chapter 2 Flashcards
movement of substances
what are biological membranes
membrane found in living cells
examples of biological membranes
- plasma membrane
- cell membranes
function of plasma membrane
- separates the contents of the cell from their external environment
- ensures the maintenance of constant internal environment within the cell
function of cell membranes
form separate compartments for specific metabolic processes
components of membrane
- lipids
- proteins
- carbohydrates
type of lipid
phospholipids
what is hydrophilic
substances that are attracted to water
(soluble in water)
what is hydrophobic
substances that are not attracted to water
(insolube in water)
what do phospholipids consists of
- hydrophilic phosphate head
- 2 hydrophobic hydrocarbon phosphate tail
what is amphipathic
substances that is part hydrophilic part hydrophobic
what happens when phospholipid molecules are surrounded on all sides by water
become arranged in a bilayer
what forms the core of a membrane
the hydrophobic hydrocarbon chains/tails of the phospholipids
what are the 2 major populations of membrane proteins
- integral protein
- peripheral protein
what is concentration gradient
difference in concentration between 2 regions
what is diffusion
net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient until equilibrium is reached
2 types of transport
- passive
- active
types of passive transport
- simple diffusion
- facilitated diffusion
- osmosis
what is passive transport
- passive process which take place as mloecules move randomly
- no energy input provided by hydrolysis of ATP is required
factors affecting the rate of diffusion
- concentration gradient
- diffusion distance
- temperature
- surface area-to-volume ratio
steeper concentration gradient
faster the rate of diffusion
what is diffusion distance
the time taken for a substance to move from one point to another depending on the distance between 2 points
larger the diffusion distance
the slower the rate of diffusion
(more distance needed to travel)
higher temperature
faster the rate of diffusion
what is surface area-to-volume ratio
the rate of movement of a substance across a plasma membrane depending on how large the cell membrane is
the greater the surface area-to-volume ratio of the cell
the higher the rate at which substances move in and out
how to calculate surface area
- length x breadth x2
- breadth x height x2
- length x height x2
- 2(lb) + 2(bh) +2(lh)
how is simple diffusion important to living organsims
- oxygen and carbon dioxide move into and out of cells through a process called gas exchange.
- Nutrients such as dissolved amino acids and glucose are absorbed by diffusion into the blood capillaries in the small intestine
what is facilitated diffusion
the movement of particles from a region of higher concentration to a region of lower concentrataion down a concentration gradient with the help of specific channel proteins
(special form of diffusion)
what types of particles require facilitated diffusion
charged particles
why cant the charged particles go through the plasma membrane through simple diffusion
they are repelled by the hydrophobic region of the membrane and thus, diffuse across the membrane extremely slowly (not enough to fulfill the needs of the cell)
types of charged particles
- chloride ions
- potassium ions
- amino acids
- sugars
- fatty acids
- glycerol
2 types of transport proteins
- channel protein
- carrier protein
what does the channel proteins have that allows charged particles to diffuse across the plasma membrane easily
have interior which is hydrophilic so water-soluble materials can pass through
difference between simple diffusion and facilitated diffusion
(simple diffusion)
- occurs directly across the plasma membrane
- substances to be transported are hydrophobic and uncharged
difference between simple diffusion and facilitated diffusion
(facilitated diffusion)
- transport proteins embedded in the plasma membrane are needed to carry particles of substances
- substances are charged and hydrophilic
what is osmosis
net movement of particles from a region of higher water potential to a region of lower water potential down a concentration gradient through a partially/selectively permeable membrane
what does solute concentration affect
water potential as solutes form weak hydrogen bonds with water molecules
what affects the rate of osmosis
- water potential gradient
- distance over which water molecules need to move
- temperature
- surface area-to-volume ratio
what is water potential
the measure of tendency of water molecules to move from a region of higher water potential to a region of lower water potential
higher water potential
lower solute concentration
greater the distance water molecules need to move
slower rate of osmosis
higher the temperature
faster rate of osmosis
larger the surface area-to-volume ratio
faster rate of osmosis
what is hypertonic solution
lower water potential
what is hypotonic solution
higher water potential
what happens to animal cell when put in hypotonic solution
- water enters the cell by osmosis
- will expand and burst/lysed
what happens to plant cell when put in hypotonic solution
- water enters the cell into the vacuole by osmosis
- cell swells and becomes turgid
what happens to animal cell when put in hypertonic solution
- water exits the cell by osmosis
- shriveled and crenated
what happens to plant cell when put in hypertonic solution
- water leaves the cell out of the vacuole by osmosis
- plasma membrane of the cell starts to pull away from the cell wall, leaving a visible gap (plasmolysis)
- plasmolysed and flaccid
how does the cell wall prevent the plant cell from bursting
- it is strong and relatively inelastic
- prevents over expansion of the cell by exerting an opposing pressure as water enters the cell
what is the pressure exerted by the water in the vacuole
turgor pressure
when is the cell fully turgid
cell wall is stretched to the maximum so that the cell cannot take in anymore water by osmosis
what is importance of turgor in plants
maintaining the shape of soft tissues in plants
example of how the movement of certain plant parts are due to change in turgor
changes in the turgor of the guard cells cause the opening the closing of the stomata
why is it not advisable to add too much fertiliser around the roots of plants
- soil solution will become very concentrated and water will move out of the root by osmosis
- the inability of the roots to absorb water, together with continued evaporation of water from the leaves, cause plant to wilt
what happens to cell when put in isotonic solution
no net movement of water molecules in or out of cell
what is active transport
net movement of particles from a region of lower concentration to a region of higher concentration against a concentration gradient
what is required in active transport
- energy from ATP
- carrier protein in the plasma membrane
how does active transport work
living cells are able to absorb certain substances even though these substances are of higher conentration in the cell compared to external environment
why is energy needed for active transport
breakdown ATP to ADP (hydrolysis)
where does active transport occur
living cells
