Cell Physiology: pt.1

1. physical isolation
2. metabolic isolation
3. sensitivity
4. structural support

What are the 4 functions of the plasma membrane?

permeability

the ease with which a substance may pass through a membrane

permeable

will allow a substance to pass freely

semipermeable

will allow some substances to pass, but not others

impermeable

will not allow a substance to pass

passive/active membrane processes

What are the 2 methods of metabolic isolation?

passive membrane processes

methods that do not involve the expenditure of cell energy

active membrane processes

methods in which cell energy is expended to move substances across the plasma membrane

passive membrane processes

What are these examples of?
-diffusion
-facilitated diffusion
-osmosis
-filtration
-dialysis

active membrane processes

What are these examples of?
-active transport (solute pumping)
-bulk transport

diffusion

the movement of molecules or ions from areas of high concentration to lower concentration

concentration gradient

the difference between the high and low concentration; in diffusion

equilibrium

the point of even molecular distribution; in diffusion

1.size
2.solubility in a lipid
3.ionization
4.prescence of carrier molecules

What are the factors that determine whether a substance can diffuse across the plasma membrane?

solubility in a lipid

the head of the lipid is polar

ionization

ability of the substance to separate into positively or negatively charged ions

presence of carrier molecules

special molecules that can transport substances across the plasma membrane regardless of other factors

facilitated diffusion

diffusion of substances across the plasma membrane w/ the help of carrier molecules; involves large intestines & insoluble substances like glucose

osmosis

the net movement of water across a selectively permeable membrane driven by a difference in solute concentration on the two sides of the membrane; water flows from lower to higher solute concentration

-isotonic
-hypotonic
-hypertonic

What are the solutions based upon solute concentration for osmosis?

isotonic

the solutions being compared have equal concentration of solutes

hypertonic

the solutions with the higher concentration of solutes

hypotonic

the solution with the lower concentration of solutes

does not

The size of the solute particle ___ influence osmosis

hydrostatic pressure

the pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity

filtration

the process by which water and solutes are forced across a body membrane vessel wall by the hydrostatic pressure of the blood (blood pressure); substances move along pressure gradient

dialysis

the process by which small molecules are separated from larger ones by passing a solution through a semipermeable membrane; substances move along a pressure gradient

-too large
-unable to dissolve in the lipid bi-layer
-move against the concentration gradient

What are the reasons cell expend energy to move substances across the plasma membrane?

-active transport (solute pumping)
-passive transport

What are the 2 major types of active membrane processes?

active trasnport

involves carrier proteins; substances move against the concentration gradient and ATP is required

-amino acids
-ions ( Na+, K+, Ca+2)

What are the most important substances transported during active transport?

bulk transport

large particles and macromolecules are transported through the plasma membrane; two types- exocytosis & endocytosis

exocytosis

substances are moved from the cell interior to the extracellular space; includes hormone secretion, mucus secretion, neurotransmitter release, and ejection of waste

exocytosis

What do these steps describe?
1. product is enclosed in a vacuole
2. vacuole migrates to the plasma membrane
3. vacuole fuses with plasma membrane
4. vacuole ruptures releasing its contents

endocytosis

substances are moved from the extracellular space to the cell interior; involves vesicle formation

endocytosis

What do these steps describe?
1. substances enclosed by a portion of the plasma membrane
2. a vesicle is formed
3. vesicle pinches off from the plasma membrane and moves into the cytoplasm
4. vesicle fuses with a lysosome and its contents are digested

phagocytosis, pinocytosis, and receptor-mediated

What are the 3 types of endocytosis?

phagocytosis

large or solid materials are taken in by the cell; "cell eating"

phagocytosis

What do these steps describe?
1. parts of the plasma membrane and cytoplasm extend around the material
2. a phagosome (vesicle) forms
3. a lysosome fuses with the phagosome
4. contents of the phagosome are digested

pinocytosis

small droplets containing dissolved materials are taken in by the cell; particularly important in the cells function in absorption (intestinal cells)

pinocytosis

What do these steps describe?
1. part of the plasma membrane invaginates (sinks inward)
2. whatever substance is found at the site of invagination is brought into the cell
3. a vesicle forms around the fluid
4. vesicle fuses with a lysosome nd its contents are digested

receptor-mediated endocytosis

the active uptake of specific substances from the extracellular environment; invagination is stimulated when specific molecules (ligands) bind the receptor (integral proteins) in the plasma membrane

receptor-mediated endocytosis

What do these steps describe?
1. ligands bind to the receptor molecule
2. plasma membrane invaginates forming a vesicle
3. vesicle fuses with a lysosome and its contents are digested

sensitivity

the ability to respond to a stimulus environmental change

transmembrane potential

the measured difference in positive and negative charges across the plasma membrane from one side to the other

electrolytes

+ or - charged ions; associated with both extracellular and intracellular solutions (Na+ K+); separated from each other in unequal concentrations

positively

What type of ions are charged higher outside the plasma membrane?

negatively

What type of ions are charged higher inside the plasma membrane?

positive

What is the net charge along side the outside of the PM?

negative

What is the net charge along side the inside of the PM?

voltage

the electrical potential energy resulting from the separation of oppositely charged particles (ions)

volt

units used to describe the electrical potential; the higher they are the greater the difference in charges

mV (millivolt)

1/1000th of a volt. (1000 mV per volt); used to measure transmembrane potential since its so small

85mV & -75mV

What does transmembrane potential range between?

peptide

Ribosomes link amino acids together by ___ bonds to form polypeptides

nucleus

Where does protein synthesis begin?

- What amino acid?
- Sequence of amino acids?
- How many of each amino acid?
- Total number of amino acids?
*referred to as genetic code

What info do ribosomes need to form polypeptides?

genetic code

stored in the nucleus on the nucleic acid called DNA; broken into groups of 3 nitrogen bases (triplet/codon); groups pf triplets form genes

genes

contains all the codons necessary to produce a given polypeptide (protein)

mRNA

a messenger that carriers info from the nucleus (DNA) to the cytoplasm and ribosomes

gene activation

weak hydrogen bonds between nitrogen bases are broken

RNA polymerase binding

an enzyme that promotes bonding between DNA and RNA nitrogen bases' binds initial segment of the gene

RNA polymerase reading

links RNA nucleotides w/DNA nucleotides to form a strand of mRNA- accomplished by complimentary base pairing

RNA polymerase unbinding

RNA polymerase encounters a stop codon; RNA polymerase and mRNA detach and DNA RE-ALIGNS or zips back together

polypeptide

the primary structure of a protein

ribosome reading

What does this describe?
- ribosome spins and moves down the mRNA strand
- ribosome reads the sequence of nitrogen bases or codons (representing amino acids)
- as the ribosome reads the codons, the proper amino acids are brought into place via transfer RNA and CBP

polypeptide release

What does this describe?
- ribosome encounters a STOP codon, the polypeptide is complete and released