Biology Exam #2

The cell membrane is composed of

phospholipid bilayer

phospholipids

-structural component of the membrane
-amphipathic
-selectively permeable

Cell membranes are also composed of

proteins, glycoproteins, glycolipids, cholesterol

Proteins are the ___________________ components of of membranes.

functional

Transporters, receptors, enzymes, anchors

examples of functional proteins

Cholesterol in cell membranes

maintains an optimum fluidity of the membrane in animal cells
-prevents the membrane becoming too solid in cold temperatures or too fluid in high temperatures

Glycosylation

process of attaching a carbohydrate chain to a protein or lipid

glycolipid

lipid with carbohydrate attached

glycoprotein

protein with carbohydrate attached

The carbohydrate chain in cell membranes

-provides a distinctive cellular marker
-helps protect proteins from damage

This type of model describes the cell membrane's structure

fluid-mosaic

The fluid mosaic model means that the cell membrane is

semi-flexible and a "tapestry" of several types of molecules

Since the cell membrane is semi-permeable, this allows the cell to maintain its internal conditions separate from the __________________

environment

Factors for molecules to cross membrane are

size, polarity, change

The membrane is MOST permeable to

small, hydrophobic molecules

The membrane is LEAST permeable to

large, hydrophilic, charged molecules.

Cells maintain

transmembrane gradients

chemical gradient

concentration of SOLUTE higher on one side than the other

electrochemical gradient

a chemical and electrical gradient (difference in electrical charges between the inside and outside of the cell)

Why is it important to maintain gradients?

-maintain water balance
-transmission of nerve impulses
-production of ATP

Ways that molecules move across cell membrane include

passive transport and active transport

passive transport

molecules move from area of HIGH concentration to an area of LOW concentration

Passive transport requires NO ___________ and movement is DOWN a gradient.

energy

The 3 types of passive transport

simple diffusion, facilitated diffusion, osmosis

simple diffusion

molecule passes across the membrane without help

facilitated diffusion

molecule passes across membrane with the help of membrane protein

osmosis

the net movement of a solvent (WATER) across a semi-permeable membrane into a solution with a higher solute concentration (SALT WATER)

_______________ molecules can NOT move across the membrane in osmosis.

solute

Osmosis _______________ the concentrations of solute on either side of the membrane

equalizes

Osmosis is responsible for

reabsorption of water in the kidneys
uptake of water by plant roots
dehydration resulting from cholera infection

Tonicity

relative solute concentration of one solution compared to another

HYPOtonic solution

solution has LOWER solute concentration than other solution

Isotonic

EQUAL solute concentration in both solutions
net movement 0

HYPERtonic

HIGHER solute concentration than other solution

Water movement can make a cell _________ or _________ so cells must remain isotonic across the membrane

shrink, swell

crenation

shrinking of cell in a HYPERtonic solution

osmotic lysis

swelling and bursting of a cell in a hypotonic solution

osmosis in plants:

turgor pressure and plasmolysis

turgor pressure

pushes plasma membrane against cell wall and maintains shape and size; cell in a HYPOtonic solution

Plasmolysis

plants wilt because water leaves plant cells; cell in a HYPERtonic solution

active transport

molecule is transported from an area of LOW concentration to an area of HIGH concentration and requires ENERGY; moves AGAINST the gradient

Na+K+ ATPase- transmission of nerve impulses , H+/K+ ATPase- acidifies stomach juices required for digesting food.

active transport proteins

exocytosis

material inside cell is packages into vesicles and EXPORTED OUT of the cell; active transport

endocytosis

import of a molecule INTO cell through vesicle; active transport

cell communication AKA signal transduction

process of cells detecting and responding to signals in the extracellular environment

The 3 stage process of cell responsiveness

1. receptor activation 2. signal transductions 3. cellular response

receptor activation

receptor binds signaling molecule and becomes activated

signal transduction

signal gets transmitted through the cell; a series of proteins form a signal transduction pathway

cellular response

activity of target molecules is altered to change cell behavior

Target proteins:

1. enzyme-alter metabolism
2. structural proteins-alter cell shape or movement
3. transcription factor-alter gene expression

True or false: some signaling proteins and receptors travel a short distance and bind receptors on a nearby target

True

neurotransmitters

signaling protein that travels a short distance

FSH

signaling molecules (called hormones) are released in the bloodstream and travel long distances to bind their receptors on target cells

protein kinase

enzyme that adds a phosphate to a target protein to switch them on or off

protein phosphatases

Enzymes that can rapidly remove phosphate groups from proteins.

Adding/removing a phosphate group is a way to ________________ and ________________ alter protein activity

quickly, reversibly

second messenger

amplify signal throughout the cell

cyclic AMP

second messenger

cell communication steps

1. signaling molecule binds to receptor
2. signal is transmitted via a series of proteins in the cell
3. activity of target proteins is altered to bring about cellular response

target proteins

ultimately receive a message to alter cell activity

energy

the ability to do work

the two basic forms of energy

kinetic and potential

kinetic energy

associated with movement

potential energy

stored energy

chemical energy

Energy stored in chemical bonds (form of potential energy)

chemical reaction

when one or more substances change into one or more new substances
REACTANTS to PRODUCTS

True or False: In chemical reactions, existing chemical bonds are broken and new ones are formed

True

exergonic reaction

A chemical reaction that RELEASES energy

Gibbs free energy

the difference in energy stored in the chemical bonds of reactants and products

If the energy stored in products is less than the energy stored in the old bonds THEN

products have LESS energy than reactants
Reaction is exergonic
Reaction is spontaneous

a NEGATIVE gibbs free energy indicates a

exergonic reaction

endergonic reaction

A non-spontaneous chemical reaction in which energy is ABSORBED and REQUIRED for use of reaction

If the energy stored in the products is more than the reactants THEN

products have more energy than reactants
reaction is endergonic
reaction is NOT spontaneous

Metabolism

All of the chemical reactions that occur within an organism

catabolic reactions

breakdown of molecules
used to RELEASE energy
recycle monomers (building blocks)
EXERGONIC bonds

anabolic reactions

build molecules and macromolecules
ENDERGONIC reactions

endergonic reactions

REQUIRE ENERGY

In exergonic reaction because products have less energy than reactants, there is a net _______________ of energy

release

In endergonic reactions because products have more energy than reactants, there is a net ______________ of energy

input

The energy source for many endergonic cellular reactions is

ATP

ATP is a product, what is it converted from?

ADP

catalyst

substance that speeds up the rate of a chemical reaction; is not consumed and remains unchanged at the end of the reaction

enzymes

protein catlysts

ribozymes

RNA molecules that function as catalysts.

activation energy

Energy needed to get a reaction started and to transition state

True or False: Activation energy is only needed for endergonic reactions

FALSE- it is needed for BOTH endergonic and exergonic reactions

transition state

intermediate state between reactants and products

common ways to OVERCOME activation energy

1. large amounts of heat
2. using enzymes to lower activation energy

________________ lowers activation energy

enzymes

active site

location where chemical reaction occurs

substrates

reactants, that are first affected by enzyme, that bind to active site

enzyme-substrate complex

formed when enzyme and substrate bind

Products

molecules that are formed after the reaction

The steps of an enzyme catalyzed reaction are

1. substrates bind
2. enzyme undergoes conformational change that binds substrates more tightly
3. substrates are converted to products
4. products are released

induced fit model

explains conformational change an enzyme undergoes after binding substrate.

prosthetic group

small, non-protein helper molecule permanently attached to the enzyme

cofactor/coenzymes

non-protein helper molecules NOT permanently attached to the enzyme

Coenzymes are _______________ like vitamins, but cofactors are _____-_______________ like Sulphur phosphate

organic, non-organic

True or False: ALL chemical reactions in the body are catalyzed reactions

True

factors that affect the rate of enzyme catalyzed reactions

substrate concentration, pH, temperature, and inhibitors