BIO EXAM: Fifth lecture

Transmembrane Domains

Hydrophobic amino acids arranged in alpha-helixes

Is this part of a transmembrane domain hydrophobic or hydrophilic?

Hydrophobic

Is this part of a transmembrane domain hydrophobic or hydrophilic?

Hydrophilic

DNA has…

planned information!

Pores

Interior is polar and allows water and small polar molecules to pass through the membrane

What is this?

Beta-Barrel protein

Passive Transport

Movement of molecules through the membrane in which - NO ENERGY IS REQUIRED

What do molecules move in response to?

A concentration gradient

What is diffusion?

Movement of molecules from high concentration to low concentration
• Will continue until the concentration is the same in all regions. until it hits (Equilibrium)

The membrane is selectively permeable because of

The channels and carriers→ specific target solute

Facilitated diffusion?

-Molecules that can’t cross membrane easily will move through proteins

Channel proteins

Hydrophilic channel when open

Carrier proteins

Bind specifically to molecules they assist

What does not need energy?

Facilitated diffusion of ions → It uses a concentration gradient

This is?

Diffusion in!

This is?

Diffusion out

Facilitated Diffusion By Carrier Proteins

Channel proteins→Ion channels

Allow the passage of ions through nonpolar interior of
plasma membrane

Gated channels

open or close in response to stimulus
(chemical or electrical)

Three conditions determine direction:

Relative concentration, voltage differences, and gated channels

Relative concentration

on either side of membrane

Voltage differences

across membrane

Gated channels

is channel open or closed

Carrier Proteins

Can help transport both ions and other solutes, such as some sugars and amino acids→ must bind to the molecule they transport

Saturation

rate of transport limited by number of transporters

Active Transport requires

Requires energy – ATP is used directly or indirectly to fuel
active transport

Active Transport

Moves substances from low to high concentration
• Requires the use of highly selective carrier proteins

Carrier Proteins used in active transport include:

Uniporters, symporters, antiporters

Uniporters

– move one molecule at a time

Symporters

– move two molecules in the same direction

Antiporters

– move two molecules in opposite directions

Sodium-Potassium Pump Function

3 Na(+) ions out and 2 K(+) ions in

Why does Sodium-Potassium Pump Function use ATP

It goes against our concentration gradient

What can be used instead of ATP for coupled transport?

Glucose

Endocytosis

Movement of substances into the cell→ requires energy

Phagocytosis

– cell takes in particulate matter

Pinocytosis

– cell takes in only fluid

Receptor-mediated endocytosis

– specific molecules are taken in after they bind to a receptor

What can cause heart attacks?

In the human genetic disease familial hypercholesterolemia, the LDL receptors lack
tails, so they are never fastened in the clathrin-coated pits and as a result, do not
trigger vesicle formation. The cholesterol stays in the bloodstream of affected
individuals, accumulating as plaques inside arteries and leading to heart attacks

Hydration Shells and Osmosis

The hydration shells “trap” some water molecules

The Diffusion of Water

Water tends to move toward areas where more solute is dissolved (where free water
is scarce)

Osmosis

net diffusion of water across a membrane toward a
higher solute concentration (Hypertonic solution)

How does water move?

From higher water potential (lower solute concentration) to lower water potential
(higher solute concentration).

Osmosis Across a Semipermeable Membrane

What is going on here?

-More free water potential

What is going on here?

-Less free water

-Low water potential

Hypertonic solution

= higher solute concentration

Hypotonic solution

= lower solute concentration

Isotonic

When two solutions have the same osmotic concentration

Aquaporins

Specialized channels for water in cell membrane, facilitate osmosis

Explain what is the different between the oocytes?

-The control oocyte (without aquaporins) allowed water to diffuse in, but very slowly

-The test oocyte (with aquaporins) rapidly allowed water to diffuse inward through the specialized channels, causing the cell to swell significantly

Water Channel

Water Intoxication

• Drinking excess water diluted plasma(hypotonic)

• Osmosis- water moves into cells

• Endosmosis- Cellular swelling

• Brain edema- Increased in cranium pressure

Isotonic drinks

The drinks are designed to replenish fluids, electrolytes, and
carbohydrates during physical activity

Isotonic

Concentration of salt and sugar in the drink is similar to that of human blood

Osmotic pressure

Force needed to stop osmotic flow

Cell walls vs. animal cells

-can reach balance of osmotic pressure driving
water in with hydrostatic pressure driving water out

-animals cells MUST BE ISOTONIC environments

Hypertonic

-EX: Sea water

Hypotonic

EX: Tap water

Isotonic

EX: Gatorade