BHS Biology Semester 1

2025 edit

Chloroplast

organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy

Photosynthesis

process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches

light-dependent reactions

part of photosynthesis that absorbs energy from sunlight and transfers energy to the light-independent reactions

Light Independent Reactions (Calvin Cycle)

set of reactions in photosynthesis that do not require light; energy from ATP and NADPH is used to build high-energy compounds such as sugar; also called the Calvin cycle

Glucose

A simple sugar that is an important source of energy.

Thylakoid

each of a number of flattened sacs inside a chloroplast, bounded by pigmented membranes on which the light reactions of photosynthesis take place, and arranged in stacks or grana.

grana (granum)

the stacks of thylakoids embedded in the stroma of a chloroplast.

Stroma

The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.

Chemosynthesis

process in which chemical energy is used to produce carbohydrates

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Mitochondria

An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.

ATP

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

aerobic respiration

Respiration that requires oxygen

anaerobic respiration

Respiration that does not require oxygen

Glycolysis

A metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP

lactic acid fermentation

the chemical breakdown of carbohydrates that produces lactic acid as the main end product

alcoholic fermentation

the anaerobic process by which yeasts and other microorganisms break down sugars to form carbon dioxide and ethanol

Photosynthesis equation

6CO2 + 6H2O + light energy --> C6H12O6 + 6O2

cellular respiration equation

C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP

Prokaryote

A unicellular organism that lacks a nucleus and membrane bound organelles

Eukaryote

A cell that contains a nucleus and membrane bound organelles

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

Nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Cell membrane (plasma membrane)

phospholipid bilayer that surrounds all cells and regulates what enters and leaves the cell

Ribosome

Makes proteins

Homeostasis

process by which organisms maintain a relatively stable internal environment

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

Osmosis

Diffusion of water through a selectively permeable membrane

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

active transport

the movement of ions or molecules across a cell membrane into a region of higher concentration requiring energy.

hypertonic solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution that causes a cell to shrink

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution that causes a cell to swell

Isotonic

Describes a solution whose solute concentration is equal to the solute concentration inside a cell

Autotroph

An organism that makes its own food

Heterotroph

organism that obtains energy from the foods it consumes; also called a consumer

Macromolecules

A very large organic molecule composed of many smaller molecules

Monomer

small chemical unit that makes up a polymer

Polymer

A long molecule consisting of many similar or identical monomers linked together.

Carbohydrates

the starches and sugars present in foods

Protein

An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells

amino acids

monomers of proteins

Lipids

Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen.

nucleic acids

macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus such as DNA and RNA

Nucleotide

monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

Enzymes

Proteins that speed up chemical reactions

catalyst

substance that speeds up the rate of a chemical reaction

activation energy

the minimum amount of energy required to start a chemical reaction

Denature

A change in the shape of a protein (such as an enzyme) that can be caused by changes in temperature or pH (among other things).

Biology

the scientific study of life

asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

cell cycle

series of events in which a cell grows, prepares for division, and divides to form two daughter cells

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

Mitosis

cell division in which the nucleus divides into nuclei containing the same number of chromosomes

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Prophase

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

Metaphase

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

Anaphase

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

Telophase

the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.

Cytokinesis

division of the cytoplasm to form two separate daughter cells

somatic cells

body cells

food web

network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem

food chain

A series of steps in which organisms transfer energy by eating and being eaten

energy pyramid

A diagram that shows the amount of energy that moves from one feeding level to another in a food web

Producer

An organism that can make its own food.

Consumer

An organism that obtains energy by feeding on other organisms

apex predator

the top predator in an ecosystem

Meiosis

A type of cell division that reduces the chromosome number by half, resulting in four genetically diverse gametes.

Gametes

Reproductive cells (sperm and eggs) that carry half the genetic information of an organism.

Diploid

A cell or organism that has two complete sets of chromosomes, one from each parent.

Haploid

A cell or organism that has only one set of chromosomes, typical of gametes.

Crossing Over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Independent Assortment

The random distribution of maternal and paternal chromosomes into gametes during meiosis.

Prophase I

The first stage of meiosis where homologous chromosomes pair up and crossing over occurs.

Metaphase I

The stage of meiosis where homologous chromosome pairs align at the cell's equatorial plane.

Anaphase I

The phase in meiosis where homologous chromosomes are pulled apart to opposite poles of the cell.

Telophase I

The stage of meiosis that follows anaphase I, where the cell divides into two haploid cells.

Meiosis II

The second division of meiosis that separates sister chromatids, resulting in four haploid cells.

Nondisjunction

An error in meiosis where chromosomes fail to separate properly, leading to gametes with abnormal chromosome numbers.

Genetic Variation

The diversity in gene frequencies, which is increased through processes like crossing over and independent assortment during meiosis.

Karyotype

A visual representation of an individual's complete set of chromosomes, arranged in pairs according to size and shape.

Chromosome

A thread-like structure made of DNA and proteins, carrying genetic information.

Autosome

Any chromosome that is not a sex chromosome, typically present in pairs in both sexes.

sex chromosomes

Chromosomes that determine the sex of an individual, typically X and Y in humans. Pair 23 in a karyotype

Trisomy

A genetic condition where an individual has three copies of a particular chromosome instead of the usual two.

Monosomy

A genetic condition where an individual has only one copy of a particular chromosome instead of the usual two.

cell wall

A rigid outer layer found in plant cells, fungi, and some bacteria that provides structural support and protection.

Golgi Apparatus

A cellular structure responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

Endoplasmic Reticulum

A network of membranes in the cytoplasm that synthesizes proteins and lipids, often divided into rough and smooth sections.

Ribosomes

Cellular structures that synthesize proteins by translating messenger RNA. They can be found free in the cytoplasm or attached to the endoplasmic reticulum.

Centrioles

Structures that assist in cell division by organizing the mitotic spindle and helping in the formation of cilia and flagella.

Vacuole

A membrane-bound organelle found in plant and fungal cells that stores nutrients, waste products, and helps maintain turgor pressure.