CHAPTER 4 Flashcards
Cytology
study of cells
produces a 2-D image, passes light though specimen
light microscope
beam of electrons illuminates specimen, greater magnification and resolution than light microscope
electron microscope
transmission electron microscope
directs an electron beam through thin-cut sections, get 2-D images
scanning electron microscope
directs an electron beam across the surface of specimen; get 3D images
Forms outer, limiting barrier separating internal contents from
external environment
plasma membrane
cilia, flagellum, and microvilli are modified extensions of ___
plasma membrane
nucleus
largest structure in cell, enclosed by nuclear envelope. contains DNA and a nucleolus. contains nucleoplasm
cytoplasm
Cellular contents between plasma membrane and nucleus
* Includes: cytosol, organelles, and inclusions
cytosol
intracellular fluid
true or false : cytosol has high water content
true
true or false? cytosol contains dissolved macromolecules and ions
true
organelles
complex, organized structure within cells. unique shape and function
2 types of organelles
membrane-bound, non-membrane-bound
membrane-bound organelle
enclosed by a membrane, separates contents from cytosol
Which organelles are membrane-bound?
endoplasmic reticulum, golgi apparatus, lysosomes, peroxisomes, mitochondria
Which organelles are non-membrane bound?
ribosomes, cytoskeleton, centrosome, proteasomes
inclusions
cytosol stores temporarily. not considered organelles. molecules are added and removed continuously.
3 examples of inclusions
pigments, glycogen, triglycerides
fluid mixture composed of equal parts lipid and protein by weight
plasma membrane
lipids found in plasma membranes
phospholipid, cholesterol. glycolipid
True or false? plasma membranes regulate movement of most substances in and out of cell
true
describe the structure of a phospholipid
“Balloon with 2 tails”. polar and hydrophilic “head” ; 2 nonpolar and hydrophobic “tails”
ensures that cytosol stays inside the cell, and interstitial fluid remains outside the cell
phospholipid bilayer
describe the structure of cholesterol
4-ring lipid molecule scattered within phospholipid bilayer. strengthens membrane. stabilizes membrane against temperature extremes
describe the structure of glycolipids
lipids with attached carbohydrate groups. located on outer phospholipid region only. helps form glycocalyx
2 structural types of membrane proteins
integral, peripheral
half of plasma membrane by weight, float and move in fluid bilayer, performs most of membrane’s functions
membrane proteins
describe the structure of integral proteins
embedded within, and extend across phospholipid bilayer. hydrophobic regions interact with hydrophobic interior
* Hydrophilic regions are exposed to aqueous environments
on either side of membrane
* Many are glycoproteins with attached carbohydrate
groups
Not embedded in lipid bilayer
* Loosely attached to external or interior surfaces of
membrane
Peripheral proteins
Transport proteins
Regulate movement of substances across membrane
* For example, channels, carrier proteins, pumps, symporters, and
antiporters
Cell surface receptors
Bind molecules called ligands
* For example, neurotransmitters released from a nerve cell that
binds to a muscle cell to initiate contraction
Identity markers
Communicate to other cells that they belong to the body
* These markers are used to distinguish healthy cells from cells to be
destroyed
May be attached to either internal or external surface of a cell
* Catalyze chemical reactions
enzymes
Secure cytoskeleton to plasma membrane
anchoring sites
Cell-adhesion proteins
perform cell-to-cell attachments
Process of obtaining and eliminating substance across the
plasma membrane
membrane transport
2 categories of membrane transport
passive, active
Passive processes of membrane transport
do not require energy, depnd on substances moving down concentration gradient
active process of membrane transport
require enrgy, substance must be moved up its concentration gradient (active transport) membrane-bound vesicle must be released (vesicular transport)
Net movement of ions or molecules from area of greater
concentration to area of lesser concentration
Diffusion
If unopposed, diffusion continues until substance reaches
equilibrium
True or false? simple diffusion is not regulated by a plasma membrane.
true
2 types of facilitated diffusion
channel-mediated, carrier-mediated
movement of small ions through water-filled protein channels
channel-mediated diffusion
true or false: channels are specific for one ion type
true
leak channel vs gated channel
leak channel= continuously open. gated channel= continuously closed and only opens in response to stimuli for a fraction of a second
uniporter
carrier transporting only one substance
what determines the max rate of substance transport?
the number of channels and carriers
In carrier-mediated diffusion, small polar molecules are assisted across membranes by
carrier proteins
true or false? osmosis is the movement of solutes.
false. osmosis is the movement of water
Osmosis involves passive movement of water through
semipermeable membrane
true or false : membranes are selectively permeable
true
aquaporin
water channel
osmotic pressure
pressure exerted by movement of water across semipermeable membrane