Topic 3B- More Exchange and Transport Systems Flashcards
1
Q
Why are large molecules of food broken down into smaller molecules during digestion?
A
Because the large biological molecules are too big to cross cell membranes, meaning they cant be absorbed from the gut into the blood
2
Q
What is amylase?
A
Amylase is a digestive enzyme that catalyses the conversion of starch into the smaller sugar maltose (a disaccharide).
3
Q
How does amylase convert starch into maltose?
A
Hydrolysis of the glycosidic bonds in starch
4
Q
Where is amylase produced?
A
Salivary glands, pancreas (releases amylase into small intestine)
5
Q
What are carbohydrates broken down by?
A
amylase and membrane-bound disaccharidases
6
Q
What are membrane-bound disaccharidases?
A
enzymes that are attached to the cell membranes of epithelial cells lining the ileum. They help to break down disaccharides into monosaccharides. (involves hydrolysis of glycosidic bonds)
7
Q
How are lipids broken down?
A
Lipase (with the help of bile salts)
8
Q
What are lipids broken down into?
A
monoglycerides and fatty acids
9
Q
What bonds are broken in lipids as they are broken down?
A
ester bonds
10
Q
Where are lipids made, and where do they work?
A
made- pancreas
work- small intestine
11
Q
Where are bile salts produced?
A
the liver
12
Q
What is the purpose of bile salts?
A
They emulsify lipids (cause lipids to form small droplets). This means there is a larger SA:V ratio, for a faster rate of reaction
13
Q
What happens once the lipid has been broken down?
A
The monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles.
14
Q
What are proteins broken down by?
A
Endopeptidases and exopeptidases
15
Q
Where do endopeptidases hydrolyse the protein’s peptide bonds?
A
within the protein
16
Q
Give two examples of endopeptidases, and describe where they occur
A
trypsin and chymotrypsin
synthesised in the pancreas and secreted in the small intestine
17
Q
What is pepsin an example of and describe it.
A
endopeptidase
Its released into the stomach by cells in the stomach lining. Pepsin only works in acidic conditions- these are provided by hydrochloric acid in the stomach.
18
Q
Where do exopeptidases hydrolyse the protein’s peptide bonds?
A
Exopeptidases act to hydrolyse peptide bonds at the ends of protein molecules. They remove single amino acids from proteins
19
Q
What are dipeptidases?
A
Exopeptidases that work specifically on dipeptides. They act to separate the two amino acids that make up a dipeptide by hydrolysing the peptide bond between them.
20
Q
Where are dipeptidases located?
A
In the cell-surface membrane of epithelial cells in the small intestine
21
Q
Where are the products of digestion absorbed into the blood?
A
Across the ileum epithelium in the bloodstream
22
Q
How are monosaccharides absorbed into the blood?
A
Glucose and galactose- absorbed by active transport with sodium ions via a co-transporter protein
Fructose- absorbed via facilitated diffusion through a different transporter protein
23
Q
Why can whole micelles not be taken up across the epithelial cell membrane?
A
because they constantly break up and ‘reform’ they can ‘release’ monoglycerides and fatty acids, allowing them to be absorbed.
24
Q
How do monoglycerides and fatty acids travel across the epithelial cell membrane?
A
They are lipid soluble so can diffuse straight across
25
How are amino acids absorbed?
co-transport (sodium ions, active transport)
26
Explain how amino acids are absorbed during co-transport
sodium ions actively transported out of ileum epithelium into blood
creates a sodium ion concentration gradient
sodium ions can then diffuse from lumen of the ileum into the epithelium cells through sodium-dependent transporter proteins, carrying amino acids with them
27
What is haemoglobin?
a large protein with a quaternary structure
each polypeptide chain has a haem group, which contains an iron ion, gives it red colour
28
Why is haemoglobin useful for carrying oxygen?
It has a high affinity for oxygen- each molecule can carry four oxygen molecules
29
What reaction occurs in the lungs and body between oxygen and haemoglobin?
oxygen joins to haemoglobin to form oxyhaemoglobin, reversible reaction
30
How can you measure oxygen concentration?
the partial pressure of oxygen
31
What does a greater partial pressure mean?
the greater the concentration of dissolved oxygen in cells, the higher the partial pressure
32
What is does the partial pressure of CO2 measure?
the concentration of CO2 in a cell
33
Describe the movement of oxygen using haemoglobin
oxygen loads onto haemoglobin to form oxyhaemoglobin where there's a high pO2
oxyhaemoglobin unloads its oxygen where there's a lower pO2
34
What level of pO2 do alveoli have?
high
35
What does a dissociation curve show?
how saturated the haemoglobin is with oxygen at any given partial pressure
36
On a dissociation curve, what does 100% saturation show?
that each haemoglobin molecule is carrying the maximum of 4 molecules of oxygen
37
What does 0% saturation mean on a dissociation curve?
none of the haemoglobin molecules are carrying any oxygen
38
What happens when pO2 is high?
haemoglobin has a high affinity to oxygen, so it has a high saturation of oxygen
39
What happens when pO2 is low?
haemoglobin has a low affinity for oxygen, which means it releases oxygen rather than combines with it
40
Why is the dissociation curve S-shaped?
The graph is S-shaped because when haemoglobin (Hb) combines with the first O2 molecule, its shape alters in a way that makes it easier for other molecules to join too. But as the Hb starts to become saturated, it gets harder for more oxygen molecules to join, so curve has a steep bit in the middle where it is really easy for molecules to join, and shallow bits at each end where it's harder. When the curve is steep, a small change in pO2 causes a big change in the amount of oxygen carried by the Hb
41
What is haemoglobins affinity affected by?
higher partial pressures of CO2 means haemoglobin gives up its oxygen more readily
42
Why is the Bohr effect useful during physical activity?
more oxygen can get to cells in lower pO2
43
Describe the Bohr effect
1. When cells respire they produce carbon dioxide which raises the pCO2
2. this increases the rate of oxygen unloading so the dissociation curve 'shifts' to the right
the saturation of blood with oxygen is lower for a given pO2, meaning that more oxygen is being released
The Bohr Effect
44
How can organism adapt to survive in environments with lower concentrations of oxygen?
they have haemoglobin with a higher affinity to oxygen
45
How does an organisms haemoglobin with a higher affinity look as a dissociation curve compared to humans?
The dissociation curve is to the left of ours
46
What is the circulatory system made up of?
the heart and blood vessels
47
Name the vessels entering and leaving the kidneys
renal artery
renal vein
48
Describe the role of arteries
carry blood from the heart to the rest of the body
49
Describe the structure of arteries
thick, muscular
elastic tissue to stretch and recoil as the heart beats, which helps maintain the high pressure
the inner layer (endothelium) is folded, allowing the artery to stretch, helps to maintain high pressure
50
What are arterioles?
smaller vessels of arteries
51
Describe the function of a vein
they take deoxygenated blood back to the heart under low pressure
52
Describe the structure of a vein
they have a wider lumen than the equivalent arteries, with very little elastic or muscle tissue
they contain valves to stop backflow of blood
53
What is the only veins which carry oxygenated blood?
pulmonary vein- taking oxygenated blood to the heart from the lungs
54
Describe the structure of capillaries
endothelium one cell thick
55
Where are capillaries found?
very near cells in exchange tissue
56
What is tissue fluid?
the fluid that surrounds cells in tissues
57
Name three things you would find in tissue fluid
oxygen
water
nutrients
hormones
58
Why aren't proteins and red blood cells in tissue fluid?
they're too large to be pushed out through capillary walls.
59
What is plasma?
a straw coloured liquid largely composed of water
60
What happens in a capillary bed?
substances move out of the capillaries, into the tissue fluid, by pressure filtration
61
Why don't proteins move into the tissue fluid?
the molecules are too large to fit through the gaps in capillary walls so they remain in the blood
62
What is the difference in hydrostatic pressure between the capillaries and the tissue fluid?
the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid, so pressure forces fluid out of the capillaries into the spaces around the cells
63
What happens to the hydrostatic pressure in the capillaries as fluid leaves?
the hydrostatic pressure reduces in the capillaries, so the hydrostatic pressure is much lower at the venule end of the capillary bed
64
What are the two ends of the capillary?
arteriole end
venule end
65
What effect does the fluid loss and the increasing concentration of plasma proteins have on water potential?
the water potential at the venule end of the capillary bed is lower than the water potential in the tissue fluid
66
What does the difference in water potential between the venule end and the tissue fluid mean?
it means that some water re-enters the capillaries by osmosis from the tissue fluid at the venule end
67
What happens to excess tissue fluid?
it is drained into the lymphatic system
68
What is the lymphatic system?
it transports excess fluid from the tissues and puts it back into the circulatory system
69
What do the left and the right side of the heart do?
the right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the whole body
70
Describe and explain the structure of the left ventricle
The left ventricle of the heart has thicker, more muscular walls than the right ventricle
This is because it needs to contract more powerfully to pump blood all the way round the body
71
Why do the ventricles have thicker walls than the atria?
because they have to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles
72
Describe the atrioventricular valves
they link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract
73
Describe the semi-lunar valves
They link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract
74
How does blood only flow in one direction through the heart?
the valves only open one way
75
Describe atrial systole
ventricles relaxed
atria contract, decreases volume of chambers so increasing pressure, pushes blood into the ventricles
slight increase in ventricular pressure and chamber volume as they fill with blood
AV valves open
SL valves closed
76
Describe ventricular systole
atria relax
ventricles contract, decreasing volume, increasing pressure
AV valves shut
SL valves open
pressure in ventricles is higher than aorta and pulmonary artery, which forces open SL valves, and blood forced out
77
Describe diastole
ventricles and atria relax
higher pressure in the pulmonary artery and aorta closes the SL valves
blood returns to the heart and atria fill
slight increase in atria pressure
AV valves open, and decreasing ventricle pressure means blood can flow passively from atria to ventricles
78
What is an atheroma?
A fatty substance that builds up in your arteries over time
79
How do most cardiovascular diseases start?
atheroma formation
80
How can damage occur to the endothelium of an artery?
high blood pressure
81
How do fatty streaks form in the artery endothelium?
white blood cells and lipids from the blood clump together under the lining to form fatty streaks
82
Describe the formation of an atheroma
damage occurs to endothelium (high blood pressure)
white blood cells and lipids clump together under the lining to form fatty streaks
overtime, the fatty streaks build up and harden to form atheroma
83
Describe CHD
a type of cardiovascular disease
occurs when coronary arteries have lots of atheromas in them, which restricts blood flow to the heart muscle
84
What can CHD lead to?
myocardial infection
85
What are two diseases that effect the arteries?
aneurysm
thrombosis
86
How do aneurysms form?
atheroma plaques can damage, narrow, and weaken arteries
when blood travels through a weakened artery at high pressure it may push the inner layers of the artery through the outer elastic layer to form a balloon-like swelling - an aneurysm
87
What happens when aneurysms burst?
causes a haemorrhage
88
Describe the formation of a thrombus
an atheroma plaque can rupture the endothelium of an artery
this damages the artery wall and leaves a rough surface
platelets and fibrin accumulate at the site of damage and form a blood clot
this blood clot can cause a complete blockage of the artery, or it can become dislodged and block a blood vessel elsewhere
debris from the rupture can cause another blood clot to form further down the artery
89
What is a myocardial infarction?
heart attack
90
How can a heart attack occur?
if a coronary artery becomes completely blocked
91
State three factors that increase the risk of cardiovascular disease
- high blood cholesterol and poor diet
- cigarette smoking
- high blood pressure
- age
- sex
- weight
92
Explain how high blood cholesterol increases the risk of heart disease
- cholesterol is one of the main constituents of the fatty deposits that form atheromas
- atheromas can increase blood pressure and cause blood clots
- this could block the flow of blood to coronary arteries, which could cause a myocardial infarction
93
Explain how cigarette smoking can increase the risk of heart disease
nicotine increases high blood pressure
carbon monoxide binds with haemoglobin, so can lead to heart attack
94
Explain how high blood pressure increases the risk of cardiovascular disease
- increases risk of damage to artery walls, which leads to increased risk of atheroma formation
- atheromas can also cause blood clots to form, which could block flow of blood to heart
95
What is the function of xylem tissue?
xylem tissue transports water and mineral ions in solution
96
Describe the structure of xylem vessels
long, tube like structures formed from dead cells
no end walls
97
Describe the cohesion-tension theory
1. water evapourates from the leaves at the top of the xylem (transpiration)
2. this creates tension, which pulls more water into the leaf
3. water molecules are cohesive, so when some are pulled into the leaf, others follow
4. water enters the stem through the roots
98
What is transpiration?
the evaporation of water from a plant's surface, especially the leaves
99
Name four factors that effect transpiration rate
light
temperature
humidity
wind
100
Describe how light effects transpiration rate
the lighter it is, more transpiration
because stomata are open when it gets light to let in CO2 for photosynthesis
101
Describe how temperature effects transpiration rate
the hotter it is, the faster transpiration
because warmer water molecules have more energy, so evaporate from cells inside the leaf faster
increases conc gradient, so water molecules diffuse out of leaf faster
102
Describe how humidity effects transpiration rate
the lower the humidity, the faster the transpiration rate
because if air around plant is dry, conc gradient between leaf and the air is increased, which increases transpiration
103
Describe how wind effects transpiration rate
the windier it is, the faster the transpiration rate
lots of air movement blows away water molecules from stomata, this increases conc gradient, which increases rate of transpiration
104
When using a potometer, why is it assembled underwater?
so no air can enter
105
How can transpiration rate be measured using a potometer?
by measuring the distance moved by a bubble, per unit amount of time
106
Describe the structure of the phloem
