Cell Structure and Function: Key Organelles and Cell Cycle

Cell

Smallest living units in the body that obtain nutrients, make molecules needed to survive, dispose of wastes, maintain shape, and replicate.

Plasma membrane

The outer boundary of the cell that separates intracellular fluid from extracellular fluid and determines which substances enter or leave the cell.

Cytoplasm

The internal environment of the cell that contains cytosol, organelles, and inclusions.

Nucleus

The control center of the cell that directs cellular activities and provides instructions for protein synthesis.

Organelles

Subunits of cells with specific functions; most cells contain the same basic organelles but not all have them in the same abundance.

Selectively permeable

A characteristic of the plasma membrane that allows certain substances to enter or leave the cell.

Fluid mosaic model

Description of the structure of the plasma membrane.

Cytosol

Jelly-like fluid in which cellular elements are suspended, consisting of water, ions, and enzymes.

Ribosomes

Non-membrane-bound organelles that are the site of protein synthesis.

Endoplasmic reticulum

A system of membrane-walled envelopes and tubes throughout the cytoplasm.

Rough ER

Endoplasmic reticulum with ribosomes on its surface, involved in protein synthesis.

Smooth ER

Endoplasmic reticulum without ribosomes, involved in lipid synthesis.

Golgi apparatus

A stack of disc-shaped envelopes that sorts products of rough ER and sends them to their proper destination.

Lysosomes

Membrane-walled sacs containing digestive enzymes that digest unwanted substances.

Mitochondria

Double-walled membrane organelles that generate most of the cell's energy and produce ATP.

Cytoskeleton

An elaborate network of rods in the cell, consisting of microtubules, microfilaments, and intermediate filaments.

Nuclear envelope

Two parallel membranes separated by a fluid-filled space that surrounds the nucleus.

Nuclear pores

Pores that penetrate the nuclear envelope, allowing large molecules to pass in and out of the nucleus.

Nucleolus

'Little nucleus' located in the center of the nucleus.

Cell life cycle

The series of changes a cell undergoes, including interphase and cell division.

Interphase

The phase of the cell life cycle where the cell is metabolically active and prepares for division.

G1 phase

The first part of interphase where the cell is metabolically active.

S phase

The synthetic phase of interphase where DNA replicates itself.

G2 phase

The second growth phase of interphase where enzymes needed for cell division are synthesized.

M phase

The mitotic phase where cells divide.

Mitosis

The division of the nucleus during cell division.

Cytokinesis

The division of the cytoplasm that occurs after the nucleus divides.