3.3 Exchange With The Environment Flashcards
How do you calculate the perimeter of a square?
4 x side length
How do you calculate the perimeter of a rectangle?
2 x (length + width)
How do you calculate the circumference of a circle?
2 x pi x radius
How do you calculate the area of a square?
side^2
How do you calculate the area of a rectangle?
Length x width
How do you calculate the area of a circle?
Pi x radius squared
How do you calculate the surface area of a cube?
6 x side squared
How do you calculate the surface area of a sphere?
4 x pi x radius squared
How do you calculate the surface area of a cylinder?
2(pi x radius squared) + 2 x pi x radius x height
How do you calculate the volume of a cube?
Side^3
How do you calculate the volume of a rectangular prism?
Side 1 x side 2 x side 3
How do you calculate the area of a sphere?
(4/3) x pi x radius ^3
How do you calculate the volume of a cylinder?
Pi x r^2 x height
how can single celled organisms provide their nutrients?
they can use diffusion and diffusion alone as the diffusion pathway is short
how do multicellular organisms provide all of their cells with the nutrients they need?
they require transport systems and specialised exchange surfaces
why do organisms with a high metabolic rate need an increased diffusion rate?
they exchange more nutrients
as size increases, what happens to the SA:V ratio?
it decreases
what is exchange like in small organisms?
large SA:V ratio, exchange directly with the environment
what is exchange like in large organisms?
smaller SA:V ratio, specialist exchange surfaces to meet the organisms demands, mass transport system to deliver and remove material
describe how single celled organisms are adapted for gas exchange (3 marks)
they have a large surface area to volume ratio so there is more space for the gas to diffuse across, they are only one cell thick therefore there is a short diffusion pathway to allow for quicker gas exchange, only have a cell surface membrane, no cell wall, so no additional barrier to diffusion
why can insects not use their body for gas exchange?
this would result in water loss, increasing their surface area for gas exchange conflicts with water conservation, they need to balance the needs to exchange gases with the need to conserve water as they are terrestrial they have mechanisms to conserve water
how do insects limit water loss?
have exoskeletons/shells to stop water loss (rigid exoskeleton made of chitin, waterproof cuticle), small SA:V ratio minimises water loss area, spiracles open and close to limit water loss
what are the limitations of the tracheal system in insects?
relies on diffusion rather than a transport system, diffusion distance must be short, limits the size that insects can grow to
are fish adapted to exchange materials via their surface?
no, relatively large so small SA:V ratio, waterproof, gas tight outer coating, surrounded by water, less dissolved gas, specialised internal gas exchange surface/system via the gills
how are the gills adapted for gas exchange?
large surface area provided by gill lamellae on the gill filaments at right angles, rich blood supply, counter current flow, blood passes opposite way to water
how does counter current flow optimise gas exchange at the gills?
the flow of water over the gill lamellae and the flow of blood within them are in opposite directions, maintains a favourable concentration gradient across the whole gill, the blood is always next to water with higher level of oxygen, blood already loaded with O2 meets water which has maximum concentration of oxygen, therefore oxygen diffuses into the blood, blood with low O2 concentration meets water that has had most of its O2 removed so diffusion still happens. 80% of the available O2 is absorbed compared to 50% in parallel flow
How do insects use the tracheal system to exchange gases?
They have microscopic air filled pipes called tracheae which they use for gas exchange, air moves into the tracheae through pores on the surface called spiracles, oxygen travels down the concentration gradient toward the cells, the tracheae branch off into smaller tracheoles which have thin, permeable walls and go to individual cells meaning oxygen diffuses directly into the respiring cells, the insects circulatory system doesn’t transport O2. Carbon dioxide from the cells moves down its concentration gradient towards the spiracles to be released into the atmosphere, they ie rhythmic abdominal movements to move air in and out of the spiracles,
Why are the end of the tracheoles filled with water?
anaerobic respiration produces lactate, lactate is water soluble so lowers WP of muscle cells, water moves into muscle cells from tracheoles, volume in tracheole ends decreases, drawing air in
how do spiracles open and close?
by a valve
what are dicotyledonous plants?
flowering plants, the seed bears two cotyledons (seed leaves)
what is the symbol equation for aerobic respiration?
6O2 + C6H12O6 -> 6CO2 + 6H2O + energy
what is the symbol equation for photosynthesis?
6CO2 + 6H2O -> C6H12O6 + 6O2
how is a large surface area beneficial for diffusion?
greater surface for diffusion to take place
how is being thin beneficial for diffusion?
one cell thick, short diffusion pathway
how is being selectively permeable beneficial for diffusion?
control what goes into and out of the cell
how is a steep diffusion gradient beneficial for diffusion?
increased rate of diffusion
what are the structures found in a leaf?
upper epidermis; cuticle, upper epidermis cells. upper mesophyll; palisade mesophyll cells. lower mesophyll; xylem. phloem, sheath, spongy mesophyll cells, sub-stomatal air space. lower epidermis; lower epidermis cells, guard cells, stoma
what sub cellular structures are found in a palisade cell?
ribosomes, Golgi apparatus, chloroplasts, mitochondria, cell membrane, vacuole, amyloplast, SER, nucleus, RER, cell wall
what is the function of the stomata?
small pores, allow gases in and out, all cells are close to the stomatal pore therefore there is a short diffusion pathway
what is the function of sub stomatal air spaces?
interconnected air spaces throughout the mesophyll layer so gases can move around mesophyll cells
what is the function of the spongy mesophyll layer?
large surface area of mesophyll cells allows for maximum diffusion
what is the transpiration stream?
transports water from the roots to the leaves, created as water is evaporated from the surface of the leaf
what are xerophytes?
plants adapted to living in areas with a short supply of water
why do xerophytes need a thick cuticle?
acts as a waterproof barrier
why do xerophytes need rolled up leaves?
stomata on lower epidermis protected/ trap still air, traps water vapour = high WP so no WP gradient
why do xerophytes need a sunken stomata?
traps still, moist air, lower water potential gradient
why do xerophytes need hairs on leaves?
traps still, moist air, lower WP gradient
why do xerophytes need non typical leaves to reduce SA:volume ratio?
slower rate of diffusion, still able to photosynthesise
what is the equation for aerobic respiration in humans?
oxygen + glucose -> carbon dioxide + water + ATP
what structures are found in the pulmonary system?
nasal cavity, rib cage, intercostal muscles, diaphragm, alveoli, lungs, trachea, bronchi, bronchioles
what are the features of the lungs?
lobed structures
what are the features of the trachea?
flexible airway supported by cartilage rings, muscular walls lined with ciliated epithelium and goblet cells
what are the features of the bronchi?
trachea splits into two bronchi, larger bronchi are supported by cartilage rings, lined with ciliated epithelium and goblet cells
what are the features of the bronchioles?
subdivisions of bronchi, muscular walls lined with epithelium cells, can constrict to control airflow
what are alveoli?
located at the end of bronchioles, site for gas exchange, between the alveoli there are some collagen and elastic fibres, they are lined with epithelium, the elastic fibres allow the alveoli stretch as they fill with air when breathing in, they then spring back when breathing out in order to expel carbon dioxide rich air, the alveolar membrane is a gas exchange surface
how is the diffusion gradient maintained at the alveoli?
surrounded by capillaries (good blood supply), and CO2 is exhaled and O2 inhaled constant supply of air and blood
how do the alveoli increase the surface area?
many alveoli (300million) and a large surface area to volume ratio
how are alveoli adapted for fast diffusion?
large surface area, only one cell thick, maintained concentration gradient due to have good blood supply by being surrounded by capillaries
what is meant by breathing?
the constant movement of air into and out of the lungs
what is meant by inspiration?
pressure outside the lungs is greater than inside so air moves in
what is meant by expiration?
pressure inside the lungs is greater than outside the lungs, air is forced out
how does the bell jar demonstrate inspiration and expiration?
when the rubber sheet moves down the volume increases therefore the pressure decreases- the pressure is greater outside the jar so air moves in
what type of process is inspiration?
an active process
what type of process is expiration?
a passive process
what is the process of inspiration?
external intercostal muscles contract, internal intercostal muscles relax, rib cage is pulled up and out, increases the volume of thorax, diaphragm muscles contract and diaphragm moves down, increases volume in thorax further and reduces pressure inside, atmospheric pressure is now greater than pulmonary pressure so air is forced into the lungs
what is the process of expiration?
external intercostal muscles relax, internal intercostal muscles contract, rib cage moves down and in, decreases the volume of the thorax, diaphragm muscles relax and diaphragm moves up, decreases volume of the thorax and increases pressure inside, atmospheric pressure now lower than pulmonary pressure so air forced out of the lungs
what is meant by tidal volume?
the volume of air inhaled and exhaled in a normal breath
what is meant by expiratory reserve volume?
volume of a maximum exhalation after normal exhalation
what is meant by inspiratory reserve volume?
additional volume that can be inhaled after inhalation of tidal volume
what is meant by residual volume?
volume remaining in the lung after maximum exhalation
what is meant by vital capacity?
maximum volume of exhalation after lungs are maximally filled
What is meant by pulmonary ventilation?
The total volume of air that is taken into the lungs in a given time (one minute)
How do you calculate pulmonary ventilation?
pulmonary ventilation (dm^3min^-1) = tidal volume (dm^3) x breathing rate
What is pulmonary fibrosis?
Scarring forms on the epithelium lining if the lungs, this causes the lining to thicken, reduces the amount of oxygen able to diffuse across the membrane into the blood, the volume of air entering the lungs decreases, reduces elasticity inhibits ventilation
What are the symptoms of pulmonary fibrosis?
Shortness of breath when exercising, chronic dry cough, pain and discomfort in the chest, weakness and fatigue
What is tuberculosis?
Formation of small, hard lumps called tubercles, stimulation of the white blood cells to fight, these result in scar tissue
What is the cause of tuberculosis?
Bacteria
What are the symptoms of tuberculosis?
Coughing up blood, wheezing cough, persistent cough, fatigue, loss of appetite, high temperature, chest pains, fever
What is asthma?
Larger quantities of mucus, allergens stimulate white blood cells found in the lining of the bronchi and bronchioles to release histamines causing inflammation, reduce ventilation
What causes asthma?
Localised allergic reaction including: pollen, animal fur, faeces of house dust mites
What are the symptoms of asthma?
Difficulty breathing, wheezing, tightness in chest, coughing
What is emphysema?
Loss of elasticity preventing expansion and contraction, elastin permanently stretched, can’t expel all the air from alveoli, surface area of alveoli reduced, some burst, little gas exchange occurs
What causes emphysema?
Smoking
What are the symptoms of emphysema?
Shortness of breath, chronic cough (attempt to remove damaged tissue), bluish skin
What are the components of the digestive system?
Salivary glands, tongue, oesophagus, liver, stomach, pancreas, gall bladder, transverse limb of the large intestine, ascending limb of the large intestine, small intestine (ileum), descending limb of the large intestine (colon), rectum, anus
What is the role of the oesophagus?
Carries food from the mouth to the stomach
What is the role of the stomach?
A muscular sac with an inner layer that produces enzymes, it’s role is to store and digest food, especially proteins, it has glands that produce enzymes which digest proteins
What is the role of the ileum?
A long, muscular tube, food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into it, the inner walls of the ileum are folded into villi which gives them a large surface area, the surface area of the villi is further increased by millions of tiny projections called microvilli on the epithelial cells of each villus, this adapts the ileum for its purpose of absorbing the products of digestion into the blood stream
What is the role of the large intestine?
Absorbs water, most of the water that is absorbed is water from the secretions of many digestive glands
What is the role of the rectum?
The final section of the intestines, the faeces are stored here before periodically being removed via the anus in a process called egestion
What is the role of the salivary glands?
Situated near the mouth, pass their secretions via a duct into the mouth, these secretions contain the enzyme amylase, which hydrolyses starch into maltose
What is the role of the pancreas?
A large gland situated below the stomach, produces a secretion called pancreatic juice containing protease to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch
What is the physical breakdown in digestion?
Large food is broken down into smaller pieces by structures such as the teeth, makes it possible to ingest food and provides large surface area for chemical digestion, food is churned by the muscles in the stomach wall to physically break it down
What is chemical digestion?
enzymes hydrolyse large, insoluble molecules into smaller, soluble ones, all digestive enzymes function by hydrolysis (the splitting up of molecules by adding water to the chemical bonds that hold them together)
What are the three types of enzymes that are particularly important?
Carbohydrates, lipases and proteases
What is involved in carbohydrate digestion?
Firstly the enzyme amylase is produced in the mouth and the pancreas, amylase hydrolyses the alternate glycosidic bonds of the starch molecule to produce the disaccharide maltose, the maltose is in turn hydrolysed into the monosaccharide alpha glucose by a second enzyme, a disaccharide called maltase, maltase is produced by the lining of the ileum
What is the function of sucrase?
Hydrolyses the single glycosidic bond in the sucrose molecule, this hydrolysis produces the two monosaccharides, glucose and fructose
What is the function of lactase?
Hydrolyses the single glycosidic bond in the lactose molecule, this hydrolysis produces the two monosaccharides glucose and galactose
What is the process of lipid digestion?
Hydrolysed by lipases produced in the pancreas, hydrolyse ester bonds to form fatty acids and monoglyceride, lipids are first broken down into micelles by bile salt produced by the liver, this process is called emulsification
What are bile salts?
One end is soluble in fat (lipophilic) but not in water (hydrophobic) the other side is insoluble in fat (lipophobic) but soluble I’m water (hydrophilic) fat is prevented from sticking back together
What is the process of protein digestion?
Peptidases (proteases) hydrolyse peptide bonds in proteins
What are endopeptidases?
Hydrolyse the peptide bonds in the central region of a protein, forming a series of peptide molecules
What are exopeptidases?
Hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases
What are dipeptidases?
Hydrolyse the bonds between the two amino acids of a dipeptide, they are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum
How is the ileum adapted for the absorption of the products of digestion?
Villi and microvilli increase the surface area, capillary next maintains concentration/diffusion gradient as good blood supply, muscle layer contracts which helps maintain concentration gradient (movements mix food), thin walls give a short diffusion pathway
What is the process of co transport in the ileum?
Na+ actively transported out of epithelial cell by Na/K+ pump into the blood, maintains higher concentration of Na+ in the lumen than inside the epithelial cells, Na+ diffuse into epithelium down concentration gradient, they carry with them amino acids or glucose, glucose/amino acids pass into the blood plasma by facilitated diffusion
How are triglycerides absorbed?
Monoglycerides and fatty acids are absorbed through the membrane of the ileum, monogylcerides and fatty acids are converted back to triglycerides in the endoplasmic reticulum, triglycerides are packaged into chylomicrons, chylomicrons move out of the epithelial cells by exocytosis, they enter lymphatic capillaries called lacteals that are found at the centre of each villus, from here the chylomicrons pass via lymphatic vessels into the blood stream, the triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of blood capillaries from where they diffuse into cells
What are chylomicrons?
Small milky globules (chylo=milky, micron=small) a small fat globule composed of protein (1-2%) and lipid, transport fat from the intestine to the liver and to adipose (fat) tissue
what happens when spiracles are closed?
oxygen levels fall because it is used in respiration
why do spiracles open?
open when CO2 concentration becomes too high
what factor is limited in insects due to them relying on diffusion/gas exchange?
size
are fish adapted to exchange substances via their surface? Explain your answer.
No, relatively large, small SA:V ratio, waterproof, gas tight outer coating, surrounded by water, less dissolved gas, salt water, they have a specialised internal gas exchange surface/system via the gills
How does the structure of the gills make them efficient for gas exchange?
gills are behind the head, water enters the mouth and is forced over the gills then out through an opening on each side of the body, made of gill filaments, gill filaments are stacked on top of each other, gill filaments are covered in lamella which are at right angles to the filaments, rich blood supply
what is counter current flow?
the flow of water over the gill lamellae and the flow of blood within them are in opposite directions
why is counter current flow important?
the blood is always next to water with a higher level of oxygen, blood already loaded with O2 meets water which has maximum concentration of oxygen, therefore oxygen diffuses into the blood, blood with low O2 conc meets water that has already had most of its O2 removed, diffusion still happens
what does the counter current flow system result in?
the maintenance of a favourable O2 gradient across the whole gill, this allows max O2 diffusion, 80% of available O2 absorbed compared to 50% with parallel flow
what does the graph for countercurrent flow look like?
what does the graph for parallel flow look like?
describe the graph for parallel flow
water enters that contains lots of O2, diffusion occurs along the lamella, oxygen reaches equillibrium, diffusion only occurs halfway across the lamella, only 50% of available O2 diffuses into the blood
what is the tracheal system?
insects have an internal network of tubes called tracheae, supported by rings to prevent collapse
