Biology First Semester Exam Review Topics

active site

The region of an enzyme where substrate molecules bind and undergo a chemical reaction.

aerobic

Processes that require oxygen to occur.

anaerobic

Processes that do not require oxygen to occur.

asexual reproduction

A mode of reproduction that does not involve the fusion of gametes.

autosomes

Chromosomes that are not sex chromosomes.

biodiversity

The variety of life in the world or in a particular habitat or ecosystem; highest in tropical rainforests.

carbohydrates

Organic compounds made of carbon, hydrogen, and oxygen, typically in a ratio of 1:2:1.

carbon cycle

The process by which carbon is cycled through the environment, involving organic carbon in living organisms and inorganic carbon in the atmosphere.

catalyst

A substance that increases the rate of a chemical reaction without undergoing any permanent chemical change.

centromere

The region of a chromosome where the two sister chromatids attach.

compound

A substance formed when two or more chemical elements are chemically bonded together.

concentration gradient

A difference in the concentration of a substance across a space.

consumers (heterotrophs)

Organisms that cannot produce their own food and must obtain it by consuming other organisms.

cytoplasm

The jelly-like substance within a cell that contains organelles.

dehydration synthesis

A chemical reaction that involves the loss of a water molecule from the reacting molecules.

dependent variable

The variable that is measured in an experiment; represented on the y-axis of a graph.

diploid

A cell that contains two complete sets of chromosomes, one from each parent; examples in humans include somatic cells.

electron transport chain

A series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions.

element

A pure substance consisting of one type of atom.

enzyme

A protein that acts as a catalyst to speed up chemical reactions in the body.

facilitated diffusion

The process of passive transport of molecules across a biological membrane via specific transmembrane integral proteins.

fermentation

A metabolic process that converts sugar to acids, gases, or alcohol; two types discussed are lactic acid fermentation and alcoholic fermentation.

fertilization

The process of combining male and female gametes to form a zygote.

fluid mosaic model

A model that describes the structure of cell membranes as a mosaic of various components.

gametes

Sex cells involved in sexual reproduction.

gametogenesis

The process by which gametes are produced.

glycolysis

The metabolic pathway that converts glucose into pyruvate, producing ATP and NADH.

grana

Stacks of thylakoids in chloroplasts where light-dependent reactions of photosynthesis occur.

haploid

A cell that contains one complete set of chromosomes; examples in humans include gametes.

homeostasis

The ability of an organism to maintain stable internal conditions despite changes in the external environment.

homologous chromosomes

Chromosome pairs, one from each parent, that are similar in shape, size, and genetic content.

hydrolysis

A chemical reaction that involves the breaking down of a compound by the addition of water.

hypertonic

A solution that has a higher concentration of solutes compared to another solution.

hypothesis

A proposed explanation for a phenomenon, which can be tested; a good hypothesis is testable and falsifiable.

hypotonic

A solution that has a lower concentration of solutes compared to another solution.

independent variable

The variable that is changed or controlled in an experiment; represented on the x-axis of a graph.

inner membrane

The membrane that surrounds the mitochondrial matrix.

inner membrane space

The space between the inner and outer membranes of a mitochondrion.

ion

An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

isotonic

A solution that has the same concentration of solutes as another solution.

karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Krebs cycle

A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins.

light-dependent reaction

The first stage of photosynthesis where light energy is converted into chemical energy in the form of ATP and NADPH.

light-independent reaction

The second stage of photosynthesis that does not require light directly, using ATP and NADPH to synthesize glucose.

lipids

A group of organic compounds that are insoluble in water, including fats, oils, and waxes.

matrix

The space within the inner membrane of a mitochondrion where the Krebs cycle occurs.

meiosis

A type of cell division that reduces the chromosome number by half, producing four haploid cells; in humans, meiosis produces cells with 23 chromosomes.

mitosis

A type of cell division that results in two daughter cells, each with the same number of chromosomes as the parent cell; in humans, mitosis produces cells with 46 chromosomes.

molecule

A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound.

nucleic acids

Biomolecules essential for all known forms of life, including DNA and RNA.

organelles

Specialized structures within a cell that perform specific functions.

osmosis

The movement of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

outer membrane

The membrane that surrounds the mitochondrion.

phospholipid bilayer

A double layer of phospholipids that makes up the cell membrane.

producers (aka autotrophs)

Organisms that produce their own food through photosynthesis or chemosynthesis.

products

The substances that are produced in a chemical reaction.

proteins

Large biomolecules composed of one or more long chains of amino acid residues.

reactants

The starting materials in a chemical reaction.

semipermeable membrane

A membrane that allows certain molecules or ions to pass through it by diffusion.

sex chromosomes

Chromosomes that determine the sex of an organism.

sexual reproduction

A mode of reproduction that involves the fusion of male and female gametes.

simple diffusion

The process by which molecules move from an area of higher concentration to an area of lower concentration without the need for energy.

sister chromatids

Identical copies of a chromosome connected by a centromere.

solute

The substance that is dissolved in a solution.

solvent

The substance in which the solute is dissolved.

somatic cells

Any cell of a living organism other than the reproductive cells.

species

A group of organisms that can interbreed and produce fertile offspring.

stroma

The fluid-filled space surrounding the thylakoids in chloroplasts.

substrate

The reactant on which an enzyme works.

system

A group of interacting or interrelated entities that form a unified whole.

thylakoid

A membrane-bound compartment inside chloroplasts and cyanobacteria where the light-dependent reactions of photosynthesis occur.

transgenic organism

An organism that has been genetically modified to contain a gene from another species.

zygote

The fertilized egg that results from the union of a sperm cell and an egg cell.