Unit 3:
Cells - The living
units
Cells - Basis of Life
● Highly organized
● Made of four primary elements –
N, O, C, H
● About 60% water
● Bathed in a dilute saltwater solution
(something like seawater) called
interstitial fluid
● Vary in shape and function
Structure of a Generalized Cell
Anatomy of a Cell
• Cells are not all the same
• All cells share general structures
• Cells are organized into three main regions:
• Nucleus
• Cytoplasm
• Plasma membrane
The Nucleus
•
Control center of the cell
•
Contains genetic material (DNA)
•
Three regions:
•
Nuclear membrane
• Nucleolus
• Chromatin
Nuclear Membrane
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•
Double-layered barrier of nucleus
Contain nuclear pores that allow for
exchange of material with the rest of
the cell
Nucleolus
•
•
•
Sites of ribosome production
Ribosomes then migrate to the cytoplasm
through nuclear pores
Nucleus contains one or more nucleoli
•
•
•
•
Chromatin
Genetic information
Composed of DNA and protein
Scattered throughout the nucleus
Chromatin condenses to form
chromosomes when the cell
divides
Cytoplasm
• Material outside the nucleus and inside the plasma membrane
• Cytosol
• Fluid that suspends other structures
• Organelles
• Metabolic machinery of the cell
• Inclusions
• Non-functioning units; stored nutrients or cell products (i.e. fat
droplets, pigments, glycogen, mucus)
Cytoplasmic Organelles
Ribosomes
• Sites of protein synthesis
• Made of protein and RNA
• Found in two locations
• Free in the cytoplasm
• Attached to rough endoplasmic reticulum
• ‘Factory Worker’
Endoplasmic Reticulum
• Fluid-filled tubules for carrying substances
• Two types of ER
• Rough ER:
• Site where proteins are folded and transported
• Studded with ribosomes (makes it look ‘rough’)
• ‘Factory that houses the factory workers’
• Smooth ER:
• Functions in cholesterol synthesis and breakdown, fat metabolism, and
detoxification of drugs
• No ribosomes
Golgi Apparatus
• Modifies and packages proteins
• Produces different types of packages
• Secretory vesicles
• Cell membrane components
• Lysosomes
• ‘Stack of flattened sacs’
• ‘FedEx Shipping Plant’
Lysosomes and Peroxisomes
• Lysosomes
• Contain enzymes that digest materials within the cell
• Used in programmed cell death
• Peroxisomes
• Detoxify harmful substances
• Break down free radicals (highly reactive, dangerous chemicals) to H2O2
• Membranous sacs of special enzymes (like catalase)
• Replicate by pinching in half
Mitochondria
• Mitochondria
• Carry out reactions where oxygen is used to break down food
• Provides ATP for cellular energy
• Change shape continuously
• ‘Mighty Mitochondria’
• ‘Powerhouse of the cell’
Cytoskeleton
•
•
•
•
Cytoskeleton
Provides the cell with an internal framework
Network of protein structures that extend throughout the cytoplasm
‘Scaffold of the cell’
Cytoskeleton
• Cytoskeleton
• Three different types:
• Microfilaments-cell motility and change in shape- actin
and myosin
• Intermediate filaments-form desmosomes and internal
guy wires-fibrous subunits
• Microtubules-determine shape of cell-tubulin subunits
Centrioles
• Centrioles
• Site for formation of mitotic spindle during
cell division
• Able to form cilia and flagella in special
cells
• Rod-shaped bodies made of microtubules
• Arranged in a 9+3 formation
Cell Diversity
• 75 to 100 trillion cells in human body
• 200 different cell types
• 1. Connect body parts
• Fibroblast
• Erythrocyte (RBCs)
Cell Diversity
•
2. Cover and line body organs
•
Epithelial Cell
Cell Diversity
•
3. Move organs and body parts
•
•
Skeletal muscle
Smooth muscle
Cell Diversity
•
4. Stores nutrients
•
Fat cell
Cell Diversity
•
5. Fight disease
•
Macrophage cell
Cell Diversity
•
6. Gathers information and controls body functions
•
Nerve cell
Cell Diversity
•
7. Reproduction
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Ovum (egg)
Sperm