Anatomy of the cell

The Cell

• All Living things are composed of cells
• All Cells have/contain the following:
• Cell Membrane - Lipid Bilayer - Separates inside from outside

• Cytoplasm - everything but DNA/Nucleus

Cytoplasm

Cell Types

• Two major types of cells:

• Prokaryotic Cells

• Primitive cells
• No nucleus
• No Membrane-bound organelles
• Very Small 1-10 micrometers
• Single Strand of Circular "naked" DNA
• Contain Ribosomes

• Eukaryotic Cells

• Contain a Nucleus which protects DNA / Chromosomes
• Much larger than prokaryotic cells


• Have many different types of Membrane bound organelles - compartmentalization = efficiency

Animal Cell

Plant Cell

Organelles

• Membrane-Bound organelles only found in Eukaryotes
• Localize Chemical Reactions making the cell far more efficient
• Major organelles of the Eukaryotic Cell
• The Nucleus
• "eukaryotic" means "true nucleus"
• Contains & protects the cell’s DNA
• Helps coordinate the division of cells
• Surrounded by a Nuclear Envelope
• Envelope is double layered with an Inner & Outer membrane
• Has perforations called Nuclear Pores which allow large molecules to pass in/out of the nucleus

• Contains a Nucleolus
• Ribosomes are made in this region

The Nucleus

• Contains DNA packaged in structures called chromosomes

Chromosomes

Mitochondria

• Serves as the "powerhouse of the cell" by generating chemical energy
• Has it’s own DNA*
• Can divide on its own*

Chloroplasts (PLANT CELL ONLY)

• Is the "cell’s farm" - meaning food is generated here.
• Does this by photosynthesis - the conversion of CO₂, H₂O and sunlight into sugar
• Contain Chlorophyll - a green pigment - which does this
• Has it’s own DNA*
• Can divide on its own*

Ribosomes

• Are NOT membrane-bound & also exist in prokaryotes
• Are used to manufacture proteins
• Granular in appearance
• Often found on "rough" endoplasmic reticulum*

Ribosomes

Ribosomes on Rough endoplasmic reticulum

Endoplasmic Reticulum

• Are folds of membranes used to package & modify proteins made by ribosomes. They also make lipids
• 2 types
• "Rough" - which is usually near nucleus and covered with ribosomes giving it its "rough" appearance.
• "Smooth" - which is usually away from the nucleus

Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum

Golgi Bodies - Are the post offices of the cell

• Modify (address) proteins & lipids and send them in packages (vessicles) throughout (or out of) the cell.

Lysosomes

• Small Vessicles which serve to digest particles and clean-up cells
• Contain Lysozyme – a powerful digestive enzyme
• Digests food particles
• Destroys worn-out organelles
• Self-Destructs worn-out cells

Centrioles (Animals Only)

• Serve as construction/organization points for cellular microtubules
• Organize and transfer chromosomes and other organelles during Meiosis & Mitosis
• Occur in some prokaryotes, protists & animals. Do not occur with fungi and plants
• Tube like structures usually at right angles to each other.
• Some animals have centriole-like structures at the base of flagella called basal bodies.

Vacuole (PLANTS ONLY)

• Large H₂O / Lipid / waste storage tank
• Provides pressure (Turgor pressure) to maintain cell structure

Vacuole

Cell Wall (PLANT ONLY)

• Provides support / protection for plant cell
• Two layers of cell wall
• Primary Cell Wall – Outer – Cellulose only
• Secondary Cell Wall – Inner – Cellulose & Lignin
• Cell membrane is innermost layer

Cytoskeleton

• Network of fibers which help organize the internal arrangement within cells.
• Three basic types of fibers compose cytoskeleton:
• Actin Filaments
• Thinnest fibers ~7nM
• Formed from protein Actin

• Microtubules
• Largest component of cytoskeleton ~25 nM
• Formed from protein Tubulin

• Intermediate filaments
• Intermediate in size and can vary
• Form from several proteins inluding vimentin & keratin

Intercellular Junctions

 

q       Allows attachment and communication between cells.  This aids cells in behaving as a unified organism.

o       Plants utilize Plasmodesmata

§         Perforations and channels through cell walls of adjacent plant cells.

§         Allows cytoplasm from adjacent cells to pass between cells.

 

o       Animals Utilize several different junctions to provide communication, structure & support.

§         Tight Junctions – Belts joining cell membranes of neighboring cells.  Prevent materials from passing between cells

§         Desmosomes – “rivets” made from keratin which anchor neighboring cells together.  These also have pores allowing communication between cells.

§         Gap Junctions – Channels connecting cytoplasm from adjacent cells