Biology Exam #2

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The cell membrane is composed of

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The cell membrane is composed of

phospholipid bilayer

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phospholipids

-structural component of the membrane -amphipathic -selectively permeable

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Cell membranes are also composed of

proteins, glycoproteins, glycolipids, cholesterol

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Proteins are the ___________________ components of of membranes.

functional

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Transporters, receptors, enzymes, anchors

examples of functional proteins

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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

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Glycosylation

process of attaching a carbohydrate chain to a protein or lipid

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glycolipid

lipid with carbohydrate attached

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glycoprotein

protein with carbohydrate attached

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The carbohydrate chain in cell membranes

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

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This type of model describes the cell membrane's structure

fluid-mosaic

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The fluid mosaic model means that the cell membrane is

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

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

environment

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Factors for molecules to cross membrane are

size, polarity, change

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The membrane is MOST permeable to

small, hydrophobic molecules

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The membrane is LEAST permeable to

large, hydrophilic, charged molecules.

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Cells maintain

transmembrane gradients

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chemical gradient

concentration of SOLUTE higher on one side than the other

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electrochemical gradient

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

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Why is it important to maintain gradients?

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

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Ways that molecules move across cell membrane include

passive transport and active transport

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passive transport

<p>molecules move from area of HIGH concentration to an area of LOW concentration</p>

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

<p>molecules move from area of HIGH concentration to an area of LOW concentration</p>
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Passive transport requires NO ___________ and movement is DOWN a gradient.

energy

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The 3 types of passive transport

simple diffusion, facilitated diffusion, osmosis

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simple diffusion

molecule passes across the membrane without help

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facilitated diffusion

molecule passes across membrane with the help of membrane protein

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osmosis

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

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_______________ molecules can NOT move across the membrane in osmosis.

solute

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

equalizes

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Osmosis is responsible for

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

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Tonicity

relative solute concentration of one solution compared to another

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HYPOtonic solution

solution has LOWER solute concentration than other solution

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Isotonic

EQUAL solute concentration in both solutions net movement 0

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HYPERtonic

HIGHER solute concentration than other solution

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

shrink, swell

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crenation

shrinking of cell in a HYPERtonic solution

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osmotic lysis

swelling and bursting of a cell in a hypotonic solution

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osmosis in plants:

turgor pressure and plasmolysis

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turgor pressure

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

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Plasmolysis

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

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active transport

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

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

active transport proteins

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exocytosis

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

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endocytosis

import of a molecule INTO cell through vesicle; active transport

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cell communication AKA signal transduction

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

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The 3 stage process of cell responsiveness

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

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receptor activation

receptor binds signaling molecule and becomes activated

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signal transduction

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

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cellular response

activity of target molecules is altered to change cell behavior

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Target proteins:

  1. enzyme-alter metabolism

  2. structural proteins-alter cell shape or movement

  3. transcription factor-alter gene expression

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

True

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neurotransmitters

signaling protein that travels a short distance

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FSH

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

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protein kinase

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

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protein phosphatases

Enzymes that can rapidly remove phosphate groups from proteins.

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

quickly, reversibly

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second messenger

amplify signal throughout the cell

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cyclic AMP

second messenger

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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

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target proteins

ultimately receive a message to alter cell activity

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energy

the ability to do work

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the two basic forms of energy

kinetic and potential

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kinetic energy

associated with movement

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potential energy

stored energy

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chemical energy

Energy stored in chemical bonds (form of potential energy)

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chemical reaction

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

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

True

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exergonic reaction

A chemical reaction that RELEASES energy

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Gibbs free energy

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

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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

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a NEGATIVE gibbs free energy indicates a

exergonic reaction

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endergonic reaction

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

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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

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Metabolism

All of the chemical reactions that occur within an organism

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catabolic reactions

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

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anabolic reactions

build molecules and macromolecules ENDERGONIC reactions

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endergonic reactions

REQUIRE ENERGY

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

release

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

input

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The energy source for many endergonic cellular reactions is

ATP

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ATP is a product, what is it converted from?

ADP

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catalyst

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

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enzymes

protein catlysts

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ribozymes

RNA molecules that function as catalysts.

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