CELL TRANSPORT MECHANISMS Flashcards
What substances are excreted from the cell surface membranes? (2)
-ammonia
-urea (animals)
what substances are secreted from the cell surface membrane? (3)
-neurotransmitter substances
-hormones
-enzymes
what are the types of protein molecules involved in facilitated diffusion? (2)
-carrier proteins
-protein channels
what is the lipid bilayer permeable to? (2)
-non - polar substances (including steroids and glycerol)
-oxygen and carbon dioxide in solution
what substances are always moving across the cell membrane? (4)
-water
-respiratory gases (O2 and CO2)
-nutrients (glucose and essential ions)
-excretory products
how is ATP converted back down to ADP? (2)
when ATP reacts with water (a hydrolysis reaction) and is converted back to ADP and Pi (e.g muscle contraction).
what nutrients pass across the cell surface membrane? (4)
-sugars
-amino acids
-fatty acids
-vitamins
what is diffusion? (1)
the free passage of molecules (atoms and ions) from a region of their high concentration to a region of low concentration until they are evenly distributed.
what concentration of ATP is usually present within cell? (1)
0.5 - 2.5 mgcm(-3)
what are the important features of ATP? (3)
-move easily within cells, by facilitated diffusion
-take part in many steps in cellular respiration and in very many reactions of the metabolism
-transfer energy in relatively small amounts, sufficient to drive individual reactions.
what is ATP formed from? (1)
formed from ADP and a phosphate ion by transfer of energy from other reactions.
what does ADP stand for? (1)
adenosine diphosphate
what substances pass through the cell surface membrane in respiration? (2)
in: oxygen
out: carbon dioxide
what free energy is available in ATP? (1)
30 - 34 KJ mol(-1)
what does ATP stand for? (1)
adenosine triphosphate
what are peripheral proteins? (1)
proteins present in the cell surface membrane that are superficially attached to the lipid bilayer.
what molecules is ATP? (2)
ATP is a soluble organic molecule. it carries three phosphate groups linked together in a linear sequence.
what is energy transferred to within the cytoplasm of a cell? (1)
ATP
who proposed the fluid mosaic model? (2)
S. J Singer and G. L Nicolson
what are integral proteins? (1)
proteins present in the cell surface membrane that are partially or totally buried within the lipid bilayer.
what molecules does facilitated diffusion transport? (2)
-carbohydrates
-amino acids
what molecules does exocytosis transport? (2)
-enzymes
-hormones
what molecules does simple diffusion transport? (3)
-oxygen
-carbon dioxide
-hydrophobic molecules
what molecules does active transport, transport? (1)
ions e.g sodium
what does the lipid bilayer contain? (7)
-glycoproteins
-glycolipids
-channel proteins
-integral proteins
-peripheral proteins
-phospholipids
-cholesterol
how do molecules travel across the membrane in osmosis? (1)
between phospholipids (aquaporins)
how do molecules travel across the membrane in simple diffusion? (1)
between the phospholipid bilayer
how do molecules travel across the membrane in phagocytosis? (1)
through vesicles
which cell transport mechanisms require energy? (4)
-active transport
-phagocytosis
-pinocytosis
-exocytosis
how do molecules travel across the cell membrane in active transport? (1)
through carrier proteins
what direction do molecules move in osmosis? (1)
down a concentration gradient
what direction do molecules move in facilitated diffusion? (1)
down a concentration gradient
how do molecules travel across the membrane in facilitated diffusion? (1)
through carrier and channel proteins.
how do molecules travel across the membrane in exocytosis? (1)
through vesicles
how do molecules travel across the membrane in pinocytosis? (1)
through vesicles
what are carrier proteins? (1)
have a binding site for a specific chemical, when binded it causes the tertiary structure of the protein to change.
what direction do molecules move in active transport? (1)
against a concentration gradient.
what direction do molecules move in simple diffusion? (1)
down a concentration gradient.
what direction do molecules move in exocytosis? (1)
either direction.
what direction do molecules move in pinocytosis (endocytosis)? (1)
either direction.
when does diffusion occur? (2)
-the cell surface membrane is fully permeable to the solute
-the pores in the membrane are large enough for a solute to pass through
what is facilitated diffusion? (1)
the process of spontaneous passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins.
what is kinetic energy? (1)
the energy possessed by a particle because it is in continuous motion.
what direction do molecules move in phagocytosis (endocytosis)? (1)
either direction
what is osmosis? (1)
the net movement of water molecules (solvent) from a region of high concentration of water molecules to a region of lower concentration of water molecules across a partially permeable membrane.
what are protein channels? (1)
a protein with a central pore which is lined with hydrophilic amino acids and contains water.
what ions pass across the cell surface membrane? (4)
-sodium
-potassium
-calcium
-trace elements (iron and copper)
what are ligand - gated ion channels? (1)
carrier proteins channels that are sensitive to chemical signals.
what is meant by active transport being highly selective? (2)
for example in the situation where potassium ions and chlorine ions are available, potassium ions are more likely to be absorbed. this ensure that the needs of the cell are met and that unwanted are excluded.
what is active transport? (1)
the movement of substances across a cell surface membrane against a concentration gradient, using energy in the form of ATP.
what does active transport involve? (3)
involve carrier proteins, movement by these carrier proteins require reaction with ATP. most of the proteins are specific to particular ions and molecules. if the carrier for a particular substance is not present, the substance will not be transported.
what are gated ion channels? (1)
ion channels in the carrier proteins have controlled opening and closing.
what are voltage-gated ion channels? (1)
carrier proteins which are controlled by small potential differences.
what is endocytosis? (1)
movement of materials into cells.
what are vesicles? (1)
membrane bound cell organelles containing liquid or solid particles.
what is exocytosis? (1)
movement of material out of the cell.
what is cytosis? (1)
the bulk transport of materials across cell membranes contained in vesicles.
how does the size of aa particle effect how it can be transported? (2)
-very large molecules are too big through carrier channels or between the molecules of the membrane itself (bulk transport is the only way)
-smaller particles are transported faster than larger molecules.
what are macrophages? (1)
large white blood cells that are able to engulf cell debris and foreign particles by the process of phagocytosis
what is the principle of bulk transport? (1)
is one way in which very large molecules, which are not able to be moved in other ways can be transported into the cell.
what is pinocytosis? (1)
movement of materials in liquid form in and out of cells.
what is phagocytosis? (1)
this occurs when cells (phagocytes) use their membranes to surround external particles to form vesicles within their own cytoplasm.
how are larger polar molecules transported? (1)
facilitated diffusion using specialised carrier proteins.
how does the charge present effect how it can be transported? (2)
-structure of cell surface membrane makes it hard for charged particles to pass through )electrostatic attraction or repulsion will prevent free movements)
-most ions and charged particles pass through by specialised protein channels.
what factors of a substance effects how it can be transported? (3)
-the size of the particle
-the solubility of the particle
-the charge present
how are small non-polar molecules transported? (1)
direct diffusion
how does the solubility of a particle effect how it can be transported? (2)
almost all transport takes place in solution (particles with limited solubility will be transported slowly)
-when substances dissolve they dissociate into charged ions (makes them smaller and ions are more mobile)
what are some examples of small polar molecules? (1)
H2O
How are small polar molecules transported? (1)
facilitated diffusion through special protein channels (aquaporins) and sometimes directly through the phospholipid bilayer by osmosis.
How are small charged atoms transported? (1)
active transport using carrier proteins; passive movements can occur through protein channels when the concentration gradient is favourable.
How are lipid-soluble molecules transported? (1)
direct diffusion
How are large polar molecules transported? (1)
move in and out of mitochondria by facilitated diffusion.
what are some examples of lipid-soluble molecules? (3)
-glycerol
-fatty acids
-steroids; vitamins A, D and E
what are some examples of small non-polar molecules? (3)
O2, CO2 and N2
what are some examples of large polar molecules? (1)
glucose
what are some examples of large polar molecules? (2)
ATP and ADP
what are some examples of small charged atoms? (1)
ions
