Chapter 1: Cell Membrane Flashcards
What does a cell membrane do?
Maintains the contents of the cell and regulates movement of substances into and out of the cell
What does the fluid mosaic phospholipid bilayer model suggest about cell membranes?
It describes them as having a double layer of lipids, a lipid bilayer, that has the ability to change shape
What are phospholipids?
Is a type of lipid where the head is hydrophobic and the tail is hydrophobic; a major component of cell membranes
What is the role of cholesterol in the cell membrane?
It is an essential structural component that stabilises and strengthens the membrane and maintains it at a suitable fluidity
What is the plant version of cholesterol?
Phytosterol
How are cell membranes fluid?
During cell division and vesicle formation, membranes can break apart and reassemble themselves
What are the advantages of having a fluid membrane?
It enables cells to repair themselves before some of the cytoplasm can leak out
What is the function of protein channels?
Protein channels act as a passageway that allows specific substances to move across the membrane
What is passive movement?
Movement that does not require energy
What is diffusion?
The passive movement of molecules from a region of high concentration to region of low concentration
What is the concentration gradient?
The difference in concentration of a substance between two different regions
What happens when an equilibrium is reached?
Particles will move at equal rates in all directions
What can increase the rate of diffusion?
Temperature, due to the particles moving faster with higher temperatures, and increasing the concentration gradient
What substances can easily move through a cell membrane by diffusion?
O2, H2O, CO2, and other small, uncharged particles
What is facilitated diffusion?
A form of diffusion that requires a substance to be attached to a specific carrier molecule to move across a membrane
What particles require facilitated diffusion?
Charged particles, such as sodium and potassium ions, and relatively large molecules, such as glucose and amino acids
What two types of transport proteins are involved in facilitated diffusion?
Carrier proteins and channel proteins
How to carrier proteins assist with facilitated diffusion?
They bind to specific molecules on one side of the membrane, change shape, and release on the other side
How is glucose diffused into the cell?
Through the glucose transport protein, located in the plasma of all mammalian cell types
What is osmosis?
The movement of water across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration
What is isotonic?
Fluid with an equal solute concentration to another fluid
What is hypotonic?
Solution with a lower solute concentration than another solution
What is hypertonic?
Solution with a higher solute concentration than another solution
What does permeable mean?
Able to be passed through
What does turgid mean?
Describes a cell that is tight and rigid from absorbing water
How does a plant cell become turgid?
Water enters the cell through osmosis, where the water first goes to the cytoplasm and then into the vacuole, this causes the vacuole to swell and to much against the cell wall and membrane
What is the purpose of turgor?
It maintains their shape and form and helps to keep them rigid, and keeps non-woody stems erect as well as keeping leaves open
What is plasmolysis?
The point at which the cell membrane pulls away from the cell wall because of water loss
What are contractile vacuoles?
A vacuole found in some freshwater unicellular organisms that maintains osmotic balance by collecting water and emptying it from the cell
What is active transport?
The process of using energy to move a substance across a membrane from a region of low concentration to a region of higher concentration
What is the function of the mitochondria?
To make energy available to the cell
What is the energy source for active transport of most substances?
Adenosine Triphosphate (ATP)
What is the sodium-potassium pump used for?
To create high concentrations of potassium ions but low concentrations of sodium ions in animal cells
What is the sodium-potassium pump?
A membrane protein that’s uses energy to transport sodium ions into cells against their concentration gradient
What is endocytosis?
The movement of solids or liquids from the environment into a cell via vesicle formation
What is the process of endocytosis?
The cell changes shape by sending out projections that surround the material, when the projections meet, the membrane fuses and forms a vesicle, which then stores or transports the substance within the cytoplasm
What is phagocytosis?
The bulk transport of solids into a cell inside a vesicle. It is a form of endocytosis in which large particles, such as cells or cellular debris, are transported into the cell
What is exocytosis?
The movement of solids or liquids from a cell to the environment via vesicle formation
What is the process of exocytosis?
A membrane-bound vesicle moves to the plasma membrane, fuses with it and then releases its contents to the exterior of the cell
What particles are able to easily pass through membranes?
Uncharged molecules
What particles cannot pass the hydrophobic interior of the membrane?
Charged particles
What does polar mean?
A molecule with an uneven distribution of charge, giving it distinct charged ends
What is the surface-area-to-volume ration?
The mathematical ratio of the size of the surface area (in two dimensions) to the volume of an object (in three dimensions)
What would be better, a big SA:V ratio or a smaller one?Why?
A smaller one, due to cells obtaining its nutrients and removing waste through the cell membrane, if the volume of the cell is too big compared to the SA, then the cell will not get enough nutrients
