Study Unit 1

Cell Theory

The scientific theory that states: 1) Cells are the fundamental units of life; 2) All living organisms are composed of cells; 3) All cells come from preexisting cells.

Unicellular Organisms

Organisms that consist of a single cell, such as bacteria, archaea, and amoeba.

Multicellular Organisms

Organisms composed of many cells, which can range from hundreds to trillions, such as mammals and plants.

Cell Division

The process by which a parent cell divides to produce daughter cells.

Surface Area to Volume Ratio

A ratio that decreases as a cell's size increases, impacting the cell's efficiency in exchanging materials with its environment.

Homeostasis

The ability of a cell to maintain a stable internal environment despite changes in external conditions.

Cytoplasm

Everything inside the cell except for the nucleus.

Cytosol

The fluid portion of the cytoplasm that is not contained within organelles.

Organelles

Membrane-enclosed compartments in eukaryotic cells that separate various biochemical reactions from the rest of the cell.

Prokaryotic Cells

Simple cells without a nucleus, typically ranging from 1–10 μm in diameter.

Eukaryotic Cells

More complex cells with a defined nucleus, typically ranging from 10–100 μm in diameter.

Lysosomes

Cellular compartments that contain digestive enzymes for breaking down macromolecules.

Mitochondria

Organelles that generate ATP through cellular respiration by harvesting energy from food molecules.

Chloroplasts

Organelles in plant cells that contain chlorophyll and are the sites of photosynthesis.

Cytoskeleton

A network of fibers that maintains cell shape, supports organelles, and aids in cell movement.

Microfilaments

Fibers made from actin that assist in cell movement and shape stabilization.

Microtubules

Hollow tubes made from tubulin that provide structural support and pathways for organelle movement.

Endomembrane System

A system composed of the cell membrane, nuclear envelope, endoplasmic reticulum, Golgi apparatus, and lysosomes, which facilitates the transport of materials within the cell.

Extracellular Matrix

A complex network that provides structural and biochemical support to surrounding cells in animal tissues.

Endosymbiosis

The theory that some organelles originated from free-living prokaryotes that were engulfed by ancestral cells.

Cell Membrane

Protects the cell, controls the movement of substances in and out, and maintains homeostasis.

Nucleus

Acts as the control center for the cell, housing DNA and coordinating cell activity such as growth and reproduction.

Ribosomes

Synthesizes proteins by translating messenger RNA (mRNA).

Endoplasmic Reticulum (ER)

Involved in the synthesis of proteins (rough ER) and lipids (smooth ER), and facilitates transport of materials within the cell.

Golgi Apparatus

Packages and modifies proteins and lipids for transport to their destinations.

Vesicles

Small membrane-bound sacs that transport materials within the cell.

Centrioles

Involved in cell division by helping to organize the mitotic spindle.

Peroxisomes

Contains enzymes to break down fatty acids and detoxify harmful substances.

Cell Wall

A rigid structure that provides support and protection in plant cells.

Intercellular Communication

Allows cells to send and receive signals, coordinating tissue and organ function.

Chlorophyll

A green pigment found in chloroplasts that is essential for photosynthesis.

Carotenoids

Pigments that provide yellow, orange, and red colors in plants and are involved in photoprotection and photosynthesis.

Xanthophylls

Yellow pigments in plants that assist in light harvesting and protection against damage from excess light.

Phycobilins

Water-soluble pigments found in cyanobacteria and red algae, important for capturing light energy during photosynthesis.

Granum

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

Stroma

The fluid-filled space in chloroplasts where the light-independent reactions (Calvin cycle) take place.

Thylakoids

Membrane-bound compartments inside chloroplasts that host the chlorophyll and are site of the light-dependent reactions.

Ribulose-1,5-bisphosphate (RuBP)

A five-carbon sugar involved in the Calvin cycle that reacts with CO₂ to help fix carbon during photosynthesis.

Proteins in Organelles

Various proteins within organelles are crucial for their specific functions, including enzyme activity and structural roles.

Lipid Bilayer

A double layer of phospholipids that makes up the cell membrane and organelle membranes, providing structure and selective permeability.