occur
- having water storage organs to store water when the supply is low
20
Q
What are the features of the human gas exchange system ?
A
- nasal cavity
- lungs
- trachea
- bronchi
- bronchioles
- alveoli
21
Q
How does air pass through the human gas exchange system ?
A
- air enters the nasal cavity
- air enters the trachea
- it then travels into the two bronchi , one bronchus goes to each lung
- air travels into the bronchioles
- it then travels into the air sacs at the end of bronchioles called alveoli
22
Q
What is the ciliated epithelium ?
A
- tissue that lines the airways
- it has goblet cells which trap dust and microbes
- and ciliated epithelial cells which waft the mucus up to the mouth so it can be swallowed
23
Q
How is the nasal cavity adapted for gas exchange ?
A
- has a very large surface area with rich blood supply which warms air
- hairy lining which secretes mucus to trap dust and bacteria
- most surface to increase the humidity of incoming air to prevent water loss
24
Q
How is the trachea adapted for gas exchange ?
A
- supported by rings if cartilage which keep it open
- this rings are incomplete to allow the trachea to be when food is swallowed
- lined with epithelial cells and goblet cells
- has smooth muscle which can contract or relax to constrict or dilate airway to change air flow
- elastic tissue with elastic fibres which allows stretching and recoiling
25
How are the bronchi adapted for gas exchange ?
- the same adaptation of the trachea but smaller
26
How are the bronchioles adapted for gas exchange ?
- have no cartilage
- have smooth muscle so ca contract relax to constrict/dilate airway way
- elastic tissue with elastic fibres which allows stretching for stretching and recoiling
- have a thin layer of flattened epithelium
27
How does air move from the alveoli to the blood ?
- oxygen diffuses from alveoli to pulmonary capillaries and bind to haemoglobin in ted blood cells
- carbon dioxide leaves haemoglobin and diffuses from blood into alveoli
28
How are the alveoli adapted for gas exchange ?
- one cell thick walls which gives a short diffusion distance
- large surface area which increases gas exchange
- large network of blood capillaries give a rich blood supply which warms creates a steep concentration gradient
- have colleges fibres which prevent alveoli from bursting
- moist inner surface increase diffusion rate
- partially permeable
- air ventilation also helps maintain a steep concentration gradient
29
What are the pulmonary vessels ?
- pulmonary artery which delivers deoxygenated blood from heart to pulmonary capillaries
- pulmonary vein which delivers oxygenated blood from capillaries to heart
- pulmonary capillaries which is where gas exchange happen between the blood and alveoli
30
How are he pulmonary capillaries adapted for gas exchange ?
- thin walls to maintain a short diffusion distance
- having the red blood cells pushed against the capillary walls also reduces diffusion distance
- large surface area increases rate of diffusion
- movement of blood maintains a steep concentration gradient however this movement is slow to allow for mor time for diffusion
31
What is the thoracic cavity
- the cavity where the lungs are located
32
What are the muscles involved in ventilation in mammals ?
- the diaphragm which is a sheet of muscle that moves the ribcage up and out when it relaxes
- external intercostal muscles which are found between the ribs and pull the ribcage up and out when the contract
- internal intercostal muscles which are also found between the ribs and pull the ribcage down and in when the contract
33
Describe the process of inhalation ?
- when the phrenic nerve is stimulated, the diaphragm contracts and moves downwards
- the external intercostal muscles contract whilst the internal intercostal muscles relax which moves the ribcage up and out
- this increases the volume of the thoracic cavity which means the pressure decreases
- now the pressure inside the thoracic cavity is lower than the atmospheric pressure so there is a concentration gradient an air now moves into the body
- air then inflates the lungs as it followers the route for gas exchange happen between
34
Describe the process of exhalation ?
- the diaphragm relaxes and moves in the upward direction
- the internal intercostal muscles contract and the external intercostal muscles relax which moves the ribcage down and in
- this decrease the volume of the thoracic cavity which increase the pressure
- pressure in now higher than atmospheric pressure which creates pressure gradient between atmosphere and alveoli
- so air moves out
35
What do the alveoli do during ventilation ?
- when the thoracic cavity volume increases the elastic fibres in the alveoli shrink and recoil back to there original shape
- this increased the pulmonary pressure and further helps push air out of the lungs
36
What is digestion ?
- when large insoluble biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes
37
What two enzymes are needed to hydrolyse carbohydrate into monosaccharides ?
- amylase
- membrane bound disaccharidases
38
How are carbohydrates hydrolysed into monosaccharides ?
- amylase produced in the salivary glands hydrolyses starch into maltose by hydrolysing glycosidic bonds
- then the maltose moves into the small intestine where amylase from pancreas is secreted into the duodenum to hydrolyse any more starch
- and in the ileum membrane bound disaccharidases like maltose will break down maltose into alpha glucose ( = a monosaccharide )
39
Which enzymes are involved in hydrolysing proteins ?
- endopeptidases = hydrolyse peptide bonds between amino acids in the middles of the polypeptide
- exopeptidases = hydrolyse peptide bonds between amino acids at then end of the polypeptide chain
- membrane - bond dipeptidases = hydrolyse peptide bonds between two amino acids ( dipeptide )
40
How are proteins digested
- starts in the stomach
- continues in the duodenum
- and finishes in the ileum
- protein enzymes are produced in the stomach, pancreas and small intestine
41
What is used to hydrolyse lipids ?
- lipase = produced in small intestine
- bile salts = produced in liver, stored in the gall bladder and then through bile duct are secreted into the duodenum
42
How are lipids digested ?
- lipids are coated in bile salts and emulsified into small droplets called micelles
- these smaller droplets gives a larger surface area for lipase to work on which means faster hydrolysis
- then lipase hydrolyses the micelles into fatty acids and glycerol and maybe some monoglycerides
43
How is the small intestine designed for absorption ?
- products f digestion are absorbed into cells lining the ileum
- the ileum wall is covered in villi which have thin walls to decrease diffusion distance
- epithelial cells on the villi have micro villi which increase the surface area for diffusion
- and the villi have a large capillary network to make sure the concentration gradient is always maintained
44
How are amino acids and monosaccharide absorbed ?
- by co-transport
45
How are lipids absorbed ?
- first, micelles are water soluble vesicles formed of fatty acids, glycerol, monoglycerides and bile salts
- as the fatty acids are non-polar they can diffuse straight through the epithelial cells of the ileum
- once they enter, the SER combines the fatty acids back to from triglycerides
- and the Golgi apparatus combines triglyceride and proteins to from chylomicrons
- chylomicrons move out of the cell by exocytosis and enter the lacteal ( a type of lymph vessel )
- eventually the lipids are drained into the capillaries
