Bio Chapter 6 -- Exam 2

anchored membrane proteins

Proteins that are covalently attached to fatty acids or toher lipid groups. Held in associatin with the membrane.

fluid mosaic model

The model describing cell membranes as a fluid bilayer of phospholipids with embedded proteins, mosaic because it is made up of many different types of moecules, and fluid because the components can move freely. 

glycolipid

A carbohydrate covenlently bonded to a lipid. The carbohydrate serves as the recognition signal for the interactinos between cells. 

glycoprotein

one or more short carbohydrate chains covalently bonded to a protein. The bound carbs are oligosaccharides —often function in cell recognition and adhesion. 

integral membrane proteins

Proteins that are at least partly embedded within the lipid bilayer and often span the entire membrane — must have hydrophobic and hydrophilic regions 

—

peripheral membrane proteins

Proteins that are loosely associated with the membrane surface and can be easily removed. They lack the hydrophobic groups and are not embedded. They just interact with the heads of the membrane proteins.

phospholipids

The primary structural components of cell membranes consist of a hydrophilic head and hydrophobic tails. Heads are the external portion of the membrane, while the nonpolar fatty acid tails make up the middle.

lipid bilayer — two rows of phospholipids

the saturated chains allows closer packing of the tails, but the unsaturated fatty acis make for a less dense, more fluid packing

transmembrane domains

the domains of the transmembrane protein that extends through the bilayer

transmembrane protein

An integral protein that extends all the way through the phospholipid bilayer and protrudes on both sides.

cell adhesion

one ways that cells arrage themselves in grousp — The binding of cells to other cells or to the extracellular matrix — the connection between the two cells is strengthened 

This occurs only through the interactions between the carbohydrates that are parts of glycolipids and glycoproteins

cell junctions

Specialized structures that connect adjacent cells and allow communication or adhesion

cell recognition

one of the two ways cells arrenge themselves — one cell recognizes and binds to antoher cell of a certain type

Desmosomes

act to hold neighboring cells firmly together — acting like spot welds or rivets. 

Materials can still move around unlike the tight junctions, but it provides mechanical stability for tissues like skin. 

gap junctions

Channels that run between membrane pores in adjacent cells, allowing substances to pass inbetween cells. Examples are muccles and the rapid transport of ions required to fire them.

tight junctions

Sealing junctions prevent material from passing between cells. They also maintain distinct faces of a cell within a tissue by restricting the migration of membrane proteins over the cell surface from one face to another

active transport

The movement of substances across membranes against their concentration gradient using energy — driven by energy

aquaporins

Specialized channel proteins that facilitate the rapid transport of water across membranes

carrier proteins

Transport proteins that undergo conformational changes to move specific substances across membranes — bind sith substances and speed up their diffusion across the bilayer

channel proteins

Transport proteins that form channels along the membrane that allows specific ions or molecules to pass through membranes. Think tunnels where only one thing can pass. 

concentration gradient

The difference in concentration of a substance across a space or membrane

diffusion

The passive movement of molecules from areas of high concentration to low concentration — toward a state of equilibrium

facilitated diffusion

Passive transport of molecules across membranes with the help of channel or carrier proteins

hypertonic

a hypertonic solution has a higher concentration of solutes compared to another solution

hypotonic

a hypotonic solution has a lower concentration of solutes compared to another solution

ion channels

Membrane proteins that allow specific ions to pass through the membrane — often gated, opening either in response to ligand, light or voltage 

isotonic

Having the same concentration of solutes as another solution

ligand

A molecule that binds specifically to a receptor or other protein

osmosis

The diffusion of water across a selectively permeable membrane — passive process with no energy use

passive transport

The movement of substances across membranes without the input of cellular energy

selective permeability

The property of membranes that allows some substances to pass while blocking others. Specific proteins on the membrane can also act to increase or decrease the permebility of the membrane. 

antiporter

A transport protein that moves two different ions or molecules in opposite directions, one into the cell and one out of the cell

sodium–potassium (Na+−K+) pump

An active transport protein that maintains concentration gradients by pumping Na+ out and K+ into cells — this is an integral membrance glycoprotein. Thsi is a from of primary active transport— also an antiporter

symporter

A active transport protein that moves two different substances in the same direction across a membrane

uniporter

A active transport protein that moves only one type of ion or molecule across a membrane in one direction. 

phagocytosis

The process by which cells engulf large particles or other cells — used by white blood cells to eat viruses. The food vacule that forms or phagosome usually fuses with a lysosome, so the contents can be properly digested

pinocytosis

The process by which cells take in small droplets of extracellular fluid by membrane invagination — vesicles still frm, however they are smaller and the process operates to bring fluids and dissolved substances into the cell. 

receptor-mediated endocytosis

A selective form of endocytosis where specific molecules bind to receptors on the cell surface triggering the process of endocytosis to engulf.

—the recpetor proteins here are often coated pits that create slight depressions that form into a coated vesicle of the ligand and receptors. From here it goes to fuse with a lysosome and start digestion.

receptor proteins

Membrane proteins that bind to specific signaling molecules and initiate cellular responses

phospholipid bilayer

lipids establish the integrity of the membrane —create a barrier of phospholipids the oppose the rapid transport og hydrophilic materials like polar molceules and ions

— serves as a “lake” where transmembrane proteins float

Importance of Cholesterol

Cholesterol moduates the membrane fluidity—the hydroxyl end of the cholesterol interacts with the polar heads and the nonpolar rings of the hydrocarbon chain exist in the interior — imbeded

fluidity is essential for lateral and vertical movement across the celular membrane

factors affecting membrane fluidity

1. Lipid Composition— Cholesterol and long chain, saturated fatty acids pack tightly— the more cholesterol the more fluid, the less cholesterol, the less fluid

2. Temperature— molecules move more slowely and fluidity decreases at reduced temperatures — so some animals or organisms change the lipid composition by replacing saturated bilayers with shorted unsaturated bilayers.

The three types of membrane Proteins 

Integral proteins, peripheral proteins, and achored proteins 

homotypic vs. heterotypic

describes the binding of cells — either the same molecule sticks out of both cells which fit together and bind to one another (Homo)

or different molecules bind together on different cells (hetero) — which is caused by an affinity on the groups of the molecules. 

the three types of cell junctions the connect adjacent cells

1. Tight Junctions

2. Desmosomes

3. Gap Junctions

integrin

A transmembrane protein that often mediates the attachment of the cell to the extracellular matrix. The protein can be activated or deactivated to promote stability and movement. The binding between the protein and the extracellular matrix is noncovalent and reversible

simple diffusion

smal molceules pass through the phospholipid bilayer — if a molcule is small a

nd hydrophobic, it can pass

gated ion channel 

a channel protein that opens when a stimulus causes a change in the 3D shape of the channel. — usually from the stimulus of a binding chemical signal (ligand )

active transport

movement of molecules or ions against a gradient using an input of energy —usually ATP

works wither through a uniporter, symporter, or antiporter

active transport is directional — only happens one way

primary vs. secondary active transport

primary — involves the direct hydrolysis of ATP — provides the energy for transport

secondary — does not use ATP directly, but instead uses an ion concentraion gradient established by primary active transport to work

Endocytosis

term for a group of processes that bring small molecules, macromolecules, and large particles, and even small cells, into the eukaryotic cell.

3 types: phagocytosis, pinocytosis, and receptor mediated endocytosis

Exocytosis

process by which materials or waste packaged in vesicles are secreted in the extracellular space. This is dont pretty much in a reverse to endocytosis.