Chapter 3 - the living units Flashcards
What percentage of cholesterol makes up the plasma membrane and its function?
20%
- stiffen the membrane and decrease water solubility
What are the different types of proteins in the cell membrane?
integral - protrude from one side
peripheral - are not embedded in the membrane - attached on integral proteins
transmembrane - protrude from both sides
What are the 6 tasks of the membrane?
1) transportation
2) receptors for reactions
3) enzyme activity
4) cell-cell recognition
5) cell-to-cell joining
6) attachment to the cytoskeleton and ECM - maintain cell shape, fix protein locations, cell movements
What is the function and location of carbohydrates?
help with cell recognition
- on integral proteins
what is the function of integral proteins?
- most are transmembrane
- is hydro- and hydra- philic
- transport, enzyme, receptors
what is the function of peripheral proteins?
- attached to integral proteins
- cell-to-cell connections
what are glycocalyx?
consists of sugars (carbs) sticking out
- include glycoproteins and glycolipids
- help in cell-to-cell recognition
what are the 3 types of intercellular junctions?
tight, desmosomes, and gap
what is the function of tight junctions?
- Integral proteins molecules and adjacent cells fuse together creating 2 fluid filled compartments
- Prevent molecules from passing through the extracellular space and resist movement in membrane
- Keeps digestive enzymes and microorganisms from the intestines from leaking into the blood stream
what is the function of desmosomes?
- Bind together through linker proteins (cadherins) that extend from the plaques
- Help keep cells from tearing apart
- Keratin filaments (intermediate filaments) extend from the cytoplasmic side to anchor onto the plaque of the other side.
- In skin and heart muscles
What is the function of gap junctions?
- The plasma membranes are connected by hollow cylinders called connexons
- Different gap junctions are composed of different transmembrane proteins, which determine which molecules and ions can pass through
- Found in excitable tissues: heart, smooth muscle
What are the types of passive transport?
- simple diffusion
- facilitated diffusion
- osmosis
what are the types of active transport
- primary and secondary active transports
- endocytosis (phago, Pino, receptor mediated) vesicular trafficking and exocytosis
explain simple diffusion.
substances diffusion directly into the lipid bilayer. The molecules are small nonpolar (gases, steroid hormones, and fatty acids)
explain the 2 types of facilitated diffusion.
carrier mediated
- transporting polar molecules like sugars and amino acids that are too large. The shape of the protein changes shape.
channel mediated - leakage (always open) and gated channels (chemical or electrical signal)
- transports ions through water filled channels from one side of the membrane to the other.
explain osmosis. 3 points
Water diffuses across plasma membranes (even though water is polar, it is so small that some molecules can sneak past nonpolar phospholipid tails)
through specific water channels called aquaporins (A Q P s)
- Osmosis occurs whenever the solute concentration differs on the two sides of a membrane
Osmolarity: total concentration of all solute particles in a solution - Water concentration varies with number of solute particles because solute particles displace water molecules
explain primary active transport.
- hydrolysis of ATP
- protein changes shape to pump the solute across the membrane
explain secondary active transport and the 2 types.
- concentration gradient is the source of energy created by primary AT
symport - moves 2 substances at once through the same protein
antiport - moves 2 substances across the membrane in opposite directions
what are the types of endocytosis?
phagocytosis, pinocytosis, receptor-mediated endocytosis, vesicular trafficking
explain the difference between phagocytosis and pinocytosis.
Phago: engulfs large or solid materials
- Pseudopods form and flow around the particle (phagosome)
- Ex. Macrophages
Ingesting and disposing bacterial and foreign substance.
Pino: engulfs very small volume of extracellular fluid containing dissolve molecules
- Fuses with endosomes
- Added back through exocytosis
explain what receptor mediated endocytosis is.
engulfs particles attached to receptors before endocytosis occurs.
- Engulfs ligands to be injected into the cells, the separate from the receptor, so that the receptors can join the membrane again and the ligand can join the lysosomes. The lysosomes break down the ligand and disperse it out to function throughout the cell.
explain what vesicular trafficking is.
Moves substances from one area (or organelle) in the cell to another.
explain what exocytosis is.
- Mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicles (vesicle migrating to the plasma) fuses with the plasma membrane
What are the factors effecting speed of diffusion?
- concentration gradient: greater the difference, more collisions occur
- molecular size
- temperature
explain facilitated diffusion.
Binds to carrier proteins or moves through water-filled channel proteins (Glucose, amino acids, ions).
explain hydrostatic and osmotic pressure
Hydrostatic pressure: the back pressure exerted by water against the cell wall
Osmotic pressure: the tendency of water to move into the cell by osmosis
What is tonicity and what are the 3 types
Tonicity—the capability of a solution to modify the volume of cells by altering their water content
Isotonic solution has same osmolarity as inside the cell, so volume remains unchanged
Hypertonic solution has higher osmolarity than inside cell, so water flows out of cell, resulting in cell shrinking
Hypotonic solution has lower osmolarity than inside cell, so water flows into cell, resulting in cell swelling
