Bio ch 5 Flashcards
what is the plasma membrane
the boundary between the living cell and the environment
what is a fluid mosaic
how biologists describe the structure of membranes
what is the structure of membranes
a bilayer of phospholipids with embedded and attached proteins
what does cholesterol do in animal cell membranes
helps stabilize the membrane at warm temperatures but also keeps the membrane fluid at warmer temperatures
what are the 6 major functions performed by membrane proteins
enzymatic activity cell to cell recognition intercellular junctions transport signal transduction attachment to the cytoskeleton and extracellular matrix
what is selective permeability
allowing some substances to cross more easily then others
what is a phospholipid
made of a hydrophilic head made of an alcohol and a phosphate group and and two hydrophobic tails made of chains of fatty acids
how do phospholipids get their kinked tails
double bonds
what gets through the phospholipid bilayer fairly easily
non polar molecules (O2, CO2, lipids)
what needs the help of proteins to get through the phospholipid bilayer
polar molecules
what is a glycoprotein
a carbohydrate attached to a protein
what is a glycolipid
a carbohydrate attached to a lipid
what is the function of glycoproteins and glycolipids
they are used as receptor molecules, binding with hormones or neurotransmitters to trigger a series of chemical reactions within the cell itself.
what is signal transduction
the message-transfer process in which a a protein functions as a receptor for a signaling molecule from another cell. The binding of this signaling molecule triggers a change in the protein, which relays the message to the cell, activating molecules that perform specific functions
what is passive transport
diffusion across a membrane with no energy investment
what is diffusion
the tendency for particles of any kind to spread out evenly in an available space; they spread from high concentration to low concentration - down the concentration gradient
how can ions and non polar molecules diffuse across the hydrophobic interior of a membrane
if they are moving down their concentration gradients and if they have transport proteins to help them cross
what is an example of passive transport
it happens in the lungs with CO2 and O2
what is facilitated diffusion
when polar molecules can diffuse across its concentration gradient with the help of a transport protein
what does a transport protein do
create an avenue for travel for polar molecules and/or may change its shape, polarity or charge
what is osmosis
Diffusion of water across a selectively permeable membrane to obtain equal concentration of solute
what is tonicity
loss or gain of water in a cell
isotonic
when the concentration of solute in the cell is equal to the concentration of solute outside the cell
hypotonic
when the concentration of solute in the cell is more than the concentration of solute outside the cell
hypertonic
when the concentration of solute in the cell is less than the concentration of solute outside the cell
what is osmoregulation
the control of water balance that an animal uses to survive in a hypnotic or hypertonic environment to prevent excessive uptake or loss of water
what happens to an animal cell placed in a hypotonic solution
it will burst (lyse)
what happens to an animal cell placed in hypertonic solution
it will shrivel and could die from water loss
what happened to an animal cell placed in isotonic solution
the volume remains constant
why are water balance issues somewhat different for plant cells
because of their cell walls
what happens to a plant cell placed in an isotonic solution
it is limp, flaccid
what happens to a plant cell placed in hypotonic solution
it is turgid, very firm, and this is the healthy state for most plant cells
what happens to a plant cell placed in hypertonic solution
it shrivels and its plasma membrane pulls away from the cell wall
what is plasmolysis
when a plant cell loses water, shrivels, and its plasma membrane pulls away from the cell
is facilitated diffusion active or passive transport
passive
what are two ways transport proteins help polar molecules or ions diffuse through the membrane
- by providing a hydrophilic channel that some molecules or ions use as a tunnel through the membrane
- by binding the ion/molecule, changing shape, and releasing it on the other side
what is active transport
a cell must expend energy to move a solute against its concentration gradient
what supplies the energy for active transport
ATP
describe the active transport process
- Solute in cell binds attaches to a transport protein
- ATP phosphorylates the protein
- Transport protein changes shape and releases solute onto other side of the cell
- Phosphate group detaches and transport protein returns to its normal shape
what does active transport allow for
a cell to maintain internal concentrations of small molecules and ions that are different concentrations in its surroundings (examples are potassium ions and sodium ions)
what is exocytosis
exports bulky materials like proteins or polysaccharides
how does exocytosis work
Big molecules in vesicles fuse with plasma membrane and then spill its contents outside of the cell.
what is endocytosis
the process in which a cell takes in a large molecule and forms a vesicle or vacuole in plasma energy
what are the 3 types of endocytosis
phagocytosis, pinocytosis, and receptor-mediated endocytosis
what is phagocytosis
a type of endocytosis in which a cell engulfs a particle by wrapping extensions around it called pseudopodia and packaging it within a membrane closed sac large enough to be a vacuole
what is pinocytosis
a type of endocytosis in which a cell gulps droplets of fluid into tiny vesicles; it is non-specific - it takes in any and all solutes dissolved in the droplets
what is receptor mediated endocytosis
a highly selective form of endocytosis; the plasma membrane indents to form a coated pit with receptor proteins for specific molecules. the coated pit then pinches closed to form a vesicle that carries the molecules into the cytoplasm
what is energy
the capacity to cause change or perform work
what are the 2 basic forms of energy
kinetic and potential
what is kinetic energy
the energy of motion
what is heat (thermal energy)
a type of kinetic energy associated with the random movement of atoms or molecules
what is potential energy
energy that matter possesses as a result of its location or structure
what is chemical energy
the potential energy available for release in a chemical reaction
what is thermodynamics
the study of energy transformations that occur in a collection of matter
what is an open system
it exchanges both energy and matter with its surroundings
what is the 1st law of thermodynamics
energy cannot be created or destoryed
what is entropy
a measure of disorder
what is the 2nd law of thermodynamics
energy conversions increase the disorder of the universe
what is the fuel source for cells
sugar
what 2 molecules are necessary to create the fuel for cells
glucose and oxygen
what happens in cellular respiration
chemical energy stored in organic molecules is covered to a form that the cell can use to perform work
what is an exergonic reaction
a chemical reaction that releases energy
what is an example of an exergonic reaction
wood burning
what is an endergonic reaction
they yield products that are rich in potential energy
what is an example of an endergonic reaction
photosynthesis
what is metabolism
the total of an organism’s chemical reactions
what is a metabolic pathway
a series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds
what is the metabolic pathway of cellular respiration
a sequence of reactions that slowly releases the potential energy stored in sugar
what is energy coupling
the use of energy released from exergonic reactions to drive essential endergonic reactions
how does the ATP cycle provide energy
energy released in exergonic reactions is used to regenerate ATP from ADP. In this endergonic process, a phosphate group is bonded to ADP. The hydrolysis of ATP releases energy that drives endergonic reactions
how is the ATP cycle an example of energy coupling
in the ATP cycle, it uses energy released from exergonic reactions to drive endergonic reactions
what are the 3 main types of cellular work driven by ATP
mechanical, chemical, transport
what is activation energy
the amount of energy needed for a reaction to take place
what are enzymes
proteins that act as biological catalysts
what do enzymes do
speed up a reaction by lowering the activation energy
what is a substrate
the specific reactant that an enzyme acts on; it fits into a region of the enzyme called an active site
what is an active site
typically a pocket or a groove on the surface of the enzyme; where the reaction takes place
what makes enzymes specific
their active sites fit only specific substrate molecules
what is induced fit
strain on the bonds to hold in certain orientation
what are the optimal conditions for enzymes
temps of close to our body temp and pHs close to neutrality
what are cofactors
nonproteins that help enzymes by binding to the active site and functioning in catalysis
what are coenzymes
cofactors that are organic molecules
what is an enzyme inhibitor
it interferes with an enzyme’s activity
what is a competitive inhibitor
Binds covalently to active site so it is irreversible
how can competitive inhibition be overcome
by increasing the concentration of the substrate, making it more likely that a substrate molecule rather than an inhibitor will be nearby when an active site becomes vacant
what is a noncompetitive inhibitor
binds somewhere on the enzyme and changes the shape of the enzyme so that the active site no longer fits the substrate
what is a feedback inhibitor
catalysis is blocked by its own products
