Chapter 3: Cells Flashcards
Cells
The basic units of living organisms
Consist of 3 main parts:
1) plasma membrane
2) cytoplasm
3) nucleus
Plasma membrane
Separates the intercellular from extracellular fluid.
Contains phospholipids
Function: semipermeable barrier that regulates the flow of material into and out the cell.
Fluid mosaic model
Describes the the plasma membrane;
A “sea” of phospholipids (bilayer) always moving with various proteins within the fluid
Integral (transmembrane) proteins
Proteins in the plasma membrane that extend through the phospholipid bilayer (usually to transport molecules in and out)
Peripheral membrane proteins
Associated loosely with only one side of the membrane
Membrane protein functions
- transport (as a channel or a carrier) of molecules in an out of the cell
- receptor for chemical messengers
- enzymes to catalyze reactions
- identifiers of what cell it is
- anchoring the cytoskeleton
Membrane junctions
Provides contact or adhesion between 2 neighbouring cells so they can communicate.
3 types;
- Gap junction (communicators)
- Tight junction (impermeable)
- Desmosomes (anchoring)
Gap junctions
The transmembrane proteins form a tiny fluid filled channels called connexons to connect to neighbouring cells.
They allow ions and small molecules to diffuse the cytosine of one cell to another (they communicate)
Tight junctions
Plasma membranes of adjacent cells are fused together by transmembrane proteins
They are impermeable therefore materials cannot pass through them
Desmosomes
The intermediate filaments of adjacent cells create a net-like structure to prevent cells from separating, which contributes to the stability of the tissue.
Selectively permeable
The cell membrane allows only certain things through.
Usually nonpolar, uncharged, and small molecules can. (And water). But ions, charged, and polar molecules cannot.
Membrane transport
The process of transporting substances across membranes.
2 types:
- Passive transport (substances move down their [ ] gradients, from area of high [ ] to area of low [ ], and energy is not required.)
- Active transport (substances move against the [ ] gradient, from area of low [ ] to area of high [ ], and energy is required.)
Passive transport
Involves either Diffusion or osmosis.
Diffusion - net movement of molecules from area of high [ ] to low [ ] until equilibrium is reached.
2 types of diffusion:
1) Simple
2) Facilitated
Osmosis - same as diffusion but with water.
What is diffusion rate affected by?
- Temperature (high temp = faster)
- [ ] gradient (bigger = faster)
- Distance (shorter distance = faster)
- Particle size (smaller = faster)
- Surface area (more SA = faster)
Simple diffusion
Non-polar and lipid soluble substances diffuse directly through the lipid bilayer.
Shouldn’t interact with the phospholipid polar heads since there is no charge to be attracted to.
Ex. Oxygen, O2
Facilitated diffusion
Polar and charged molecules require transmembrane proteins as carriers, or use ion channels to move through the lipid bilayer.
The molecules are attracted to the polar phospholipid head so they need to be carried across, or go through the protein channel.
Ex. Glucose, ions
Osmotic pressure
The ability of a solution to attract or draw in water.
(The greater the number of solute particles in a solution, the great the osmotic pressure)
Hypotonic solution
There is less [ ] of dissolved particles and more [ ] of water molecules.
i.e. Water rapidly enters the cell via osmosis faster than it leaves. This causes the cell to burst = hemolysis of RBC’s
Hypertonic solution
There is a higher [ ] of dissolved particles, and less [ ] of water molecules.
i.e. Water rapidly leaves the cell faster than it enters. This causes the cell to shrivel and die = crenation of RBC’s
Tonicity
The ability of a solution to modify the volume of cells by altering the water content.
3 types:
- hypotonic
- hypertonic
- isotonic (no change)
Active transport
Substances cross the membrane moving against the concentration gradient and energy is required.
3 types:
- primary active transport
- secondary active transport
- vesicle transport
Primary active transport
Energy from ATP hydrolysis changes the shape of a transported protein (opens and closes the channel), and it “pumps” the substance across the membrane.
(Uses ATP directly)
Secondary active transport
Transport of 2 molecules using energy supplied by an ion gradient given by a primary active transport pump.
(Indirectly latches onto used ATP)
2 types:
Antiporter - things transported are going the opposite direction
Symporter - things transported are going the same direction
Vesicle transport
Only used for macromolecules, and fluid.
2 types:
Exocytosis - vesicle is moved out of the cell by fusing with the cell membrane and releases its contents.
Endocytosis - moves material into the cell by forming a vesicle
Secretory vesicle
A vessel of the Golgi complex that will fuse with the cell membrane, then proteins are released via exocytosis
Membrane vesicle
A vesicle of the Golgi complex that fuses with membrane and will replenish it with new proteins.
Transport vesicle
A vesicle of the Golgi complex that brings new digestive enzymes to a lysosome, or will become a new lysosome.
Somatic cell division
When a body cell undergoes nuclear division in order to produce a new body cell
(aka mitosis)
Reproductive cell division
When a germ cell undergoes nuclear division, in order to produce a gamete.
(aka meiosis)
Cytokinesis
Cytoplasmic division that occurs during mitosis or meiosis.
