BIOL 235 3 Exam Study Guide.
Plasma membrane - answerCells flexible outer surface, separates internal and external
environments. Helps communication between cells and outside environment.
Cytoplasm - answerCellular contents between the plasma membrane and nucleus. 2 main
components: cytosol and...
Plasma membrane - answer✔Cells flexible outer surface, separates internal and external
environments. Helps communication between cells and outside environment.
Cytoplasm - answer✔Cellular contents between the plasma membrane and nucleus. 2 main
components: cytosol and organelles.
Nucleus - answer✔Large. Contains most of the cell's DNA and chromosomes that house DNA
associated with several proteins, and thousands of genes that control cellular structure and
functions.
Structure of Plasma Membrane - answer✔- Lipid bilayer
- Membrane proteins
Lipid Bilayer - answer✔Made up of phospholipids (~75%), cholesterol (~20%) and glycolipids
(~5%). Hydrophilic "head" and hydrophobic "tail".
"Heads" face outward on either side, "tails" face inward.
Amphipathic - answer✔Having both polar and non-polar parts.
- hydrophobic: water hating
- hydrophilic: water loving
Membrane Proteins - answer✔- Integral
- Peripheral
Integral Proteins - answer✔Amphipathic proteins which extend into or through the lipid bilayer.
Hydrophilic regions protrude into either watery extracellular fluid or the cytosol. Most are
transmembrane proteins and glycoproteins.
Transmembrane Proteins - answer✔Span entire lipid bilayer and protrude into both the cytosol
and extracellular fluid
Glycoproteins - answer✔Have carbohydrate groups attached to the ends that protrude into the
extracellular fluid. These carbohydrates are called oligosaccharides (2 - 60 monosaccharides,
either straight or branched). They form glycocalyx.
Glycocalyx - answer✔Extensive sugary coating formed by the carbohydrate parts of
glycoproteins and glycolipids. Acts as a molecular "signature" that enables cells to recognize
each other. e.g. detect "foreign" glycocalyx to destroy invading organisms.
Peripheral Proteins - answer✔Not firmly embedded in the membrane. Attached to the polar
heads of membrane lips or to integral proteins at the inner or outer surface of the membrane.
Help support plasma membrane, anchor integral proteins, participate in mechanical activities.
Ion Channel - answer✔Integral proteins. Pores or holes that specific ions can flow through. Most
are selective.
Carriers - answer✔Integral proteins. Selectively moves a polar substance or ion from one side of
the membrane to the other. Also known as transporters.
Receptors - answer✔Integral proteins. Serve as cellular recognition sites. Each type
recognizes/binds a specific type of molecule. The specific molecule that binds to a receptor is
called a ligand.
Enzymes - answer✔Integral or peripheral proteins. Catalyze specific chemical reactions.
Linkers - answer✔Integral or peripheral proteins. Anchor proteins in the plasma membrane of
neighbouring cells to one another or to protein filaments inside and outside of the cell.
Cell-identity markers - answer✔glycoproteins and glycolipids. Enable a cell to (1) recognize
cells of the same kind during tissue formation or (2) recognize/respond to potentially dangerous
foreign cells. e.g. wrong blood types clumping together.
Selective Permeability - answer✔Plasma membrane allows some substances to pass more readily
than others. Permeability varies.
High Permeability - answer✔Non-polar molecules (O2, CO2, steroids).
Moderate Permeability - answer✔Small, uncharged polar molecules (H2O, urea). Can cross the
membrane unassisted.
Impermeability - answer✔Ions and large uncharged polar molecules (glucose). Uses channels
and carriers
Concentration Gradient - answer✔Difference in concentration of a chemical from one place to
another, such as from inside to outside of the plasma membrane.
Electrical Gradient - answer✔Difference in distribution of positive and negative ions between
the two sides of the plasma membrane. Inner surface is more negative, while outside surface is
more positive. Because it occurs across the plasma membrane, this difference is termed
membrane potential.
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