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
steeper gradient = ____ osmotic pressure
greater
hydrostatic pressure
pressure exerted by a fluid on the inside wall of its container
Tonicity
ability of a solution to change the volume or pressure of a cell by osmosis
isotonic solution
both cytosol and solution have same relative concentration of solutes
Normal saline is a good example of isotonic solution.
true
hypotonic solution
solution has a lower concentration of solutes, higher concentration of water than in cytosol
–
–
hemolysis
rupturing erythrocytes
hypertonic solution
solution with a higher concentration of solutes than cytosol
crenation
cell shrinkage
true or false? active transport uses energy directly from breakdown of ATP
true.
breakdown of ATP results in phosphate group added to transport protein. this is referred to as
phosphorylation
true or false? phosphyloration changes a protein’s shape and results inmovement of substances across the membrane
true.
ion pumps
cellular protein pump that moves ions across membranes
true or false? ion pumps maintain internal concentrations of ions
true
Sodium-potassium (Na/K) pump
ype of exchange pump
* Moves one type of ion into cell against gradient, while
moving another type of ion out of cell against gradient
* Plasma membrane preserves steep gradient differences
* Continuously exports Na+ out of the cell and moves K into
the cell
Secondary active transport
Moves substance against concentration gradient
- Two types:
- Symport
- Antiport
symport
2 substances moved in same direction. this process is called symport secondary active transport
antiport
2 substances move in opposite directions. process is called antiport secondary active transport.
vesicular transport
Also called bulk transport
exocytosis
Large substances secreted from cell
Endocytosis
cellular uptake of large substances from external environment.
Phagocytosis
cellular eating. cell engulfs a large particle external to cell
large extension formed during phagocytosis
pseudopodia
pinocytosis
cellular drinking
receptor-mediated endocytosis
uses receptors on plasma membrane to bind molelcules within interstitial fluid and bring the molecules into the cell
Cholesterol is bound to
low density lipoproteins
resting membrane potential
electrochemical gradient established and maintained by plasma membranes
rough ER (endoplasmic reticulum)
production of protein
smooth ER
has diverse metabolic processes depending on the cell. can synthesize , transport , and store lipids. can metabolize carbohydrate. detoxification of drugs and poisons
Golgi apparatus
Composed of cisternae, elongated saclike membranous
structures
* Exhibits polarity
* Cis-face
* Proximal to ER
* Trans-face
* Distal from ER
* Functions: modification, packaging, and sorting of proteins
* Formation of secretory vesicles
* Some vesicles become part of plasma membrane
* Others release contents outside cell
Lysosomes
Small, membranous
sacs
* Contain digestive
enzymes formed by
Golgi
* Participate in digestion
of unneeded
substances
* Digest contents of
endocytosed vesicles
Figure 4.24
Peroxisomes
Membrane-enclosed sacs,
smaller than lysosomes
Pinched off vesicles from
rough ER
Proteins are incorporated to
serve as their enzymes
Metabolic functions include
* Role in chemical
digestion
* Beta oxidation
* Lipid synthesis
What is Tay-sachs disease?
when someone lacks the enzyme needed to break down complex membrane lipids. you cannot live long with this disease.
Endomembrane system
Extensive array of membrane-bound structures
* Includes ER, Golgi apparatus, vesicles, lysosomes,
peroxisomes
* Includes plasma membrane and nuclear envelope
* Connected directly or through vesicles moving between
them
* Provides means of transporting substances within cells
Mitochondria
Oblong shaped
organelles with double
membrane
* Aerobic cellular
respiration
* Complete digestion of
fuel molecules to
synthesize ATP
Ribosomes
Contain protein and ribonucleic acid
* Arranged into large and small subunit
* Large subunit with A, P, and E sites
* Made within nucleolus and assembled in cytoplasm
* Bound ribosomes attached to external surface of ER
membrane
* Synthesize proteins for export, become part of plasma membrane,
or serve as enzymes in lysosomes
* Free ribosomes suspended within cytosol
* All other proteins within cell synthesized here
Centrosome
Pair of perpendicularly oriented cylindrical centrioles
* Surrounded by amorphous protein
* Primary function: organizes microtubules within
cytoskeleton
* Functions in cellular division
Proteasomes
Large, barrel-shaped protein complexes
* Protein-digesting organelles
* Located in cytosol and cell nucleus
* Degrade cell proteins through ATP-dependent pathway
* For example, damaged proteins, incorrectly folded proteins, proteins
no longer needed
* Proteins marked with ubiquitin tag for disposal
* With age, may be unable to normally remove proteins
Cytoskeleton
Plays roles in
* Intracellular support
* Organization of organelles
* Cell division
* Movement of materials
* Extends throughout cell interior; anchor proteins in
membrane
* Includes
* Microfilaments
* Intermediate filaments
* Microtubules
Microfilaments
Smallest components of cytoskeleton
* Actin protein monomers in two twisted filaments
* Functions – maintain cell shape, internal support, cell division
Intermediate filaments
Intermediate-sized; more rigid than microfilaments
* Functions – structural support, cell junctions
Microtubules
Largest components of cytoskeleton; composed of tubulin
* May be elongated or shortened as needed
* Functions – maintain shape, cell transport, cell division
hair-like projections that move substances along cell surface
cilia
flagella
longer and wider than cilia, provides propulsion
microvili
extensions of plasma membrane that increase surface area
tight junctions
strand or rows of proteins lining cells. prevent substances form passing between cells. requires materials to move through, rather than between cells. maintain polarity of epithelia.
desmosomes
composed of proteins that bind neighboring cells. hemidesmosomes anchor basal layer of cells of epidermis to underlying components
gap junctions
form tiny, fluid-filled tunnels. provide direct passageway for substances to travel between cells
nucelus
largest structure in the cell. the control center. cells typically have one nucleus. exceptions include mature erythrocytes which have no nucleus, and skeletal muscle cells that have multiple
true or fasle? often the nucleus mirrors the shape of the cell
true
nuclear envelope
double phospholipid membrane enclosing nucleus. externally continuous with rough ER.
nuclear pores
open passageways formed by proteins. ions and water soluble molecules pass through
nucleus
dark-staining, spherical body. not membrane bound. composed of protein and RNA. prodcuses small and large ribosome subunits. not present in all cells.
4 nitrogenous bases
adenine, cytosine, guanine, thymine
in DNA, nucleotides are linked by
phosphodiester bonds
what forms the spiral ladder found in DNA?
sugar and phosphates form the struts, pairs of nucleotide bases form rungs
Each double helix of DNA is wound around nuclear proteins called
histones
When not dividing, DNA is in the form of
chromatin
When dividing, DNA is in the form of
chromosomes
Genes
stretches of nucleotides that provide instructions for synthesis of specific proteins
transcription
copy of a gene formed from Dna in nucleus
Translation
uses RNA for synthesis of protein by ribosomes in cytosol
mitosis
cell division in somatic cells (all other than sex cells)
meiosis
cell division in sex cells
Somatic cell division
one cell divides into two
centrosome
pair of cylindrical centrioles. organizes microtubules that facilitate chromosome movement
interphase
time the cell prepares for division. DNA still in form of chromatin. 3 phases G1, S, G2
g1 phase
growth and production of new organelles. structures needed for DNA replication formed. Replication of centrioles to produce two pairs of chromosomes
S phase
DNA is replicated. Requires deoxyribonucleotides and DNA polymerase
Steps of DNA replication
unwind, break, assemble, restore
sister chromatid
replicated DNA strand
G2 phase
brief phase. centriole replication completed. enzymes for cell division synthesized
4 phases of mitosis
prophase, metaphase, anaphase, telophase
prophase
first stage of mitosis. spindle fibers (microtubules) grow from centrioles. centrioles are pushed apart to opposite poles.
metaphase
second stage of mitosis. chromosomes line up on equatorial plate of cell. spindle fibers extend and attach at centromere of each chromosome
anaphase
3rd stage of mitosis. spindle fibers move sister chromatids apart toward poles. each chromatid now a chromsome of one DNA double helix with its own centromere
telophase
arrival of group of chromosomes at each pole. begin to uncoil and return to chromatin. new nucleolus formed in each cell. mitotic spindle broken up. end of nuclear division
cytokinesis
division of cytoplasm between two newly formed cells. may overlap w/ anaphase and telophase. Ring of microfilament proteins at cell periphery
* Pinch mother cell into two separate cells
* Results in a cleavage furrow, two new daughter cells
* After cytokinesis, cell division is complete
cell death by 2 mechanisms
killed by harmful agents/mechanical damage, apoptosis
apoptosis
occurs in orderly continuous steps. destroys and removes cellular components and cell remnants. initiated by ligand-receptor signaling
Why does programmed cell death (apoptosis) occur?
remove harmful cells
