cell/org exam 4

Why does product formation slow at high substrate concentration?

Enzymes become saturated at high substrate concentration since most active sites are occupied. The reaction approaches vmax, so adding more substrate causes little or no increase in product formation.

What are the units of the km?

Km has the same units as substrate concentration (mM). Substrate concentration where reaction rate is 1/2 of Vmax.

Differences facilitated diffusion (such shat a moving glucose into a red blood cell through the GLUT -1 transporter) and active transport (such as moving potassium ions into the cell through the sodium/ potassium pump)

Facilitated diffusion uses a Chanel or carrier protein to move a substance down its concentration gradient and does not require cellular energy. Glut-1 helps glucose enter red blood cells this way. Active transport uses energy, usually ATP, to move substances against their concentration gradients. The sodium-potassium pump uses ATP to move Na+ out of the cell and k+ into the cell.

Phagocytosis vs. Pinocytosis

Phagocytosis= phat = (cell-eating) engulfs large particles into a vacuole, which can fuse with a lysosome for digestion.

Pinocytosis (cell-drinking) takes in extracellular fluid and dissolved substances in small vesicles

Phosphorylation of glucose by enzyme hexokinase, 2 importante purposes

Keeps concentration of free glucose in the cell low, helps maintain a gradient that favors glucose entering the cell

First step of glycolysis

What are MDR proteins? How do they help microbes become resistant to antibiotics?

Multi-drug resistance. MDR proteins are transport proteins that pump a wide range of chemically different drugs out of cells. Pumping antibiotic out of microbes lowers their concentration inside the cell and reduces their effectiveness.

What do you need to do to increase the V- Max of an enzymatic reaction?

Increase enzyme concentration. Once the enzyme is saturated w/ substrate adding more substrate will not increase vmax.

Simple diffusion

Moves substances down concentration gradient, no energy

Facilitated diffusion

Moves down gradient , uses specific channel or carrier proteins

Active transport

Uses energy (usually ATP) to move substances against a gradient.

Osmosis

Diffusion of water across a selectively permeable membrane

Endocytosis

Brings material into cell using vesicles

Exocytosis

‘releases material from vesicles.

Phagocytosis

Takes in particles (phat=food=eat)

Pinocytosis

Takes influid(drink)

Receptor-mediated endocytosis

Selectively takes in substances that bind receptors

oxi do reduct ases

Oxidation-reduction reactions

Transferases:

Transfer functional groups

Hydrolyses

Break bonds using water

Lyases

Add/remove groups w/o hydrolysis or oxidation, often forming double bonds

ISomerase's

Rearrange atoms within a molecule

Ligases

Join molecules, usually using energy from atp

.michaelis - mention equation

V= (vmax X [s] )/(Km+[S])

V = velocity

Initial reaction

[S]

Substrate concentration

V Max

Max velocity at saturating substrate

Km

Substrate concentration at half v-max

Have same concentration units

Km and [s]

Competitive inhibitors

Bind @ active site

Compete w/ substrate (excess overcomes obvi)

Non-competitive inhibitors

Km remains unchanged while v-max decreases

Bind outside the active site and reduce catalytic activity

Feedback inhibition

Occurs when a pathways end product inhibits an earlier step, preventing waste

Metabolism

‘the totality of an organisms chemical reaction

Catabolic pathways

Break complex molecules down and release energy.

Anabolic pathways

Use energy to build complex

ATP

‘ Couples energy-releasing reactions to energy - requiring cellular work

Enzymes

Speed reactions by lowering activation energy

Aren't consumed

Some require cofactors

. Coenzymes

D.erived from vitamins

(Organic cofactors)

.substrates

Bind at the enzymes active site