Ap Bio Chap 7

Why are plasma membranes selectively permeable?

Why are plasma membranes selectively permeable?

to control what goes in and out of the cell

How do small nonpolar molecules, hydrophilic substance or large polar molecules and polar uncharged molecules (water) move across the plasma membrane

small nonpolar molecules can diffuse across the plasma membrane, larger polar molecules need to use protein channels to move into the cell

Integral proteins

permanently embedded in the plasma membrane

Transmembrane proteins

goes through the entire plasma membrane and is a type of integral protein - job is to move larger particles into and out of the cell

Peripheral proteins

attached to the surface on both the inside and outside of the plasma membrane and is more temporary - often attached to integral proteins

Glycolipids

lipids with a carbohydrate attached by a glycosidic bond and plays a role in maintaining stability of the cell membrane and also facilitates cellular recognition

Glycoproteins

A molecule that consists of a carbohydrate plus a protein and are heavily involved with the immune system

Aquaporins

protein channels specifically for the transport of water molecules across the cell membrane - used in osmosis

Phagocytosis

a type of endocytosis where psudopodia is used to engulf a food particle and pack it in a food vesicle for transport

Pinocytosis

when a cell continously gulps droplets of extracellular fluid into vesicles made by the infolding of plasma membrane and the molecules dissolved in droplet is what the cell gets

Receptor-mediated endocytosis

more specilised version of pinocytosis where theres receptors on the outside of the plasma membrane exposed to extracellular fluid that allow for specific solutes to bind onto it and this allows the cell to get in bulk certain substances

Sodium-potassium pump

3 NA+ for 2 K+

helps to maintain resting membrane potential

initially open to the inside of the cell and has spots for sodium ions to bind onto

causes electrochemical gradient

Hypotonic

when the concentration of solute is lower outside the cell and this causes water to move towards/ into the cell - will lead to cell swelling up and bursting eventually

Hypertonic

when solute concentration is greater outside the cell which causes water to move out of the cell into the solution -leads to shrivaling of cell

Osmoregulation

regulation of solute concentration and water balance

Ions channels

specialized proteins in the plasma membrane that provides a passageway where charged ions can cross the plasma membrane down their electrochemical gradient.

passive

Gated channels

has specific binding site for a given molecule or ion and a stimulus which can cause gate to open or close

ex: voltage gated, mechano stimulated, ligand gated

Membrane potential

→ the difference in electric potential between the interior and exterior of a biological cell.

resting membrane potential: determined by the uneven distribution of ions between the inside and the outside of the cell, and the different permeability of the membrane to different types of ions.

Electrochemical gradient

determines the direction that ions will flow through an open ion channel and is a combination of two types of gradients: an ion concentration gradient and an electrical field gradient

Electrogenic pump

An ion pump that generates net flow of charge
→ ex: sodium potassium pump

Proton pump

uses energy to transport protons from the matrix of the mitochondrion to the inter-membrane space

Cotransport

where a transport protein can couple it’s ‘downhill’ diffusion to the ‘uphill’ transport of a second substance against it’s gradiant

secondary active transport

uses electrochemical gradiant - kinda uses the energy generated from primary transport to move molecules against their concentration gradiant

Exocytosis

transports molecules out of the cell

1. vesicle containing secretory protein buds off of golgi

2. vesicle travels along microtuble to the cell membrane

3. the outside of the vesicle binds to cell membrane

4. the membranes fuse and releases protein out of cell

5. vesicle membrane becomes part of cell membrane

Endocytosis

transports molecules into the cell

Turgid

state of cell when it’s swollen after being put in hypotonic solution

Plasmolysis

the process of contraction or shrinkage of the protoplasm of a plant cell and is caused due to the loss of water in the cell

flaccid state of plant cell

Deplasmolysis

basically turgid state of plant cell

the swelling of a plasmolyzed cell - unshrivels

Flaccid

state of cell when it shrivels up after being put in hypertonic solution

Concentration gradient

flowing from high to low

water potential equation

Gives us a quantified way to determine where the water will move. 

pressure potential

Pressure Potential (Ψp) is how much pressure is being exerted on the cell or solution - Pressure exerted by either the atmosphere, for solutions in an open beaker or the cell wall/membrane, for solutions inside of cells

always 0 in ap bio bc we use beakers

solute potential

Measure of the amount of solute dissolved in the solvent (water in this case).

Solute potential is given a negative value because adding solute to a solution always decreases the overall water potential.

tonicity

the ability of a solution to cause a cell to gain or lose water.

osmosis

the simple diffusion of water.

predicting water movement in osmosis

Step 1: Figure out which side of the membrane has the higher concentration of water. 

step 2: Remember that water will move toward the side of the membrane that has less water

At 20°C, a cell containing 0.6M glucose is in equilibrium with its surrounding solution containing 0.5M glucose in an open container.  What is the cell’s Ψ_P? 

-2.4 bars

At 20°C, a cell with Ψ_P of 3 bars is in equilibrium with its surrounding 0.4M solution of sucrose in an open beaker.  what is the molar concentration of sucrose in the cell

0.52 M

A plant cell with Ψ_s of -7.5 bars keeps a constant volume when immersed in an open-beaker solution that has a Ψ_s of -4 bars. what is the cell’s Ψ_P

-3.5 bars

Carrier protein

specific for an ion molecule or group of substances and changes shape after the binding of of an ion/ molecule to carry it across the membrane

turgor pressure

the force within the cell that pushes the plasma membrane against the cell wall

functions of membrane proteins

helps cells to communicate, maintain their shape, carry out changes triggered by chemical messengers, and transport and share material.

fluid mosiac model

the membrane is fluid with the molecules moving and the membrane itself being able to bend - not static