Membrane Bound Organelles and Eukaryotic Cell Features

Golgi apparatus

a series of flattened membranes that sorts and packages materials before they leave the cell

Vesicle

a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer and transport of materials within the plasma membrane

Lumen

the cavity or channel within a tube or tubular organ

Plasma membrane

separates the interior of the cell from the outside environment

Intercellular junctions

regions of contact between the plasma membranes of two or more adjacent cells

Gap junctions

channels between neighboring cells that allow for the transport of ions, water, and other substances between cells

Connexins

a set of six membrane proteins that form an elongated, donut-like structure called a connexon

Connexon

an elongated, donut-like structure formed by connexins that allows for the formation of channels between cells

Tight junctions

create a watertight seal between two adjacent animal cells

Desmosomes

a type of intercellular junction that provides mechanical stability to tissues

Cis face

the receiving side of the Golgi apparatus where transport vesicles from the ER fuse

Trans face

the opposite side of the Golgi apparatus that secretes materials into vesicles

Endomembrane system

a system within the cell that includes the Golgi apparatus and is involved in the sorting and packaging of materials

Secretory vesicles

vesicles that bud from the trans face of the Golgi apparatus to transport materials

Phosphate groups

small molecules that tag modified proteins and lipids for routing to their destinations

Multicellular organism

an organism composed of multiple cells that interact and adhere to each other

Cytoplasmic connections

connections between cells that allow for the exchange of materials

Watertight seal

a type of connection that prevents the passage of water and solutes between adjacent cells

Transport vesicles

vesicles that carry materials from the endoplasmic reticulum to the Golgi apparatus

Short chains of sugar molecules

the most frequent modification added to proteins and lipids as they travel through the Golgi

Proper destination

the specific location within or outside the cell where materials are needed

Cellular materials

various substances produced or utilized by cells, including proteins and lipids

Adjacent cells

cells that are next to each other and can form intercellular junctions

Tight junctions

watertight seal between two adjacent animal cells

Claudins

proteins that make up tight junctions

Desmosomes

small spot connections between epithelial cells

Cadherins

specialized adhesion proteins that interact between cells

Gap junction

channels between neighboring cells that allow for the transport of ions, water, and other substances

Connexin

membrane protein that makes up a gap junction

Epithelial

the outer layer of a cell surface

Adhesion proteins

glycoproteins that mediate cell-cell connections

Intermediate filaments

protein fibers that contribute to cellular structural elements and are often crucial in holding together tissues

Keratin

a fibrous protein found in hair, nails, and skin

Intermediate filaments size

varying sizes that range between 8-12 nm

Cytoplasmic plaque

structure that cadherins attach to inside the cell

Tight junction purpose

to keep liquid from escaping between cells, allowing a layer of cells to act as an impermeable barrier

Desmosome function

pin adjacent cells together, ensuring that cells in organs and tissues that stretch remain connected in an unbroken sheet

Intermediate filaments role

absorb tension and support cellular shape

Tight junction structure

formed by many individual groups of tight junction proteins called claudins

Desmosome structure

involves a complex of proteins that extend across the membrane and anchor the junction within the cell

Tight junction strands

arranged into strands that form a branching network

Desmosome proteins

some extend across the membrane, while others anchor the junction within the cell

Intermediate filaments stability

do not form and disassemble quickly, playing no role in movement or transport

Intermediate filaments network

maintains the cell shape and makes a cage where the nucleus sits

Cytoskeleton

Network of protein fibers that help with cellular movement and maintaining its structure/shape.

Microtubule

Hollow, protein-based tubes that exist in eukaryotic cells and help cells move material around itself and resist compression.

Microfilaments

Thin protein fibers made up of actin proteins; their fundamental role is to absorb tension.

Lysosome

Found in animal cells, is the 'garbage disposal', breaks down molecules and old organelles.

Hydrolytic enzyme

Enzyme needing water to break chemical bonds of large molecules.

Organelles

Membrane-bound compartments with specialized functions.

Polysaccharides

A carbohydrate whose molecules consist of several sugar molecules bonded together.

Cytoplasm

A thick solution that fills each cell and is enclosed by the cell membrane.

Channel proteins

Span the membrane and make hydrophilic tunnels across it, allowing their target molecules to pass through by diffusion.

Facilitated diffusion

The diffusion process used for those substances that cannot cross the phospholipid bilayer due to their size and/or polarity.

Aquaporins

Channel proteins that allow water to cross the membrane very quickly, playing important roles in plant cells, red blood cells, and certain parts of the kidney.

channel proteins

span the membrane and make hydrophilic tunnels across it, allowing molecules to move through by diffusion

aquaporins

channel proteins that allow water to cross the membrane very quickly

diffusion

substance moves from an area of high concentration to an area of low concentration

gated ion channels

a group of transmembrane ion-channel proteins which open to allow ions to pass through the membrane in response to the binding of a chemical messenger

hydrophilic

water-loving, usually in contact with aqueous environments

facilitated diffusion

proteins move polar molecules in or out of the cell depending on its concentration gradient

plasma membrane

separates the interior of a cell from its outside environment and can be best represented by the fluid mosaic model

fluid mosaic model

describes the structure of the plasma membrane as a mosaic of components that are fluid and dynamic

phospholipid bilayer

composed of phospholipid molecules that can move around within the plasma membrane

transbilayer diffusion

the process where a phospholipid can 'flip-flop' to the opposite layer, which is very slow

lateral diffusion

the process when a phospholipid moves side to side within its layer, which is very fast

flippase

a protein that brings a phospholipid from the outer leaflet to the inner leaflet and requires ATP

floppase

a protein that brings a phospholipid from the inner leaflet to the outer leaflet and requires ATP

scramblase

a protein that brings a phospholipid from the outer leaflet to the inner leaflet AND a phospholipid from the inner leaflet to the outer leaflet, and does not require ATP

transbilayer diffusion

a phospholipid can "flip-flop" to the opposite layer, is very slow

lateral diffusion

phospholipid moves side to side within its layer, is very fast

flippase

brings a phospholipid from the outer leaflet to the inner leaflet

floppase

brings a phospholipid from the inner leaflet to the outer leaflet

scramblase

brings a phospholipid from the outer leaflet to the inner leaflet AND a phospholipid from the inner leaflet to the outer leaflet

fluid mosaic model

describes the plasma membrane as a fluid combination of phospholipids, cholesterol, and proteins

plasma membrane

the semipermeable barrier that surrounds the cytoplasm (inside contents) of a cell

phospholipids

a major component of cell membranes consisting of two hydrophobic fatty acid tails and a hydrophilic head consisting of a phosphate group

membrane potential

a cell's membrane potential is negatively charged when it is resting and non-signalling and is determined by the concentrations of ions across the membrane

resting membrane potential

non-signalling neuron has a voltage of about -30 to 90 mV

depolarized

membrane potential is more positive than it is at the resting potential

hyperpolarized

membrane potential is more negative than it is at the resting potential

membrane potential

a measurement of the potential gradient that forces ions to passively move in one direction across a membrane

neurons

nerve cells

polarized

the electrical charge on the outside of the membrane is positive while the electrical charge on the inside of the membrane is negative

potential difference

the difference in voltage across the membrane, typically about 30 to 90 mV in resting neurons

ion distribution

the uneven distribution of ions (charged particles) between the inside and the outside of the cell

membrane permeability

the different permeability of the membrane to different types of ions

depolarization

the process by which the membrane potential becomes less negative or more positive

action potentials

the electrical signals that neurons use to transmit information

ligands

external molecules that bind to membrane receptors and cause an internal cellular response

Membrane receptors

Proteins that facilitate the transport of molecules, change a cell's internal environment, or communicate between cells.

Cell-surface receptors

Transmembrane receptors that bind to external ligand molecules and span the plasma membrane to perform signal transduction.

Signal transduction

The process of converting an extracellular signal into an intracellular signal.

Ion channel-linked receptors

Receptors that bind a ligand and open a channel through the membrane, allowing specific ions to pass through.

G-protein-linked receptors

Receptors that bind a ligand and activate a G-protein, which interacts with either an ion channel or an enzyme in the membrane.

Enzyme-linked receptors

Cell-surface receptors with intracellular domains associated with an enzyme that activate a signal chain within the cell.

Gated ion channels

Pores that open when a signaling molecule binds, allowing ions to flow into or out of the cell.

Hydrophobic amino acids

Amino acids in the membrane-spanning region that interact with the phospholipid fatty acid tails of the plasma membrane.

Hydrophilic amino acids

Amino acids that line the inside of the ion channel, allowing for the passage of water or ions.

Conformational change

A structural change in a protein that occurs when a ligand binds to the extracellular region of the channel.