Intro and Membrane Transport

What is genetic diversity?

An inheritable difference based on genes that affects fitness

What is a phenotypic plasticity?

Phenotype differences based on environment within a lifetime; changes in phenotype based on environment

What is acclimation?

adjust/adapt within a lab

What is acclimatization?

adjust/adapt within nature

What is a mechanistic explanation?

• the mechanism by which a function is accomplished

• describes the biophysical/biochemical steps that brings about a particular cellular or organismal response

• ex. hemoglobin carries O2 to bring O2 to cells for cellular respiration

What is the teleological explanation?

• describes WHY a certain cellular or organismal response is desirable, but doesn’t give the mechanism that produces the response

• ex. blood circulates O2 to get O2 to cells for aerobic repsiration

What is homeostasis?

• maintenance of the internal environment within limits conducive to proper function

• NOT a properly constant internal environment

What external changes can affect homeostasis?

• water availability

• salinity

• food availability

• temperature

• O2 availability

• pH

How is homeostasis maintained?

1. sense and detect changes in the internal and external environment (sensory physiology) via nervous system

2. integrate a system-wide response to these changes, which requires communication between cells and tissues via nervous and endocrine system

3. can lead to physical activity and other responses (ex. muscles, metabolism, feelings, etc.)

How does positive feedback affect homeostasis?

drives system farther from original set point; perpetuates change

What is a feed forward mechanism?

• body anticipates future disturbance and prepares in a way that reduces the disturbance when it occurs

• counteracts disturbance before it occurs

• ex. salivate when food comes, bracing for impact

What is a temperature conformer?

• internal env matches external

• poikolotherm

What is a termperature regulator?

• internal env does not change with external environment

• homeotherm

What do enzymes do?

• regulate metabolism

• facilitate/speed up naturally occurring reactions

• lower activation energy of a reaction (do not affect thermodynamics)

How can enzymes be regulated?

• covalent modifications

• proteolytic cleavage

• association with other polypetides

• allosteric regulation

Describe enzyme regulation via covalent modification

• adding or removing a chemical via a covalent bond

• ex. phosphorylation

Describe enzyme regulation via proteolytic cleavagte

• regulates enzymes by cutting peptide bonds in the enzyem

• ex. zymogens

• ex. trypsinogen → trypsin

Describe enzyme regulation via association with other polypeptides

• enzyme regulated by binding another protein or protein subunit

• can change enzyme’s shape or inhibit/activate its activity

• enzyme does not have to chemically modfiied

• ex. cyclin-dependent kinase

Describe enzyme regulation via allosteric regulation

• molecule binds to enzyme at allosteric site

• allosteric activator increases enzyme activity

• allosteric inhibitor decreases enzyme activity

• ex. feedback inhibition

What is activation energy in regards to enzymes?

• Energy required to get a reaction going

• enzymes lower activation energy in both directions but DO NOT change delta G

What is negative feedback in regards to enzymes?

• product of reaction inhibits enzymes earlier in pathways

• maintains homeostasis

Describe enzyme kinetics, including what happens at low/high concs, and Vmax and Km

• describes how fast an enzyme-catalyzed reaction occurs and how reaction rate changes with different amounts of substrate

• at low substrate conc, adding more substrate causes the reaction rate to increase because more enzyme active sites are being occupied

• at high substrate conc, enzymes become saturated, meaning essentially all active sites are occupied, so adding more substrate no longer greatly increases the reaction rate

• Vmax = fastest possible reaction rate, saturation point

• Km = substrate concentration at which the reaction rate is ½ Vmax; measure of enzyme affinity for substrate

What is Vmax?

fastest possible reaction rate, saturation point

What is Km? What does a high and low Km indicate?

• Km = substrate concentration at which the reaction rate is ½ Vmax; measure of enzyme affinity for substrate

• low Km = enzyme has high affinity, needs less substrate

• high Km = enzyme has low affinity, needs more substrate

When [substrate] is significantly less than [enzyme], what does increasing the substrate conc. do to the rate (v)?

increases V linearly

When [substrate] is approximately equal to [enzyme], what does increasing the substrate conc. do to the rate (v)?

increases V slightly

When [substrate] is significantly more than [enzyme], what does increasing the substrate conc. do to the rate (v)?

stays at or goes to Vmax

What is competitive Inhibition and how does it affect the enzyme kinetics graph?

• enzyme regulation where inibitor competes with substrate for enzyme activate site

• takes more substrate to reach Vmax

• can be overcome by increasing substrate concentration

What is non-competitive Inhibition and how does it affect the enzyme kinetics graph?

• enzyme regulation where inhibitor binds allosterically to enzyme

• not affected by substrate concentration

• lowers Vmax

What is cooperativity and how does it affect the enzyme kinetics graph?

• form of allosteric regulation where binding of a substrate/regulator at one site changes how easily the substrate binds at other sites

• has a sigmoidal curve

• often causes conformational change to neighboring subunits

• ex. hemoglobin

What is passive transport?

• transport across plasma membrane that does not use energy

• relies on gradients

What is facilitated diffusion?

• type of passive transport

• moves small, hydrophobic molecules across membranes

• relies on help of pores, channels, or carriers

• ex. ions, glucose, H2O

What do pores move across plasma membranes?

• help charged/large substances cross

• ex. porins

What do channels move across plasma membranes?

• specific for specific molecules or types of molecules

How do carriers move things across plasma membranes?

shape changes, no hole (conformational change)

What is simple diffusion?

• movement of small, hydrophobic molecules across plasma membrane down concentration gradient

• no energy required

• ex. steroids, O2, CO2

What is active transport and its types?

• movement of molecules againt gradients, requires Energy

• primary and secondary

Describe primary active transport

• uses ATP directly to move substances against conc gradient

• Ex. Na/K ATPase pump

What is the Na/K ATPase pump and why is it important?

• primary active transport that pumps 2 K in and 3 Na out (pumpkin)

• helps cell maintain osmotic balance

• sets up resting membrane potential

• sets up gradient for secondary active transport

What is secondary active transport?

• uses energy stored in conc gradient of another susbtances (set up by primary active transport) to move molecules across gradients

• requires E

• potential energy stored in pump (created by primary active transport using ATP to set up gradient) pushes moleucles out

• ex. sodium-glucose co transporter; uses Na+ gradient set up by ATPase

What is phagocytosis?

• cellular eating

• engulfs large particles

What is pinocytosis?

liquid uptake via vesicle

What is receptor-mediated endocytosis?

uses receptors to bring specific molecules into a cell