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any substance in the universe that has mass and occupies space


small particles that make up all matter


negatively charged subatomic particles that are transferred and shared between atoms


a charged particle


any substance that dissociates in water to increase the concentration of H+ ions; pH values of acids are from 1-7


any substance that combines with H+ ions when dissolved in water; pH values from 7-14


the loss of an electron


the gain of an electron


groups of atoms held together by energy in a stable association

chemical bond

joins atoms in a molecule

ionic bond

attraction between ions of opposite charge in an ionic compound

covalent bond

a stable chemical bond formed when two atoms share one or more pairs of electrons


indicates concentration of hydrogen ions in a solution (the more H+ ions a solution produces, the lower its pH; pH scale- less than 7 is acidic, 7 is neutral, above 7 is basic)

chemical reactions

formation and breaking of chemical bonds

hydrogen bonds

the weak bond bridging hydrogen atoms and atoms of the opposite charge


attraction of water molecules to other molecules


attraction of water molecules to water molecules


original molecules before the reaction starts


molecules resulting from the chemical reaction


when nonpolar molecules do not form hydrogen bonds with water ("fearing water")


when polar molecules readily form hydrogen bonds with water ("water-loving")


biological molecules consisting only of carbon and hydrogen

functional groups

specific groups of atoms with definite chemical properties that they retain no matter where they occur

dehydration synthesis

condensation reaction in which the -OH and H groups are removed during the synthesis of a new molecule- water is removed


process in which a hydrogen atom is attached to one subunit and a hydroxyl group to the other- water is added


process in which a protein's shape is changed due to a change in its environment- pH change, temperature, or ionic concentration of surrounding solution affect it


Biological catalyst made of amino acids.


Reactant an enzyme catalyzes

Active Site

structure on the enzyme


The molecules needed for a chemical reaction to occur


Molecules that are made when a chemical reaction is over

Activation Energy

The amount of energy needed for a reaction to occur.

Heat of Reaction

The difference in energy between the reactants and products of a chemical reaction


a reaction that has a "-" heat of reaction b/c it releases more energy that it stores


a reaction that has a "+" heat of reaction and stores more energy than it releases.


Speeds up a chemical reaction

Variables that effect enzyme reaction rate

Temperature, pH, enzyme concentration, substrate concentration


enzyme becomes "inactive" due to changes in the active site structure

enzyme specificity

enzyme only bonds to one substrate due to shape of active site

cell membrane

regulates movement of materials in and out of cells, maintains cell shape and allows cells to communicate with each other

smooth endoplasmic reticulum

makes or synthesizes lipids, detoxification of drugs/medicines

rough endoplasmic reticulum

has ribosomes associated with it and transports proteins


makes proteins


modifies, sorts and packages substances made by the cell and sends them to vacuoles, other organelles or out of the cell


cell organelle filled with enzymes needed to break down certain materials in the cell


store food and water


Powerhouse of the cell, organelle that is the site of ATP (energy) production


organelle in plant cells that converts the energy in sunlight into sugars


Located near the nucleus and help to organize cell division


the control center of the cell


makes ribosomes


threadlike structures made of DNA molecules that contain the genes


a jellylike fluid inside the cell in which the organelles are suspended

nuclear membrane

double membrane surrounding the nucleus that controls what enters and leaves the nucleus


a tiny cell structure that carries out a specific function within the cell

Cell theory

idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells


A type of lipid that makes up the cell membrane.


network of protein filaments within some cells that helps the cell maintain its shape and is involved in many forms of cell movement


A unicellular organism that lacks a nucleus and membrane bound organelles


A cell that contains a nucleus and membrane bound organelles

Cell Wall

strong layer around the cell membrane in plants, algae, and some bacteria


a lipid made of a phosphate head and two fatty acid tails

lipid bilayer

cell membranes composed of two layers of phospholipids, with the tails pointed inwards towards each other, and the heads facing outward

cell surface markers

a membrane protein that identifies the cell type

receptor proteins

a membrane protein that binds to signals outside the cell

transport proteins

transports substances unable to diffuse across a cell membrane

active transport

energy is required to move a substance across a cell membrane

passive transport

no energy is required to transport substances across cell membranes


when randomly moving molecules fill up a space evenly


the amount of a particular substance in a given volume

concentration gradient

a difference in the concentration of a substance across a distance


substances moving down the concentration gradient (from high to low concentration)

simple diffusion

small, nonpolar molecules passing directly through the lipid bilayer

facilitated diffusion

transport proteins helping ions and polar molecules to diffuse through the bilayer

channel proteins (pores)

tunnels that open for ions and polar molecules to pass through the cell membrane

carrier proteins

a protein that transports substances across a cell membrane by changing shape


the process of water diffusing across a selectively permeable membrane

water channels

channel proteins that aid in osmosis, and only allow water molecules to pass through

hypertonic solution

the solute has high concentration, the water has low, water moves out of the cell

hypotonic solution

the solute has low concentration, the water has high, water moves into the cell

isotonic solution

the solute and water have an equal concentration to the cell's cytoplasm, water moves into and out of the cell at equal rates

contractile vacuoles

colllect excess water in unicellular eukaryotes and force the water out of the cell

sodium-potassium pump

a carrier protein that uses ATP to actively transport 3 sodium ions out of a cell, and 2 potassium ions into a cell


the process of a large substance moving into a cell using a vesicle


the process of a large substance moving out of a cell by means of a vesicle

signaling cell

a cell that produces a signal that is detected by a target cell


anything that serves to direct, guide or warn

target cell

a cell that responds to a signal sent by a signaling cell

receptor proteins

a protein that binds to specific signal molecules, causing the cell to respond

binding site

the outer folds of a receptor protein, where the signal binds

permeability change

transport proteins opening or closing in response to a signal

second messenger

a signal molecule inside a cell, generated when a substance attaches to the outside of the cell membrane, causes changes in the cytoplasm and nucleus


in eukaryotic cells, a process of cell division that forms two new nuclei, each of which has the same number of chromosomes


(genetics) cell division that produces reproductive cells in sexually reproducing organisms


organic process consisting of the division of the cytoplasm of a cell following karyokinesis bringing about the separation into two daughter cells


The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, it exists as a mass of very long, thin fibers that are not visible with a light microscope.

Sister Chromatids

Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.


a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape

Cell Cycle

series of events that cells go through as they grow and divide


the period of the cell cycle during which the nucleus is not undergoing division, typically occurring between mitotic or meiotic divisions


Located near the nucleus and help to organize cell division


dense masses of RNA and protein that manufacture ribosomes, several of these are located in the nucleus.


first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus


second phase of mitosis, during which the chromosomes line up across the center of the cell


the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles


the final stage of meiosis or mitosis, in which the separated chromosomes reach the opposite poles of the dividing cell and the nuclei of the daughter cells form around the two sets of chromosomes

Cell Plate

A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.

Cleavage Furrow

pinching of the cell ("drawstring"): develops in animal cells only

Meiosis II

the second phase of meiosis consisting of chromatids separating, along with the two diploid cells splitting in two

Prophase I

The first phase of meiosis I. the replicated chromosomes condense, homologous chromsomes pair up, crossing over occurs between homologous chromosomes, the spindle is formed, and the nuclear envelope breaks apart into vesicles. the longest phase of meiosis.

Anaphase I

The third phase of meiosis I. the replicated homologous chromosomes are separated (the tetrad is split) and pulled to opposite sides of the cell.

Metaphase I

The second phase of meiosis I. the paired homologous chromsomes (tetrads) align at the center of the cell (the metaphase plate).

Telophase I

The fourth of meiosis I. the number of chromosoms is now reduced by half. After this phase the cell is considered to be haploid. Note however, that the chromosomes are still replicated, and the sister chromatids must still be separated during meiosis II.

Prophase II

The first phase of meiosis II. identical to the mitotic step, except that the number of chromosomes was reduced by half during meiosis I.

Metaphase II

The second phase of meiosis II. identical to the mitotic step, except that the number of chromosomes was reduced by half during meiosis I.

Anaphase II

The third phase of meiosis II. the sister chromatids are finally spearated at their centromeres and puled to opposite sides of teh cell. is identical to mitotic anaphase, excep the number of chromosmes was reduced by half during meiosis I.

Telophase II

The fourth and final phase of meiosis II. the number of chromosomes was reduced by half during meiosis. I.


term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes


(genetics) an organism or cell having two sets of chromosomes or twice the haploid number


the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis


the paired chromosomes consisting of four chromatids

Crossing Over

the interchange of sections between pairing homologous chromosomes during the prophase of meiosis

Somatic Cells

any cell other than a gamete, has 46 chromosomes, body cells


sex cells


a fertilized egg

g1 Checkpoint

checks to see if cell size is adequate; chromosomes replication is successfully completed and checks for DNA errors

g0 Checkpoint

if condidtions are not apporpiate for the cell to divide or if it is not programmed to divide they are in this phase

g2 Checkpoint

asses if DNA replication has occured, go ahead signal triggers mitosis

Cyclin Dependent Kinases

cdk enzymes activate proteins to regulate the cell

Growth Factors

factors that stimulate the cell to divide

Density Dependent Inhibition

The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.

Anchorage Dependence

the requirement that to divide, a cell must be attached to a solid surface.


one of two alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

Law of Independent Assortment

states that allele pairs separate independently during the formation of gametes

Monohybrid Cross

hybridization using a single trait with two alleles (as in Mendel's experiments with garden peas)

Dihybrid Cross

hybridization using two traits with two alleles each

Incomplete Dominance

creates a blended phenotype; one allele is not completely dominant over the other


a condition in which both alleles for a gene are fully expressed

Multiple Alleles

three or more forms of a gene that code for a single trait (such as blood types)


A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited., One gene masks the expression of a different gene for a different trait


A single gene having multiple effects on an individuals phenotype (more than one phenotypic expression)

Linked Genes

genes located on the same chromosome that tend to be inherited together in genetic crosses

Sex Linked Inheritance

Traits located on the sex cells. EX: Colorblindness, hemophilia.

X Inactivation

During development, females inactivate half of their X gene elles in order to prevent producing double the amount of the protein.


error in meiosis in which homologous chromosomes don't separate; gametes end up with wrong number of chromosomes


condition in which an organism has extra sets of chromosomes

Point Mutations

changes in a DNA sequence caused by substitution of one nucleotide for another


an abnormality involving a chromosome number that is not an exact multiple of the haploid number (one chromosome set is incomplete)(causes down sydrome and turners syndrome)

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