2A Cell Membranes Flashcards
When does passive transport take place?
When there is a connection, pressure or electrochemical gradient, and no energy from the fell is involved
Active transport
- involves moving substances across cell membranes using adenosine triphosphate which is produced during cellular respiration
- it always involves carrier proteins
Give 2 examples of particles that diffuse across membranes by diffusion
- oxygen
- carbon dioxide
cell membrane
the selectively permeable membrane which surrounds the cytoplasm of a cell, acting as a barrier between the cell contents and their surroundings
phospholipids
chemicals in which glycerol bonds with two fatty acids and an inorganic phosphate group
hydrophilic
a substance with an affinity for water that will readily dissolve in or mix with water
polar lipids
lipids with one end attached to a polar group so that one end of the molecules is hydrophilic and one end is hydrophobic
hydrophobic
a substance that tends to repel water and that will not mix with or dissolve in water
monolayer
a single closely packed layer of atoms or molecules
micelles
a spherical aggregate of molecules in water with hydrophobic areas int eh middle and hydrophilic ares outside
endocytosis
the movement of large molecules into cells through vesicle formation (active transport)
- phagocytosis
- pinocytosis
exocytosis
the movement of large molecules out of cells by fusing of a vesicle containing the molecules with the surface cell membrane
the process requires ATP
osmotic concentration
a measure of the concentration of the solutes in a solution that have an osmotic effect
isotonic solution
a solution in which the osmotic concentration of the solutes is the same as that in the cells
hypotonic solution
a solution in which the osmotic concentration of solutes is lower than that in the cell contents
hypertonic solution
a solution in which the osmotic concentration of solutes is higher than that in the cell contents
turgor
the state of a plant cell when the solute potential causing water to be moved into the cell by osmosis is balanced by the force of the cell wall pressing on the protoplasm
hydrostatic pressure
the pressure exerted by a fluid in an equilibrium
incipient plasmolysis
the point at which so much water has moved out of the cell by osmosis that turgor is lost and the cell membrane begins to pull away form the cell wall as the protoplasm shrinks
plasmolysis
the situation when a plant cell is placed in hypertonic solution when so much water leaves the cell by osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away form the cell walls
solute
a substance that can be dissolved in a solution by a solvent
carrier protein
protein that moves a substance through the membrane in active transport using energy from the breakdown of ATP or in facilitated diffusion down a conc. gradient
phagocytosis (cell eating)
the active process when a cell engulfs something relatively large such as a bacterium and encloses it in a vesicle
pinocytosis (cell drinking)
the active process by which cells take in tiny amounts of extracellular fluid by tiny vesicles
why do larger organisms need specialised exchange systems?
- smaller surface area to volume ratio
- higher metabolic rate
- very active
- control own body temperature
- higher amount of waste products
where in animals, fish, insects and plants does gas exchange take place?
animals - lungs
fish - gills
insects - tracheal system
plants - leaves
