Bio 2010 Test 2

Front 1

What are cell junction proteins, and why are they important for multicellular organisms?

Back 1

Neighboring cells in tissues, organs or organ systems often interact, adhere and communicate through direct physical contact. There are tight junctions (help prevent leakage of intracellular fluid), desmosomes (fasten cells together) and gap junctions (provide cytoplasmic channels between adjacent cells).

Front 2

List the two types of membrane transport proteins and explain how each works.

Back 2

Channel proteins: function by having a hydrophilic channel that molecules or ions can use as a tunnel. Aquaporins facilitate the passage of water.

Carrier Proteins: bind to molecules and change shape to shuttle them across the membrane.

A transport protein is specific for the substance it moves.

Front 3

Explain the difference between active transport and cotransport. What type of transport protein is required for active transport? How is ATP important?

Back 3

Active Transport: moves substances against their concentration gradient. ATP binds to the carrier protein to induce the change needed to move the substance.

Cotransport: occurs when active transport of a solute indirectly drives transport of other solutes. Plants commonly use the the gradient of hydrogen ions generated by proton pumps (this is where ATP comes in) to drive active transport of nutrients into the cell.

Front 4

Explain metabolism

Back 4

totality of an organisms chemical reaction (manages the the material and energy resources of the cell)

Front 5

Explain catabolism

Back 5

Release of energy by breaking down complex molecules to simpler compounds (cellular respiration)

Front 6

Explain anabolism

Back 6

Consume energy to build complicated molecules from simpler ones, sometimes referred to as biosynthetic pathways. (synthesis of amino acids from simpler molecules.)

Front 7

How are all three related?

Back 7

Catabolic and anabolic pathways are the "downhill" and "uphill" avenues of the metabolic landscape. Energy from downhill reactions can be stored and used for uphill reactions.

Front 8

Explain the first two laws of thermodynamics and how they apply to cells. Why must cells be open systems?

Back 8

1st Law: Principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.

2nd Law: Every energy transfer or transformation increases the entropy of the universe.

Open systems: In an open system energy and matter can be transferred between system and surroundings. Organisms, absorb energy, release heat.

Front 9

What is free energy, and what does it have to do with cellular work?

Back 9

Free energy is the portion of a system's energy that can perform work when temperature and pressure are uniform throughout a system, like a living cell.

Front 10

How does free energy change in chemical reactions or processes? How is (Delta)G calculated? What does the sign of (Delta)G tell you about the reaction or process?

Back 10

(Delta)G= (Delta)H- T(Delta)S

Change in free energy= enthalpy - absolute temp X Change in system's entropy.

If it is negative, the process is spontaneous.

Front 11

Relate the terms exergonic and endergonic to free energy change. Then explain how the total energy and entropy change in these reactions.

Back 11

Exergonic: net release of free energy and are spontaneous (less energy at the end, but are more stable)

Endergonic: absorbs energy from surroundings and is not spontaneous (more energy at end, less stable)

Front 12

When can exergonic reactions drive/fuel and endergonic one? What is the specific exergonic reaction that is commonly 'coupled' to endergonic ones in cells?

Back 12

Then energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction.

Front 13

What type of monomer is ATP?

Back 13

Nucleotide (nucleoside triphosphate)

Front 14

How is its chemical energy liberated?

Back 14

It is liberated through ATP (Free energy change)

Front 15

How do cells use ATP to drive endergonic reactions?

Back 15

Cells use the energy from the hydrolysis of ATP (an exergonic reaction) for the many endergonic processes (reactions) of the cell. ATP drives the reaction specifically by phosphorylation, transferring a phosphate group to another molecule, like a reactant.

Front 16

What other function does ATP have in cells?

Back 16

Maintaining homeostasis

Front 17

What is the "activation energy" of a reaction?

Back 17

The initial energy needed to begin a chemical reaction, also known as free energy of activation

Front 18

What type of kinetic energy allows reactants to overcome the activation energy?

Back 18

Thermal energy

Front 19

How do enzymes help reactants to over come activation energy?

Back 19

Enzymes catalyze by lowering the activation energy barrier, they hasten reactions that would occur eventually.

NOTE: They do not make an endergonic reaction exergonic, they just lower the energy needed for an already exergonic reaction to happen quicker.

Front 20

Why does a substrate bind to an enzymes active site? How does it do this?

Back 20

It binds to the active site because this is where the catalysis occurs. When the substrate is close to the enzyme it allows a shape change in order to have a snug fit (induced fit) for a successful reaction.

Front 21

Give examples of what active sites physically do to substrates to speed up chemical reactions

Back 21

The active site lowers the activation energy by:

-orienting substrates correctly

-straining substrate bonds

-providing a favorable microenvioronment

-covalently bonding to substrate

Front 22

What is an allosteric site and how does it affect an enzymes functioning?

Back 22

allosteric regulation is the regulation of a protein by binding an effector molecule at a site other than the protein's active site. The site the effector binds to is termed the allosteric site.

Front 23

Do all enzymes have allosteric sites? Active sites?

Back 23

No. To have an allosteric site, an enzyme must have multiple binding site and not all enzymes do. Yes, all have active sites, they need at least one in order for the substrate to attach.

Front 24

Explain how substrate concentration, enzyme concentration, temperature and pH affect the rate of an enzyme catalyzed reaction. Which of these are subject to change within a cell?

Back 24

All of these factors can make the reaction go quicker or slower. Each enzyme has a set of optimal conditions to favor the reaction. Temp can speed up a reaction to a certain point, and certain enzymes work better in basic or acidic environments.

Front 25

Compare and contrast competitive inhibition with noncompetitive inhibition. Which of these can be overcome by additional substrate?

Back 25

CI: bind to the active site of an enzyme, competing with the substrate

NCI: bind to another part of the enzyme, causing the enzyme to change shape and making the active site less effective.

Competitive inhibition can be overcome by substrate.

Front 26

Explain how feedback inhibition regulates the abundance of a given biomolecule.

Back 26

Prevents a cell from wasting chemical resources by synthesizing more product than is needed.

Front 27

Describe three ways that cells localize their enzymes for more efficient functioning in metabolic pathways

Back 27

Some are grouped into complexes, some are incorporated into membranes and some are contained inside organelles.

Front 28

Explain what Redox Reactions are

Back 28

Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions.

Front 29

What is oxidation and reduction?

Back 29

O: substance that loses electrons

R: substance gains electrons (positive charge is reduced)

Note: The substance that is reduced is called the oxidizing agent and vise versa.