Biology Honors - Chapter 5

good luck

aquaporins

common in cells involved in water; a transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (EX: kidneys use them to filter water)

fluid Mosaic Model

the currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids

selective permeability

it allows some substances to cross more easily than others

attachment protein

proteins that attach to the extracellular matrix and cytoskeleton help support the membrane and can coordinate external and internal changes

receptor protein

signaling molecules bind to receptor protein which relay messages by activating other molecules inside the cell

active transport protein

transport proteins allow specific ions or molecules to enter or exit the cell

glycoprotein

may serve as ID tag that are recognized by membrane proteins of other cells

biological membrane

built by phospholipids & proteins; largest and most primitive organelle that gives compartmentalization; semi-permeable; lipids make it impermeable to water and proteins are used for transport

in the origin of the cell, why would the formation of a simple lipid bilayer membrane not be sufficient? what else would have to be apart of such membrane?

the membrane would need embedded proteins that could regulate the movement of substances into and out of the cell

diffusion

the tendency for particles of any substance to spread out into the available space

concentration gradient

an increase or decrease in the density of a chemical substance in an area; cells often maintain concentration gradients of ions across their membranes; when a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated

dynamic equilibrium

solutions on both side will at a point have equal concentrations on both sides and molecules still move back and forth, but there is no net change in concentration on either side of the membrane

passive transport

requires NO energy, movement of molecules from high to low concentration, moves with the concentration gradient

traffic across the cell membrane mostly occurs by?

diffusion

why is diffusion across a membrane called passive transport?

the cell does not expend energy to transport substances that are diffusing down their concentration gradients

what is one of the most important substances that crosses membranes by passive transport?

water

osmosis

diffusion of water through a selectively permeable membrane

solute

a substance that is dissolved in a solution

list as high or low solute concentration- 0.5% & 2%

0.5% = lower solute concentration & 2% = higher solute concentration

tonicity

the ability of a surrounding solution to cause a cell to gain or lose water; depends on its concentration of solutes relative to the concentration of solutes inside the cell

isotonic

the cells volume remains constant

what way is red blood cells transported in the blood?

isotonic plasma

hypotonic

a solution with a solute concentration lower than that of the cell

hypertonic

Having a higher concentration of solute than another solution

osmoregulation

in animals; a way to survive in hypotonic and hypertonic; to prevent excessive uptake or loss of water and regulate the solute concentration of its body fluids

osmoregulation (plants)

differ due to cell walls; hypotonic plants usually are turgid or very firm which is healthy and will exert back a turgor pressure to ensure it will not take in too much; when there is not net movement the plant is flaccid or limp

plasmolysis

a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

facilitated diffusion

a process in which substances are transported across a plasma membrane with the concentration gradient with the aid of carrier (transport) proteins; does not require the use of energy.

active transport

a cell must expend energy to move a solute against its concentration gradient - that is across the membrane toward the side where the solute is more concentrated; allows a cell to maintain internal concentrations of small molecules and ions that are different from concentrations in its surrounding

cells actively transport Ca2+ out of the cell. Is calcium more concentrated inside or outside of the cell?

outside: active transport moves against its concentration gradient

exocytosis

the movement of materials OUT of a cell by the fusion of vesicles with the plasma membrane (used in large cells)

endocytosis

a transport process through which a cell TAKES IN large molecules

phagocytosis

"cellular eating"

pseudopodia

extensions

receptor-mediated endocytosis

enables a cell to acquire specific solutes

low-density lipoproteins

LDLs; the form of lipoprotein in which cholesterol is transported in the blood

atherosclerosis

a disorder in which cholesterol and calcium build up inside the walls of the blood vessels, forming plaque, which eventually leads to partial or complete blockage of blood flow

as a cell grows, its plasma membrane expands; does this involve endocytosis or exocytosis?

exocytosis: when a transport vesicle fusses with the plasma membrane its contents are released and the vesicle membrane adds to the plasma membrane

energy

the capacity to cause change or to preform work

Kinetic energy

the energy of motion

thermal energy

a type of kinetic energy associated with the random movement of atoms or molecules

heat

thermal energy in transfer from one object to another

potential energy

second main form of energy, is energy that matter possesses as a result of its location or structure

chemical energy

the potential energy available for release in a chemical reaction

thermodynamics

study of energy transformation that occurs in a collection of matter

system

word used by scientists for the matter under study and refer to the rest of the universe

surroundings

everything out side of the system

1st law of thermodynamics

known as the law of energy conservation, states that the energy in the universe is constant

it can be TRANSFERRED and TRANSFORMED but cannot be CREATED or DESTROYED

cellular respiration

the chemical energy stored in organic molecules is used to produce ATP, which the cell can use to perform work

2nd law of thermodynamics

energy transformations result in the universe becoming more disordered

exergonic

energy RELEASED

endergonic

any process that ABSORBS energy

metabolism

the total of an organism's chemical reaction

metabolic pathway

a series of chemical reactions that either build a complex molecule or break down a complex molecule into simple compounds

energy coupling

the use of energy released from exergonic reactions to drive endergonic reactions

ATP

adenosine triphosphate; powers nearly all forms of cellular work; consist of an organic molecule called adenosine and a triphosphate tail of three phosphate groups. all negatively charged ; bonds are unstable

adenosine diphosphate

ADP; when the bond of the 3rd group in ATP breaks and a phosphate will leave; energy is released

phosphorylation

the transfer of a phosphate group, usually from ATP, to a molecule. nearly all cellular work depends on ATP energizing other molecules by phosphorylation

what type of work does a cell do?

chemical, transport, and mechanical

ordered structures tend towards _____.; high energy systems tend to change toward a more ______ state of energy.

disorder; stable

activation energy

energy needed to get a reaction started

enzymes

molecules that function as biological catalysts

substrate

a specific reactant acted upon by an enzyme

active site

typically a pocket or groove on the surface of the enzyme

catalytic cycle

substrate + enzyme --> enzyme substrate complex --> product + enzyme

induced fit

brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction.

human enzymes work best at ?

35-40 degrees Celsius (95-104 degrees F)

prokaryotes enzymes living in hot springs work best at?

70 *C (158*F)

optimal ph for enzymes is?

around neutral

cofactors

NONPROTEIN helpers

coenzyme

ORGANIC molecule in a cofactor

inhibitor

a chemical that interferes with an enzyme's activity

competitive inhibitor

reduces an enzyme's productivity by blocking substrate molecules from entering the activity site

noncompetitive inhibitor

does not enter the active site, instead binds to a site elsewhere on the enzyme

cells use inhibitors for what purpose?

important regulators of cellular metabolism

feedback inhibition

a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway

what is the advantage to feedback inhibition ?

it prevents the cell from wasting valuable resources by synthesizing more of a particular product that is needed

name a common drug that inhibits an enzyme involved in the production of prostaglandins - messenger molecules that increase the sensation of pain and inflammation?

Ibuprofen

what determines whether enzyme inhibition is reversible or irreversible?

if the inhibitor binds to the enzyme with covalent bonds, the inhibition is usually irreversible; when weak chemical interactions bind inhibitor and enzyme, the inhibition is reversible