Exam 2 Prep- Definitions

A flashcard set to help prepare for the upcoming biology exam

Nucleus

Contains DNA and controls cell activities

Ribosomes

Protein synthesis

Rough ER

Protein processing and transport

Smooth ER

Lipid synthesis, detoxification

Golgi Apparatus

Modifies, sorts, and ships proteins

Lysosomes

Digestion and recycling of macromolecules

Mitochondria

ATP production through cellular respiration

Vacuoles

Storage and transport

Plasma Membrane

Selective permeability

Ampipathic

Both hydrophilic and hydrophobic regions

Fluid mosaic model

The currently accepted model of cell membrane structure

Integral proteins

Penetrate the hydrophobic interior of the lipid bilayer

Transmembrane proteins

Span the membrane; other integral proteins extend only partway into the hydrophobic interior. The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids

Peripheral proteins

Are not embedded in the lipid bilayer at all; loosely bound to the surface of the membrane, often to exposed parts of integral proteins

Glycolipids

A lipid with one or more covalently attached carbohydrates

Active transport

Requires ATP in order to move molecules against concentration gradients

Passive transport

Does NOT require ATP to function

Cotransport

The coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient

Sodium-Potassium pump

A transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell

Voltage

Potential energy

Membrane potential

The difference in electrical charges across a cell’s plasma membrane as a result of different distributions of ions

Chemical force

The ion’s concentration gradient

Electrical force

The effect of the membrane potential on an ion’s movement

Electrochemical gradient

The combination of forces acting on an ion

Electrogenic pump

An active transport protein that generates voltage across a membrane while pumping ions

Proton pump

An active transport protein that uses ATP to transport H+ ions out of a cell against their concentration gradient, which generates membrane potential

Tight junctions

Intercellular junction between animal cells that prevents the leakage of material through the space between cells

Desmosomes

Intercellular junction in animal cells that functions as a rivet, fastening cells together

Gap Junctions

Intercellular junction in animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells

Plasmodesmata

Open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells

Middle lamella

In plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells

Hypertonic

Water leaves cell. Cells with no walls will shrivel, plant cells become plasmolyzed.

Hypotonic

Water enters cell. Cells with no walls lyse and can burst, cells with walls like plant cells become flaccid.

Isotonic

No net water movement

ATP

Primary energy used by cells

Endergonic

Require energy, positive ΔG

Exergonic

Release energy, negative ΔG

1 ATP

7kcal/mol

Enzyme

A macromolecule (usually a protein) that speeds up a chemical reaction without being consumed in the process. They bind to substrates to create products

Substrate

Reactant an enzyme acts on. Is converted into the product(s) of the total reaction

Product

The molecule (or molecules) that are formed after an enzyme has acted on its substrate

Active site

The specific region of an enzyme where its substrate(s) bind and the chemical reaction is catalyzed. It is usually a pocket or groove on the enzyme’s surface

Enzyme substrate complex

The temporary, combined structure formed when an enzyme binds to its specific substrate(s)

Cofactors

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Usually metal and inorganic, and can bind permanently or temporarly to an active site and be reversible

Coenzymes

An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions

Glycolysis

A series of reactions that ultimately splits glucose into pyruvate. The starting point of fermentation or cellular respiration in almost all living cells

Krebs Cycle

Also known as the citric acid cycle. Produces CO2, NADH, FADH2, and ATP

Electron Transport Chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make most ATP

Substrate-level phosphorylation

The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism

Oxidative phosphorylation

Takes place in the inner mitochondrial membrane and accounts for about 90% of the ATP produced by respiration. End product is water

Chemiosmosis

A mechanism cells use to convert energy stored in an H⁺ gradient into useful work, especially ATP synthesis. Creates proton motive force. Protons diffuse back down into gradient through ATP synthase, which uses the energy to phosphorylate ADP to ATP

Oxidation

Loss of electrons

Reduction

Gain of electrons

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. Carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells)

Pinocytosis

Type of endocytosis in which a cell continually “gulps” droplets of extracellular fluid into tiny vesicles formed by infoldings of the plasma membrane

Receptor-mediated endocytosis

A specialized form of pinocytosis that lets a cell take in large quantities of specific substances, even when those substances are present at low concentration outside the cell

Catabolism

The part of metabolism that breaks down organic molecules into smaller products. When these molecules (like carbohydrates, fats, and proteins) are degraded, their chemical energy is released, and the products formed have greater entropy (more disorder)

Anabolism

The set of biosynthetic pathways in metabolism that consume energy (often ATP) to build larger, more complex molecules from smaller, simpler ones

Food vacuoles

Formed by phagocytosis

Contractile vacuoles

– Found in freshwater protists

– Pump excess water out of cells

Central vacuoles

– Found in mature plant cells

– Stores organic compounds

and water

– Turgor pressure

Peroxizomes

– Enzymes oxidize substances. End product is water

Microtubules

– “Monorail” of cytoskeleton

– Separates chromosomes

during cell division

– Motility

– Maintenance of cell shape

-Hollow rods

Cilia and flagella

• Anchored by a basal body

– Structure similar to centriole

• Motor protein called dynein

-– Core of microtubules sheathed

by the plasma membrane

Dynein

Moves flagella and cilia

Microfilaments (Actin)

• Function:

– Maintain cell shape

• Bear tension

• Cell cortex

– Core of microvilli

– Muscle contraction

– Cell motion

– Cytoplasmic streaming

-Solid rods

-Twisted double chain

Microfilaments

• Function:

– Maintain cell shape

• Bear tension

• Cell cortex

– Core of microvilli

– Muscle contraction

– Cell motion

– Cytoplasmic streaming

Amoeboid movement

Localized contraction by actin and myosin

Pseudopodia (cellular extensions)

Extend and contract through reversible assembly and contraction of actin subunits into microfilaments

Intermediate filament

-Structure: super coiled cables, keratin subunits

• Function:

– Cell shape

– Tension-bearing

– Hold organelles in place

– Nuclear lamina

Primary cell wall

Relatively thin and flexible

Middle lamella

– Glues adjacent cells

– Thin layer between primary walls of adjacent cells

Secondary cell wall

Added between the plasma membrane and the primary cell wall

Plasmodesmata

– Channels between adjacent plant cells

– Pores: water and solutes pass from cell to cell

Aquaporins

A channel protein that determines water movement

Ion channels

Opens/closes in response to stimulus

Carrier proteins

Binds solutes, changes shape, and moves across membrane

Ligand

Molecule that specifically binds receptor

Endergonic reactions

-Positive ∆G

– NOT spontaneous

– Work must be applied for reaction to occur

Exergonic reactions

-Negative ∆G

– Spontaneous

– Increases stability of the system (equilibrium)

– Can be harnessed to perform work

Reactive

Higher amount of free energy available

Cooperativity

– Form of allosteric regulation

– Can amplify enzyme activity

– Binding by a substrate stabilizes active form

Allosteric regulation

A molecule binds to a protein at a site other than its active site, causing a shape change that turns the protein's activity up or down

Feedback Inhibition

• Final product inhibits an earlier enzyme.

• Prevents overproduction