Molecular and Cellular Biology Exam 3 terms

Lipid Bilayer

Membrane around cells made up of primarily amphipathic molecules and embedded proteins, arranged in multiple layers, essential for cell function.

Posphatidylcholine

Most abundant phospholipid in eukaryotic cells.

Cholesterol

Commonly found lipid in cell mebranes, a sterol.

Glycolipid

Commonly found class of lipids in cell mebranes.

Leaflet/Face

Commonly used termed for a monolayer within the lipid bilayer.

Smooth Endoplasmic Reticulum

Organelle that synthesizes lipids, cholesterol, and steroid hormones.

Breakdown drugs and metabolic waste.

Stores calcium

Scramblases

Enzymes that move necessary components to the lumenal leaflet.

Transmembrane proteins

Proteins that have a hydrophobic region extending through the bilayer and the hydrophilic regions are exposed on both sides of the membranes.

Monolayer-associated proteins

embedded in one face of the membrane but do not extend all the way through.

Membrane attached proteins.

Are linked to lipids or transmembrane proteins.

FRAP

Fluorescence Recovery After Photobleaching; a technique used to study lateral diffusion of membrane proteins using fluorescence and photobleaching.

Simple diffusion

net movement of something from a region of higher concentration to a region of lower concentration.

Concentration gradient

a difference in the concentration of a substance between two areas

Passive transport

Use of proteins to transport molecules or ions across the membrane. Does not require energy and is required by concentration gradient.

Channel proteins

Proteins that form a pore through the membrane that allows for free diffusion of appropriately charged molecules and direct connection across the cell membrane

Aquaporins

Water channels; selective filter, improves rate of water transport compared to simple diffusion.

Ion channels

Mediate passage of ions across membrane; allows for rapid transport and is highly selective.

Transport proteins

Bind to a specific molecule and undergoes a conformational change, allows molecules to move down their concentration gradient.

Active transport

Use of proteins to move a solute from a lower to higher concentration gradients. Requires an energy source.

Protein Pumps

Alternative name for proteins used in active transport

Symport

moving both solutes in the same direction.

Antiport

Moves each solute in a different direction.

Na+ glucose symport

Uses Na+ gradient to transport glucose

The diffusion of Na+ is coupled to the movement of glucose against its concentration.

Active transport with ATP Hydrolysis

Uses ATP as energy source

Active Transport using coupled gradients

Coupled transport

Gated ion channels

channels that switch between open and closed conformations in response to a specific signal.

Mechanically-gated channels

channels respond to movement

Ligand gated channels

channels respond to binding of a specific molecule (ligand)

Voltage Gated channels

channels respond to a change in the membrane potential

Action potentials

a rapid change in the voltage across a cell membrane that occurs when a cell is stimulated

Membrane Potential

the difference in electric charge across a cell membrane, crucial for the generation of action potentials.

Depolarization

the process by which the membrane potential becomes less negative, often leading to the initiation of an action potential.

Threshold Potential

the critical level of depolarization that must be reached for an action potential to be initiated.

Synapses

The places where neurons connect and communicate with each other

Synaptic Vesicles

organelles that store and release neurotransmitters in neurons, enabling nerve impulses to travel between neurons and facilitating communication at synapses.

matrix

the innermost compartment; location of the oxidation of pyruvate and fatty acids, and citric acid cycle

inner mitochondrial membrane

folded into cristae to increase surface area, this contains electron transport proteins and ATP synthase, and is the location of the electron-transport chain and contains proteins that carry out oxidative phosphorylation

outer mitochondrial membrane

controls the movement of molecules in and out of the mitochondria; contains large, channel-forming proteins

intermembrane space

includes enzymes that phosphorylate other nucleotides; the location of oxidative phosphorylation

metabolism

the sum of chemical reactions that sustain life within the cell

glycolysis

the process by which sugar is broken down; one glucose molecule breaking down into 2 pyruvate molecules

substrate-level phosphorylation

the addition of a phosphate group to ADP to make ATP from a substrate that contains a phosphate group

Pyruvate Oxidation

The process by which pyruvate is converted into acetyl-CoA, which enters the citric acid cycle; it involves decarboxylation and occurs in the mitochondria.

Acetyl CoA

a component in cellular respiration that is a metabolic intermediate. the acetyl group just helps to move the CoA, which is the group necessary for the citric acid cycle

citric acid cycle

the reaction of acetyl CoA with oxaloacetate within the matrix to produce citrate, which cycles until it results back into oxaloacetate, with each cycle producing 3 NADH, 1 GTP, 1 FADH2, and releasing 2 CO2

oxidative phosphorylation

the production of ATP by transferring electrons along a series of proteins and forming a gradient, resulting in the easy flow and production of ATP by ATP synthase at the end of the chain

Electron Transport Chain

the process by which NADH and FADH2 donate their electrons to produce more ATP

ATP synthase

an enzyme that generates ATP during oxidative phosphorylation by being physically rotated

energy transduction reactions

light energy is captured and converted into chemical energy (light-dependent)

carbon fixation reaction

carbohydrates formed from stripped CO2 and H2O (light-independent)

chloroplasts

an organelle in plants and algae that performs photosynthesis, converting light energy to chemical energy

thylakoid membrane

the location of the light-capturing pigments and ATP generating system

thylakoid matrix/lumen

important in photophosphorylation, this location is kept acidic and is typically high in concentration in protons

stroma

fluid-filled space between thylakoids in a chloroplast that contain DNA, starch, ribosomes, and enzymes

chlorophyll

molecules found in chloroplasts, responsible for harvesting/absorbing almost all of the wavelengths of light that reach the earth

reaction center

the center of a photosystem where the chlorophyll dimer special pair is located, which is what energizes an electron

antenna complexes

the chlorophyll-containing molecules that surround the reaction center, that transfer energy from one chlorophyll molecule to another

photosystem 2

the first photosystem that appears that sends high-energy electrons to a hydrogen pump and forms a gradient, which then goes through ATP synthase, generating ATP

photosystem 1

the second photosystem that appears that transfers electrons to an enzymes that converts NADP+ to NADPH

Calvin Cycle

the use of ATP and NADPH to synthesize carbon compounds from CO2 and H2O

glyceraldehyde-3-phosphate (G3P)

made in the second stage of the Calvin cycle, and can be used as a base for many sugar building blocks (one is made as a result of three Calvin cycles)

protein sorting

the delivering of proteins to their assigned/correct locations, according to its signal sequence

signal sequence

the label/amino acid added to a protein to tell it where to go/direct it to a specific organelle, which is recognized by transport proteins

nuclear envelope

the outer part of the nucleus, composed of two membrane layers with a space in between

nuclear pores

octagonal locations that move proteins across the nuclear envelope

Nuclear Localization Signal (NLS)

signal on protein detected by import proteins/receptors that bind to it and move the protein into the nucleus

nuclear import receptors

special receptors that recognize the nuclear localization signals, and then bind to fibrils on the nuclear pores, allowing the receptor and cargo to move through the pore

translocators

proteins that span across one membrane and link with another protein that spans across the other membrane

mitochondrial signal sequence

special signal sequence on proteins intended for the mitochondria that bind to the import receptors on the outside of mitochondria

ER signal sequence

special signal sequence on the N-terminus of proteins intended for the ER that bind to the receptors in the ER, and threaded into ER as they are made

signal recognition particle (SRP)

a molecule that recognizes and binds to the ER signal sequence, stalling protein synthesis until the translation complex binds to the ER

SRP receptor

the receptor on the ER membrane that binds to the SRP translation complex, and transfers the ribosome to the ER translocation channel

signal peptidase

the enzyme that removes signal sequences from secreted/completed proteins

glycosylation

the addition of sugars to proteins

endomembrane system

the secretory pathway, how proteins are moved between membrane-bound organelles

transport vesicles

small molecules that carry proteins between organelles of the endomembrane system

cargo receptors

proteins that recognize and bind to molecular tags on protein cargo

coat proteins

proteins that bind to the cargo receptors on the cytosolic side, and pull the molecules in via forming a sphere shape, eventually forcing it to be pinched off, and then the coat proteins fall off once the vesicle is fully formed

tethering proteins

a long, extending protein, that binds to its specific and matching Rab protein

Rab proteins

a small protein on the outside of a vesicle that binds to its specific tethering protein

v-SNARE proteins

SNARE protein on the vesicle that eventually binds to another protein and induces fusion of the vesicle and the target membrane

t-SNARE

SNARE protein on the target membrane that eventually binds to another protein and induces fusion of the vesicle and the target membrane

Golgi

a series of flattened membrane sacs that function together to sort and package proteins into transport vesicles

constitutive secretion

the constant, unregulated movement of vesicles from the Golgi to the surface of the cell; continuous secretion/exocytosis

regulated secretion

exocytosis in response to an external signal; vesicles wait after formation for a signal to fuse with the cell membrane

exocytosis

secretion via vesicular transport; occurs when contents of a vesicle are released from a cell to the extracellular environment

endocytosis

the uptake of extracellular material through vesicle formation at the plasma membrane

pinocytosis

cell “drinking” through primarily pit formation

the uptake of small amounts of extracellular fluid and solutes; constant in all cells

phagocytosis

cell “eating” through cell projections going up and around the “food”

cell engulfs another cell or fragments of cell; way of food for protozoans; immune system consume bacteria and damaged cells/debris

receptor-mediated endocytosis

the selective uptake of extracellular components through specific receptor proteins

endosomes

involved in intracellular sorting and transportation post-endocytosis- things may be sent to lysosome to be destroyed (degradation), another area for transcytosis, or back out of the cell (receptors) for recycling