BBE 3013 Final Exam

How do you determine the sign for the term ZFΔV based upon different ions and their transport across a membrane?

-If an ion is moving towards a region with the opposite charge (positive ion moving towards a negative region) then the sign will be Negative (Favorable).

-If an ion is moving towards a region with the same charge (positive ion moving towards a positive region), then the sign will be Positive (Unfavorable).

In facilitated diffusion, what limits the maximum rate of diffusion that can be achieved?

-The number of available carrier proteins in the cell membrane.
-The carrier proteins reach a saturation point where all the carrier proteins are bound to molecules, which prevents further transport.

Passive Diffusion

Diffusion of molecules from an area of higher concentration to an area of lower concentration.

Active Transport

Diffusion of molecules from an area of lower concentration to an area of higher concentration (against the gradient)

What common energetic compound in the cell is often associated with active transport or membrane pumps?

ATP

What is ATP?

-adenosine triphosphate
-provides the energy required for active transport.

Cholesterol

Found between non-polar chains to make the cell more rigid and strong.

Differences between uniport, symport, and anti-port

All 3 move molecules across the cell membrane through carrier proteins.
Uniport: moves a SINGULAR molecule
Symport: moves TWO different molecules in the SAME direction.
Antiport: moves TWO different molecules in OPPOSITE directions.

How do you calculate delta G for membrane transport?

G= RTln(c2/c1)+ZF(delta)V
c1- concentration of the starting side of the membrane.
c2- concentration of the ending side of the membrane.
Z- charge of the ion
F- Faraday's constant
Delta V - membrane potential difference across the membrane.

Facillitated diffusion

A type of passive diffusion that utilizes a carrier protein to move from high to low concentrations of molecules.

What does it mean when a substance is coupled to an ion in a transporter?

The movement of the substance is directly linked to the movement of the ion, the substance cannot move without the ion.

How do you convert Celsius to Kelvin?

Kelvin = Celsius + 273.15

How do you determine μm from a double reciprocal plot for a chemostat operating at varying dilution rates (D)?

μm = D(Ks+[S])/[S]

How do you determine Yx/s(M) from a double reciprocal plot for a chemostat operating at varying dilution rates (D)?

Yx/s(M)= -(Delta)X/(Delta)S

How do you determine Ks from a double reciprocal plot for a chemostat operating at varying dilution rates (D)?

Ks = [S] when uG is 1/2 max

How do you determine Kd from a double reciprocal plot for a chemostat operating at varying dilution rates (D)?

Kd = -1/X-intercept

What does Ks represent in biological terms?

-Interchangeable with Km
-Michaelis constant
-Represents the substrate concentration when the reaction is at half of its rate (Vmax=1/2)

What does Kd represent in biological terms?

Loss of cell mass due to cell death OR metabolism.

What does Yx/s(M) represent in biological terms?

Maximum growth rate

What does Yx/s(AP) represent in biological terms?

Apparent growth rate

How do you calculate Yx/s(AP)

Yx/s(AP)= X/(S0-S)

How would you calculate the theoretical value of S for a chemostat at steady state?

S= Ks(D+Kd)/(uM-D-Kd)

How would you calculate the theoretical value of X for a chemostat at steady state?

X= Yx/s(M)[S0-S](D/D+Kd)

Membrane Function

-separate two aqueous solutions
-non-polar regions can act as an insulator
-if a difference in charge builds up on one side of the membrane, an energy can be associated with the membrane.

How do channels work?

-Facilitate transport via diffusion from thermodynamically favorable situations (ex: concentration gradients).
-Driven by entropy

What do pumps require?

-An energy import (usually ATP) to drive transport uphill.

Lipids

Form the structure of the bilayer

Sterols

give the membrane structure (ex: cholesterol)

Proteins

Make up a significant % of the membrane overall, perform a variety of functions.

Lipid bilayers

-forms a barrier to the passage of molecules in and out of the cell.
Impermeable to: proteins, amino acids, nucleic acids, and carohydrates.
Permeable to: lipids, lipid-like structures, and gasses. (AND WATER)

What makes up the lipid bilayer

Phospholipids
-Aligned tail to tail, the non-polar tails form a hydrophobic region between the hydrophilic polar head.

Role of membrane proteins

-Catalytic: they are an anchoring point for enzymes and filaments, also binding sites for messenger molecules.
-Receptors for signals such as hormones.
-Transport
-Structural integrity

Na+/K+ pump

-transports Na+ ions out of cell and K+ ions into cell.
-present in every cell, it maintains the Na/K gradient

Four functions required for a carrier to transport a substance.

1. Recognition: specifically bind to the substance being transported.
2. Translocation: movement from one side of the membrane to the other.
3. Release: on the other side of the protein
4. Recovery: return of the carrier to its original condition so it can go through another cycle of transport.

Why are membrane potentials important to cell function?

-energy transduction
-solute transport
-cell signaling

Enthalpy

The heat content of a reacting system
-negative value --> exothermic
-positive value --> endothermic

Entropy

Measure of disorder

Gibbs free energy

an expression of the amount of energy capable of doing work during a reaction at constant temperature and pressure.

Why do biological systems couple reactions?

-They need to be able to drive unfavorable reactions.
-Couple a favorable one with an unfavorable one so the overall reaction is favorable.

What is the main energy donor in biological systems?

ATP

Reducing agent

electron donor

Oxidizing agent

electron acceptor

Types of batch reactors

1. Test tubes (Erlenmeyer)
2. Fermentation
3. Anaerobic Growth

Test tubes (erlenmeyer)

-oxygen can be limited
-can have temperature control in incubator

Fermentations

-can add oxygen
-can add pH control and temperature control.

Chemostat

Cells are removed at a rate that should be equal to their growth rate, so the growth rate is equal to the dilution rate.

When will you reach washout?

Dilution rate > Um
At this point the culture is diluted to a point it cannot maintain.

What will happen if you operate a chemostat for a significant amount of time?

You will reach a steady state.

Continuous reactor ran in chemostat

-Regulated by limiting a specific nutrient in the media.
-Dilution rate is constant
-Nutrients control the cell growth rate

One run in turbidostat mode

-Regulated by adjusting the flow rate based on the culture.
-Cell concentration remains constant
-Specific growth rate controls cell growth.

Utility of chemostat

Studying the effects of the different dilution rates or limiting nutrients on microbial growth

Utility of turbidostats

Useful for maintaining cultures in the exponential growth phase.