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Biology 1001
Scott Crousillac Chapter 5
53
Biology
Undergraduate 1
03/16/2011

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Term
what is the plasma membrane?
Definition
is the membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the cell’s chemical environment
Term
what provides a 'fingerprint' for the cell type?
Definition
the membrane proteins
Term
why it is unlikely that you will contract HIV through casual contact?
Definition
HIV binds to cell receptors that are present on cells inside the body, but not present on skin cells. Called CD receptors (cluster of differentiation).
Term
what are the plasma membranes made of?
Definition
primarily lipids
Term
what are phospholipids?
Definition
molecules which can form membranes naturally?
Term
what does fluidity in membranes mean?
Definition
there is lateral two-dimensional movement of the lipids and some proteins in the plane of the membrane
Term
what does the 'mosaic' aspect of membranes mean?
Definition
that there are proteins interspersed within the lipid bilayer
Term
what are the three main funtions of membrane proteins?
Definition
1. transport proteins
2. receptors
3. cell-to-cell recognition
Term
what are glycoproteins?
Definition
proteins which have a corbohydrate attached to them and they are a recognition keys on the surface of cells
Term
movement of molecules requires which two factors?
Definition
1. movement must be through a fluid (liquid or gas)
2. there must be a concentration gradient (defference in amount of molecules from one place to another)
Term
passive transport is:
Definition
diffusion of a substance across a biological membrane
Term
what is concentration gradient?
Definition
it is a concentration change over a distance in a particular direction
Term
what is diffusion?
Definition
the net movement of a substance down a concentration gradient
Term
movement is from _____ concentration to _______ concentration
Definition
greaeter; lower
Term
the ______ the concentration difference, the _____ the diffusion
Definition
greater; faster
Term
when does net movement stop?
Definition
when the system reaches equilibium
Term
what is selective permeability?
Definition
the property of biological membranes which allows some substances to cross more easily than others
Term
what are the 2 factors that influence permeability?
Definition
1. solubility characteristics of the substance crossing the membrane
2. facilitated diffusion by a carrier protein or a channel protein
Term
is the phosphlipid layer nonpolar of polar?
Definition
nonpolar
Term
how is water able to enter a cell?
Definition
through specialized protein channels called aquaporins
Term
what are the interior of protein channels called aquaporins lined with?
Definition
hydrophilic amnio acids
Term
what is facilitated diffusion?
Definition
diffusion across a membrane with the help of a protein
Term
what are the 3 types of facilitated diffusion?
Definition
1. bind-and-release
2. selective channel (pore the size of the solute)
3. gated channel (selective channel only with a door)
Term
what is osmosis?
Definition
passive transport of water and/or the diffusion of water across a defferentially permeable membrane
Term
in osmosis, water moves from a ___ concentration of a solute to a ___ concentration of a solute.
Definition
low;high
Term
what does isotonic mean?
Definition
a solution of equal concentration to another solution

(as in i so equal - gay i know, but it helps me remember... lol.)
Term
what does hypertonic mean?
Definition
a solution with a greater concentration of a solute than another solution

(one solution is more hyper because of the HIGHER concentration of sugar than another... again, dont laugh... just helps me remember)
Term
what does hypotonic mean?
Definition
a solution with a lower concentration of solute than another solution

(hypo = smaller, hippo = big!, opposites! again, jusr trying to remember... lol)
Term
in a hypotonic enviorment what happens to the cell?
Definition
water rushes into the cel, causing it to swell
Term
in a hypertonic enviorment what happens to the cell?
Definition
water leaves the cell, causing it to shrivel
Term
in an isotonic enviorment what happens to the cell?
Definition
it stays the same. no change.
Term
The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will:
Definition
shrink
Term
The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will:
Definition
shrink
Term
The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will:
Definition
shrink
Term
wha is active transport?
Definition
an energy-requiring process during which a transport protein pumps a molecule across a membrane against its concentration gradient (uses ATP)
Term
In active transport, the energy source that moves a molecule against its concentration gradient is:
Definition
ATP
Term
what is endocytosis?
Definition
the cellular uptake of large molecules (a.k.a. macromolecules) and particulate substances (food) by the localized pinching off of a region of the plasma membrane to form a vesicle
Term
three types of endocytosis are:
Definition
1. phagocytosis
2. pinocytosis
3. receptor-mediated endocytosis
Term
what happens in phagocytosis?
Definition
(cell eating) - endocytosis of solid particules

(phattie!)
Term
what happens in pinocytosis?
Definition
(cell drinking) - endocytosis of fluid droplests

('pin'a coladas!)
Term
what happens in receptor-mediated endocytosis?
Definition
importing of specific macromolecules into the cell by the inward buddinf of vesicles formed from coated pits, occurs in response to the binding of specific nutrients to receptors on the cell's surface
Term
what is exocytosis?
Definition
is the cellular secretion of large molecules (a.k.a. macromolecules) by the fusion of vesicles with the plasma membrane

(moves material out of the cell)
Term
how are neurotransmitters such as serotonin releases from cells in the brain?
Definition
exocytosis
Term
cells are connected by _______
Definition
desmosomes
Term
if the connection between cells needs to be watertight, then ____________ connect the cells
Definition
tight junctions
Term
communication between cells occurs via ____________ and ________
Definition
gao junctions; plasmodesmata
Term
animal cells communicate through _________ where two channel proteins in adjacent cells line up
Definition
gap junctions
Term
how do gap junctions arise?
Definition
by a stable alignment of channel proteins in adjacent cells so the pores are directly across from each other
Term
what is the suspected reason cells continue to divide after meeting other cells? (becoming cancer)
Definition
it is suspected cancer cells have fewer gap junctions and lose the communication ability of normal cells
Term
In order for plants to move large amounts of macromolecules or water they need to use:
Definition
wide interconnects known as plasmodesmata
Term
what are plasmodesmata?
Definition
are large non-protein channels through both the cell membranes and the cell wall of neighboring plant cells
Term
What type of cell junctions are needed for a tissue that must prevent fluids from leaking across its cell layer?
Definition
tight junctions
Term
Animal cells communicate with one another through:
Definition
gap junctions
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