AP Biology: Chapter 5

Peter Agre received the Nobel Prize in 2003 for the discovery of aquaporins. What are they?

Aquaporins are specialized channels for water

What is the difference between phagocytosis and pinocytosis.

Both are forms of endocytosis (uptake of bulk material by the formation of a vesicle through the plasma membrane). Phagocytosis is "cell eating" (solid object) and pinocytosis is "cell drinking" (extracellular fluid).

Distinguish between channel proteins and carrier proteins

channel - passively transports molecules across membrane by creating a selective tunnel carrier proteins - actively or passively transports molecules through conformational changes

How do the follow cross the membrane: - CO2 - Glucose - O2 - H2O

co2 - simple diffusion (passive ) from high concentration to low concentration regions glucose - active transport of ions to form a gradient. glucose transport is coupled with the ions movement down the concentration gradient (i.e. Na+ moves back from outside the cell where there is a high concentration of Na+ and takes with it glucose). An example of symport transport O2 - simple diffusion (passive) from high concentration to low cconcentration regions Osmosis (passive) of water from areas of low solute concentration to high solute concentration or high water potential to low water potential or from pure water to less pure water

What is countertransport?

coupled transport where the inward movement of a substance drives the outward movement of another substance

exocytosis

discharge of material from vesicles

pinocytosis

endocytosis of a liquid

phagocytosis

endocytosis of a particulate

What is facilitated diffusion? Is it active or passive? Cite two examples.

facilitated = diffusion mediated by membrane proteins; passive transport Two examples: - movement of ions through a protein channel - movement of amino acids through a carrier protein

Distinguish between glycolipids and glycoproteins

glycoproteins - proteins/carbohydrate chain characteristic of an individual (ie MHC - helps recognize the individual) glycolipids - lipid/carbohydrate chain shape characteristic of tissue

Membrane carbohydrates are important in cell-cell recognition. What are two examples of this?

glycoproteins = major histocompatibility complex glycolipid = A B O blood group marker

water moves from areas of _____________ water potential to areas of ____________ water potential

high; low

What is the ionization constant for C6H12O6

i=1

osmosis

the diffusion of water across a selectively permeable membrane which goes from the side containing the lower concentration of solute to the side containing higher concentration in absence of differences in pressure or volume

What types of microscopes support the fluid-mosaic model of the cell membrane

Transmission Electron Microscope and Scanning Electron microscopes

Define concentration gradient

a difference in concentration of a substance from one location to another, often across a membbrane

What is the purpose of the phospholid bilayer in membranes

provides permeability barrier and allows proteins to stay in place; excludes water-soluble molecules from nonpolar interior of bilayer and cell

flaccid

state of a plant cell placed in an isotonic solution

Define diffusion

the net movement of dissolved molecules or other particles from a region where they are more concentrated to a region where they are less concentrated

Are transport proteins specific? Cite an example that supports your response

yes - transport proteins are specific Na/K pump only move Na out of the cell and K into the cell

Describe active transport. What type of transport proteins are involved, and what is the role of ATP in the process

Active transport uses energy to move materials against a concentration gradient with the use of a carrier protein or pump ATP provides the energy to power the conformation changes

What is the function of the proteins in the cell membrane

1. Support 2. Transport through the membranes 3. Communication & cell identification

What are the 3 types of transmembrane proteins

1. carriers - actively or passively transport molecules across membranes 2. Channel proteins - passively transport molecules across membrane 3. Receptor proteins - transmit information into the cell

Cellular membrane contain four components

1. phospholipid bilayer 2. transmembrane proteins 3. Internal protein network providing structural support 4. cell-surface markers (glycoproteins and glycolipids)

Describe the fluid-mosaic model of membrane structure by Singer and Nicolson

A mosaic of proteins float in or on a fluid lipid bilayer

Integral Membrane Protein

Make sure you know which region is the hydrophilic region, hydrophobic region. Here you can see the alpha-helical configuration. In these two proteins, the left side is a single pass protein and the right side protein is a multi-pass protein. Integral proteins are mainly found either fully or partially submerged in the phospholipids bilayer of the plasma membrane. These proteins have both polar and non-polar regions on them. Polar heads protrude from the surface of the bilayer while non-polar regions are embedded in it. Usually only the non-polar regions interact with the hydrophobic core of the plasma membrane by making hydrophobic bonds with the fatty acid tails of the phospholipids. The integral proteins that span the entire membrane from the inner surface to the outer surface are called transmembrane proteins. In transmembrane proteins, both ends that project out of the lipid layer are polar or hydrophilic regions. The middle regions are non-polar and have hydrophobic amino acids on their surface

What are two general types of transport? Talk about whether it uses ATP or not and talk about the concentration.

Passive Transport: No ATP High Concentration --> Low Concentration Active Transport: Uses ATP Low Concentration --> High Concentration

Peripheral membrane protein

Peripheral proteins (extrinsic proteins) are present on the innermost and outermost of phospholipids bilayer. These proteins are loosely bound to the plasma membrane either directly by interactions with polar heads of phospholipids bilayer or indirectly by interactions with integral proteins. Most of the peripheral proteins are found on the innermost surface or cytoplasmic surface of the membrane.

5 Forms of Active Transport

Proton Pump Sodium Potassium Pump Phagocytosis Pinocytosis Receptor mediated endocytosis

What is meant by membrane fluidity? Describe the movements seen in the fluid membrane?

The phospholipids are free to move along the plane of the lipid bilayer. Unanchored proteins may also move slowly .

hypotonic

a solution with a lower concentration of solute

Describe how each of the following can affect membrane fluidity - decreasing temperature - phospholipids with unsaturated hydrocarbon chains - cholesterol

decreasing temperature - decreases fluidity by causing membrane to "freeze." phospholipids with unsaturated hydrocarbon chains - increases fluidity because "kinks" prevent packing in of molecules cholesterol - increases fluidity when cold & decreases fluidity when hot. Cholesterol acts as a buffer,

Membrane proteins are the mosaic part of the model. Describe each of the two main categories: - integral proteins - peripheral proteins

integral proteins - proteins embedded in the membrane that protrude through to the interior and exterior peripheral proteins - proteins associated with the surface of the membrane. Some act as identification proteins (MHC), others act as receptor proteins.

plasmolysis

the shrinking of a plant cell in a hypertonic solution such that it pulls away from the cell wall

What is the water potential equation?

Water potential = Water potential P + Water potential S

What is the equation in finding out Water solute potential?

Water solute potential = iRCT

receptor-mediated endocytosis

bulk transport of substances into the cell where the molecules must first bind to specific receptors in the plasma membrane

What is the ionization constant for NACL --> Na+ + CL-

i=2

What is the ionization constant for MgCl2 MgCl2--> Mg2+ + 2Cl-

i=3

endocytosis

infolding of the plasma membrane allowing for bulk transport of substances into a cell

What is membrane potential? Which side of membrane is positive?

membrane potential = voltage difference; an electrical potential difference across a membrane; from the Na/K pump, the outside of the cell membrane is more +

turgid

pressurized state of a plant cell resulting from osmotic intake of water pressing the cell wall against the cell membrane and the membrane against the wall

isotonic

a solution having the same concentration of solute

hypertonic

a solution with a higher concentration of solute

Describe 3 types of Passive Transport

Diffusion Osmosis Facilitated Diffusion

Water potential is the combined effects of ______________ concentration and ___________ ______________; this determines water movement.

solute concentration; physical pressure

What are the two forces that drive the diffusion of ions across the membrane? What is the combination of these forces called?

the chemical force (concentration gradient) and the electrical force (repulsion & attraction)

passive transport

the movement of substances across a cells' membrane without the expenditure of energy

Describe major functions of membrane proteins - Transport - Enzymatic Activity - Cell Surface Receptor (signal transduction) - Cell-surface (cell-cell) recognition cell-to-cell adhesion (intercellular joining) - attachment to cytoskeleton and ECM

transport - transmembrane proteins that move specific molecules through the membrane in a series of conformational changes or providing a tunnel (ie carrier proteins, Na/K pump, etc.) - Enzymatic activity: carry out many chemical reactions on the interior surface of the plasma membrane Cell Surface Receptor (signal transduction) - transmembrane proteins that bind signal molecules which in turn induces activity within the cell Cell-surface recognition- glycoproteins such as the MHC is used for cell recognition by creating a protein/carbon chain characteristic of an individual Cell to cell adhesion - proteins that "glue" cell together by forming temporary interactions and more permanent bonds attachment to cytoskeleton and ecm: surface proteins that interact with other cells and are often anchored to the cytoskeleton by linking proteins