Unit 2 - Cell Structure and Function

Eukaryotes

Organisms with most of their DNA stored in the nucleus, which is bounded by a double membrane.

Prokaryotes

Organisms characterized by the absence of a nucleus, with DNA located in an unbound region called the nucleoid, and no membrane-bound organelles.

Ribosomes

Structures found in all cells that are responsible for protein synthesis.

Organelles

Functioning parts of a cell that perform the work of keeping cells alive, often referred to as "tiny organs."

Cytoplasm

Semi-fluid substance that fills the interior of the cell and suspends organelles.

Cell membrane

Separates the cell from the outside environment, controls what enters or leaves the cell, and recognizes signals from other cells.

Vacuoles & Vesicles

Membrane sacs involved in moving materials around the cell and storage.

Lysosomes

Membrane sacs containing digestive enzymes that digest food, recycle cellular components, and clean up waste.

Mitochondria

Double-membrane organelles responsible for producing ATP energy from sugar via cellular respiration.

Nucleus

Control center of the cell that protects DNA and contains instructions for building proteins.

Nucleolus

Located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis, where ribosomes are made.

Endoplasmic Reticulum (ER)

Site of protein synthesis and membrane lipid production.

Golgi Apparatus

Finishes, sorts, labels, and ships proteins within the cell.

Semipermeable

Material or membrane that allows some substances to pass through but not all.

Cholesterol

Regulates membrane fluidity, maintaining fluidity at cool temperatures and restraining movement of phospholipids at warm temperatures.

Integral proteins

Penetrate the hydrophobic interior of the lipid bilayer.

Peripheral (surface) proteins

Loosely bound to the surface of the membrane.

Passive transport

Movement of substances across a membrane without the use of energy.

Diffusion

Net movement of molecules from an area of high concentration to an area of low concentration.

Osmosis

Diffusion of free water across a selectively permeable membrane.

Isotonic solution

Solute concentration is the same as inside the cell, resulting in no net water movement.

Hypertonic solution

Solute concentration is greater than that inside the cell, causing the cell to lose water.

Hypotonic solution

Solute concentration is less than that inside the cell, causing the cell to gain water.

Facilitated diffusion

Passive transport aided by proteins.

Active transport

Movement of substances against their concentration gradients, requiring energy.

Sodium-potassium pump

Example of active transport that moves sodium ions out of the cell and potassium ions into the cell.

Exocytosis

Process in which transport vesicles fuse with the cell membrane, releasing their contents outside the cell.

Endocytosis

Process in which the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane.

Hypothesis

Proposed explanation for a set of observations that can be tested.

Scientific Theory

In-depth explanation of an observed phenomenon that is supported by repeated testing and evidence.

Cell Theory

All living things are made of cells, cells are the basic unit of structure and function, and all new cells come from pre-existing cells.

Endosymbiotic Theory

Explanation of the evolution of membrane-bound organelles in eukaryotic cells, suggesting that mitochondria and chloroplasts were once prokaryotic microbes.