Winter Break Vocab

Partially Permeable

(Internet Definition) A membrane which only allows particular substances cross it, and not others

Freely Permeable

(Internet Definition) Allows all substances to flow freely across the membrane such as water and nutrients

Cell Surface Membrane

A very thin membrane (about 7nm diameter) surrounding all cells; it is partially permeable and controls the exchange of materials between the cell and its environment

Nucleus

A relatively large organelle found in eukaryotic cells, but absent from prokaryotic cells; the nucleus contains the cell's DNA and therefore controls the activities of the cell

Chromatin

The loosely coiled form of chromosomes during interphase of the cell cycle; chromatin is made of DNA and proteins and is visible as loosely distributed patches or fibers within the nucleus when stained

DNA

Deoxyribonucleic acid, a molecule which contains the instructions that control the activities of the cell

Nucleolus

A small structure, one or more of which is found inside the nucleus; the nucleolus is usually visible as a densely stained body; its function is to manufacture ribosomes using the information in its own DNA

Cytoplasm

The contents of a cell, excluding the nucleus

Organelles

A functionally and structurally distinct part of a cell

Mitochondria

The organelle in eukaryotes in which aerobic respiration takes place

Golgi Apparatus

An organelle found in eukaryotic cells; the Golgi apparatus consists of a stack of flattened sacs, constantly forming at one end and breaking up into Golgi vesicles at the other end; Golgi vesicles carry their contents to other parts of the cell, often to the cell surface membrane for secretion; the Golgi apparatus chemically modifies the molecules it transports; for example, sugar may be added to proteins to make glycoproteins

Secretion

The release of a useful substance from a cell of gland

Cristae

a fold of the inner membrane of the mitochondrial envelope on which are found stalked particles of ATP synthase and electron transport chains associated with aerobic respirations

ATP

Adenosine triphosphate - the universal energy currency of cells

ADP

Adenosine diphosphate

Microtubules

Tiny tubes made of a proteins called tubulin and found in most eukaryotic cells; microtubules have a large variety of functions, including cell support and determining cell shape; the 'spindle' on which chromosomes separate during nuclear divisions is made of microtubules

Centrosome

(Internet Definition) an organelle near the nucleus of a cell which contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division

Prokaryote

A cell that does not contain a nucleus or any other membrane-bound organelles; bacteria and archeans are prokaryotes

Eukaryote

A cell containing a nucleus and other membrane-bound organelles

Centriole

One of two small, cylindrical structure, made from microtubules, found just outside the nucleus in animal cell, in a region known as the centrosome; they are also found at the bases of cilia and flagella

Cell Wall

A wall surrounding prokaryote, plant and fungal cells; the wall contains a strengthening material which protects the cell from mechanical damage, supports it and prevents it from bursting by osmosis if the cell is surrounded by solution with a higher water potential

Plasmodesmata

A pore-like structure found in plant cell walls; plasmodesmata of neighboring plant cells line up to form tube-like pores through the cell walls, allowing the controlled passage of materials from one cell to the other; the pore contain ER and are lined with the cell surface membrane

Vacuole

An organelle found in eukaryotic cells; a large, permanent central vacuole is a typical feature of plant cells where it has a variety of functions, including storage of biochemicals such as salts, sugars, and waste products; temporary vacuoles, such as phagocytic vacuoles ( also known as phagocytic vesicles), may form in animal cells

Tonoplast

The partially permeable membrane that surrounds plant vacuoles

Chloroplast

The photosynthetic organelles in eukaryotes

Grana

A stack of circular thylakoids in a chloroplast

Magnification

The number of times greater that an image is than the actual object; magnification = image size/actual size of the object

Resolution

The ability to distinguish between two objects very close together; the higher the resolution of an image, the greater the details that can be seen

Ultrastructure

(Internet Definition) A biological structure and especially fine structure (as of a cell) not visible through an ordinary microscope.

Endoplasmic Reticulum

A network of flattened sacs running through the cytoplasm of eukaryotic cells; molecules, particularly proteins, can be transported through the cell inside the sacs separate from the rest of the cytoplasm; ER is continuous with the outer membrane of the nuclear envelope

Nuclear Pores

Pores founds in the nuclear envelope which control the exchange of material between the nucleus and the cytoplasm

Ribosomes

A tiny organelles found in large numbers in all cells; prokaryotic ribosomes are smaller (20 nm diameter) than eukaryotic ribosomes (25 nm diameter); ribosomes are made of proteins and ribosomal RNA and consist of two subunits; they are the sites of protein synthesis in cells

Virus

Very small (20-300 nm) infectious particle which can replicate only inside living cells and consists essentially of a simple basic structure of a genetic code of DNA or RNA surrounded by a protein coat

Macromolecule

A large biological molecules such as a protein, polysaccharides or nucleic acids

Polymer

A giant molecule made from many similar repeating subunits joined together in a chain; the subunits are much smaller and simpler molecules known as monomers; polymers may also be referred to as macromolecules

Monomer

A relatively simple molecule which is used as a basic building block for the synthesis of a polymer; many monomers are joined together to make the polymer, usually by condensation reactions; common examples of molecules used as monomers are monosaccharides, amino acids and nucleotides

Nucleotide

A molecule consisting of a nitrogen-containing base, a pentose sugar and a phosphate group

Monosaccharide

A molecule consisting of a single sugar unit with the general formula (CH₂O)ₙ

Disaccharide

A sugar molecule consisting of two monosaccharides joined together by a glycosidic bond

Condensation

A chemical reaction involving the joined together of two molecules by removal of a water molecule

Glycosidic bond

A C-O-C link between two monosaccharide molecules, formed by a condensation reaction

Hydrolysis

A reaction in which a complex molecule is broken down to a simpler one, involving the addition of water

Polysaccharide

A polymer whose subunits are monosaccharide joined together by glycosidic bonds

Amylose

A polymer of α-glucose monomers linked by 1,4 linkage

Amylopectin

A polymer of α-glucose monomers linked by 1,4 and 1,6 linkages, forming a branched chain; amylopectin is a constituent of starch

Glycogen

A polysaccharide made of many glucose molecules linked together, that acts as a glucose store in liver and muscles cells

Hydrogen bonds

A relatively weak bond formed by the attraction between a group with a small positive change on a hydrogen atom and another group carrying a small negative charge

Triglyceride

A lipid whose molecule are made up of a glycerol molecule and three fatty acids

Phospholipid

A substance whose molecules are made up of a glycerol molecule, two fatty acids and a phosphate group; a bilayer of phospholipids forms the basic structure of all cell membranes

Peptide bond

A C-N link between two amino acid molecules, formed by a condensation reaction

Polypeptide

a long chain of amino acids formed by condensation reactions between the individuals amino acids; proteins are made of one or more polypeptide chains

Primary structure

The sequence of amino acids in a polypeptide or protein

a-helix

A helical structure formed by a polypeptide chain, held in place by hydrogen bonds; an α-helix is an example of secondary structure in a protein

b-pleated sheet

a loose, sheet-like structure formed by hydrogen bonding between parallel polypeptide chains

Primary structure

The sequence of amino acids in a polypeptide or protein

Secondary structure

The structure of a protein molecule resulting from the regular coiling or folding chain of amino acids

Tertiary structure

The compact structure of a protein molecule resulting from the three-dimensional coiling of the already-folded chain of amino acids

Fibrous protein

A protein whose molecules have a relatively long, thin structure that is generally insoluble and metabolically inactive, and whose function is usually structural, e.g. keratin and collagen

Prosthetic group

A non-protein component that is attached to a protein to form a complex molecule; it aids the protein in its function; an example is the iron-containing haem group, which is attached to \n α-globin and β-globin to form hemoglobin

Globular protein

A protein whose molecules are folded into a relatively spherical shape, and which is often water-soluble and metabolically active, e.g. insulin and hemoglobin

Hemoglobin

The red pigment found in red blood cells, whose molecules contain four iron atoms within a globular protein made up of four polypeptides, and that combines reversibly with oxygen

Active site

An area on an enzyme molecule where the substrate can build

Lock and key hypothesis

A model for enzyme action; the substrate is a complementary shape to the active site of the enzyme, and fits exactly into the site

Induced fit hypothesis

A model for enzyme action; the substrate is a complementary shape to the active site of the enzyme, but not an exact fit - the enzyme or sometimes substrate can change shape slightly to ensure a perfect fit

Activation energy

The energy that must be provided to make a reaction take place, enzymes reduce the activation energy required for a substrate to change into a product

Noncompetitive inhibition

When a substance reduces the rate of activity of an enzyme, but increasing the concentration of the substrate does not reduce the degree of inhibition; many non-competitive inhibitors bind to areas of the enzyme molecule other than the active site itself

Michaelis Menten constant

The substrate concentration at which an enzyme works at half its maximum rate (1/2\*Vmax), used as a measure of the efficiency of an enzyme; the lower the value of Km, the more efficient the enzyme

Immobilized enzyme

Enzymes that have been fixed to a surface or within a bead of agar gel

Channel and Carrier Proteins

Channel: A membrane protein of fixed shape which has a water-filled pore through which selected hydrophilic ions or molecules can pass (facilitated diffusion)

Carrier: A type of membrane protein which changes shape to allow the passage into or out of the cell of specific ions or molecules by facilitated diffusion or active transport

Cholesterol

A small, lipid-related molecule with a hydrophilic head and a hydrophobic tail which is an essential constituent of membranes, particularly in animal cells, conferring fluidity, flexibility, and stability to the membrane

Facilitated Diffusion

The diffusion of a substance through transport proteins in a cell membrane; the proteins provide hydrophilic areas that allow the molecules or ions to pass through the membrane which would otherwise be less permeable to them

Antigens

A substance that is foreign to the body and stimulates an immune response

Cell Signaling

The molecular mechanisms by which cells detect and respond to external stimuli, including communication between cells

Diffusion

The net movement of molecules or ions from a region higher concentration to a region of lower concentration down a gradient, as a result of the random movement of particles

Osmosis

The net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane, as a result of their random motion (diffusion)

Endocytosis

The bulk movements of solids and/or liquids into a cell, by the infolding of the cell surface membrane to form vesicles containing the substance; endocytosis is an active process requiring ATP

Phagocytosis

The bulk movement of solids

Pinocytosis

The bulk movement of liquids

Exocytosis

The bulk movement of liquids or solids out of a cell, by the fusion of vesicles containing the substance with the cell surface membrane; exocytosis is an active process requiring ATP

Active Transport

The movement of molecules or ions through transport proteins across a cell membrane, against their concentration gradient, using energy from ATP

Sodium Potassium Pump

A membrane protein (or proteins) that moves sodium ions out of a cell and potassium ions into it, using ATP

Protoplast

The living contents of a plant cell, including the cell surface membrane, but excluding the cell wall

Solute Potential

Pressure Potential

Water potential

A measure of the tendency of water to move from one place to another; water moves from a solution with higher water potential to one with lower water potential; water potential is decreased by the addition of solute, and increased by the application of pressure, symbol is Ψ or Ψw

Gametes

A haploid cell specialized for fertilization

Zygotes

A cell formed by the fusion of two gametes; normally the gametes are haploid and the zygote is diploid

Chromosome

A structure made of DNA and histones, found in the nucleus of a eukaryotic cell; the term bacterial chromosome is now commonly used for the circular strand of DNA present in a prokaryotic cell

Chromatids

One of two identical parts of a chromosome, held together by a centromere, formed during interphase by the replication of the DNA strand

Cell Cycle

The sequence of events that takes place from one cell division until the next; it is made up of interphase, mitosis and cytokinesis

Kinetochores

A protein structure found at the centromere of a chromatid to which microtubules attach during cell division

Telomeres

Repetitive sequences of DNA at the end of chromosomes that protect genes from the chromosome shortening that happens at each cell

Cancer

A disease, often but not always treatable, that results from a breakdown in the usual control mechanisms that regulate cell division; certain cells divide uncontrollably and form tumors, from which cells may break away and form secondary tumors in other areas of the body (metastasis)

Stem Cell

A relatively unspecialized cell that retains the ability to divide an unlimited number of times

Mutation

An unpredictable change in the structure of DNA, or in the structure and number of chromosomes

Carinogen

A substance that can cause cancer

Nucleotide

A molecule consisting of a nitrogen-containing base, a pentose sugar, and a phosphate group

Polynucleotide

A chain of nucleotides

Complementary Base Pairing

The hydrogen bonding of A with T or U and of C with G in nucleic acids

Semi-conservative Replication

The method by which a DNA molecule is copied to form two identical molecules, each containing one strand from the original molecule and one newly synthesized strand