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element

A pure substance that cannot be broken down into other substances by chemical or physical means

atom

The basic particle from which all elements are made; the smallest particle of an element that has the properties of that element

compound

A substance made of two or more elements chemically combined in a specific ratio, or proportion

molecule

A neutral group of two or more atoms held together by covalent bonds

DNA

Deoxyribonucleic acid; the genetic material that carries information about an organism and is passed from parent to offspring

cell

The basic unit of structure and function in living things

unicellular

Made of a single cell

multicellular

Consisting of many cells

tissue

A group of similar cells that perform a specific function organ-A body structure that is composed of different kinds of tissues that work together

organ system

A group of organs that work together, performing major functions

microscope

An instrument that makes small objects look larger

cell theory

A widely accepted explanation of the relationship between cells and living things

homeostasis

The condition in which an organism's internal environment is kept stable in spite of changes in the external environment

cellular respiration

The process in which oxygen and glucose undergo a complex series of chemical reactions inside cells, releasing energy

photosynthesis

The process by which plants and other autotrophs capture and use light energy to make food from carbon dioxide and water

cell membrane

A thin, flexible barrier that surrounds a cell controls which substances pass into and out of a cell

diffusion

The process by which molecules move from an area of lower concentration

cell division

A process in which one cell splits into two new cells that are genetically identical to the original cell

cell wall

A rigid supporting layer that surrounds the cells of plants and some other organisms

nucleus

In cells, a large oval organelle that contains the cell's genetic material in the form of DNA and controls many of the cell's activities

organelle

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

ribosome

A small grain-shaped organelle in the cytoplasm of a cell that produces proteins

cytoplasm

The thick fluid region of a cell located inside the cell membrane or between the cell membrane and nucleus

mitochondria

Rod-shaped organelles that convert energy in food molecules to energy the cell can use to carry out its functions

endoplasmic reticulum

An organelle that forms a maze of passageways in which proteins and other material are carried from one part of the cell to another

Golgi apparatus

An organelle in a cell that receives proteins and other newly formed materials from the endoplasmic reticulum, packages them, and distributes them to other parts of the cell

vacuole

A sac-like organelle that stores water, food and other materials

chloroplast

An organelle in the cells of plants and some other organisms that captures energy from sunlight and changes it to an energy form that cells can use in making food

lysosome

A cell organelle which contains chemicals that break down large food particles into smaller ones and that can be used by the rest of the cell

cell cycle

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

replication

An attempt to repeat a scientist's experiment by a different scientist or group of scientists

chromosome

A threadlike structure within a cell's nucleus that contains DNA that is passed from one generation to the next

mitosis

The second stage of the cell cycle during which the cell's nucleus divides into two new nuclei and one set of DNA is distributed into each daughter cell

cytokinesis

The final stage of the cell cycle, in which the cell's cytoplasm divides, distributing the organelles into each of the two new daughter cells

interphase

The first stage of the cell cycle that takes place before cell division occurs, during which a cell grows and makes a copy of its DNA

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