Plasma Membrane Transport (2.4) Flashcards
State the 2 major bulk transport mechanisms
- Endocytosis
2. Exocytosis
Describe the type of substance transported across the cell membrane via osmosis
Water
Describe the type of substances transported across the plasma membrane via simple diffusion
Hydrophobic molecules
Provide 3 examples of substances transported across the plasma membrane via simple diffusion
- Water
- Oxygen
- Carbon dioxide
Describe the type of substances transported across the plasma membrane via facilitated diffusion
Hydrophilic molecules
Provide 4 examples of substances transported across the plasma membrane via facilitated diffusion
- Glucose
- Amino acids
- Sodium ions
- Potassium ions
Describe concave plasmolysis
Contraction of the protoplasm and plasma membrane -> results in pocket formation
Points of attachment between cell wall and protoplasm remain
Outline solution reversibility of concave plasmolysis
Hypotonic solutions
Describe flaccidity
Loss of turgor due to the lack of net water movement between the plant cell and environment
State solution type associated with flaccidity
Isotonic solution
State cell type associated with flaccidity
Plant cells
Describe protoplasm
Fluid lining the contents of a cell
including cytoplasm and cell membrane
Describe cytolysis
Bursting of cell due to influx of water
State solution type associated with cytolysis
Hypotonic solution
State cell type associated with cytolysis
Animal cells
Describe plasmolysis
Shrinking of the protoplasm away from the cell wall
State solution type associated with plasmolysis
Hypertonic solution
State cell type associated with plasmolysis
Plant cells
Describe turgidity
State of being turgid (especially due to high fluid content)
State solution type associated with turgidity
Hypotonic solution
State cell type associated with turgidity
Plant cells
Describe hydrostatic (or turgor) pressure
Pressure exerted by fluid against the plant cell wall
Describe ‘particle size’ as a factor affecting the rate of diffusion
The smaller the particles, the faster the rate of diffusion through a membrane
Describe ‘temperature’ as a factor affecting the rate of diffusion
The higher the temperature, the higher the rate of diffusion
State the 3 main factors which affect the rate of diffusion across the plasma membrane
- Concentration
- Temperature
- Particle size
Describe ‘concentration’ as a factor affecting the rate of diffusion
The greater the concentration gradient the faster the rate of diffusion
Name the process by which proteins change shape to bind to specific molecules which cross the plasma membrane
Conformation
carrier proteins
Describe the process used by carrier proteins to transport molecules across the cell membrane
Process: Conformation
Protein changes shape to allow specific molecules to bind and cross membrane
Protein is restored to original shape once molecule crosses
Describe the structure of channel proteins which allows for the transport of molecules across the cell membrane
Specific for substance (don’t bind)
Function like pores which open/close
Describe channel proteins
A type of protein found on the plasma membrane that is involved in facilitated diffusion
Describe carrier proteins
A type of protein found on the plasma membrane that is involved in facilitated diffusion and active transport
State the 2 major membrane transport proteins employed in facilitated diffusion
- Channel proteins
- Carrier proteins
Describe crenation
Cell shrinks due to efflux of water
State solution type associated with crenation
Hypertonic solution
State cell type associated with crenation
Animal cells
Outline the effect of turgor pressure on cell water uptake
Prevents further water uptake in plant cells
Describe convex plasmolysis
Plasmolysed cell becomes a spherical protoplast which completely detaches from the cell wall
State 2 types of plasmolysis in plant cells
- Concave
- Convex
Outline solution reversibility of convex plasmolysis
Irreversible
State the major membrane transport protein employed in active transport processes
Carrier proteins
Outline what active transport allows a cell to do
Enables cells to maintain internal concentrations of small solutes which differ from concentrations in its’ environment
Describe active transport
Movement of a molecule across the cell membrane with the expenditure of energy
Describe passive transport
Movement of a molecule across the cell membrane without the expenditure of energy
Describe endosmosis
Net water influx
Describe the osmotic gradient
Difference in concentration between solutions on either side of a semi-permeable membrane
Describe osmolarity
Concentration of a solution expressed as the total number of solute particles per litre
State the major type of molecule that can diffuse across the plasma membrane via simple or facilitated processes
Small polar molecules
very slowly throughout simply diffusion
State the 2 major types of molecules that cross the plasma membrane via facilitated diffusion
- Small ions
2. Large, polar, water-soluble molecules
State the permeability of small, uncharged molecules across the plasma membrane
Permeable
State 2 examples of large, polar, water-soluble molecules
- Amino acids
2. Glucose
Describe hypertonic solution
Solution with a higher concentration of solute
low concentration of free water molecules
Describe hypotonic solution
Solution with the lower concentration of solute
high concentration of free water molecules
Describe isotonic solution
Solutions being compared have equal concentrations of the solutes
Diffusion occurs because of the…?
Concentration gradient
State the transport classification of simple diffusion
Passive
State the transport type of facilitated diffusion
Passive
State 2 types of molecules that cross the plasma membrane via simple diffusion
- small, uncharged molecules
2. lipid-soluble, non-polar molecules
Define osmosis
Movement of free water molecules through a semipermeable membrane from a region of higher free water concentration to a lower free water concentration
Describe the polarity of the water molecule
Electrons are not shared equally between the O and H molecules
There is greater concentration of electrons at the O end making O (negatively charged) and H (positively charged)
State the permeability of large, polar, water-soluble molecules across the plasma membrane
Non-permeable
pass through protein carriers
State 2 examples of small, uncharged molecules
- Oxygen
- Carbon dioxide
State 3 examples of lipid-soluble, non-polar molecules
- Steroids
- Alcohol
- Chloroform
State 2 examples of small polar molecules
- Water
- Urea
State 3 examples of small ions
- Potassium (K+)
- Sodium (Na+)
- Chloride ion (Cl-)
State the permeability of small, polar molecules across the plasma membrane
Permeable/selectively permeable
State the permeability of lipid-soluble, non-polar molecules across the plasma membrane
Permeable
State which organelle synthesises secretory proteins providing an exact location
Ribosomes bound to the RER
Describe transport vescicles
Vesicles that move form one part of the cell to another
Describe the path of the secretory protein through the Golgi Apparatus
Moves from one cisternae to the next, carried by vesicles
State to what face transport vesicles from the Golgi fuse to during exocytosis
Transport vesicles fuse to the ‘cis’ face of the Golgi
Describe the process that occurs when the secretory vesicle and plasma membrane contact one another
Specific proteins alter the arrangement of the phospholipids enabling membrane fusion
List the 5 basic stages of secretory protein exocytosis and briefly outline the major stages
- RER ribosomal synthesis of secretory protein
- Protein introduced to transport vesicles
- Transport vesicles fuse to ‘cis’ face
- Secretory vesicles carry protein from ‘trans’ face
- Secretory vesicle fuses to plasma membrane (exocytosis)
Describe the 2 faces of the plasma membrane
- Cytoplasmic
2. Extracellular
Describe endocytosis
Cell takes in particles from outside the cell by engulfing it within the plasma membrane to form a vesicle
Describe exocytosis
Movement of materials out of a cell via a vesicle
Vesicles fuse with membrane and contents released into extracellular fluid
Describe ‘cis’ face of the Golgi Apparatus
The side of the Golgi facing the nucleus
usually near endoplasmic reticulum
Describe the ‘trans’ face of the Golgi Apparatus
Side of the Golgi facing the plasma membrane
Describe secretory vesicles
Vesicle that buds from the Golgi Apparatus and contains material to be secreted from cell
(via exocytosis)
List the 3 types of endocytosis
- Phagocytosis
- Pinocytosis
- Receptor-mediated endocytosis
State whether or not bulk transport requires the expenditure of energy
Yes. Bulk transport requires energy. It is an active transport process.
State the bulk transport process employed in the movement of material from the extracellular fluid into the cellular cytoplasm
Endocytosis
State the major cellular function of endocytosis
Take in materials in bulk by forming new vesicles from the plasma membrane
State the 2 major cellular functions of exocytosis
- Protein secretion
- Release of cellular waste and lysosomal breakdown products
Describe phagocytosis
Engulfment of solid materials in which the plasma membrane surrounds the material, forming a phagosome
Describe pinocytosis
Engulfment of a liquid in which the plasma membrane surrounds the substance, forming a vesicle
Describe phagosome
Vacuole in cell cytoplasm that contains a phagocytosed particle
Describe phagocyte
Cells capable of engulfing pathogens or foreign particles to destroy them
Describe pseudopodia
Temporary protrusion of cell cytoplasm that has the capacity to take up food or other particulate matter
Describe receptor-mediated endocytosis
Transport of substances into a cell in which a receptor binds to a molecule to trigger its’ entry into the cell
Describe 2 major types of phospholipid movement within the phospholipid bilayer and relative frequency
- Later movement
(approx. 1-^7 times/second) - Transverse movement
(once per month)
Describe polar molecule
Water soluble (slight charge)
Describe non-polar molecule
Water insoluble (no charge)
State the 3 types of passive transport across membranes
- Diffusion
- Facilitated diffusion
- Osmosis
Describe a reason supporting the fact that the phospholipid bilayer is impermeable to charged atoms or molecules
Ions have a surrounding shell of water and are consequently too large to move across the membrane via the phospholipid bilayer
(move through protein channels)
State whether molecules move up or down the concentration gradient in diffusion
Down the concentration gradient
State 3 chemical properties which affects the way molecules cross the plasma membrane
- Size
- Charge
- Polarity
Describe exosmosis
Net water efflux
Describe solvent
The substance in which a solute dissolves to form a solution
Describe solute
A substance that is dissolved in a solvent to form a solution
Describe concentration gradient
The difference in concentration of a solute between one region and another. (E.g. across membrane)
Describe simple diffusion
Passive movement of a solute from a region of higher concentration to an area of lower concentration
Describe facilitated diffusion
Molecules move down the concentration gradient across the plasma membrane by carrier proteins or channel proteins
Describe cytoplasm
Jelly like substance surrounding the nucleus (not including the cell membrane)
Compare and contrast cytoplasm and protoplasm
Protoplasm is the content of the cell including the cell membrane, cytoplasm and the cell nucleus whereas cytoplasm is the jelly like substance surrounding the nucleus, within the cell membrane.
State whether or not most hydrophobic molecules can dissolve in the lipid bilayer and move freely without the aid of membrane proteins
Yes.
Describe the relationship between polar and non polar molecules and hydrophobic/hydrophilic classification
Polar molecules - hydrophilic
Non-polar molecules - hydrophobic
Describe the function of a porin
Acts as a protein channel to allow movement of ions/water soluble/polar molecules across the cell membrane
