Midterm - Cells, Tissues, Organs & Organ Systems (P.2) Flashcards
Cell membranes are composed mainly of _____________ and __________, allowing certain materials to move across them.
PHOSPHOLIPIDS; PROTEINS
What is the certain quality of the cell membrane called?
SELECTIVE PERMEABILITY
The _______________ is based on the knowledge of the cell membrane?
FLUID-MOSAIC MODEL
This region is composed mainly of PHOSPHOLIPIDS and PROTEINS, allowing certain materials to move across them.
CELL MEMBRANE
Give the SIX (6) CELL MEMBRANE FUNCTIONS!
- Regulate the movement of material
- Separate the inside of the cell from the outside
- Separate various organelles within the cell
- Provide a large surface area
- Are a site for receptors
- Separate cells from one another
In water, phospholipids spontaneously form a _________.
BILAYER
Cell membranes contain zones called ____________.
LIPID RAFTS
What is the cell membrane heavily enriched in?
CHOLESTEROL
Lipis move __________ in a membrane, but flip=-flopping across the membrane is quite rare.
(a) MOVEMENT OF PHOSPHOLIPIDS; laterally
Unsaturated ______________ tails of phospholipids have _________ that keep the molecules from packing together, enhancing membrane fluidity!
(b) MEMBRANE FLUIDITY
HYDROCARBON; KINKS
____________ reduces membrane fluidity at moderate temperatures by reducing phospholipid ___________, but at _____ temperature it hinders solidification by disrupting the regular packing of phospholipids.
(c) CHOLESTEROL WITHIN THE ANIMAL CELL MEMBRANE
CHOLESTEROL; MOVEMENT; LOW
A protein that spans the membrane may provide a ___________ channel across the membrane that is selective for a particular solute.
Other ________ proteins shuttle a substance from one side to the other by changing shape.
Some of these proteins __________ ATP as an energy source to actively pump substances across membranes.
(A) TRANSPORT
HYDROPHILIC
TRANSPORT
HYDROLYZE
A protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. In some cases, several enzymes in a membrane are organized as a team that carries out sequential steps of a metabolic pathway.
ENZYMATIC ACTIVITY
A membrane protein (receptor) may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The external messenger (signaling molecule) may cause a shape change in the protein that relays the message to the inside of the cell, usually by binding to a cytoplasmic protein.
SIGNAL TRANSDUCTION
Some glycoproteins serve as IDENTIFICATION TAGS that are specifically recognized by membrane proteins of other cells.
CELL-CELL RECOGNITION
The membrane proteins of adjacent cells may hook together in various junctions such as GAP JUNCTIONS or TIGHT JUNCTIONS.
INTERCELLULAR JOINING
Microfilaments or other elements of the cytoskeleton may be noncovalently bound to membrane proteins, a function that helps maintain cell shape and stabilizes the location of certain membrane proteins. Proteins that can bind to ECM molecules can coordinate extracellular and intracellular changes.
ATTACHMENT OF THE CYTOSKELETON AND EXTRACELLULAR MATRIX (ECM)
Some molecules use their own energy to move.
PASSIVE TRANSPORT
Molecules move from an AREA of HIGHER CONCENTRATION to an AREA of LOWER CONCENTRATION
DIFFUSION