Cell Biology Mid Term Exam

DNA

Double-stranded polynucleotide formed from two separate chains of covalently link deoxyribonucleotides. Serves as the cell’s storage of genetic information that is transmitted from generation to generation

RNA

Molecule produced by the transcription of DNA; usually single stranded, it is a polynucleotide composed of covalently linked ribonucleotide subunits. Serves a variety of informational, structural, catalytic, and regulatory functions in cells

Protein

Macromolecule built from amino acids that provides cells with their shape and structure and performs most of their activites

Central Dogma

The flow of genetic information from DNA to RNA to Proteins

Evolution

Process of gradual modification and adaptation that occurs in living organisms over generations

Genome

The total genetic information carried by all the chromosomes of a cell or organism; in humans, the total number of nucleotide pairs in the 22 autosomes plus the X and Y chromosomes (23 in total)

Fluorescence microscope

Instrument used to visualize a specimen that has been labeled with a fluorescent dye; samples are illuminated with a wavelength of light that excites the dye, causing it to fluoresce

Electron microscope

Instrument that passes a beam of electrons through the specimen to reveal and magnify the structures of very small objects, such as organelles, and large molecules

Eukaryotes

An organism whose cells have a distinct nucleus and cytoplasm

Prokaryotes

Major category of living cells distinguished by the absence of a nucleus; includes the archaea and the eubacteria (commonly called bacteria)

Archaeon

Microscopic organism that is a member of one of the two divisions of prokaryotes; often found in hostile environments such as hot springs or concentrated brine

Bacterium

Microscopic organism that is a member of one of the two divisions of prokaryotes; some species cause disease. The term is sometimes used to refer to any prokaryotic microorganism

Cell

The basic unit from which a living organism is made; aqueous solution of chemicals, enclosed by a membrane, that has an ability to self-replicate

Chloroplast

specialized organelle in algae and plants that contains chlorophyll and serves as the site for photosynthesis

Chromosome

Long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism; becomes visible as a distinct entity when a plant or animal cell prepares to divide

Cytoplasm

Contents of a cell that re contained within its plasma membrane but, in the case of eukaryotic cells, outside the nucleus

Cytoskeleton

System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules, and intermediate filaments

Cytosol

Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as the endoplasmic reticulum and mitochondria.

Endoplasmic Reticulum (ER)

Labyrinthine membrane-enclosed compartment in the cytoplasm of eukaryotic cells where lipids and proteins are made

Golgi apparatus 

Membrane-enclosed organelle in eukaryotic cells that modifies the proteins and lipids made in the endoplasmic reticulum and sorts them for transport to other sites 

Homologous 

Describes genes, chromosomes, or any structures that are similar because of their common evolutionary origin. Can also refer to similarities between protein sequences or nucleic acid sequences 

Mitochondrion

membrane-enclosed organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells

Model organism

A living thins selected for intensive study as a representative of a large group of species.

Mouse - multicellular eukaryotic organism

Yeast - unicellular eukaryotic organism

Escherichia coli (E. coli) - bacteria

Nucleus

Refers to the prominent, rounded structure that contains the DNA of a eukaryotic cell

Organelle

A discrete structure or subcompartment of a eukaryotic cell that is specialized to carry out a particular function

Photosynthesis

The process by which plants, algae, and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water

Plasma membrane

The protein-containing lipid bilayer that surrounds a living cell

Protozoan

a free-living, non photosynthetic, single-celled, motile eukaryote 

Ribosome

Large macromolecular complex, composed of RNAs and proteins, that translate a messenger RNA into a polypeptide chain

Acid

A molecule that releases a proton when dissolved in water; this dissociation generates hydronium (H3O+) ions, thereby lowering the pH

Amino acid

small organic molecule containing both an amino group and a carboxyl group; it serves as the building blocks for proteins

Atom

The smallest particle of an element that still retains its distinctive chemical properties; consists of positively charged nucleus surrounded by a cloud of negatively charged electrons

ATP

Activated carrier that serves as the principal carrier of energy in cells; a nucleoside triphosphate compsed of adenine, ribose, and three phosphate groups

Base

Molecule that accepts a proton when dissolved in water; also used to refer to the nitrogen containing purines and pyrimidines in DNA and RNA

Buffer

mixture of weak acids and bases that maintains the pH of a solution be releasing and taking up protons

Chemical bonds

an attraction that holds two atoms together

Chemical Group

A combination of atoms, such as a hydroxyl group (-OH) or an amino group (-NH2), with distinct chemical and physical properties that influence the behavior of the molecule in which it resides

Condensation reaction

chemical reaction in which a covalent bond in formed between two molecules as water is expelled; used to build polymers, such as proteins, polysaccharides, and nucleic acids

Covalent bond

stable chemical link between two atoms produced by sharing one or more pairs of electrons

Electron

Negatively charged subatomic particle that occupies space around an atomic nucleus

Electronegativity

the tendency of an atom to attract electrons

Electrostatic attraction

force that draws together oppositely charged atoms

Fatty Acid

molecule that consists of a carboxylic acid attached to a long hydrocarbon chain. Used as a major source of energy during metabolism and as a starting point for the synthesis of phospholipids

Hydrogen bonds

A weak non covalent interaction between a positively charged hydrogen atom in one molecule and a negatively charged atom, such as nitrogen or oxygen, in another; these bonds are key to the structure and properties of water

Hydrolysis

chemical reaction that involves cleavage of a covalent bond with the accompanying consumption of water (its -H being added to one product of the cleavage and its -OH to the other); the reverse of a condensation reaction

Hydrophilic

molecule or part of a molecule that readily forms hydrogen bonds with water, allowing it to readily dissolve; “water loving”

Hydrophobic 

Nonpolar, uncharged molecule or part of a molecule that forms no hydrogen bonds with water molecules and therefore does not dissolve; “water fearing” 

Hydrophobic force

a non covalent interaction that forces together the hydrophobic portions of dissolved molecules to minimize their disruption of the hydrogen bonded network of water; causes membrane phospholipids to self-assemble into a bilayer and helps fold proteins into a compact, globular shape

inorganic

not composed of carbon atoms

ion

an atom carrying an electrical charge, either positive or negative

ionic bond

interaction formed when one atom Dontaes electrons to another; this transfer of electrons causes both atoms to become electrically charged

lipid

an organic molecule that is insoluble in water but dissolves readily in non polar organic solvents; typically contains long hydrocarbon chains or multiple rings. One class, the phospholipids, forms the structural basis for biological membranes

lipid bilayer

thin pair of closely juxtaposed sheets, composed mainly of phospholipid molecules, that forms the structural basis for all cell membranes

macromolecule

polymer built from covalently linked subunits; includes proteins, nucleic acids, and polysaccharides with a molecular mass greater then a few thousand daltons

molecule

group of atoms joined together by a covalent bond

monomer 

small molecule that can be linked to others of a similar type to form a larger molecule (polymer)

non covalent bond

chemical association that does not involve the sharing of electrons; singly they are relatively weak, but they can sum together to produce strong, highly specific interactions between molecules

nucleotide

basic building blocks of nucleic acids, DNA and RNA; a nucleoside linked to a phosphate

organic molecule

chemical compound that contains carbon and hydrogen 

pH Scale

Concentration of hydrogen ions in a solution, expressed as a logarithm

Polar

described a molecule or bond in which electrons are distributed unevenly

Polymer

Long molecule made by covalently linking multiple similar or identical subunits

Proton

positively charged particle found in the nucleus of every atom

Sequence

the linear order of monomers in a large molecule

subunit

a monomer that forms part of a larger molecule, such as amino acids in a protein or nucleotides in nucleic acids

van der Waals attraction

weak non covalent interaction, due to fluctuations electrical charges, that comes into play with two atoms located very closely to each other

Acetyl CoA

activated carrier that donates the carbon atoms in it readily transferable acetyl group to many metabolic reactions, including the citric acid cycle and fatty acid biosynthesis; the acetylene group is linked to coenzyme A (CoA) by a thioester bond that releases a large amount of energy when hydrolyzed

activated carrier

a small molecule that stores energy or chemical groups in a form that can be donated to many different metabolic reactions

activation energy

the energy that must be acquired by a molecule to undergo a chemical reaction

ADP

nucleoside diphosphate produced by hydrolysis of the terminal phosphate ATP

ATP

activated carrier that serves as the principal carrier of energy in cells; a nucleoside triphosphate composed of adenine, ribose, and three phosphate groups

anabolism

set of metabolic pathways by which large molecules are made from smaller ones

biosynthesis

an enzyme-catalyzed process by which complex molecules are formed from simpler substances by living cells

catabolism

set of enzyme-catalyzed reactions by which complex molecules are degraded to simpler ones with release of energy; intermediates in there reactions are sometimes called catabolites 

catalyst

substance that accelerates a chemical reaction by lowering its activation energy; enzymes perform this role in cells

cell respiration

process by which cells harvest the energy stored in food molecules; usually accompanied by the uptake of O2 and the release of CO2

coupled reaction

linked pair of chemical reactions in which free energy released by one reaction serves to drive the other reaction

diffusion

process by which molecules and small particles move from one location to another by random, thermally driven motion

entropy

thermodynamic quantity that measures the degree of disorder in a system

enzyme

a protein that catalyzes a specific chemical reaction

equilibrium

state in which the forward and reverse rates of a chemical reaction are equal so that no net chemical change occurs 

equilibrium constant, k

for a reversible chemical reaction, the ratio of substrate to product when the rates of the forward and reverse reactions are equal

free energy, G

energy that can be harnesses to do work, such as driving a chemical reaction

free energy change, delta G

in a chemical reaction, the difference in free energy between reactant and product molecules. A large negative value indicates that the reaction has a strong tendency to occur

metabolism

the sum total of the chemical reactions that take place in the cells of a living organism

NAD+

a molecule that accepts a hydride ion (H-) from a donor molecule, thereby producing the activated carrier NADH. Widely used in the energy-producing breakdown of sugar molecules

NADH

activated carrier of electrons that is widely used in the energy-producing breakdown of sugar molecules

NADP+

molecule that accepts a hydride ion (H-) from a donor molecule, thereby producing the activated carrier NADPH; widely used as an electron donor in biosynthetic pathways 

NADPH

activated carrier closely related to NADH and used an an electron donor in biosynthetic pathways

oxidation

removal of electrons from an atom, as occurs during the addition of oxygen to a carbon atom or when a hydrogen is removed from a carbon atom; can also refer to a partial shift of electrons between atoms linked by a covalent bond

photosynthesis

the process by which plants, algae, and some bacteria use the energy of sunlight to drive the synthesis of organic molecules from carbon dioxide and water

reduction

addition of electrons to an atom as occurs during the addition of hydrogen to a carbon atom or the removal of oxygen from it; can also refer to a partial shift of electrons between atoms linked by a covalent bond