Exchange & Transport 3.3. Flashcards
(292 cards)
1
Q
Digestion and absorption (AO1)
During digestion, large biological molecules are ____________________ to smaller molecules that can be absorbed across cell membranes.
A
hydrolysed
2
Q
Digestion and absorption (AO1)
Amylase hydrolyses which bonds?
A
Glycosidic bonds
(in starch)
3
Q
Digestion and absorption (AO1)
Where is amylase produced in the body?
A
Salivary glands
Pancreas
4
Q
Digestion and absorption (AO1)
Starch is hydrolysed into which disaccharide
A
Maltose
5
Q
Digestion and absorption (AO1)
Maltase location
A
Membrane-bound
6
Q
Digestion and absorption (AO1)
Membrane-bound
A
This means the enzyme is located in the cell surface membrane of epithelial cells lining the ileum of the small intestine
7
Q
Digestion and absorption (AO1)
Disaccharidase examples
A
Maltase
Sucrase
Lactase
8
Q
Digestion and absorption (AO1)
Disaccharidase location
A
Membrane-bound
9
Q
Digestion and absorption (AO1)
Describe the complete digestion of starch by a mammal (4 marks).
A
1. Hydrolysis;
2. (Of) glycosidic bonds;
3. (Starch) to maltose by amylase;
4. (Maltose) to glucose by disaccharidase/maltase;
5. Membrane-bound (disaccharidase/maltase);
10
Q
Digestion and absorption (AO1)
Process by which glucose and amino acids are absorbed into the blood via the epithelial cells of the small intestine
A
Co-transport
11
Q
Digestion and absorption (AO1)
Role of sodium-potassium
pump in co-transport
A
Actively transports sodium ions out of epithelial cell into the blood
This lowers the concentration of sodium ions inside the cell
12
Q
Digestion and absorption (AO1)
TRUE or FALSE
Sodium ions are needed to absorb glucose and amino acids via co-transport
A
TRUE
13
Q
Digestion and absorption (AO1)
Name of transport protein that allows sodium ions AND glucose OR amino acids into the epithelial cell
A
Co-transporter
14
Q
Digestion and absorption (AO1)
TRUE or FALSE:
Sodium ions and glucose bind to the same site on the co-transporter
A
FALSE
(they bind to different sites, each with a specific and complementary shape)
15
Q
Digestion and absorption (AO1)
Epithelial cells lining the ileum of mammals absorb glucose by co-transport with sodium ions. Explain how (3 marks).
A
1. Sodium ions actively transported from ileum cell into blood;
2. Lowers concentration of sodium ions, so they enter epithelial cells from lumen of small intestine;
(Sodium and glucose bind to co-transporter at different binding sites)
3. Glucose enters cell by facilitated diffusion along with sodium ions
4 This is co-transport;
5. Glucose then leaves epithelial cell and moves into blood via faciliated diffusion;
16
Q
Digestion and absorption (AO1)
A
1 ATP hydrolysis releases energy;
2. This energy allows ions to be moved against a concentration gradient
OR allows active transport of sodium ions;
17
Q
Digestion and absorption (AO1)
Epithelial cells contain ______________ to increase surface area for absorption
A
microvilli
18
Q
Digestion and absorption (AO1)
Describe and explain two features you would expect to find in a cell specialised for absorption (2 marks).
A
**1. Highly folded cell-surface membrane called microvilli so large surface area for absorption;
2. Large number of co-transport/carrier/channel proteins so fast rate of absorption;
3. Large number of mitochondria so make more ATP by aerobic respiration;
4. Membrane-bound enzymes so maintains concentration gradient (for fast absorption);
19
Q
Digestion and absorption (AO1)
Section of small intestine where most absorption takes place
A
ileum
20
Q
Digestion and absorption (AO1)
What are microvilli?
A
Highly folded cell-surface membrane which increases the surface area (for absorption)
21
Q
Digestion and absorption (AO1)
Protease examples
A
Endopeptidase
Exopeptidase
Dipeptidase
22
Q
Digestion and absorption (AO1)
Bond hydrolysed by proteases
A
peptide
23
Q
Digestion and absorption (AO1)
Endopeptidases hydrolyse ____________ peptide bonds within the polypeptide chain
A
internal
24
Q
Digestion and absorption (AO1)
Exopeptidases hydrolyse the peptide bonds at the ________________ ends of the polypeptide chain
A
terminal
25
# **Digestion and absorption (AO1)**
Products of dipeptidase action
x2 amino acids
26
# **Digestion and absorption (AO1)**
**TRUE OR FALSE**
Dipeptidases are produced
in the stomach
**FALSE**
*(They are **membrane-bound** enzymes located in the cell surface membrane of the ileum)*
27
# **Digestion and absorption (AO1)**
The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how (*2 marks*).
**1.** Exopeptidases hydrolyse peptide bonds at the terminal ends of a polypeptide AND endopeptidases hydrolyse internal peptide bonds within a polypeptide;
**2.** This produces more surface area for faster hydrolysis;
28
# **Digestion and absorption (AO1)**
Endopeptidases and exopeptidases are involved in the hydrolysis of proteins. Name the other type of enzyme required for the complete hydrolysis of proteins to amino acids.
Dipeptidase
29
# **Digestion and absorption (AO1)**
Similarities between co-transport of glucose and amino acids
**Both** require sodium ions to be actively transported out of the epithelia cell into blood;
**Both** require sodium ions to bind to a co-transporter to help faciliate diffusion;
**Both** glucose and amino acids enter the blood via facilitated diffusion;
30
# **Digestion and absorption (AO1)**
Differences between co-transport of glucose and amino acids
Co-transporter for glucose has a different tertiary structure to co-transporter for amino acid
Channel/carrier protein for glucose has a different tertiary structure to channel/carrier protein for amino acid
31
# **Digestion and absorption (AO1)**
Describe the mechanism for the absorption of amino acids in the ileum (*4 marks*).
**1.** Sodium *ions* **actively transported** from ileum cell **into** blood;
**2.** **Lowers concentration** of sodium ions, so they enter epithelial cells from lumen of small intestine;
*(Sodium and amino acids bind to co-transporter at different binding sites)*
**3.** Amino acids enter cell by facilitated diffusion along with sodium ions
**4.** This is co-transport;
**5.** Amino acids then leaves epithelial cell and moves into blood via facilitated diffusion;
| Note: these are the same steps as those involved in glucose absorption
32
# **Digestion and absorption (AO2)**
**1.** No/less ATP produced OR No active transport;
**2.** Sodium (ions) not moved (into/out of cell);
**3.** No diffusion/concentration gradient for sodium (to move into cell with amino acid via co-transport);
33
# **Digestion and absorption (AO1)**
Bile contains bile salts, which ____________ fat droplets
emulsify
34
# **Digestion and absorption (AO1)**
Describe two functions of bile salts
**1.** Emulsify lipids;
**2.** Increases surface area for
fast**er** lipase activity;
**3.** Form micelles
35
# **Digestion and absorption (AO1)**
Emulsification increases the ____________ of lipids for faster hydrolysis by lipases
surface area
36
# **Digestion and absorption (AO1)**
Lipases hydrolyse triglycerides into ____________
Glycerol &
3 fatty acids
37
# **Digestion and absorption (AO1)**
Describe the hydrolysis reactions involved in the digestion of triglycerides (*2 marks*).
**1.** Breaking of ester bonds;
**2.** By addition of water;
38
# **Digestion and absorption (AO1)**
Explain the advantages of lipid droplets following emulsification.
**1.** Droplets increase surface areas for lipase action;
**2.** So fast**er** hydrolysis triglycerides
39
# **Digestion and absorption (AO1)**
Micelles are made up of..........
Bile salts & fatty acids
40
# **Digestion and absorption (AO1)**
Explain the advantage of micelle formation
Micelles bring fatty acids to lining of the ileum epithelial cell;
This helps maintain concentration gradient of fatty acids;
Makes fatty acids soluble in water;
41
# **Digestion and absorption (AO1)**
Describe the role of micelles in the absorption of fats into the cells lining the ileum (*3 marks*).
**1.** Micelles include bile salts and fatty acids;
**2.** Make the fatty acids more soluble in water;
**3.** Bring fatty acids to the lining of the ileum epithelial cells;
**4.** Maintain high(er) concentration of fatty acids at the lining of the ileum epithelia cells;
**5.** Fatty acids absorbed by diffusion;
42
# **Digestion and absorption (AO1)**
Process by which fatty acids enter the ileum epithelial cell
Diffusion
43
# **Digestion and absorption (AO1)**
**TRUE or FALSE:**
Micelles enter the ileum epithelial cell by simple diffusion
**FALSE**
| Fatty acids enter by simple diffusion
44
# **Digestion and absorption (AO1)**
Organelle that (re)synthesises triglyceride
Smooth endoplasmic reticulum
45
# **Digestion and absorption (AO1)**
Organelle that modifies proteins by combining them with triglycerides
Golgi body / apparatus
46
# **Digestion and absorption (AO1)**
Name of modified protein produced after lipid absorption
Chylomicron
47
# **Digestion and absorption (AO1)**
Lipids are absorpted directly into the blood OR lymph vessels
Lymph vessels
48
# **Digestion and absorption (AO1)**
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5 marks).
**1.** Micelles contain bile salts and fatty acids;
**2.** Make fatty acids more soluble in water
OR Bring fatty acids to lining of ileum epithelial cells
OR Maintain high concentration of fatty acids at lining of ileum epithelial cells;
**3.** Fatty acids absorbed by diffusion;
**4.** Triglycerides (re)formed in smooth endoplasmic reticulum;
**5** Chylomicrons produced in Golgi body;
**6.** Vesicles containing chylomicrons move to cell surface membrane via exocytosis;
49
# **Digestion and absorption (AO2)**
Vitamin A is a fat-soluble substance. Micelles are involved in the process of vitamin A absorption.
Describe the process of vitamin A absorption into cells lining the ileum (**3**).
**1.** Vitamin A combines/join with bile salts (forming micelles);
**2.** Micelles make vitamin A more soluble in water
**3.** Micelles bring vitamin A to lining of ileum epithelial cells
OR maintains high concentration of vitamina A at lining of ileum epithelial cells;
**4.** Vitamin A absorbed by diffusion (into ileum cells)
50
# **Surface area to volume ratio (AO1)**
As an organism gets ____________, the smaller the surface area : volume ratio.
larger
51
# **Surface area to volume ratio (AO1)**
The smaller the organism, the ____________ surface area : volume ratio.
larger
52
# **Surface area to volume ratio (AO1)**
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake (*2 marks*).
**1.** Larg**er** organisms have a small**er** surface area : volume (ratio);
OR *accept converse*
**2.** (Specialed exchange) system provides a short**er** diffusion pathway / enables fast**er** diffusion;
53
# **Surface area to volume ratio (AO2)**
In large cells of U. marinum, most mitochondria are found close to the cell-surface membrane. In smaller cells, the mitochondria are distributed evenly throughout the cytoplasm.
Use this information and your knowledge of surface area to volume ratios to suggest an explanation for the position of mitochondria in large U. marinum cells (*2 marks*).
**1.** Larg**er** cells have small**er** surface area to volume ratio;
**2.** The diffusion distance/pathway is long**er**;
OR slow**er** diffusion (to mitochondira)
OR
Less/no oxygen diffuses (to mitochondria)
| *i.e. mitochondria close to the membrane = faster diffusion of oxygen*
54
# **Surface area to volume ratio (AO1)**
What adaptations to cells or specialised exchange surfaces enable a FASTER rate of diffusion?
**1.** Large surface area
**2.** Large concentration gradient
**3.** Short diffusion distance
55
# **Surface area to volume ratio (AO1)**
For smaller organsisms with a larger surface area : volume ratios, what is the main disadvantage?
heat loss
| (via the larger surface area)
56
# **Surface area to volume ratio (AO1)**
How do smaller organisms compensate for heat loss?
**increased** metabolic activity
e.g. **respiration**
57
# **Surface area to volume ratio (AO1)**
By-product of increased respiration that allows smaller organisms to maintain an optimal body temperature
heat
58
# **Surface area to volume ratio (AO2)**
Mammals such as a mouse and a horse are able to maintain a constant body temperature.
Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse.
**1.** Mouse is smaller so larg**er** surface area to volume ratio;
**2.** Fast**er** heat loss OR lose **more** heat easily (per gram/in relation to body size);
**3.** Fast**er** rate of respiration/metabolism releases heat;
59
# **Surface area to volume ratio (Maths)**
How to calculate the
surface area : vol ratio?
Divide the surface area by volume
Always present like this "X **: 1**"
For exampe, if SA = 25cm^2, volume = 5cm^3.
SA : VOL = 25 / 5 = 5 : 1
60
# **Surface area to volume ratio (Maths)**
Calculate SA : VOL ratio
Surface area = 17cm^2
Volume = 34cm^3
Working: 17 / 34
Answer: **0.5 : 1**
61
# **Surface area to volume ratio (Maths)**
Complete Table 1. State your calculated volume and surface area : volume ratio to 2 significant figures.
62
# **Gas Exchange (AO1)**
How does oxygen enter a single-celled organism e.g. amoeba?
Simple diffusion
*(across the cell-surface membrane)*
63
# **Gas Exchange (AO1)**
What adaptations does the single-celled single-celled amoeba have for a faster rate of gas exchange?
Large surface area to volume ratio;
Short diffusion distance;
64
# **Gas Exchange (AO1)**
Describe how gas exchange occurs in a single-celled organism **and** explain why this method cannot be used by large, multicellular organisms?
**1.** Diffusion across the cell surface membrane;
**2.** Larger organisms have a smaller surface area : volume ratio;
**3.** Diffusion pathway would be too long OR
Diffusion would be too slow;
65
# **Gas Exchange (AO2)**
Name the process by which oxygen reaches the cells inside the body of a tubifex worm shown below.
Simple diffusion
66
# **Gas Exchange (AO2)**
Using the information provided below, explain how two features of the body of the tubifex worm allow efficient gas exchange.
**1.** Thin/small so short diffusion pathway;
**2.** Flat/small so large surface area to volume ratio
67
# **Gas Exchange (AO1)**
Name of insect gas exchange system
the tracheal system
68
# **Gas Exchange (AO1)**
Location of gas exchange in the tracheal system
tracheoles
69
# **Gas Exchange (AO1)**
**TRUE or FALSE:**
Tracheoles supply oxygen direct
into insect tissues
TRUE
70
# **Gas Exchange (AO1)**
Name the structure through which gases enter and leave the body of an insect.
spiracles
71
# **Gas Exchange (AO1)**
Adaptations of tracheoles for efficient gas exchange
**1.** **Highly branched** so provide a large surface area for faster rate of diffusion
**2.** Their **walls are thin** so there is short diffusion distance;
**3.** **Supply tissues** (e.g. muscle fibres) so diffusion is **direct into cells**
72
# **Gas Exchange (AO1)**
Describe how atmospheric oxygen reaches respiring cells in an insect
**1.** Oxygen enters the insect through spiracles and into the tracheae.
**2.** Spiracles close
**3.** Oxygen diffuses (down a conc gradient) through the tracheae into the tracheoles (where gas exchange occurs)
**4.** Oxygen is delivered directly to respiring tissues
73
# **Gas Exchange (AO1)**
Explain the movement of oxygen into the gas exchange system of an insect when it is at rest
(*3 marks*).
**1.** Oxygen used in (aerobic) respiration;
**2.** (so) oxygen (concentration) gradient (established);
**3.** (so) oxygen diffuses in;
74
# **Gas Exchange (AO1)**
Explain the role of abdominal pumping in insects during gas exchange
Movement of the insect body by its muscles;
Increases pressure so forces carbon dioxide out (via
spiracles which open);
Maintains concentration gradient of carbon dioxide and oxygen;
75
# **Gas Exchange (AO1)**
Insects must balance minimising ___________ loss with efficient gas exchange.
water
76
# **Gas Exchange (AO1)**
Describe and explain how the insect gas exchange system limits water loss (*2 marks)*.
**1.** **Exoskeleton is impermeable to water** so reduces water loss.
**2.** **Spiracles close** to prevent water loss
**3.** **Small hairs around the spiracles**
77
# **Gas Exchange (AO1)**
Describe and explain how the structure of the insect gas exchange system provides cells with sufficient oxygen (*4 marks*).
**1.** Spiracles, tracheae, tracheoles;
**2.** Spiracles allow diffusion (of oxygen)
OR (Oxygen) diffusion through tracheae/tracheoles;
**3.** Tracheoles are highly branched so large surface area for exchange;
**4.** Tracheole walls thin so short diffusion distance (to cells)
**5.** Tracheole walls are permeable to oxygen/air;
78
# **Gas Exchange (AO1)**
F = Filament
G = Lamella(e)
79
# **Gas Exchange (AO1)**
Gills have many finger-like projections called gill ____________.
filaments
80
# **Gas Exchange (AO1)**
Each gill filament has many _____________
lamellae
| (singular lamella)
81
# **Gas Exchange (AO1)**
Lamellae contain ____________ and are the site of gas exchange.
capillaries
82
# **Gas Exchange (AO1)**
The capillaries bring ___________ blood to the lamellae.
deoxygenated
83
# **Gas Exchange (AO1)**
Site of gas exchange in fish gills
lamellae
| (singular lamella)
84
# **Gas Exchange (AO1)**
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
**many gill filaments/lamellae** provide a large surface area;
lamellae have a **thin epithelium** for short diffusion distance (between water and blood)
85
# **Gas Exchange (AO1)**
Name two structural features of the gills of a fish that increase their surface area.
Lamella(e) **and** filament(s)
86
# **Gas Exchange (AO1)**
Describe and explain the **counter current mechanism in fish gills**.
**1.** Water and **blood** flow in opposite directions;
**2.** Maintains diffusion/concentration gradient of oxygen
**3.** Diffusion along length of lamellae / filament / capillary;
87
# **Gas Exchange (AO2)**
**(Difference)**
1. More cells (between water and capillary/ blood)
OR Wider/thicker lamella/filament/epithelieum;
**(Explanation)**
2. Longer diffusion pathway/distance
3. (So) slower gas exchange
OR (So) slower absorption of oxygen
OR (So) slower rate of diffusion;
88
# **Gas Exchange (AO1)**
Draw and label a cross section
of leaf tissue
89
# **Gas Exchange (AO1)**
Why is the concentration of carbox dioxide low in the palisade mesophyll cell?
Used in photosynthesis
90
# **Gas Exchange (AO1)**
Through which structures does carbon dioxide enter the leaf.
stomata
| (Singular stoma)
91
# **Gas Exchange (AO1)**
What cells open and close the stomata?
guard cells
92
# **Gas Exchange (AO1)**
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf (*3 marks*).
**1.** Carbon dioxide enters via stomata;
**2.** (Stomata opened by) guard cells;
**3.** Diffuses through air spaces (in the spongy mesophyll layer);
**4.** **Down** diffusion/concentration gradient;
93
# **Gas Exchange (AO1)**
Describe and explain how the leaf is adapted for efficient gas exchange.
**1.** They are **flat** so have **larger surface area** to volume ratio
**2.** Contain **many stomata** which **allow air to move in and out** of the leaf
**3.** **Air spaces** in the spongy mesophyll so **short distance pathway**
(between air spaces the palisade mesophyll cells)
94
# **Gas Exchange (AO1)**
**TRUE or FALSE:**
Water is lost from the leaf via the stomata due to transpiration
TRUE
95
# **Gas Exchange (AO1)**
How do plants minimise water loss?
At night, the guard cells close the stomata so less transpiration;
Upper & lower surfaces have a waxy cuticle which increases diffusion distance / impermeable to water;
96
# **Gas Exchange (AO1)**
Group of plants adapted to live in dry conditions
Xerophytes
97
# **Gas Exchange (AO1)**
List the adaptations of xerophytes to dry conditions
Small leaves
Spines
Rolled leaves
Stomata in pits
Hairs
Thick waxy cuticle
98
# **Gas Exchange (AO1)**
How does a small leaf reduce water loss in xerophytes?
Smaller surface area so **reduced number of stomata**
99
# **Gas Exchange (AO1)**
How does a thick waxy cuticle reduce water loss in xerophytes?
Increased diffusion distance so reduces transpiration
100
# **Gas Exchange (AO1)**
How do spines reduce water loss in xerophytes?
Reduces the surface area : volume ratio
101
# **Gas Exchange (AO1)**
What features of a xerophyte **reduce the water potential gradient** by trapping water vapour?
Hairs;
Stomata in pits;
Rolled leaves;
102
# **Gas Exchange (AO2)**
Species B (no mark)
**1.** Smaller surface area so less evaporation ;
**2.** Thicker leaves so greater diffusion distance (for water);
**3.** Fewer stomata so less diffusion / evaporation (of water);
**4.** Smaller surface area to volume ratio so less evaporation.
103
# **Gas Exchange (AO2)**
Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly (*2 marks*).
**1.** Stomata close (to reduce water loss);
**2.** Less carbon dioxide (uptake) for less photosynthesis;
104
# **Gas Exchange (AO1)**
Describe the gross structure of the human gas exchange system
(*2 marks*)
**1.** Trachea, bronchi, bronchioles, alveoli;
**2.** Above structures named in **correct order**
105
# **Gas Exchange (AO1)**
Bronchiole
106
# **Gas Exchange (AO1)**
Site of gas exchange in human lungs
Alveoli
107
# **Gas Exchange (AO1)**
Describe the pathway taken by an oxygen molecule from an alveolus to the blood (*2 marks*).
**1.** First across alveolar epithelium;
**2**. Then across endothelium of capillary;
108
# **Gas Exchange (AO1)**
What adaptation of the lungs provides a large surface area for rapid gas exchange?
Many alveoli
109
# **Gas Exchange (AO1)**
What adaptation of the lungs provides a short diffusion distance for rapid gas exchange?
Alveolar epithelium is single layer of cells / one cell thick
110
# **Gas Exchange (AO1)**
What adaptation of the lungs provides a large concentration for rapid gas exchange?
Alveoli have a good blood supply / surrounded by many capillaries;
Brings deoxygenated blood;
Concentration of oxygen in blood lower than alveoli;
111
# **Gas Exchange (AO1)**
Describe and explain features of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange.
*Mark in pairs:*
**1.** Single layer of cells / one cell thick
**2.** Reduces diffusion distance
OR
**3.** Permeable
**4.** Allows diffusion of oxygen/carbon dioxide
OR
**5.** Large surface area
**6.** Lots of membrane for diffusion of oxygen/carbon dioxide
112
# **Gas Exchange (AO1)**
Explain how one feature of an alveolus allows efficient gas exchange to occur
**1.** Single layer of cells / one cell thick;
**2.** Reduces the diffusion distance / creating a short diffusion pathway;
113
# **Gas Exchange (AO1)**
Ventilation is a result of the difference in ______________ between the lungs and the air outside the body.
pressure
114
# **Gas Exchange (AO1)**
Which muscles contract during inhalation (i.e. breathing in).
Diaphragm
**External** intercostal muscles
115
# **Gas Exchange (AO1)**
Which muscle contracts during exhalation (i.e. breathing out).
**Internal** intercostal muscle
116
# **Gas Exchange (AO1)**
Which muscles relax during exhalation (i.e. breathing out).
Diaphragm
**External** intercostal muscle
117
# **Gas Exchange (AO1)**
Describe the mechanism of breathing that causes air to **enter** the lungs (*3 marks*).
**1.** Diaphragm contract **AND** diaphragm flattens/pulled down;
**2.** **External** intercostal muscles contract **AND** ribcage pulled up/out;
**3.** Causes volume increase **AND** pressure decrease in **thoracic cavity**;
(to below atmospheric pressure)
118
# **Gas Exchange (AO1)**
Describe the mechanism of breathing that causes air to **exit** the lungs (*3 marks*).
**1.** Diaphragm (muscles) relaxes **AND** diaphragm moves up;
**2.** External intercostal muscles relax **AND** ribcage moves down/in;
*Accept internal intercostal muscles contract*
**3.** (Causes) volume decrease **AND** pressure increase in thoracic cavity (to above atmospheric pressure);
119
# **Gas Exchange (AO1)**
Interaction between internal and external intercostal muscles
Antagonistic
| *One contracts, the other relaxes*
120
# **Gas Exchange (AO1)**
(A) Trachea
(B) **External** intercostal muscle
121
# **Gas Exchange (Maths)**
Pulmonary ventilation rate =
(include units)
122
# **Gas Exchange (Maths)**
123
# **Gas Exchange (AO2)**
Tidal volume is the volume of air inhaled and exhaled during a single breath when a person is resting. The tidal volume in a person with emphysema is reduced compared with the tidal volume in a healthy person.
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli (*3 marks*).
**1.** Less carbon dioxide exhaled/moves OR More carbon dioxide remains (in lung);
**2.** So reduced concentration **gradient**;
(between blood and alveoli)
**3.** Slower movement of carbon dioxide out of blood OR More carbon dioxide stays in blood;
124
# **Gas Exchange (AO1)**
K = bronchiole and
L = artery/arteriole/vein/venule;
125
# **Gas Exchange (AO2)**
What is a risk factor?
Environmental and genetic factors that can increase/ decrease the risk of developing a disease
126
# **Gas Exchange (AO2)**
Correlation does not mean _____________
causation
127
# **Gas Exchange (AO2)**
Risk factors for lung disease
Smoking
Air pollution
Risk alleles / genes
Infections
Occupation
128
# **Gas Exchange (AO3)**
Draw out a linear relationship
## Footnote
Look for a straight line / constant gradient
129
# **Gas Exchange (AO3)**
**Linear or non-linear:**
Non linear
130
# **Gas Exchange (AO3)**
**Linear or non-linear:**
There is a proportional Y increase as X increases
Linear
131
# **Gas Exchange (AO3)**
When to use a t test?
When comparing the **differences between two means** (e.g. control vs. treatment group)
132
# **Gas Exchange (AO3)**
Name of statistical test used to assess the strength of relationship between two continuous variables.
Correlation coefficient
133
# **Gas Exchange (AO3)**
A t-test produced a p value = 0.03.
What can you conclude?
**Significant** difference between means;
**LESS** than 5% probability the **DIFFERENCE** is due to chance
OR 3% probability the **DIFFERENCE** is due to chance
134
# **Gas Exchange (AO3)**
A t-test produced a p value > 0.11
What can you conclude?
**NO Significant** difference between means;
**MORE** than 5% probability the **DIFFERENCE** is due to chance
135
# **Gas Exchange (AO3)**
A t-test produced a p value = 0.001.
What can you conclude?
**HIGHLY Significant** difference between means;
**LESS** than 5% probability the **DIFFERENCE** is due to chance
OR 0.01% probability the **DIFFERENCE** is due to chance
136
# **Gas Exchange (AO3)**
A correlation coefficient produced a p value > 0.2.
What can you conclude?
**NO Significant correlation**
**MORE** than 5% probability the **CORRELATION** is due to chance
137
# **Gas Exchange (AO3)**
A correlation coefficient produced a p value < 0.045.
What can you conclude?
**Significant correlation**
**LESS** than 5% probability the **CORRELATION** is due to chance
138
# **Gas Exchange (AO3)**
A correlation coefficient produced a p value < 0.001.
What can you conclude?
**Highly significant correlation**
**LESS** than 5% probability the **CORRELATION** is due to chance
OR **LESS** than 0.1% probability the **CORRELATION** is due to chance
139
# **Gas Exchange (AO3)**
Researchers carried a correlation coefficient to assess the relationship between the concentration of carbon monoxide and the number of asthma attacks.
They found R = 0.50, with P <0.0001
Explain the meaning of the result of their calculations.
**1.** **Positive** correlation - as carbon monoxide increases, the number of asthma attacks increases;
**2.** P value of <0.0001 shows a highly significant correlation;
**3.** Less than a 5% probability this correlation is due to chance;
140
# **Gas Exchange (AO3)**
Write out an alternative hypothesis for an experiment that requires a t test.
e.g. there is a (significant) **difference between the mean** tidal volume between the control group (+placebo) and the treatment group (+new asthma drug)
| **Always use context of the question**
141
# **Gas Exchange (AO3)**
Write out a null hypothesis for an experiment that requires a t test.
e.g. there is a **NO** (significant) **difference between the mean** tidal volume between the control group (+placebo) and the treatment group (+new asthma drug)
| **Always use context of the question**
142
# **Gas Exchange (AO3)**
Write out a null hypothesis for an experiment that requires a correlation coefficient.
e.g. There is **no correlation** between exercise per day (mins) and the % of people with lung cancer
| **Always use context of the question**
143
# **Gas Exchange (AO2)**
*Mark in pairs, 1, and 2 OR 3. and 4.*
**1.** Water has low(er) oxygen partial pressure/concentration (than air);
**2.** So (system on outside) gives large surface area (in contact with water)
OR
So (system on outside) reduces diffusion distance (between water and blood);
**3.** Water is dense(r) (than air);
**4.** (So) water supports the systems/gills;
144
# **Gas Exchange (AO2)**
Particulate matter is solid particles and liquid particles suspended in air. Polluted air contains more particulate matter than clean air.
A high concentration of particulate matter results in the death of some alveolar epithelium cells. If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs (*3 marks*).
**1.** Reduced surface area;
**2.** Increased distance for diffusion;
**3.** Reduced **rate** of gas exchange;
145
# **Haemoglobin (AO1)**
**TRUE or FALSE**
The haemoglobins are a group of chemically similar molecules found in many different organisms.
TRUE
146
# **Haemoglobin (AO1)**
Haemoglobin is a protein with a _____________ structure.
quaternary
147
# **Haemoglobin (AO1)**
Haemoglobin in red blood cells transports _______ around the body.
oxygen
148
# **Haemoglobin (AO1)**
Haemoglobin has a quaternary structure with four [1] chains, each containing a [2] group.
[1] polypeptide
[2] haem
149
# **Haemoglobin (AO1)**
Each haem group contains an [1] ion which can associate with one [2] molecule.
[1] iron
[2] oxygen
150
# **Haemoglobin (AO1)**
oxygen + haemoglobin =
oxyhaemoglobin
151
# **Haemoglobin (AO1)**
Haemoglobin is a protein with a quaternary structure.
Explain the meaning of quaternary structure.
**More than one** polypeptide chain.
OR
**two or more** polypeptide chains
152
# **Haemoglobin (AO1)**
153
# **Haemoglobin (AO1)**
Describe the role of haemoglobin (Hb) in the **loading** of oxygen
**1.** (Hb) loads/associates/binds oxygen in the lungs;
**2.** At high partial pressure of oxygen;
**3.** Binding of an oxygen (molecule to Hb) makes binding of another oxygen molecule easier;
154
# **Haemoglobin (AO1)**
Describe the role of haemoglobin (Hb) in **transporting** oxygen
(Oxygen transported as) oxyhaemoglobin in red blood cells
155
# **Haemoglobin (AO1)**
Describe the role of haemoglobin (Hb) in the **unloading** of oxygen
**1.** (Hb) unloads/dissociates oxygen at the respiring cells/tissues;
**2.** At low partial pressure of oxygen
*OR*
At high partial pressure of carbon dioxide;
156
# **Haemoglobin (AO1)**
Draw out and fully annotate an oxygen dissociation curve
157
# **Haemoglobin (AO1)**
What type of mathematical curve is the oxygen dissociation curve?
sigmoid
| i.e. it is 'S' shaped = very steep gradient in the middle of curve
158
# **Haemoglobin (AO1)**
Haemoglobin has a high [1] for oxygen at a high partial pressure of oxygen therefore [2] occurs.
[1] affinity
[2] association
159
# **Haemoglobin (AO1)**
Haemoglobin has a [1] affinity for oxygen at a low partial pressure of oxygen and [2] occurs.
[1] low
[2] **dis**sociation
160
# **Haemoglobin (AO1)**
Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why (*2 marks*).
**1.** Binding of first oxygen changes tertiary / quaternary structure of haemoglobin;
**2.** Uncovers second **binding site**
OR uncovers another iron / Fe / haem group to bind to;
161
# **Haemoglobin (AO1)**
Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin (*3 marks*).
**1.** Decreases blood pH/increasing acidity;
**2.** Changes the tertiary/quatenary structure of haemoglobin
**3.** Decreases haemoglobin affinity for O2;
**4.** Increases/more oxygen dissociation/unloading
162
# **Haemoglobin (AO1)**
The Bohr effect shifts the oxygen dissociation curve in which direction?
to the **right**
163
# **Haemoglobin (AO1)**
Describe the advantage of the Bohr effect during intense exercise (*2 marks*).
**1.** Decreased haemoglobin affinity for oxygen;
**2.** Increases dissociation of oxygen;
**3.** More oxygen for aerobic respiration at the cells/tissues/muscles;
164
# **Haemoglobin (AO2)**
**d)**
**curve drawn to the right**, following the same pattern and **starting at Y = 0** and **finishing at the same percentage** saturation as original curve;
**e)**
**1.** During exercise
OR At low pO2 (in the tissues);
OR ‘high altitude’ or ‘lack of red blood cells’
**2.** More oxygen for respiration;
OR More aerobic respiration;
165
# **Haemoglobin (AO2)**
**1.** **Curve to the right so lower affinity** / % saturation of haemoglobin;
**2.** **Increased dissociation of oxgyen** (from haemoglobin)
**3.** **More oxygen to cells** / tissues / muscles;
**4.** For greater / more / **faster respiration**;
166
# **Haemoglobin (AO1)**
Explain a property of iron ions that enables these ions to carry out their role in red blood cells (*2 marks*).
**1.** charged/polar
OR part of haem(oglobin);
**2.** Binds to oxygen
OR Transports oxygen;
167
# **Haemoglobin (AO1)**
Shifting the oxygen dissociation curve **to the left** means that haemoglobin has a _________ affinity for oxygen.
higher
168
# **Haemoglobin (AO2)**
The oxygen dissociation curve of the foetus is to the left of that for its mother.
Explain the advantage of this for the foetus (*2 marks*).
**1.** Higher affinity at low / same partial pressure / pO2;
**2.** Oxygen moves from mother to fetus;
169
# **Haemoglobin (AO2)**
**1.** Binding of first oxygen changes tertiary / quaternary structure of haemoglobin;
**2.** Uncovers second **binding site**;
**3.** Allows more O2 to bind (easily) / greater saturation with O2;
170
# **Haemoglobin (AO2)**
**1.** Less (oxygen) loaded at high pO2 / lungs (compared with no CO)
OR Maximum Hb saturation is 50% (oxygen);
OR Accept ‘levels (off)’ OR ‘plateau at 50%’ for maximum
**2.** At low pO2 Hb has higher affinity (for oxygen);
**3.** Hb has more oxygen at low pO2
OR Hb unloads less oxygen at low pO2;
171
# **Haemoglobin (AO2)**
**1.** **Higher affinity** for oxygen (than haemoglobin)
OR Associates more readily;
**2.** Allows aerobic respiration when diving/at low(er) pO2;
OR provides oxygen when haemoglobin unloaded;
172
# **Haemoglobin (AO2)**
The oxygen dissociation curve of a mouse is to the right of the curve for a horse.
Suggest how this allows the mouse to have a higher metabolic rate than the horse (*2 marks*).
1. **Mouse haemoglobin** has a **lower** affinity for oxygen
2. **More oxygen can be dissociated** / released / unloaded (for metabolic reactions/respiration);
173
# **Haemoglobin (Maths)**
574
174
# **Haemoglobin (Maths)**
175
# **Haemoglobin (AO1)**
**TRUE or FALSE:**
Many animals are adapted to their environment by possessing different types of haemoglobin with different oxygen transport properties.
TRUE
| e.g. llama haemoglobin = high affinity for oxygen owing to high altitude
176
# **Mass Transport in Animals (AO1)**
Aorta - D;
Renal vein - G;
Vena cava - F;
177
# **Mass Transport in Animals (AO1)**
Name the blood vessels that carry blood to the heart muscle
coronary arteries
178
# **Mass Transport in Animals (AO1)**
Name the blood vessels that carry blood to the kidney
renal artery
179
# **Mass Transport in Animals (AO1)**
Name the blood vessel that carries deoxygenated blood to the lung
pulmonary artery
180
# **Mass Transport in Animals (AO1)**
Name the blood vessel that carries oxygenated blood to the left atrium
pulmonary vein
181
# **Mass Transport in Animals (AO1)**
Give the pathway a red blood cell takes when travelling in the human circulatory system **from a kidney to the lungs** (*3 marks*).
**1.** Renal vein;
**2.** Vena cava to right atrium;
**3.** Right ventricle to pulmonary artery;
182
# **Mass Transport in Animals (AO1)**
Name of valve that separates the atria from the ventricles on both sides of the heart
atrioventricular valve
(AV valve)
183
# **Mass Transport in Animals (AO1)**
Name of valve that separates the ventricles from the aorta (left side) and pulmonary artery (right side)
semi-lunar valve
184
# **Mass Transport in Animals (AO1)**
What side of the heart pumps oxygenated blood around the body?
LEFT
185
# **Mass Transport in Animals (AO1)**
In a healthy person, blood moves in one direction as it passes through the heart. Give two ways in which this is achieved (*2 marks*).
**1.** Pressure gradient moves blood from high to low pressure;
**2.** Valves prevent backflow;
186
# **Mass Transport in Animals (AO1)**
Explain how the atrioventricular valve maintains a unidirectional flow of blood (*2 marks*).
**1.** Pressure in atrium is higher than in ventricle **causing** valve to open;
**2.** Pressure in ventricle is higher than in atrium **causing** valve to close;
187
# **Mass Transport in Animals (AO1)**
What can you conclude from the appearance of valves in the image below about heart muscle activity and blood movement between:
**1.** ventricles and arteries?
**2.** atria and ventricles?
(ventricles and arteries)
**1.** Ventricle muscles relaxed
**2.** No backflow of blood into ventricles;
(atria and ventricles)
**3.** Atria muscle contracted;
**4.** Blood pumped from atria into ventricles;
188
# **Mass Transport in Animals (AO1)**
Which blood vessel carries blood at the lowest blood pressure?
Vena cava
189
# **Mass Transport in Animals (AO2)**
**1.** Semi-lunar valves is closed;
**2.** Because pressure in aorta higher than in ventricle;
190
# **Mass Transport in Animals (AO2)**
Use the graph to explain why the AV valve is closed
Pressure in ventricle is **higher** than pressure in the atria
191
# **Mass Transport in Animals (AO2)**
Use the graph to explain why the semi-lunar valve is open
Pressure in ventricle is **higher** than pressure in the aorta
192
# **Mass Transport in Animals (AO1)**
Describe one way in which the graphs of cardiac cycles on the right and left ventricle would similar to and one way it would be different (*2 marks*).
(Similarity)
1. Peaks/contractions at the same/similar time
OR Same/similar pattern;
(Difference)
2. **Lower** pressures on the right hand side;
193
# **Mass Transport in Animals (AO2)**
194
# **Mass Transport in Animals (AO1)**
The maximum pressure in the ventricle is much higher than that in the atrium.
Explain what causes this (*2 marks*).
**1.** Ventricle has thick wall / more muscle;
**2.** So contractions are stronger / harder;
195
# **Mass Transport in Animals (AO1)**
**i)** C
**ii)** A
196
# **Mass Transport in Animals (AO1)**
197
# **Mass Transport in Animals (AO2)**
Some babies are born with a hole between the right and the left ventricles.
These babies are unable to get enough oxygen to their tissues. Suggest why (2 marks).
**1.** Blood flows from left ventricle to right ventricle/ mixing of oxygenated and deoxygenated blood;
**2.** Lower volume of oxygenated blood leaves left ventricle/flows into aorta
OR Lower pressure in blood leaving left ventricle/flowing into aorta
198
# **Mass Transport in Animals (AO1)**
Function of coronary arteries (*2 marks*)
**1.** Carry oxygen / glucose;
**2.** To heart muscle / cells / tissues.
199
# **Mass Transport in Animals (AO2)**
**1.** Ventricle pressure rises then blood starts to flow into aorta because pressure **causes** semilunar valve to open;
**2.** Ventricle pressure starts to fall so blood flow falls;
200
# **Mass Transport in Animals (AO1)**
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta (*5 marks*).
**1.** Atria contract and this increases pressure
**2.** Atrium has higher pressure than ventricle causing atrioventricular valves to open;
**3.** Ventricle contract and this increases pressure
**4.** Ventricle has higher pressure than atrium causing atrioventricular valves to close;
**5.** Ventricle has higher pressure than aorta causing semilunar valve to open;
**6.** Higher pressure in aorta than ventricle (as ventricle relaxes) causing semilunar valve to close;
201
# **Mass Transport in Animals (Maths)**
Cardiac output equation
Cardiac output (CO) = stroke volume (SV) x heart rate (HR)
202
# **Mass Transport in Animals (Maths)**
Cardiac output unit
203
# **Mass Transport in Animals (Maths)**
What is stroke volume?
Volume of blood pumped out of the left ventricle during each cardiac cycle (cm^3)
204
# **Mass Transport in Animals (AO1)**
**TRUE or FALSE:**
The cardiac cycle describes the contraction and relaxation of both the atria and ventricles during each heart beat.
TRUE
205
# **Mass Transport in Animals (Maths)**
**TRUE or FALSE:**
Heart rate is the length of one cardiac cycle in seconds
FALSE
| Heart rate is the number of cardiac cycles / heart beats **per minute**
206
# **Mass Transport in Animals (Maths)**
Heart rate of 75 bpm and a cardiac output of 5175cm^3 min^-1 - what is the stroke volume?
69 cm^3
207
# **Mass Transport in Animals (Maths)**
One cardiac cycle of 0.7s, what is the heart rate?
60 / 0.7 = 85.7 or 86 bpm
208
# **Mass Transport in Animals (Maths)**
Use the below graph to determine the length of one cardiac cycle.
Peak to peak OR trough to trough
e.g.1.24 - 0.48 = 0.76s
209
# **Mass Transport in Animals (Maths)**
Use the below graph to determine stroke volume.
120 - 40 = 80cm^3
210
# **Mass Transport in Animals (Maths)**
Convert 770 milliseconds (ms) into seconds (s)
770 / 1000 = 0.77s
211
# **Mass Transport in Animals (Maths)**
Convert 3.5 seconds (s) into milliseconds (ms)
3.5 x 1000 = 3500ms
212
# **Mass Transport in Animals (Maths)**
8 beats in 800 ms
1 beat = 100 ms / 0.1s
Heart rate = 60 / 0.1 = 600bpm
CO = SV x HR
CO = 0.03 x 600 = 18cm^3 min^-1
213
# **Mass Transport in Animals (Maths)**
60 / 0.9 =
66.7 or 67 bpm
| One cardiac cycle or heart beat = 0.9 seconds
214
# **Mass Transport in Animals (AO1)**
Arteries have [1] muscle walls that can withstand [2].
[1] thick
[2] pressure
215
# **Mass Transport in Animals (AO1)**
Arteries contain [1] tissue to stretch when the ventricles contract and [2] when the ventricle relaxes. This recoil helps to [3] the high pressure.
[1] elastic
[2] recoil
[3] maintain
216
# **Mass Transport in Animals (AO1)**
Describe one key feature and function of the endothelieum in arteries.
**Feature:** smooth
**Function:** reduces friction.
217
# **Mass Transport in Animals (AO1)**
What is the **only artery** that contains valves?
Aorta
| contains semi-lunar valve
218
# **Mass Transport in Animals (AO1)**
Explain **four ways** in which the structure of the aorta is related to its function.
**1.** Thick muscle withstands/resists high pressure
**2.** Elastic tissue stretches when ventricles contract OR recoils when ventricle relaxes;
**3.** Elastic tissue to allow stretching / recoil which maintains pressure;
**4.** Smooth endothelium reduces friction;
**5.** Wall contains fibrous protein withstands/resists high pressure OR stop bursting;;
**6.** Semi-lunar valve prevents backflow;
219
# **Mass Transport in Animals (AO1)**
Give two structural features of an **aorta wall** and explain how they are related to the function of an aorta
**1.** Thick muscle withstands/resists high pressure
**2.** Elastic tissue stretches when ventricles contract OR recoils when ventricle relaxes;
**3.** Elastic tissue to allow stretching / recoil which maintains pressure;
**4.** Smooth endothelium reduces friction;
**5.** Wall contains fibrous protein withstands/resists high pressure;
220
# **Mass Transport in Animals (AO1)**
Explain how an arteriole can reduce the blood flow into capillaries (*2 marks*).
**1.** Muscle contracts;
**2.** Constricts the lumen of the arteriole;
| This is an example of vasoconstriction
221
# **Mass Transport in Animals (AO1)**
When the muscles in the walls of the arterioles relax, this increases the flow of blood to the tissues. This is known as __________________ .
Vasodilation
222
# **Mass Transport in Animals (AO1)**
Capillary walls are only one cell [1], which allows the short [2] pathway.
[1] thick
[2] diffusion
223
# **Mass Transport in Animals (AO1)**
The capillary wall is **permeable OR impermeable**
permeable
224
# **Mass Transport in Animals (AO1)**
Capillaries contain [1] which allow small biological molecules e.g. [2], to leave the blood vessel to be delivered to cells.
[1] fenestrations
[2] glucose / amino acids
225
# **Mass Transport in Animals (AO1)**
Capillaries have a [1] lumen which reduces flow rate giving more time for [2].
[1] narrow
[2] diffusion
226
# **Mass Transport in Animals (AO1)**
Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.
**1.** Permeable capillary wall / membrane;
**2.** One cell thick, reduces diffusion distance;
**3.** Fenestrations, allows large molecules through;
**4.** Small diameter / narrow, gives a short diffusion distance;
**5.** Narrow lumen, reduces flow rate giving more time for diffusion;
**6.** Red blood cells in contact with wall / pass singly, gives short diffusion distance;
227
# **Mass Transport in Animals (AO1)**
Veins have [1] at intervals throughout to ensure no [2] of blood due to the low pressure.
[1] valves
[2] backflow
228
# **Mass Transport in Animals (AO1)**
Veins have wide [1] which provides reduced [2].
[1] lumen
[2] friction
229
# **Mass Transport in Animals (AO1)**
Explain how blood in the vein of a leg is returned to the heart (*4 marks*).
**1.** Muscles surrounding veins contract and press on walls of vein and squeezes blood along veins;
**2.** Valves prevent backflow
**3.** Wide lumen little resistance / friction
**4.** Low pressure in heart muscle after contraction;
**5.** Draws blood from veins into atria;
230
# **Mass Transport in Animals (AO1)**
130 bpm
231
# **Mass Transport in Animals (AO2)**
**1.** Aorta pressure is directly linked to ventricle pressure which is higher;
**2.** Aorta has elastic tissue;
**3.** So stretches and recoils;
232
# **Mass Transport in Animals (AO1)**
Describe how tissue fluid is formed
- High blood OR hydrostatic pressure;
- Forces water / fluid out;
*(which contains glucose and amino acids)*
- Large proteins remain in capillary;
233
# **Mass Transport in Animals (AO1)**
Describe how tissue fluid is returned to the circulatory system.
- Low water potential in capillary;
- Due to plasma proteins;
- Water enters capillary;
- By osmosis;
- Any fluid not returned is absorbed by lymphatic vessels;
234
# **Mass Transport in Animals (AO2)**
**Blood vessel:** vein;
**Explanation:** wide(r) lumen
OR thinner wall;
235
# **Mass Transport in Animals (AO1)**
Explain the role of the heart in the formation of tissue fluid (*2 marks*).
**1.** Contraction of ventricle(s) produces high blood OR hydrostatic pressure;
**2.** This forces water (and some dissolved substances e.g. glucose) out of capillaries;
236
# **Mass Transport in Animals (AO2)**
Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.
Suggest how a blockage in the lymphatic system could cause lymphoedema (*1 mark*).
Excess tissue fluid cannot be (re)absorbed / builds up
237
# **Mass Transport in Animals (AO2)**
**1.** (Overall) outward pressure of 3.2 kPa;
**2.** Forces small molecules out of capillary;
238
# **Mass Transport in Animals (AO1)**
The hydrostatic pressure falls from the arteriole end of the capillary to the venule end of the capillary.
Explain why (*1 mark*).
Loss of water / loss of fluid
(pushing against capillary lining).
239
# **Mass Transport in Animals (AO1)**
Endothelium
240
# **Mass Transport in Animals (AO1)**
Plasma
| Plasma = solution part of blood separate from red & white blood cells
241
# **Mass Transport in Animals (AO1)**
242
# **Mass Transport in Plants (AO1)**
Which plant tissue transports water and mineral ions up the stem into the leaves?
Xylem
243
# **Mass Transport in Plants (AO1)**
Describe the structures of the xylem
No cytoplasm and no organelles;
Long tubes with no end walls - forms a continuous tube;
Lignin cell walls;
Lateral pits in cell wall;
244
# **Mass Transport in Plants (AO1)**
Function of no cytoplasm and no organelles in xylem
No obstruction to flow of water
245
# **Mass Transport in Plants (AO1)**
Function of long tubes with no end walls in xylem
Allows continuous columns of water to form
246
# **Mass Transport in Plants (AO1)**
Function of lignin in xylem cell wall
Strengthens xylem;
Waterproofs xylem;
Prevents collapse of xylem under tension.
247
# **Mass Transport in Plants (AO1)**
Function of lateral pits in xylem cell wall
Allows lateral movement around blockages (in xylem)
248
# **Mass Transport in Plants (AO1)**
Explain how xylem tissue is adapted for its function (*4 marks*).
**1.** Long tubes with no end walls allow continuous columns of water to form;
**2.** No cytoplasm / no organelles to obstruct flow of water;
**3.** Lignin provides support / withstand tension / waterproofs the tissue;
**4.** Pits in walls allow lateral movement / get around blocked vessels;
249
# **Mass Transport in Plants (AO1)**
Theory that explains movement of water up the xylem
Cohesion tension
250
# **Mass Transport in Plants (AO1)**
Bond that enables 'cohesion' between water molecules
hydrogen
251
# **Mass Transport in Plants (AO1)**
What is tension?
A pulling force
252
# **Mass Transport in Plants (AO1)**
Describe the cohesion-tension theory of water transport in the xylem (*5 marks*).
**1.** **Water lost via stomata** due to **transpiration**
**2.** **Lowers water potential** of mesophyll / leaf cells;
**3.** **Water pulled up xylem** via tension (to replace water lost via transpiration);
**4.** Water molecules have **cohesion** so ‘stick’ together by **hydrogen bonds**;
**5.** Forming **continuous column of water** column;
**6.** **Adhesion** of water molecules to walls of xylem;
253
# **Mass Transport in Plants (AO1)**
Lignin is a polymer found in the walls of xylem vessels in plants. Lignin keeps the xylem vessel open as a continuous tube.
Explain the importance of the xylem being kept open as a continuous tube (*3 marks*).
**1.** Transpiration creates tension (in column)
OR Water moves from xylem (into cells) creates tension
**2.** Form continuous column of water
OR (So) no barrier to (water) movement;
**3.** Cohesion from hydrogen bonds between (all) water (molecules)
254
# **Mass Transport in Plants (AO2)**
1. Stomata open;
2. Transpiration highest around mid-day as middle of day warmer (higher temperature) / lighter (higher light intensity);
3. Increased tension on column of water as greatest water potential gradient;
(this leads to negative pressure in xylem);
255
# **Mass Transport in Plants (Maths)**
256
# **Mass Transport in Plants (AO2)**
**1.** Initial and final mass
(of beaker and all contents);
Accept change in mass/weight
**2.** Number of (groups of) xylem vessels;
257
# **Mass Transport in Plants (AO2)**
**1.** Water is transpired (from leaves / stalk / celery / plant);
**2.** Water potential gradient/lower water potential creates tension / pulls up water
**3.** Hydrogen bonds / cohesion maintains column of water;
258
# **Mass Transport in Plants (AO2)**
Short diffusion pathway (to cells)
OR
It has a surface permeable (to water/ions into cells);
259
# **Mass Transport in Plants (AO1)**
Use your knowledge of leaf structure to explain why less water is lost through the upper surface of leaves than is lost through the lower surface (*2 marks*).
**1.** more stomata on the lower surface;
**2.** (thicker) waxy cuticle on the upper surface;
260
# **Mass Transport in Plants (AO1)**
Factors that affect transpiration
Temperature
Light intensity
Wind speed
Humidity
261
# **Mass Transport in Plants (AO1)**
Explain how increasing light intensity affects the rate of transpiration
1. More stomata open
2. Faster rate of transpiration;
262
# **Mass Transport in Plants (AO1)**
Explain how increasing temperature affects the rate of transpiration
1. Increases kinetic energy;
2. Water molecules diffuse faster;
3. Faster rate of transpiration;
263
# **Mass Transport in Plants (AO1)**
Explain how decreasing humidity affects the rate of transpiration
1. Less water vapour in the atmosphere
2. Increases the water potential gradient between atmosphere and mesophyll / air spaces
3. Faster rate of transpiration;
264
# **Mass Transport in Plants (AO1)**
Explain how increasing humidity affects the rate of transpiration
1. More water vapour in the atmosphere
2. Decreases the water potential gradient between atmosphere and mesophyll / air spaces
3. Slower rate of transpiration;
265
# **Mass Transport in Plants (AO1)**
Explain how increasing wind speed affects the rate of transpiration
1. Moves water vapour away from leaf
2. Increases the water potential gradient between atmosphere and mesophyll / air spaces
3. Faster rate of transpiration;
266
# **Mass Transport in Plants (AO2)**
Suggest an explanation for the difference in transpiration rate between conditions A and B (*2 marks*).
**1.** Removes water vapour;
**2.** Increases water potential gradient;
267
# **Mass Transport in Plants (AO2)**
Suggest an explanation for the difference in transpiration rate between conditions A and C (*2 marks*).
**1.** Increases kinetic energy so water molecules move faster;
**2.** Increases diffusion;
268
# **Mass Transport in Plants (AO2)**
Give one environmental factor that the student should have kept constant during this investigation.
Temperature /
Light intensity /
Wind speed /
Humidity
269
# **Mass Transport in Plants (AO2)**
The student cut the shoot and put it into the potometer under water. Explain why.
Prevent air entering the continuous water column;
270
# **Mass Transport in Plants (AO2)**
The student wanted to calculate the rate of water uptake by the shoot in cm^3 per minute. What measurements did she need to make?
1. Distance and time;
2. Radius / diameter / area
(of capillary tube);
271
# **Mass Transport in Plants (AO2)**
The student assumed that water uptake was equivalent to the rate of transpiration.
Give two reasons why this might not be a valid assumption.
1. Water used in photosynthesis
2. Apparatus not sealed / ’leaks’;
3. Water used to provide turgidity / support;
272
# **Mass Transport in Plants (AO2)**
The student measured the rate of water uptake three times.
Suggest how the reservoir allows repeat measurements to be made (*1 mark*).
Returns bubble (to start);
273
# **Mass Transport in Plants (Maths)**
The air bubble moved 7.5 mm in 15 minutes along the capillary tube in a potometer.
The diameter of the capillary tube was 1.0 mm.
Calculate the rate of water uptake by the shoot in this experiment.
Give your answer in mm^3 per hour.
The area of a circle is found using the formula, area = πr^2.
π x 0.5^2 x 7.5 = 5.89 mm^3 in 15 minutes
π x 0.5^2 x 7.5 = **23.56 mm^3 per hour**
274
# **Mass Transport in Plants (AO1)**
Which plant tissue transports sucrose and other organic molecules up AND down the stem to shoot tips and roots?
phloem
275
# **Mass Transport in Plants (AO1)**
Name the two specialised cells that make up the phloem
companion cells
sieve tube elements
276
# **Mass Transport in Plants (AO1)**
What is translocation?
The movement of organic molecules (e.g. sucrose) from sources such as leaf cells to sinks such as root hair cells.
277
# **Mass Transport in Plants (AO1)**
What hypothesis explains translocation in plants?
Mass flow hypothesis
278
# **Mass Transport in Plants (AO1)**
Describe the structure of the sieve tube elements.
No nucleus;
Few organelles;
Very little cytoplasm;
Connected to each other through sieve plates;
279
# **Mass Transport in Plants (AO1)**
Companion cells contain large numbers of which organelle.
Mitochondria
280
# **Mass Transport in Plants (AO1)**
Describe the transport of carbohydrates in plants (*5 marks*).
**1.** Sucrose is **actively transported** into the sieve tubes;
**2.** **by companion cells**;
**3.** This **lowers water potential** in sieve tubes and **water enters by osmosis** from xylem;
**4.** This produces **higher hydrostatic pressure** inside the sieve tubes at the source end of the phloem;
**5.** **Mass flow to respiring cells**; or storage tissue
**6.** Sucrose is moved into the sinks e.g. root tips or shoot tips by **active transport or facilitated diffusion**.
281
# **Mass Transport in Plants (AO1)**
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube (*3 marks*).
**1.** Sucrose actively transported
(into phloem by companion cells);
**2.** Lowering water potential;
**3.** Water moves into phloem by osmosis (from xylem);
282
# **Mass Transport in Plants (AO1)**
Use the below diagram to suggest and explain one other way in which sieve cells are adapted for mass transport.
**1.** No / few organelles / very little cytoplasm
**2.** (So) easier / more flow
OR
**3.** Thick walls
**4.** Resist pressure.
283
# **Mass Transport in Plants (AO1)**
Using the below diagram to suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.
**1.** Mitochondria release energy / produce ATP / site of aerobic respiration;
**2.** For active transport
OR
**3.** Ribosomes / rough endoplasmic reticulum produce(s) proteins;
**4.** (Proteins) linked to transport e.g. carrier proteins.
284
# **Mass Transport in Plants (AO1)**
What is 'ringing'?
Removal of outer layer of bark that includes the phloem but leaves the xylem in tact.
285
# **Mass Transport in Plants (AO1)**
Draw a diagram that shows the result of ringing.
286
# **Mass Transport in Plants (AO1)**
After a ringing experiment, why does a bulge appear above where the phloem has been removed?
Bulge has a higher concentration of sugars than the fluid from below the ring;
This is because the sugars can’t move past the area where the bark has been removed;
This is evidence that there can be a downward flow of sugars (via mass flow)
287
# **Mass Transport in Plants (AO1)**
What molecule is radioactively labelled to test the mass flow hypothesis?
Carbon dioxide
288
# **Mass Transport in Plants (AO1)**
Describe how radioactively labelled carbon dioxide is used to test the mass flow hypothesis (*3 marks*)?
Leaf supplied with radioactive carbon dioxide;
Via photosynthesis, leaf converts carbon dioxide into the glucose, then sucrose;
Radioactivity enables tracing of organic molecules throughout the plant;
Autoradiography detects radiation;
289
# **Mass Transport in Plants (AO2)**
Leaf-chewers and insects that feed on xylem sap are active feeders; this means they use their jaw muscles to obtain their food.
In contrast, insects that feed on phloem sap are passive feeders; this means they do not use their jaw muscles to take up sap from phloem.
Explain why phloem feeders can take up sap without using their jaw muscles.
**1.** Active transport of sucrose into phloem via companion cells;
**2.** Lowers water potential and water enters by osmosis;
**3.** Contents of phloem vessel pushed into insect’s mouth by high pressure;
290
# **Mass Transport in Plants (AO2)**
PCMBS is a substance that inhibits the uptake of sucrose by plant cells.
Scientists investigated the effect of PCMBS on the rate of translocation in sugar beet. The figure below shows their results.
During their experiment, the scientists ensured that the rate of photosynthesis of their plants remained constant.
Explain why this was important.
**1.** Rate of photosynthesis related to rate of sucrose production;
**2.** Rate of translocation higher when sucrose concentration is higher.
291
# **Mass Transport in Plants (AO2)**
PCMBS is a substance that inhibits the uptake of sucrose by plant cells.
Scientists investigated the effect of PCMBS on the rate of translocation in sugar beet. The figure below shows their results.
The scientists concluded that some translocation must occur in the spaces in the cell walls.
Explain how the information in the figure above supports this conclusion.
**1.** Rate of translocation does not fall to zero / translocation still occurs after 120 minutes;
**2.** But sucrose no longer able to enter cytoplasm of phloem cells.
292
# **Mass Transport in Plants (AO1)**
Explain what structures in the phloem provide evidence 'against' the mass flow hypothesis
Seive plates (at the ends of seive tube elements)
Act as a 'barrier' to mass flow
