Exchange & Transport 3.3 Flashcards
Digestion and absorption (AO1)
During digestion, large biological molecules are ____________________ to smaller molecules that can be absorbed across cell membranes.
hydrolysed
Digestion and absorption (AO1)
Amylase hydrolyses which bonds?
Glycosidic bonds
(in starch)
Digestion and absorption (AO1)
Where is amylase produced in the body?
Salivary glands
Pancreas
Digestion and absorption (AO1)
Starch is hydrolysed into which disaccharide
Maltose
Digestion and absorption (AO1)
Where are disaccharidases (e.g. maltase) located?
Membrane-bound
(in the cell surface membrane of epithelial cells lining the ileum of the small intestine)
Digestion and absorption (AO1)
Describe the complete digestion of starch by a mammal (4 marks).
1. Hydrolysis;
2. (Of) glycosidic bonds;
3. (Starch) to maltose by amylase;
4. (Maltose) to glucose by disaccharidase/maltase;
5. Membrane-bound (disaccharidase/maltase);
Digestion and absorption (AO1)
What is the name of the process by which glucose and amino acids are absorbed into the blood via the ileum of the small intestine?
Co-transport
Digestion and absorption (AO1)
Epithelial cells lining the ileum of mammals absorb glucose by co-transport with sodium ions. Explain how (3 marks).
1. Sodium ions actively transported from ileum cell into blood;
2. Forms concentration/diffusion gradient for sodium to enter cells from small intestine
(Sodium and glucose bind to co-transporter at different binding sites)
3. Glucose enters cell by facilitated diffusion along with sodium ions (co-transport);
4. Glucose then leaves epithelial cell and moves into blood via faciliated diffusion
Digestion and absorption (AO1)
TRUE or FALSE
Active transport requires ATP
**TRUE **
Digestion and absorption (AO1)
Describe and explain two features you would expect to find in a cell specialised for absorption (2 marks).
- Folded membrane/microvilli so large surface area (for absorption);
- Large number of co-transport/carrier/channel proteins so fast rate (of absorption)
- Large number of mitochondria so make (more) ATP (by aerobic respiration)
- Membrane-bound (digestive) enzymes so maintains concentration gradient (for fast absorption);
Digestion and absorption (AO1)
- (ATP to ADP + Pi ) releases energy;
- (energy) allows ions to be moved against a concentration gradient
OR
(energy) allows active transport of ions / Na+;
Digestion and absorption (AO1)
Endopeptidases hydrolyse _____________ peptide bonds within the polypeptide chain.
internal
Digestion and absorption (AO1)
Exopeptidases hydrolyse the peptide bonds at the ________________ ends of the polypeptide chain.
terminal
Digestion and absorption (AO1)
Describe the role of enzymes in the digestion of proteins in a mammal (4 marks).
- Hydrolysis of peptide bonds;
- Endopeptidase act in the middle of protein/polypeptide
OR Endopeptidase produces short(er) polypeptides/ increase number of ends;
- Exopeptidases act at terminal end of protein/polypeptide
OR Exopeptidase produces dipeptides/amino acids;
- Dipeptidase acts on dipeptide/between two amino acids
OR Dipeptidase produces (single) amino acids;
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)
Digestion and absorption (AO1)
The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how (2 marks).
- Exopeptidases hydrolyse peptide bonds at the terminal ends of a polypeptide/protein AND endopeptidases hydrolyse internal peptide bonds within a polypeptide/protein;
- (This produces) more ‘ends’ OR more surface area (for further hydrolysis);
Digestion and absorption (AO1)
Describe the mechanism for the absorption of amino acids in the ileum (4 marks).
- Sodium ions actively transported from cell to blood
Accept ‘pumped’ for transported - Creating sodium ion concentration/diffusion gradient;
- Co-transport;
- Facilitated diffusion of amino acid
- Facilitated diffusion of amino acid into blood;
Note: these are the same steps as those involved in glucose absorption
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(s);
Digestion and absorption (AO2)
- No/less ATP produced OR No active transport;
- Sodium (ions) not moved (into/out of cell);
- No diffusion/concentration gradient for sodium (to move into cell with amino acid)
Digestion and absorption (AO1)
Bile contains bile salts, which ____________ fat droplets
emulsify
Digestion and absorption (AO1)
Describe two functions of bile salts.
1. Emulsify lipids/fats;
2. Increases surface area (of lipid/fat) for
increased/faster lipase activity;
3. Form micelles
Digestion and absorption (AO1)
Emulsification increases the _____________ of the lipids for faster action of lipase enzymes.
surface area
Digestion and absorption (AO1)
Lipases hydrolyse triglycerides into ____________
Glycerol &
(3) fatty acids
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;
(during condensation reaction)
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 cell/lining (of the iluem)
OR
Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
3. Fatty acids absorbed by diffusion;
4. Triglycerides (re)formed (in cells);
Accept chylomicrons form (in the Golgi apparatus)
5. Vesicles move to cell membrane;
Accept exocytosis for ‘vesicles move’
Digestion and absorption (AO1)
Explain the advantages of lipid droplets following emulsification.
- Droplets increase surface areas (for lipase / enzyme action);
- (So) faster hydrolysis / digestion (of triglycerides / lipids);
Digestion and absorption (AO1)
Explain the advantage of micelle formation.
Micelles bring fatty acids and glycerol to membrane / to (intestinal epithelial) cell;
Digestion and absorption (AO1)
Describe the role of micelles in the absorption of fats into the cells lining the ileum (3 marks).
- Micelles include bile salts and fatty acids;
- Make the fatty acids (more) soluble in water;
- Bringfatty acids to cell/lining (of the ileum);
- Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
- Fatty acids (absorbed) by diffusion;
Digestion and absorption (AO1)
What is the process by which fatty acids and glycerol enter the intestinal epithelial cell.
Diffusion
Surface area to volume ratio (AO1)
As an organism gets ____________, the smaller the surface area : volume ratio.
larger
Surface area to volume ratio (AO1)
The smaller the organism, the ____________ surface area : volume ratio.
larger
Surface area to volume ratio (AO1)
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake (2 marks).
1. Large(r) organisms have a small(er) surface area : volume (ratio);
OR
Small(er) organisms have a large(r) surface area:volume (ratio);
2. Provide a shorter diffusion pathway
OR
Faster diffusion;
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. Large(r) cells have small(er) surface area to volume ratio;
2. Diffusion distance/pathway is long(er);
OR
(Takes) longer for oxygen to diffuse (to mitochondria)
OR
Less/no oxygen diffuses (to mitochondria)
Surface area to volume ratio (AO1)
What adaptations to cells or specialised exchange surfaces enable a FASTER rate of diffusion?
- Large surface area
- Large concentration gradient
- Short diffusion distance
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)
Surface area to volume ratio (AO1)
How do smaller organisms compensate for heat loss?
increased metabolic activity
e.g. respiration
Surface area to volume ratio (AO1)
What is a by-product of increased respiration that allows smaller organisms to maintain an optimal body temperature?
heat
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 larger surface area to volume ratio;
2. Faster heat loss (per gram/in relation to body size);
3. Faster rate of respiration/metabolism releases heat;
Surface area to volume ratio (Maths)
Complete Table 1. State your calculated volume and surface area : volume ratio to 2 significant figures.
Gas Exchange (AO1)
How does oxygen enter a single-celled organism e.g. amoeba?
Simple diffusion
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;
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;
Gas Exchange (AO2)
Name the process by which oxygen reaches the cells inside the body of a tubifex worm shown below.
Simple diffusion
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
Gas Exchange (AO1)
Name of insect gas exchange system
the tracheal system
Gas Exchange (AO1)
Location of gas exchange in the tracheal system
tracheoles
Supply oxygen direct to tissues
Gas Exchange (AO1)
Name the structure through which gases enter and leave the body of an insect.
spiracles
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
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
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;
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
(spiracles open);
Maintains concentration gradient of carbon dioxide and oxygen;
Gas Exchange (AO1)
Insects must balance minimising ___________ loss with efficient gas exchange.
water
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
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)
OR Tracheoles enter cells so short diffusion distance;
5. Tracheole walls are permeable to oxygen/air;
Gas Exchange (AO1)
F = Filament
G = Lamella(e)
Gas Exchange (AO1)
Gills have many finger-like projections called gill ____________.
filaments
Gas Exchange (AO1)
Each gill filament has many _____________
lamellae
(singular lamella)
Gas Exchange (AO1)
Lamellae contain ____________ and are the site of gas exchange.
capillaries
Gas Exchange (AO1)
The capillaries bring ___________ blood to the lamellae.
deoxygenated
Gas Exchange (AO1)
Site of gas exchange in fish gills
lamellae
(singular lamella)
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)
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;
Gas Exchange (AO1)
Draw and label a cross section of leaf tissue
Gas Exchange (AO1)
Why is the concentration of carbox dioxide low in the palisade mesophyll cell?
Used in photosynthesis
Gas Exchange (AO1)
Through which structures does carbon dioxide enter the leaf.
stomata
(Singular stoma)
Gas Exchange (AO1)
What cells open and close the stomata?
guard cells
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;
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)
Gas Exchange (AO1)
TRUE or FALSE:
Water is lost from the leaf via the stomata due to transpiration
TRUE
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;
Gas Exchange (AO1)
Group of plants adapted to live in dry conditions
Xerophytes
Gas Exchange (AO1)
List the adaptations of xerophytes to dry conditions
Small leaves
Spines
Rolled leaves
Stomata in pits
Hairs
Thick waxy cuticle
Gas Exchange (AO1)
How does a small leaf reduce water loss in xerophytes?
Smaller surface area so reduced number of stomata
Gas Exchange (AO1)
How does a thick waxy cuticle reduce water loss in xerophytes?
Increased diffusion distance so reduces transpiration
Gas Exchange (AO1)
How do spines reduce water loss in xerophytes?
Reduces the surface area : volume ratio
Gas Exchange (AO1)
What features of a xerophyte reduce the water potential gradient by trapping water vapour?
Hairs;
Stomata in pits;
Rolled leaves;
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.
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;
Gas Exchange (AO1)
Describe the gross structure of the human gas exchange system (2 marks)
1. Named structures: trachea, bronchi, bronchioles, alveoli;
2. Above structures named in correct order
Gas Exchange (AO1)
Site of gas exchange in human lungs
Alveolar epithelieum
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;
Gas Exchange (AO1)
What adaptation of the lungs provides a large surface area for rapid gas exchange?
Many alveoli
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
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;
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
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;
Gas Exchange (AO1)
Ventilation is a result of the difference in ______________ between the lungs and the air outside the body.
pressure
Gas Exchange (AO1)
Which muscles contract during inhalation (i.e. breathing in).
Diaphragm
External intercostal muscles
Gas Exchange (AO1)
Which muscle contracts during exhalation (i.e. breathing out).
Internal intercostal muscle
Gas Exchange (AO1)
Which muscles relax during exhalation (i.e. breathing out).
Diaphragm
External intercostal muscle
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)
Gas Exchange (AO1)
Describe the mechanism of breathing that causes air to exit the lungs (3 marks).
1. Diaphragm AND external intercostal muscles relax
2. Internal intercostal muscles contract
3. Causes volume decrease AND pressure increase in thoracic cavity;
(now above atmospheric pressure)
Gas Exchange (AO1)
Interaction between internal and external intercostal muscles
Antagonistic
One contracts, the other relaxes
Gas Exchange (Maths)
Pulmonary ventilation rate =
(include units)
Gas Exchange (Maths)
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;
Gas Exchange (AO2)
What is a risk factor?
Environmental and genetic factors that can increase/ decrease the risk of developing a disease
Gas Exchange (AO2)
Correlation does not mean _____________
causation
Gas Exchange (AO2)
Risk factors for lung disease
Smoking
Air pollution
Risk alleles / genes
Infections
Occupation
Gas Exchange (AO3)
Draw out a linear relationship
Look for a straight line / constant gradient
Gas Exchange (AO3)
Linear or non-linear:
Non linear
Gas Exchange (AO3)
Linear or non-linear:
There is a proportional Y increase as X increases
Linear
Gas Exchange (AO3)
When to use a t test?
When comparing the differences between two means (e.g. control vs. treatment group)
Gas Exchange (AO3)
Name of statistical test used to assess the strength of relationship between two continuous variables.
Correlation coefficient
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