Natural Science CLEP

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

photolysis

In photosynthesis, this is the splitting of water by light

cofactor

a substance that must join with the enzyme to enable it to fit the substrate

vacuole

membrane-bound organelle that stores water and soluble substances

cristae

numerous folds in the inner membrane of a mitochondrion, the site of cellular respiration

pistil

the female part of a flower composed of ovary and style and stigma and ovules

anaphase

the stage of meiosis or mitosis when chromosomes move toward opposite ends of the nuclear spindle

filament

the stalk of a stamen that supports the anther

substrate

the substance acted upon by an enzyme

active transport

transport of a substance across a cell membrane against the concentration gradient

centrioles

tubes, One of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope; play a role in cell division.

chromatids

two identical chromosomes that split and contain the same genetic material

chromatin

consists of DNA tightly coiled around proteins

ribosomes

site of protein synthesis. Free ribosomes - float unattached; attached ribosomes - attached to the ER

prophase

the first stage of mitosis, forming spindle fibres attached to the centromere

mitochondria

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

anabolism

Process of building up complex materials (proteins) from simple materials

ovules

Structure within ovary of plant that contains egg cells

fermentation

anaerobic cellular respiration in which pyruvic acid is broken down into end products such as lactic acid

organism

living thing

perennial

plants that grow year after year

microvilli

projections on cell membrane increase surface area

enzymes

proteins that act as biological catalysts

gene

sequence of DNA that codes for a protein and thus determines a trait

cell

smallest unit of most living things

pedicel

stalk that supports the flower

ovary

the organ that bears the ovules of a flower, base of the pistil

endocytic vesicles

Formed when cell membrane surrounds a molecule outside the cell and ingests it

cell cycle

The regular sequence of growth and division that cells undergo

haploid

a cell having only one complete set of chromosomes

diploid

a cell having two sets of chromosomes or twice the haploid number

angiosperms

classification of plant which forms seeds inside a protective chamber called an ovary, inside a flower

glycolysis

first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid

transformation

modification of a cell by the incorporation of exogenous DNA

biosynthesis

production of a chemical compound by a living organism

cytoskeleton

provides structural support to a cell composed of microtubules, microfilaments, centrioles

reduction

reducing the ploidy level of nucleus from diploid to haploid in meiotic cell division

genome

the complete genetic material contained in an individual

metaphase

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

codon

three-nucleotide sequence on messenger RNA that codes for a single amino acid

electron microscope

used to examine tiny cell organelles

electron transport

uses electrons from the Krebs cycle to change ADP to ATP (cytochromes on surface of cristae of mitochondria, contain protein and heme (iron containing) groups, electrons pass along them and ATP is produced)

tonoplast

vacuole membrane

prosthetic group

A non-protein, but organic, molecule (such as vitamin) that is covalently bound to an enzyme as part of the active site

homologs

Matching Chromosomes that are similar but not identical

endosymbiont hypothesis

Theory which suggests mitochondria and chloroplasts were once prokaryotic organisms in a symbiotic relationship with eykorytic cells

DNA

a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix

interphase

a period during which the cell grows - G1, copies its DNA - S, and synthesizes proteins - G2

inhibitor

a substance that retards or stops enzymatic activity

endoplasmic reticulum

an internal membrane system in which components of cell membrane and some proteins are constructed. rough - instrumental in protein synthesis; smooth - processes lipids fats and steroids

centromere

area where the chromatids of a chromosome are attached

nucleosome

bead-like structure in chromatin, composed of a short length of DNA wrapped around a core of histone proteins

stroma

body of a chloroplast containing grana

catabolism

breakdown of more complex substances into simpler ones with release of energy

meiosis

cell division that produces reproductive cells in sexually reproducing organisms

mitosis

cell division which produces two identical cells

lysosomes

cell organelle filled with enyzmes need to break down certain materials in the cells

prokaryotes

cells that lack a membrane-bound nucleus and membrane-bound organelles

mutation

change in a DNA sequence that affects genetic information

gymnosperms

classication of plant which produce seeds which are "naked" (in cones)

annuals

classification of plant which survives only a single season

biennial

classification of plant whose life cycle survives two seasons

cell membrane

composed of a bilayer of lipids embedded with globular proteins

alleles

different forms of a gene

grana

disk-like plates which are the site of photosynthesis in chloroplasts

cytokinesis

division of the cytoplasm during cell division - new cell is formed

microfilaments

double-stranded chains of proteins which give structure to the cell

chlorophyll

green pigment contained in the grana

eukoryotic cells

has a nucleus, has organelles or other cell parts

vascular plants

have tissues made of cells that transport water and nutrients throughout the plant

microtubules

hollow tubes of protein about 25 nanometers in diameter, support the cell and moves organelles within the cell

post-transcriptional processing

modifications of pre-mRNA that make it into mature mRNA, so that it is ready for protein synthesis

secretory vesicles

packaged protein or other substance produced by golgi apparatus/endoplasmic reticulum

shoot apex

part of stem where growth occurs, contains meristem tissue that is capable of quick growth

virus

particle made up of DNA, RNA, protein, and in some cases lipids that can only replicate only by infecting living cells

facilitated diffusion

passive transport of materials across a plasma membrane by transport proteins embedded in the plasma membrane

carbon dioxide fixation

photosynthetic reaction in which carbon dioxide is attached to an organic compound (glucose - polysaccharides)

nuclear pores

pores which allows materials to move in and out of the cell nucleus

exocytosis

process by which a cell releases large amounts of material

gametes

reproductive cells, have only half the number of chromosomes

metabolism

set of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes

organelles

small structures in the cytoplasm of a cell that do special jobs

nucleolus

small, dense region within most nuclei in which the assembly of RNA proteins begins

krebs cycle

stage of cellular respiration that finishes the breakdown of pyruvic acid molecules to carbon dioxide, releasing energy

stigma

sticky portion at the top of the style which traps pollen

golgi apparatus

stores, packages and ships proteins

cell wall

strong layer around the cell membrane in plants, algae, and some bacteria made of cellulose and lignin

telophase

the final stage of mitosis or meiosis, during which a nuclear membrane forms around each set of new chromosomes

crossing over

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

stamen

the male reproductive organ of a flower consisting of anther, filament, and pollen

transcription

the organic process whereby the DNA sequence in a gene is copied into mRNA

active site

the part of an enzyme where the chemical reaction occurs

anther

the part of the stamen that contains pollen

transduction

the process of transfering genetic material from one cell to another

translation

the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm through tRNA