Cell Biology Overview

Study Notes

Cell Definition

The smallest unit of life
Organelles are structures within a cell that carry out specific metabolic functions

Simple Animal Cell

Cytoplasm is the gel-like substance within the cell membrane
DNA carries genetic information
The nucleus is the central organelle that contains DNA
The nucleoid is the region where DNA is located in prokaryotes
The cell membrane is the outer boundary of the cell

Types of Cells

Eukaryotic Cells

Cells with a nucleus and other membrane-bound organelles

Prokaryotic Cells

Small, simple cells without a nucleus

Modern Microscopes

Light microscopes use visible light to illuminate and magnify specimens
- Phase-contrast microscopes enhance contrast in transparent specimens
- Reflected light microscopes illuminate the surface of opaque specimens
- Fluorescence microscopes use fluorescent dyes to illuminate specific structures
Electron microscopes use beams of electrons to create highly magnified images
- Transmission electron microscopes (TEMs) create images by passing electrons through a thin specimen
- Scanning electron microscopes (SEMs) create 3D images by scanning a focused electron beam across the surface of a specimen

Prokaryotes

Prokaryotes include bacteria and archaea
They are the smallest and most metabolically diverse forms of life
Prokaryotes are single-celled organisms

Biofilm

A community of single-celled organisms that secrete a protective layer of polysaccharides and glycoproteins
Examples include bacteria, algae, fungi, protists, and archaeans

Eukaryotic Cells

All protists, fungi, plants, and animals are eukaryotic
Eukaryotic cells have their DNA enclosed within a nucleus
Organelles found in eukaryotic cells include:
- Cell wall: provides structural support and protection (in plants, fungi, and some protists)
- Vacuole: stores water, ions, and nutrients and helps maintain cell shape (larger in plant cells)
- Plasma membrane: regulates the passage of substances into and out of the cell
- Mitochondrion: the powerhouse of the cell, responsible for ATP production through cellular respiration
- Nucleus: the control center of the cell, containing DNA
- Central vacuole: a large, fluid-filled sac that stores water and provides structural support (in plant cells)
- Chloroplast: the site of photosynthesis in plants and some protists
- Cytoskeleton: a network of protein fibers that provides structural support, allows movement, and helps transport substances
  - Microtubules: hollow tubes that help maintain cell shape, transport substances, and form components of cilia and flagella
  - Microfilaments: thin filaments that help maintain cell shape, support cell movement, and form contractile structures
  - Intermediate filaments: tough, rope-like filaments that provide structural support and help anchor organelles
- Plasmodesma: channels that connect the cytoplasm of adjacent plant cells
- Plasma membrane: controls the movement of substances into and out of the cell
- Ribosomes: sites of protein synthesis
- Rough ER: modifies proteins made by ribosomes attached to it
- Smooth ER: synthesizes lipids, breaks down carbohydrates and fats, and detoxifies substances
- Golgi Body: packages, modifies, and sorts lipids, enzymes, and proteins
- Lysosome-Like Vesicle: digests, recycles, and breaks down waste in the cell

Human White Blood Cell

Organelles in a human white blood cell include:
- Rough ER: synthesizes and modifies proteins made by ribosomes attached to it
- Smooth ER: synthesizes lipids, breaks down carbohydrates and fats, and inactivates toxins
- Golgi Body: modifies, sorts, and packages lipids, enzymes, and proteins for delivery to other parts of the cell
- Lysosome: digests and recycles materials within the cell
- Nuclear pore: allows the passage of molecules between the nucleus and the cytoplasm

Structure of the Nucleon Envelope

The nuclear envelope is a double membrane that surrounds the nucleus
Proteins embedded in the nuclear envelope control the movement of molecules between the nucleus and the cytoplasm

Structure of the Nucleus

Nucleoplasm: a viscous fluid contained within the nuclear envelope
Nucleolus: a dense region in the nucleus where subunits of ribosomes are assembled from proteins and RNA