Exam 2 Dr. Clay

Plasma Membrane

Phospholipid arranged in bilayer

Fluid Mosaic Model (fluid-flexible)

proteins float around or anchored in place

What 4 things do all cell membranes have?

1. Phospholipid bilayer (flexible, limited permeability)

2. transmembrane proteins (proteins cross membrane)

3. interior protein network (membrane proteins)

4. cell surface markers (glycoproteins, glycolipids)

A phospholipid bilayer is used because of their nature. They spontaneously form because of the ---- head and ---- tail. Hydrogen bonding of --- holds the 2 layers together. The bilayers are ----- so unanchored proteins can move around through the membrane.

hydrophilic

hydrophobic

water

fluid

How can the phospholipid bilayer be modified?

saturated fatty acids make membrane less fluid than unsaturated fatty acids

warm temps make membrane more fluid than cold temps

Diverse functions arise from the diverse ------ of membrane proteins. However, they have common structural features related to their role as membrane proteins.

structures

Transmembrane Domain

Nonpolar regions -----

Polar regions ----- (spans the lipid bilayer)

blue

red

What are the 2 ways molecules move across a plasma membrane

Passive transport (diffusion)

-no energy, high to low concentration, continues until equal concentration

Active Transport

-energy, low to high concentration, continue until turned off

What influences rate of diffusion?

1. Temp (high temp-high rate of diffusion)

2. Molecular size (large molecules- slow rate diffusion)

3.Concentration gradient (high gradient-high rate diffusion)

Diffusion will continue until the concentration is --- on both sides of a membrane. As diffusion occurs the concentration gradient -----. Lower concentration gradient, ---- rate of diffusion.

equal

decreases

lower

What influences membrane permeability?

major barrier-hydrophobic interior

nonpolar molecules move freely

limited permeability to small polar molecules and to larger polar molecules and ions

------- are used for facilitated diffusion. Different one for different plasma membranes (selectively permeable). Still requires a concentration gradient.

transport proteins

Channel proteins allow the passage of ----. They have --- channels which are open or closed in response to stimulus.

ions

gated

What are 3 conditions that determine direction of movement.

relative concentration

voltage differences

gated channels (open or closed)

Carrier proteins help transport both ions and other solutes, such as ----- and ---------. Must bind to the molecule they transport. More specific than channel proteins.

sugars

amino acids

rate of transport limited by number of transporters.

saturation

----- is net diffusion of water across a membrane toward a higher solute concentration. It occurs when solute can't move.

osmosis

Cytoplasm of the cell is an ----- solution.

aqueous

What is an aqueous solution?

water is solvent

dissolved substances are solutes

When 2 solutions have different osmotic concentration:

----- solution has a relatively higher solute concentration

----- solution has a relatively lower solute concentration

hypertonic

hypotonic

When 2 solutions have the same osmotic concentration, the solutions are -----.

isotonic

Osmotic concentration is ------.

relative

Osmotic concentration is important because cells in a ------- solution often don't function properly.

hypertonic

Osmotic concentration is important because cells in a ----- solution gain water creating pressure. If cell is strong enough cell counterbalances osmotic pressure, cell walls help. If membrane is not strong, cell can -----. Prokaryotes, fungi, plants, protists like to be in hypotonic solutions.

hypotonic

burst

Animal cells must be kept near ------.

isotonicity

----- regulation involves keeping cells isotonic with their environment. Some cells use -------- in which water is ejected through contractile vacuoles. Marine organisms adjust internal concentration to match sea water. Terrestrial animals circulate isotonic fluid.

isosmotic

extrusion

Plant cells use ---- pressure to push the cell membrane against the cell wall and keep the cell rigid.

turgor

Why use active transport?

move molecules from low to high concentration (against concentration gradient)

requires use of energy (ATP)

require use of highly selective carrier proteins

Carrier proteins are defined by the ----- and ------ of molecules moved.

number

direction

move one type of molecules at a time

uniporters

move two different types of molecules in the same direction

symporters

move two different types of molecules in opposite directions

antiporters

How do transport proteins work?

1.------------- is an antiporter used to move 3 Na+ out of the cell and 2 K+ into the cell.

2. -------- is used directly to change the conformation of the carrier protein.

3. Affinity of the carrier protein for either Na+ or K+ changes so the ---- can be carried across the -------.

Sodium Potassium Pump

ATP energy

ions, membrane

Sodium Potassium sets up ----------. Sodium wants to come back in the cell.

concentration gradient

Glucose Na+ symporter captures the energy from Na+ ------ to move glucose into the cell. Glucose moved ------ concentration gradient.

diffusion

against

Coupling transport proteins together.

ATP is used

directly by the ------

indirectly by the ------

antiporter

symporter

How do cells move large objects across plasma membranes?

bulk transport

endocytosis

exocytosis

Endocytosis

----- for large objects

------ for small objects

can be receptor mediated

phagocytosis

pinocytosis

What are the 2 states of energy?

Kinetic (energy of motion)

Potential (stored energy)

Where does energy come from? (3)

1. sun

2. photosynthesis (light energy)

3. potential energy in chemical bonds

------- produce their own organic molecules from inorganic molecules through photosynthesis.

Autotrophs

------ live off of organic compounds produced by other organisms

heterotrophs

The First Law of Thermodynamics

energy cannot be created or destroyed

(energy only changes from one form to another, during conversion energy is lost as heat)

Second Law of Thermodynamics

Disorder (entropy) is continuously increasing

Reduction-oxidation reactions (redox) are always paired with a ---- and ----- of energy.

gain

loss

atom or molecule loses an electron

oxidation

atom or molecule gains an electron

reduction

Positive G, --------, products have more free energy than reactants.

endergonic

Negative G, ---------, products have less free energy than reactants.

exergonic

Energy required to destabilize existing bonds and start a chemical reaction.

Activation energy

Reaction rate can be increased in what 2 ways

1. Increase temperature (increase kinetic energy)

or

2. Lower activation energy (distort bonds in reactants)

What are enzymes?

molecules that lower activation energy

(mostly proteins, RNA, distort existing bonds)