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Cell

Basic unit of life; performs all essential functions.

Tissue

Group of similar cells working together; types include epithelial, connective, muscle, and nervous.

Organ

Structure composed of multiple tissue types; performs specific functions (e.g., heart, lungs).

Organ System

Group of organs that work together for complex functions (e.g., digestive system).

Organism

Individual living being made up of various organ systems.

Integumentary System

Protects body; includes skin, hair, nails.

Skeletal System

Provides structure; supports and protects organs; produces blood cells.

Muscular System

Facilitates movement; maintains posture; generates heat.

Nervous System

Controls body activities; processes information; includes brain, spinal cord, nerves.

Endocrine System

Regulates bodily functions through hormones (e.g., glands).

Cardiovascular System

Transports nutrients, gases, and waste; includes heart and blood vessels.

Lymphatic System

Returns fluid to blood; protects against infection; includes lymph nodes and vessels.

Respiratory System

Facilitates gas exchange (oxygen and carbon dioxide); includes lungs and airways.

Digestive System

Breaks down food; absorbs nutrients; includes stomach and intestines.

Urinary System

Removes waste; regulates water and electrolytes; includes kidneys and bladder.

Reproductive System

Produces offspring; includes reproductive organs.

Superior

Above; e.g., the head is superior to the abdomen.

Inferior

Below; e.g., the stomach is inferior to the heart.

Medial

Closer to the midline; e.g., the nose is medial to the eyes.

Lateral

Further from the midline; e.g., the ears are lateral to the head.

Proximal

Closer to the point of attachment; e.g., the elbow is proximal to the wrist.

Distal

Further from the point of attachment; e.g., the fingers are distal to the wrist.

Anterior

Front; e.g., the sternum is anterior to the spine.

Posterior

Back; e.g., the spine is posterior to the sternum.

Sagittal Plane

Divides the body into left and right parts.

Frontal (Coronal) Plane

Divides the body into anterior and posterior parts.

Transverse (Horizontal) Plane

Divides the body into superior and inferior parts.

Protons

Positively charged; found in the nucleus.

Neutrons

Neutral charge; also in the nucleus.

Electrons

Negatively charged; orbit around the nucleus.

Ionic Bonds

Formed when electrons are transferred from one atom to another, resulting in charged ions.

Covalent Bonds

Involve the sharing of electrons between atoms.

Nonpolar Covalent Bonds

Electrons are shared equally.

Polar Covalent Bonds

Electrons are shared unequally, creating partial charges.

Hydrogen Bonds

Weak attractions between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Synthesis Reaction

Two or more reactants combine to form a larger product (A + B → AB).

Decomposition Reaction

A single compound breaks down into two or more simpler products (AB → A + B).

Exchange Reaction

Atoms or molecules exchange places (AB + CD → AC + BD).

Reversible Reaction

Can proceed in both forward and reverse directions (A + B ⇌ AB).

Cytoplasm

Gel-like substance where organelles are suspended.

Nucleus

Contains genetic material (DNA); controls cellular activities.

Rough Endoplasmic Reticulum (Rough ER)

Studded with ribosomes; synthesizes proteins.

Smooth Endoplasmic Reticulum (Smooth ER)

Synthesizes lipids and detoxifies.

Ribosomes

Sites of protein synthesis; can be free in cytoplasm or attached to ER.

Golgi Complex

Modifies, sorts, and packages proteins for secretion or use within the cell.

Lysosomes

Contains digestive enzymes to break down waste.

Peroxisomes

Contains enzymes that detoxify harmful substances.

Mitochondria

Powerhouse of the cell; site of ATP production.

Centrioles

Involved in cell division.

Passive Transport

Movement of molecules without energy use.

Diffusion

Movement from high to low concentration.

Osmosis

Movement of water across a membrane.

Facilitated Diffusion

Requires transport proteins.

Active Transport

Requires energy (ATP) to move substances against their concentration gradient.