2B Flashcards
What do membranes do
control what passes through them,
what are the properties of plasma membranes
they are flexible and are able to break and fuse easily
allows cellular compartments to have different conditions
made up of phospholipids
what is a phospholipid made up of
1 glycerol
2 fatty acids
+ phosphate group
what is the structure of a phospholipid bilayer
fluid-mosaic model
why is the structure of a plans membrane called a fluid-mosaic model
fluid- phospholipids move freely and randomly side ways
mosaic- the proteins are distributed throughout the bilayer in a mosaic pattern
model- The agreed structure based upon experimental and chemical evidence.
what is the head of a phospholipid described as
hydrophilic- attracts water
what is the tail of a phospholipid described as
hydrophobic- repels water
how do the phospholipids arrange themselves
automatically orange themselves into a bilayer- the heads face out towards the water on either side of the membrane, the centre of the bilayer is hydrophobic so the membrane doesn’t allow water-soluble substances through it- it acts as a barrier to these dissolved substances.
what is cholesterol
a type of lipid, present in all cell membranes
what substances can diffuse straight through the bilayer
Fat soluble, non polar molecules
what substances cannot diffuse straight through the bilayer
water- soluble, polar molecules- require proteins
what is the function of a hydrophilic head
attracts water and polar molecules
what is the function of a hydrophobic tail
attracts lipid soluble/hydrophobic molecules, or barrier to polar molecules
what is the function of glycolipids
maintain the stability of the cell, to facilitate cellular recognition
what is the function of glycoproteins
receptor/antigen/recognition
what is the function of carbohydrate chain
receptor/antigen/recognition
what is the function of cholesterol
regulates membrane fluidity/ assists impermeability
what is the function of peripheral protein
Acts as a receptor or to bind carbohydrates
what is the function of carrier/channel protein
osmosis/ active transport/ diffusion.
explain why phospholipids form a bilayer in plasma membranes
-phospholipids have a polar phosphate group which are hydrophilic and will face the aqueous solution.
-The fatty acid tails are non-polar and will move away from an aqueous environment
-As both tissue fluid and cytoplasm is aqueous phospholipids form two layers with the hydrophobic tails facing inward and phosphate groups outwards interacting with the aqueous environment.
what are the 5 main roles of membranes within cells
-Control substances moving in and out of cells through diffusion, osmosis and active transport
-allow cellular compartments to have different conditions
-have large surface area for reactions
-May hold electron carriers (mitochondria)
May hold enzymes (chloroplasts)
function of the phospholipid bilayer
Forms impermeable barrier
allows cell to maintain different concentrations of either cells
what is diffusion
The net movement of molecules from a region of high concentration to a region of lower concentration, down a concentration gradient.
what does a passive process mean
no energy is needed to make the molecules move, they have natural kinetic energy
what happens as a result of diffusion
equilibrium, where all molecules are evenly spread out. No net movement of molecules from one place to another
What are the factors effecting rate off diffusion
The steepness of the concentration gradient- The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.
Distance- The shorter the route, the faster the rate of diffusion
The surface area- the greater the surface area the faster the diffusion can take place. This is because there molecules or ions fan cross the membrane
what is the equation for the rate of diffusion
rate of diffusion is proportional to=
surface area x difference in conc
__________________________________
Length of diffusion path
what is facilitated diffusion and give an example
Large polar molecules (e.g glucose), water soluble molecules , and charged molecules, require proteins to pass through the bilayer
what is osmosis
the diffusion of water molecules across a partially permeable membrane, from an area of high water potential to an area of low water potential.
what is water potential
the potential of water molecules to diffuse out of or into sodium
what has the highest water potential
pure water
what is isotonic
if two solutions have the same water potential
what are the factors that effect the rate of osmosis
the water potential gradient-the higher the water potential gradient, the faster the rate of osmosis. As osmosis takes place, the difference in water potential on either sides of the membrane decreases, so the rate of osmosis levels off over time
The thickness of the exchange surface-n the thinner the exchange surface, the faster the rate of osmosis
the surface area of the exchange surface- the larger the surface area, the faster the rate of osmosis.
what is active transport
using ATP to move molecules and ions across membranes, usually against a concentration gradient
what type of proteins are involved in active transport
carrier proteins
explain the process of the use of carrier proteins in active transport
a molecule attaches to the carrier protein, the protein changes shape and this moves the molecule across the membrane, releasing it on the other side.
what are the two main differences between active transport and diffusion
active transport usually moves solutes from a low two high concentration whereas in facilitated diffusion, they always move from a high to low concentration
active transport requires energy whereas facilitated diffusion does not.
what is ATP
common source of energy in the cell. produced by respiration
what sort of reaction does ATP undergo and why
hydrolysis reaction, splitting it into ADP and Pi(inorganic phosphate). This releases energy so that the solutes can be transported.
what are co-transporters and what do they do
type of carrier proteins
- they bind two molecules at a time
- the concentration gradient of one of the molecules is used to move other molecules against its own concentration gradient
what are the factors affecting the rate of active transport
the speed of individual carrier proteins- the faster they work, the faster the rate of active transport.
the number of carrier proteins present- the more proteins there are, the faster the rate of active transport
The rate of respiration in the cell and the availability of ATP. If respiration is inhibited, active transport cannot take place.
why can fat soluble, non polar molecules diffuse through the plasma memrane
what are the five different ways substances can diffuse through a membrane
(Simple) diffusion of small/non-polar molecules down a concentration gradient;
Facilitated diffusion down a concentration gradient via protein carrier/channel;
Active transport against a concentration gradient via protein carrier using ATP;
Co-transport of 2 different substances using a carrier protein;
examples of non polar, lipid soluble uncharged molecules
oxygen and C02
why can non polar, lipid soluble molecules diffuse through the bilayer
The lipid soluble, non polar molecules can diffuse easily through cell membranes because they are small, so they can pass through spaces between the phospholipids. Being Non polar makes Tham soluble in lipids, so they can dissolve in the hydrophobic bilayer.
what is facilitated diffusion
larger, polar molecules need channel proteins or carrier proteins in the membrane to help them diffuse through the bilayer at a fast rate.
moves particles down a concentration gradient., from higher to lower
how do carrier proteins transport molecules across the membrane
move large molecules, down the concentration gradient with facilitated or against the concentration gradient with active transport, requires ATP
The solute binds to the carrier protein, the protein changes shape, and releases the solute on the other side.
How do channel proteins transport molecules across the membrane
Forms an aqueous pore across the membrane. They allow specific charged solutes to pass through. This is a rapid movement. Passive process, no energy required.
what type of organism is an amoeba and adaptation of its size
unicellular organism
-high surface area to volume ratio
-use the cell membrane as a gas exchange surface
-diffusion can occur through the membrane as this is moist, permeable and the path of diffusion is short
what are larger organism in terms of SA
-The surface area to volume ratio is much smaller
-external SA is not large enough for diffusion of oxygen through it to take place rapidly enough to supply cells with the oxygen it needs
what is the name of insects blood
haemolymph
what does haemolymph
haemolymph flows freely through the blood cavity and make direct contact with organisms and tissue.
doe the circulation system of an insect cred blood cells and why /why not
no, the circulatory system does not carry oxygen, so the blood does not contain red blood cells as ours does.
what is the colour of haemolymph
green/yellow
how is an amoeba adapted to reduce water loss
-rigid outer skeleton 9permeable to gases) covered with a waterproof cuticle.
-relatively small surface area- reduces loss
-network of trachea (internal tubes) to bring oxygen to their cells
what is the function of the spiracle to reduce water loss
water can evaporate from the insect when the spicules are open. Most of the time they are kept closed apart from when gas exchange happens.
what is the main function of the insects gas exchange system
to bring oxygen to the respiring tissues by the tracheoles.
describe what a graph of concentration of gases in the insect against oxygen and co2 would look like
as the spiracle opens the conc of oxygen inside the insect increases and the conc of carbon dioxide decreases. After closure the concentration of oxygen decreases back to original state and the concentration of carbon dioxide increases back to its original state.
how does the respiratory system of a insect work
-oxygen enters through the spiracles
-spiracles close (maintain steep concentration gradient between the tracheoles and the muscle tissue)
-oxygen moves through the trachea into the tracheoles (by simple diffusion.
-oxygen gets delivered directly to the respiring tissues (for respiration)
how do respiring gases move in and out of the tracheal system
-down a diffusion gradient
-ventilation- movement of muscles creates mass movement of air in and out of the trachea.
what is the function of the trachea fluid
gaseous exchange happens between the fluid and air. When the demand for oxygen increases, the tracheal fluid can be withdrawn into the muscle tissue to increase the surface area of wall exposed to air, and exchange of gases occur nearer the cells
what is the limitations of system in insects
-relies on diffusions
-for diffusion can be effective the pathway must be short.
-This limits the size of the insects.
explain how the structure of the gas exchange system of an insect ensures that there is a large surface area for gas exchange
tracheoles branch off, larger surface area to volume ration, so more gas exchange can happen.
describe one way in which the transport of oxygen to a muscle in an insect is different to that of a fish
blood is involved in transporting oxygen in fish, whereas it is not in insects.
what is an advantage of an insect opening its spiracles at a lower frequency in very dry conditions suggest one advantage of this
to reduce water loss
explain the pumping water in system in fish
1 buccal floor lowered in mouth
2 volume of buccal cavity increases
3pressure inside the buccal cavity decreases
4water enters the mouth
explain how water is pumped out o the fish
1 buccal floor is raised
2 volume of buccal cavity decreases
3 pressure inside the buccal c cavity increases
4 water leave the mouth
explain the structure of the gills
-the gills are made of numerous thin filaments supported by a bony arch
-each filament is made of a thin delicate plate (lamellae), containing many capillaries, so they look dark red.
what is a lamellae
thin delicate plates found on the filaments
explain how fish use haemoglobin
helps to carry oxygen away from the gills and maintain a high concentration gradient.
how much oxygen can a fish extract from the available oxygen
80%
why can fish extract up to 80% of available oxygen
1) very large surface area for gaseous exchange
2)A short diffusion distance across the gaseous exchange system
3) A high concentration gradient between the blood in the gills and the water passing over them
4) a moist gas exchange surface
explain how a high concentration gradient benefits the fish
helps the counter current exchange in fish, the blood and the water flow over the gill lamella in opposite directions
explain how there is a short diffusion distance in fish.
gill plates (lamellae) exceedingly delicate and very thin so that the blood flowing through them is only a short distance from the water.
what is the counter current system
in boy fish, the blood and the water flow over rthe gill lamella in opposite directions, helps to maintain a diffusion gradient across the whole fish.
how is heat exchange specialised in fish
blood from the core body warms cooler blood returning from the gills.
why in cartilaginous fish is there much less efficient gas exchange
blood and water move in the same direction by co-transport exchange and only about 50% of oxygen is absorbed.
how do plants respire
aerobically so require oxygen to produce carbon dioxide
how is the structure of a leaf specialised
the surface of the mesophyll cells are in contact with air spaces in the leaf
