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91 Cards in this Set

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what cellular organelles do prokaryotes lack?

-no nucleus
-no internal membranes
-no nuclear membrane
-no ER
-no cytoskeleton
-no mitochondria
-no vacuoles
-etc.
all bacteria are what?
prokaryotes
prokaryotic cells lack nuclei and all membrane-bound internal structures, but they do have....
-ribosomes
-nucleoid (circular, naked DNA : no surrounding membrane)
-cytoplasm
-cell wall
-plasma membrane
prokaryotes have what type of metabolism?
anaerobic or aerobic
eukaryotes have what type of metabolism?
aerobic only
how do eukaryotes contain their DNA?
wrapped with histone proteins into chromosomes within a nucleus.
what do prokaryotic and plant cells have that animal cells do not?
cell wall
what happens in the nucleolus of eukaryotic cells?
ribosomal RNA (rRNA) synthesis occurs (where components of ribosomes are synthesized)
what controls cellular activities including division?
nucleus
what surrounds the nucleus?
nuclear membrane
what does the nucleus contain?
DNA complexed with histone proteins to form chromosomes.
where is the nucleolus??
INSIDE the nucleus
what are ribosomes?
the site of protein synthesis
where are ribosomes synthesized?
in the nucleolus
where are ribosomes found?
in the free cytoplasm or attached to the Endoplasmic Reticulum.
what is the endoplasmic reticulum?
membranous system of channels involved in the transport of materials throughout the cell
what is the golgi apparatus?
the golgi apparatus receives vesicles and their contents from the smooth ER, modifies them, repackages them and distributes them to the cell surface by exocytosis
what happens in the rough ER?
protein synthesis (as a result of the attached ribosomes)
what happens in the smooth ER?
-the smooth ER connects the rough ER to the golgi apparatus.
-The smooth ER has detoxification properties
-assists in synthesis of lipids and steroid hormone
what are mitochondria?
-the site of aerobic respiration within the cell and the suppliers of energy! "mighty mitochondria"
-contain their own DNA
-have outer double membrane and an inner series of membranes called cristae
what is the cytoplasm?
-where most of the cells metabolic activity occurs.
-what the cell is "filled with"
what are vacuoles?
-single, membrane bound structures for storage and transport of materials that are ingested, secreted, processed or digested.
-Vesicles are tiny vacuoles.
what are lysosomes?
sacs of HYDROLYTIC ENZYMES surrounded by a membrane that are responsible for intracellular digestion
what is autolysis?
apoptosis... cell kills itself with own lysosome contents (hydrolytic enzymes)
what are peroxisomes?
organelles found in both plant and animal calls that contain catalase which converts hydrogen peroxide (a waste product of cellular respiration) into water by releasing oxygen atoms.
what cells are peroxisomes found in?
plant and animal
chloroplasts are a type of what?
plastid
what are plastids?
organelles with a double membrane found only in plant and algae cells.

there are 3 types: chloroplasts, chromoplasts, leucoplasts
what are the 3 types of plastids?
1. chloroplasts
2. chromoplasts
3. leucoplasts.
the cytoskeleton is what?
a complex network of protein filaments that extends throughout cytoplasm and gives cell its shape (cellular scaffolding), allows the cell to move and anchors organelles to plasma membrane.
what is the cytoskeleton composed of?
microtubules and microfilaments
what are microtubules?
component of the cytoskeleton-
hollow tubes made of protein tubulin that make up
1.cilia
2.flagella
3.spindle fibers
what do spindle fibers do?
help separate chromosomes during mitosis and meiosis
what are microfilaments? what are they AKA? what do they enable?
"Actin filaments"

also help support the shape of the cell like microtubules. microfilaments enable:
1. animal cells to form cleavage furrow during cell division
2. ameoba to move by sending out pseudopods
3. skeletal muscle to contract as they slide along myosin filaments.
what are the 3 non-membranous structures that lie outside the nuclear membrane?
1.centrioles
2. centrosomes
3. microtubule organizing centers
what are centrioles?
a special type of microtubule involved in spindle organization during cell division. they lack a membrane.
what type of cells contain centrioles?
animal cells

plant cells do not !
animal cells usually have a pair of centrioles oriented at a right angle in a region called what?
the centrosome
the cell membrane is AKA...
plasma membrane
what is the cell membrane/plasma membrane?
a selectively permeable membrane that encloses the cell and regulates the passage of materials into and out of the cell.
what is the fluid mosaic model?
the cell membrane (plasma membrane) consists of a phospholipid bilayer with proteins embedded throughout.
what is the plasma membrane (cell membrane) permeable to?
1.small, nonpolar molecules (oxygen)
2.small, polar molecules (water)
how do small charged molecules cross the cell/plasma membrane?
through protein channels
how do large, charged molecules cross the plasma/cell membrane?
with the assistance of carrier proteins
phospholipids are amphipathic. what does that mean?
that the phospholipids have both a hydrophobic and hydrophilic region.
in the plasma membrane, what are integral proteins?
have nonpolar regions that completely span the hydrophobic interior of the membrane.
does facilitated diffusion require ATP?
no, it is a type of passive transport
does passive transport across the cell membrane (plasma membrane) require energy?
no
what is passive transport???
the movement of dissolved particles down a concentration gradient from a region of higher concentration to a region of lower concentration until equilibrium is reached.
what are the 2 types of passive transport?
1. diffusion
2. osmosis
what are the 2 types of diffusion?
1. simple
2. facilitated
what's the difference between simple diffusion and facilitated diffusion?
simple diffusion does not involve protein channels, but facilitated diffusion does.
what does facilitated diffusion require?
a hydrophilic protein channel (to passively transport specific substances across the membrane.
what is countercurrent exchange?
a special type of diffusion - the flow of adjacent fluids in opposite directions that maximizes the rate of simple diffusion.
what is osmosis?
the simple diffusion of water from a region of LOW solute concentration to a region of HIGH solute concentration.


water flows from LOW -> HIGH solute concentration
what is a solvent?
the substance that does the dissolving
what is a solute?
the substance that is dissolved
what does hypertonic mean?
having greater concentration of solute than another solution

=high solute concentration
what does hypotonic mean?
having lesser concentration of solute than another solution.

=low solute concentration
what does isotonic mean?
2 solutions with equal concentration of solutes.
what is osmotic potential?
the tendency of water to move across a permeable membrane into a solution
in what direction does water diffuse? (relative to solute/solvent ratio)
water diffuses towards the hypertonic area (high solute)

water
what is the water potential for pure water?
zero
when the cytoplasm of a cell has a lower concentration of nonpenetrating solutes than the extracellular medium, the medium is said to be what?
hypertonic

(high solute)
when the cytoplasm of a cell has a lower concentration of nonpenetrating solutes than the extracellular medium, what direction does water flow?
out of the cell (toward the hypertonic area)
when water flows out of the cell, towards the hypertonic area, what is said to be occurring and what does it result in?
plasmolysis occurs and the cell shrinks/shrivels
when the extracellular environment is less concentrated than the cytoplasm of the cell, the extracellular medium is said to be what?
hypotonic
when the extracellular environment is less concentrated than the cytoplasm of the cell, what direction does the water flow?
into the cell
when water flows into a cell, towards the hypertonic (high solute) area, what occurs?
the cell will swell and lyse (burst)
why do red blood cells burst when placed in distilled water?
because the water flows into the cells (the blood cells are hypertonic) and causes them to lyse (the cells have no means to excrete the diffused water)
do plant cells lyse and burst when the water from their hypotonic environement diffuses into them? why?
no, the cell wall prevents the cell from bursting. the cell will just swell up and become "turgid" (this pressure is what causes celery to be crisp)

if a plant loses too much water, it's turgor pressure drops and the plant wilts.
how do fresh water protozoa avoid swelling and bursting?
they have contractile vacuoles to pump out excess water
what are aquaporins?
special water channel proteins that facilitate the diffusion of massive amounts of water across a cell membrane.
what is active transport?
the movement of molecules against a gradient, which requires ATP (energy).
what carries particles across the membrane in active transport?
1. pumps
2. carriers
what are 3 examples of active transport?
1. plastoquinone (thylakoid membrane)
2. sodium-potassium pump (nerve signals)
3. electron transport chain (mitochondria)
what is pinocytosis?
cellular "drinking" -the uptake of large, dissolved particles.

the cell membrane invaginates (sinks in) then closes around the particle
what is phagocytosis?
the engulfing of large particles or small cells by pseudopods. the cell membrane reaches out and "eats" the particle, enclosing it in a vacuole.
(white blood cells engulf bacteria)
what is receptor-mediated endocytosis?
cell takes up large quantities of very specific substances. extracellular substances bind to receptors on the cell membrane. then endocytosis begins and the receptors carrying the ligand migrate inward and pinch off, coated in a vesicle that enters the cell.

(cholesterol enters the blood this way)
what is bulk flow?
the term used to describe the movement of a fluid in one direction (from source to sink) ex:blood in humans, sap in trees
what are 4 types of cellular junctions?
1. tight junctions
2. desmosomes
3. gap junctions
4. plasmodesmata
what are 3 examples of cell to cell communication?
1. cell junctions
2. signal transduction pathways
3. cell-to-cell recognition
what are tight junctions ?
belts around the epithilial cells that line organs and serve as a barrier against leakage into or out of those organs
what are desmosomes? (type of junction)
clusters of cytoskeletal filaments from adjacent cells that are looped together. found in tissues that are subject to a lot of stess (ex: skin epithilium or neck of uterus)
what are gap junctions?
permit the passage of materials directly from the cytoplasm of one cell to the cytoplasm of an adjacent cell (ex: cardiac cells)
what are plasmodesmata?
cell junction- connects one plant cell to another.
what are plasmodesmata analogous to?
gap junctions in animal cells
what's a signal transduction pathway?
uses plasma membrane proteins in a 3 step process where a few extracellular signal molecules induce a major cellular response.
what are the 3 steps of a signal transduction pathway?
1. reception
2. transduction
3. response
what is cell to cell recognition?
cell's ability to distinguish one type of neighboring cell from another and is crucial to the functioning of multicellular organisms

how big is an average cell?

about 80 micrometers