Topic 3-organisms exchange substances with their environment Flashcards
why do multicellular organisms require specialised exchange surfaces
Longer diffusion pathway as there is lower SA:V
What are some features that make an efficient exchange surface?
large surface area and thin to ensure a short diffusion pathway (e.g. a leaf), good blood supply or ventilation for a steep gradient for exchange
how many pairs of gills does a bony fish have?
4 pairs
Describe the structure of a fish gas exchange system
4 pairs of gills, each is supported by an arch with gill filaments (long strands), which have lamallae on them. Blood and water (from ext. environment) flow across the lamallae in countercurrent directions (opposite directions). this allows gas exchange between the blood and water, creating a steep concentration gradient. the filaments are held apart by water, so in the absence of water they stick together and fish cant survive without oxygen.
Explain how the counter current mechanism in fish gills ensures the
maximum amount of the oxygen passes into the blood flowing through the
gills (3)
- Water and blood flow in opposite directions
- Blood is always passing the water
which has a higher oxygen concentration - Diffusion gradient is maintained throughout length of gill
Describe and explain the advantage of the counter-current principle in gas
exchange across a fish gill. (3)
- Water and blood flow in opposite directions.
- Maintains diffusion concentrations of oxygen throughout length of gill
3.
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange (2)
- There is a large surface area because of the many filaments
- Thin surface so there is a short diffusion pathway
How does ventilation work in fish
The fish opens its mouth, lowering the floor of the buccal cavity, water flows in. The fish closes its mouth, bucal cavity floor raises, pressure is increased, water is forced over the gill filaments.
What does the operculum do in fish
acts as a valve and pump, lets water out and pumps it in.
Describe ventilation in terrestrial insects
Oxygen is transported directly into tissues undergoing respiration, tracheoles supply tissues with oxygen they have spiracles which are the openings. Gases move in and out through mass muscle contraction and volume change in the tracheoles.
Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange. (3)
- Trachioles have thin walls and are highly branched so short diffusion distance to cells
- Highly branched tracheoles means there is large surface area for gas exchange
- Trachioles provide tubes full of air so fast diffusion into insect tissues.
How do you calculate surface area?
SA (㎠)= H x L x no.sides
What is the benefit of having a large number of stomata in a leaf?
All cells are a short distance to the stomata
Use your knowledge of gas exchange in leaves to explain why plants
grown in soil with very little water grow only slowly.
Stomata close (1), less carbon dioxide for photosynthesis production (2)
what prevents friction between the lungs and the ribs?
a lubricating fluid is produced
Describe a feature of the airways which provides structural support
C shaped cartilage rings hold the trachea and bronchi open providing strutural support, but are incomplete to allow passage of food behind the trachea in the oesphoegus
What is the cartilage that makes the C shapes rings composed of?
Loose tissue including glandular and connective tissue, blood vessels, elastic fibres and smooth muscle
what is the inner lining of the trachea and bronchi composed of?
ciliated epithelium and goblet cells
why are the alveoli an efficient gas exchange surface?
only one cell thick, surrounded by capillaries which are also one cell thick so there is a short diffusion pathway. Constant blood supply from capillaries maintains steep concentration gradient
why is cartilage an important feature of the lungs?
Prevents lungs collapsing when pressure drops
what are ciliated epithelium and why do we have them
present in all airways, helps to move mucus towards the throat where it can be swallowed
what is the role of smooth muscle in mammalian gas exchange system
can contract to constrict the airways when necessary controlling the diameter thus controlling flow of air to and from alveoli
what are 2 parts of ventilation
Inspiration and expiration
INSPIRATION
what are the internal and external intercostal muscles doing
External contract, internal relax.
Describe inspiration
Diaphragm contracts and flattens. Intercostal muscles cause volume of lungs to increase
Ribs raise upwards
Lowering the pressure.
Pressure is higher externally, there is a steep concentration gradient and air is forced into the lungs, down the pressure gradient
EXPIRATION
what are internal and external intercostal muscles doing
External relax, internal contract. (the first letter of the name of the process is the same as the first letter of the muscles that are relaxing).
Describe expiration
Rib cage is lowered. Diaphragm relaxes and raises upwards. Volume in the lungs is decreased, pressure is increased, air is forced out of the lungs.
what does a spirometer measure?
Lung volume
what is vital capacity
Max capacity of air that can be inhaled or exhaled in a single breath.
What are the internal intercostal muscles doing during inspiration?
relaxing
what are external intercostal muscles doing during expiration?
relaxing
what are internal intercostal muscles doing during expiration?
contracting
what are external intercostal muscles doing during inspiration?
contracting
what is the residual volume in the lungs
volume of air which is always present
what do goblet cells do
present in all airways, involved in mucus secretion to trap bacteria and dust
Describe and explain one feature of the alveolar epithelium that makes the
epithelium well adapted as a surface for gas exchange. Do not refer to
surface area or moisture in your answer. (2)
Single layer of cells (1) reduces diffusion distance (2)
Describe and explain one feature of the alveolar epithelium that makes the
epithelium well adapted as a surface for gas exchange. Do not refer to
surface area or moisture in your answer. (2)
Permeable (1) allows diffusion of oxygen and carbon dioxide (2)
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)
Less carbon dioxide exhaled (1) So reduced concentration gradient between blood and alveoli (2) so slower movement of carbon dioxide out of blood (3)
Describe and explain the mechanism that causes lungs to fill with air (3)
Diaphragm contracts and external intercostal muscles contract, causes volume to increase and pressure to decrease, air moves into the lungs down the pressure gradient
Two solutions often used to stain tissues are haematoxylin solution and
iodine solution.
* Haematoxylin solution stains DNA a blue colour.
* Iodine solution stains starch a blue-black colour.
The scientist used haematoxylin solution and not iodine solution to stainthe lung tissue. Suggest why. (2)
The lung tissue doesnt contain starch (1), haematoylin makes the nucleus visible
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)
Reduced surface area (1) increased distance for diffusion (2), reduced gas exchange (3)
Describe the pathway taken by an oxygen molecule from an alveolus to the blood. (2)
Diffuses across alveolar epithelium (1) into epithelium of capillary (2)
Explain how one feature of an alveolus allows efficient gas exchange to
occur (2)
Alveolar epithelium is one cell thick (1) creating a short diffusion pathway (2).
Describe the gross structure of the human gas exchange system and how
we breathe in and out. (6)
- Trachea branches into bronchus then bronchioles with alveoli next to blood capillary. (2, correct names+order)
- During inspiration, external intercostal muscles contract, diaphragm flattens and contracts (1) volume increases, pressure decreases, air moves into lungs down pressure gradient. During expiration diaphragm relaxes, external intercostal muscles relax, volume decreases and pressure increases, air moves out of lungs down pressure gradient.
Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange.
Tracheoles have thin walls so short diffusion distance to cells (1)
Trachea provide tubes full of air so fast diffusion (2)
Fluid in end of tracheoles moves out to tissues during exercise so larger surface area for gas exchange (3)
What is the definition of digestion?
Hydrolysis of large biomolecules into smaller molecules that can be absorbed across cell membranes
What enzyme breaks down carbohydrate polymers in the mouth?
amylase
What enzyme breaks down monosaccharides in the ileum?
maltases
what enzymes break down lipids?
lipases
how do lipases break down lipids?
hydrolysing the ester bond between the monogylcerides and fatty acid
where are products of digestion absorbed?
Cells lining the ileum (last part of small intestine), these are called epithelial cells
what is the epithelium?
lining of ileum (last part of small intestine)
what does amylase do?
Catalyses polysaccharides like starch into maltose
how does amylase catalyse starch into maltose?
hydrolyses the glycosidic bonds in a starch polymer
where is amylase produced?
salivary glands and pancreas
what enzymes break down disaccharides e.g. glucose
Membrane bound disaccharidases break down disaccharides into monosaccharides
Name 3 membrane-bound disaccharidases
Maltase, sucrase, lactase
why is amylase not a disaccharidase?
it breaks down starch which is a polysaccharide
what does lactase enzyme convert lactose into?
glucose+galactose
what does maltase convert maltose into?
glucose+glucose
what does amylase convert starch into?
maltose
what does sucrase convert sucrose into?
glucose+fructose
what are the two categories of enzymes that break down carbohydrates?
membrane bound disaccharidases and amylases
Where in the body do sucrose and lactose get hydrolysed into maltose by membrane bound disaccharidases?
In the duodenum
where does protein digestion start?
in the stomach
what are the two processes of lipid digestion?
chemical-lipase
physical-bile salts
where is lipase produced and secreted into
pancreas, secreted into duodenum and ileum
how are lipids digested by lipase?
ester bond is hydrolysed in the triglyceride:
triglyceride–> monoglyceride+fatty acid
in lipid digestion, what happens before lipase action?
bile salts emulsify lipids to form many small droplets called micelles which provide a larger surface area to enable faster hydrolysis action by lipase
where are bile salts produced
liver
what are lipids coated in (which forms an emulsion?)
bile salts
Describe the processes involved in the absorption and transport of
digested lipid molecules from the ileum into lymph vessels (5)
- Micelles contain bile salts, monoglycerides and fatty acids
- Brings fatty acids and monogyclerides to cells lining the ileum
- Fatty acids and monogylcerides are absorbed by diffusion
- Triglycerides are reformed in cells
- Vesicles move to cell membrane
what are micelles? (contains 4 things)
vesicle containing bile salts, monogylcerides, glycerol and fatty acids
Describe the role of micelles in the absorption of fats into the cells lining
the ileum (3)
- Micelles include bile salts and fatty acids
- This makes the fatty acids more soluble in water
- Brings fatty acids to the lining of the ileum, maintains higher conc. of fatty acids to the lining of the ileum
- Fatty acids are absorbed by diffusion
Describe the role of enzymes in the digestion of proteins in a mammal (4)
- Endopeptidases hydrolyse peptide bonds between amino acids in the middle of a polypeptide
- Exopeptidases hydrolyse peptide bonds between amino acids at the end of a polypeptide
- Depiptidases act between two amino acids
By which process do fatty acids and glycerol enter the intestinal epithelial cell?
Diffusion
Explain the advantages of lipid droplet and micelle formation (3)
- Droplets increase surface area for lipase action
- So faster hydrolysis of triglycerides
- Micelles carry fatty acids and glycerol through membrane to intestinal epithelial cell
How is the golgi apparatus involved in the absorption of lipids? (3)
- Modifies triglycerides
- Combines triglycerides with proteins
- Forms vesicle for release
Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how (3)
- Sodium ions actively transported from ileum cell to blood
- Maintains diffusion gradient for sodium to enter from small intestine
- Glucose enters by facilitated diffusion with sodium ions
is haemoglobin water soluble?
yes
what type of molecule is haemoglobin?
a globular protein
describe the structure of haemoglobin
2 beta polypeptide chains and 2 alpha helices, each chain/helix has a haeme group and iron
how does haemoglobin carry oxygen in the blood?
Oxygen binds to each haem group, so each haemoglobin molecule contains 4 oxygen molecules
what does the affinity of oxygen for haemoglobin mean?
How easily haemoglobin binds to oxygen, in an area with a high oxygen concentration, (e.g. lungs) affinity for oxygen will be higher and the haemoglobin will attract more oxygen
what does partial pressure of oxygen mean?
the concentration of oxygen, the greater the dissolved concentration of oxygen in a cell, the higher the partial pressure. so the capillary next to the alveoli will have a high partial pressure of oxygen.
describe the relationship between partial pressure of oxygen and the affinity of oxygen for haemoglobin
As partial pressure increases, the affinity of oxygen for haemoglobin also increases (oxygen will bind to the haemoglobin tightly)
What is ‘loading’ in the lungs?
loading is when the partial pressure of oxygen is high and the affinity of oyxgen for haemoglobin is high so the oxygen binds to the haemoglobin
What happens to haemoglobin during respiration?
During respiration oxygen is used up, so partial pressure of respiring cells decreases, decreasing the affinity of oxygen for haemoglobin. As a result, haemoglobin unloads the oxygen into the respiring cell. After unloading, the haemoglobin returns to the lungs.
Binding of one molecule of oxygen to haemoglobin makes it easier for a
second oxygen molecule to bind.
Explain why (2)
Binding of first oxygen changes tertiary structure of haemoglobin, uncovering another haem group for the second oxygen to bind to. (increase in saturation=increase in affinity)
what do dissassociation curves illustrate?
the change in haemoglobin as partial pressure changes
what causes the steep increase in dissasociation curves?
Initially, the curve is shallow because it is hard for the first oxygen to bind, then when the tertiary stucture of the haemoglobin changes and more haem groups are uncovered, affinity increases causing a steep increase in saturation
what causes dissasociation curves to flatten out?
once 3 oxygens have binded to the haemoglobin the likelihood of a fourth oxygen finding a binding site is low
how does foetal haemoglobin differ from adult haemoglobin?
has a higher affinity for oxygen as the partial pressure is lower because the blood has to reach the placenta
What is the bohr effect?
In the presence of carbon dioxide, the affinity of haemoglobin for oxygen decreases, causing the oxygen to be released
give 2 factors that can affect the affinity of oxygen to haemoglobin?
partial pressure of oxygen
partial pressure of carbon dioxide
