Biology Exam 2 Flashcards
What structures are only found in plant cells?
Chloroplasts
Large Vacuole
Plant Cell Walls
Where else do chloroplasts occur?
algae protists
Where else do cell walls occur?
algae protists
fungi
What are plastids
DNA containing genomes that synthesize proteins on ribosomes
Give some examples of plastids?
chloroplasts-yellow/green
amyloplasts-colorless plastids that store starch
chromoplasts-responsible for color in ripening fruit
Chloroplasts are surrounded by…
an outer boundary membrane and an inner boundary membrane that enclose inner stroma
What is contained in the stroma?
grana containing stacked thylakoids
Thylakoids contain?
chlorophyll
____ are large vesicles that perform specialized functions unique to plants
central vacuoles
Central vacuoles take up ____ of a plant cell
90%
The membrane thtat surrounds the central vacuole is called the
tonoplast
Central Vacuole Functions
-store salts, organic acids, sugars, pigments, proteins
-contains enzymes that breakdown macromolecules
-provide chemical defense
Cell Wall Functions
support individual cells
contain the pressure from central vacuole
protect cells against invading bacteria/fungi
what part of the cell wall is soft and flexible
primary cell wall
the _______ consists of additional layers of cellulose fibers and branched carbs
secondary cell wall
lignin reinfornces secondary cell walls in
woody plants
middle lamella holds together _____ with a layer of _____
the walls of adjacent cells; polysaccharides (pectin)
Plasmodesmata are
plasma membrane line channels that connect cytosols of adjacent cells
What are the specialized structures that organize animal cells
cell adhesion molecules
cell junctions
extracellular matrix (ECM)
Cell adhesion molecules are ______ in the plasma membrane that bind to molecules on other cells
glycoproteins
cancer cells lose
cell adhesion molecules
anchoring junctions examples
desmosomes-anchoring junctions within intermediate filaments
adherens junctions- microfilaments anchor the cytoskeleton
tight junctions
gap junctions
where are anchoring junctions most common in?
tissue that stretch, shear, or perform other mechanical functions
tight junctions
regions of tight connections btwn membranes of adj cells
seal spaces btwn cells
formed by direct fusion of proteins on the outer suraces of plasma membranes of adj. cells
Gap Junctions
open direct channels that allow ions and sm moelcules to pass directly from one cell to another
the ECM consists of
proteins and polysaccharides
what does the ECM form?
skin, bones, tendons, etc
ECM effects
cell division, adhesion, motility, and embyonic development
______ are the main component of ECM
glycoprotein (collagen)
fibronectins bind to _____ in the ________
receptor proteins; plasma membrane
consistency of the ECM depends on
proteoglycans that surround the collagen fibers
biological membranes consist of
lipids and proteins assembled into a thim film
two major types of lipids in membranes
phospholipis and sterols
structure of a phospholipids
glycerol
2 fatty acids attached to the glycerol (NP and Hydrophobic)
phosphate group attached to glycerol (P and hydrophilic)
phospholipids spontaneously form a
bilayer
sterol structure
nonpolar carbon ring with nonpolar side chain and single polar -OH group
sterols are found in the
phospholipid bilayer
what is the main sterol in animal membranes
cholesterol
what is the fluid mosaic model
proposes that the membrane consists of fluid phospholipid bilayer in which embedded proteins float freely
integral proteins are embedded in the
phospholipid bilayer
peripheral proteins are held to membrane surfaces by
noncovalent bonds
purpose of membrane proteins
-transport
-recognition
-receptors
-cell adhesion
does temperature help membrane fluidity
yes
-low temp= more stiff
-high temp=more fluid
unstauration increases fluidity
true
eukaryotic organisms adapt to colder temperatures by changing membrane lipids
true
Frye and Edidin experiment summary
created chimera and discovered that proteins intermix (move about the cell)
biological membranes are not selectively permeable
false
charged atoms and molecules are blocked by ________
hydrophobic core
passive transport goes _____ gradient
with
active transport goes _____ gradient
against
Examples of passive transports
-simple diffusion
-facilitated diffusion
-osmosis
difference between primary and secondary active transport
-primary uses energy from ATP
-secondary uses energy in forms other than ATP
What is simple diffusion
diffusion through lipid part of membrane
goes with concentration gradient
nonpolar inorganic gases (O2, N2, CO2)
depends on molecular size and lipid solubility
what is facilitated diffusion
diffusion of polar and charged molecules through transport proteins
What proteins are used in facilitated diffusion
-channel proteins
-aquaporins
-ion channels
-gated channels
What are carrier proteins?
they transport ions and other solutes across the plasma membrane by physically binding molecules to one side of the membrane and releasing them on the other
what is osmosis
passive diffusion of water across selectively permeable membrane in response to concentration gradients
osmosis scan cause cells to swell and burst or shink and shrivel
true
osmotic pressure is the force needed to
stop osmotic flow
what is tonicity
property of a solution with respect to a particular membrane
Hypotonic solution
solution around the cell of nonpenetrating solutes is lower than solution in the cell
Water enters and the cell swells then the solution is….
hypotonic
Hypertonic solution
solution around the cell has more nonpenetrating solutes than solution in teh cell
water leaves and the cell shrinks then the solution is…
hypertonic
isotonic solution
concentration of solutes in and out of cell are balanced (equal)
_______ cells constantly use energy to actively transport Na+ from inside to outside in order to keep fluids on either side of the plasma membrane _______
animal; isotonic
Plasmolysis effects
contents of plant cells shrinks
Name two ways organisms can maintain osmotic balance
- extrusion
- turgor pressure
What is extrusion
water is ejected through contractile vacuoles
What is turgor pressure
pushes the cell membrane against the cell wall to keep the cell rigid
transport of substances across a membrane AGAINST concentration gradient requires….
active transport
Active transport requires….
energy input
What are the three main functions of active transport
- uptake of essential nutrients from fluid surrounding cells
- Removal of secretory or waste materials from cells/organells
- Maintenance of intracellular concentrations of H+, Na+, K+, Ca2+
What is membrane potential
active transport of ions that contribute an electrial charge across the plasma membrane
neurons and muscle cells use membrane potential in response to what
stimulus- when membrane potential changes rapidly and transiently
What are the two kinds of active transport
primary and secondary active transport
what is primary active transport
the protein that transports a substance also hydrolyzes ATP to power the transport directly
What is secondary active transport
transport indirectly driven by ATP hydrolysis
what active transport requires energy and moves substances from low to high concentration by carrier proteins
primary active transport
The sodium-potassium pump is an example of….
primary active transport
Sodium-potassium pump moves _____ Na+ ____ of the cell and ___ K+ ____ the cell
3; out; 2; in
What are the 4 domains of the sodium-potassium pump
- Nucleotide binding
- Phosphozation
- Mediator
- Transmembrane
What is the sequence of the sodium-potassium pump
inside facing, binding of Na+, binding of ATP, phosphate binds to pump, conformational change (faces outward), Na+ released, K+ binds, dephospozation, change in conformation (inside facing), releases K+
What does the calcium pump do
moves Ca2+ from cytoplasm to cell exterior and from the cytosol into the vesicles of the ER
what does the Ca2+ gradient regulate
secretion, microtubule assembly and muscle contraction
Secondary active transport pumps use an _____ concentration gradient established by a _______ as an energy source
ion; primary pump
What happens in symport secondary active transport?
the solute moves through the membrane channel in the same direction as the driving ion
What happens in antiport secondary active transport?
the solute and driving ion move through the membrane channel in opposite directions
When does endocytosis occur?
Endocytosis occurs when proteins and other substances are trapped in pit-like inward depressions from the plasma membrane
What is non-specific endocytosis (opinocytosis)?
the cell takes in only fluid
What is specific recepto-mediated endocytosis?
specific molecules are taken in after they bind to a receptor
what is the depression in the plasma membrane called during endocytosis?
coated pit
what coats and reinforces the “coated pit”? on what side?
clathrin proteins on the cytoplasm side
What is phagocytocis?
taking in of particles by phagocytes. happens in protists
