1. Cell Structure and Function
Chapter 4
BIOL 1000
Dr. Mohamad H. Termos

2. Chapter 3 objectives
Following this lecture, you should be able to describe:
The Cell
Basic functions
Cell organelles
Cell membrane

3. The Cell - The basic unit of a living organism.
- Only seen using microscopes
- Differ in shape, size, and function.
- Cell’s size: Small size with large surface area helps the cell exchanges material with its environment

4. Biology, 9th ed,Sylvia Mader
Chapter 04
Prokaryotic Cells
Cell Structure and Function
Lack a membrane-bound nucleus
Structurally smaller and simpler than eukaryotic cells (which have a nucleus).
Prokaryotic cells are placed in two taxonomic domains:
Bacteria
Archaea
Domains are structurally similar but biochemically different

5. The Structure of Prokaryotes
Extremely small
Occur in three basic shapes:
(Spherical, Rod-shaped, Spiral).
- Cell Envelope includes:
Plasma membrane
Cell wall - maintains the shape of the cell
Glycocalyx - outside of the cell wall. Well organized and resistant to removal (capsule)

6. The Structure of Prokaryotes
Biology, 9th ed,Sylvia Mader
Chapter 04
The Structure of Prokaryotes
Cell Structure and Function
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Ribosome:
site of protein synthesis
Fimbriae:
hairlike bristles that
allow adhesion to
the surfaces
Inclusion body:
stored nutrients for
later use
Conjugation pilus:
elongated, hollow
appendage used for
DNA transfer to other
bacterial cells
Mesosome:
plasma membrane
that folds into the
cytoplasm and
increases surface area
Nucleoid:
location of the bacterial
chromosome
Plasma membrane:
sheath around cytoplasm
that regulates entrance
and exit of molecules
Cell wall:
covering that supports,
shapes, and protects cell
Glycocalyx:
gel-like coating outside
cell wall; if compact, called
a capsule; if diffuse, called
a slime layer
Flagellum:
rotating filament present
in some bacteria that
pushes the cell forward
Escherichia coli
© Howard Sochurek/The Medical File/Peter Arnold, Inc.

7. Prokaryotic Cytoplasm and Appendages
Biology, 9th ed,Sylvia Mader
Chapter 04
Prokaryotic Cytoplasm and Appendages
Cell Structure and Function
Cytoplasm
Semifluid solution
Bounded by plasma membrane
Contains water, molecules, and enzymes
Nucleoid is a region that contains the single, circular DNA molecule
Plasmids are small accessory rings of DNA
Appendages
Flagella – provide motility
Fimbriae – small, bristle-like fibers that sprout from the cell surface
Conjugation pili – rigid tubular structures used to pass DNA from cell to cell

8. Introducing Eukaryotic Cells
Biology, 9th ed,Sylvia Mader
Chapter 04
Introducing Eukaryotic Cells
Cell Structure and Function
Cells contain:
Membrane-bound nucleus that houses DNA
Specialized organelles
Plasma membrane
Much larger than prokaryotic cells
Eukaryotic cells are compartmentalized
They contain small structures called organelles
Perform specific functions

9. The Cell Functions
The cell must perform some basic functions in order to survive. They must:
Obtain nutrients
Exchange material with environment
Reproduce
Detect and respond to signals
These activities sound like the same basic activities all organisms need to do!
Organisms contain organs that do individual jobs for the survival of the organism; cells have “mini organs”, called organelles to do their basic jobs!

10. An Idealized Animal Cell

11. Cell Anatomy
Major Divisions of the Eukaryotic Cell

12. Organelles: The nucleus
Cellular Anatomy
The largest cell structure
Usually a sphere in the center of the cell
Considered as the cell control center.
Houses the heredity molecules (DNA)
Anatomy of the nucleus:
Nuclear envelope (Outer and inner nuclear membranes)
Nuclear pores (permit molecule movements)
Nucleolus
We’ll start by seeing what role these parts play in making and moving proteins.

13. Cytoskeleton
Cytoskeleton: Is the cell skeleton, but it also functions as muscular system.
Able to change in shape of cells.
Example of cytoskeleton function:
This is a white blood cell using the cytoskeleton to reach out for a bacterium.
More examples: Cilia of a protozoan, tail of a sperm.

14. Ribosomes The Cytoskeleton in Action Small organelles
Protein factories of the cell
So, it is essential for cell function
Can be found “free-floating” in the cell, or attached to another organelle (the endoplasmic reticulum).

15. The Endoplasmic Reticulum (ER)
The Cytoskeleton in Action
Made up of many fattened membrane sacs
Part of it is dotted with ribosomes for protein synthesis, the rough ER (RER).
The part that has no ribosomes, is called smooth ER.
The smooth ER is a site of lipid synthesis
Smoker’s cough is due to destruction of cilia linking the airways.

16. The RER
Proteins made on the RER because some parts of proteins need a fatty environment which is found inside the cell.
The protein made here will be sent to the Golgi apparatus

17. The Golgi Apparatus Analogous to postal service for the cell
After rough ER protein is sent to Golgi
Protein will be modified, packaged, and sent to various destinations (outer membrane of the cell or secreted outside of the cell entirely)

18. Lysosomes and Peroxisomes
The cell “stomach”
Houses acidic environment and digestive enzymes
Site of molecules break down.
Peroxisomes:
Degrade lipids and alcohol
Degradation of these produce hydrogen peroxide (toxic byproduct).
Luckily, peroxisomes degrade this toxic molecule too.

19. Biology, 9th ed,Sylvia Mader
Chapter 04
Vacuoles
Cell Structure and Function
Membranous sacs that are larger than vesicles
Store materials that occur in excess
Others very specialized
Plants cells typically have a central vacuole
Up to 90% volume of some cells
Functions in: 1- Storage of water, nutrients, pigments, and waste products, 2- Development of turgor pressure

20. Biology, 9th ed,Sylvia Mader
Chapter 04
Chloroplasts
Cell Structure and Function
Bounded by double membrane
Green due to chlorophyll
Green photosynthetic pigment
Serve as the site of photosynthesis

21. Biology, 9th ed,Sylvia Mader
Chapter 04
Photosynthesis
Cell Structure and Function
Synthesizes carbohydrates from CO2 & H2O
solar energy + carbon dioxide + water → carbohydrate + oxygen
Only plants, algae, and certain bacteria are capable of conducting photosynthesis

22. Mitochondria The powerhouses of the cell Major energy source
Energy is in the form of ATP (Adenosine triphosphate)
Surrounded by outer and inner membrane
Cells may have varying number of mitochondria, according to their energy requirements.

23. Biology, 9th ed,Sylvia Mader
Chapter 04
Centrioles
Cell Structure and Function
Short, hollow cylinders of microtubules
One pair per animal cell
Located in centrosome of animal cells
Oriented at right angles to each other
Separate during mitosis to assist with division

24. The Cell Membrane
Plasma membrane of the cell is the outer wall of the cell.
Separates the inside fluids and organelles (that are found in the cytoplasm) from the outside environment (the interstitial fluid)

25. The Cell Membrane The cell membrane is made up of phospholipids.
Phospholipids are amphipathic molecules.
Remember: Amphipathic means they have a hydrophilic portion (water-loving), and hydrophobic portion (water-hating)

26. The Cell Membrane
These phospholipids are arranged in a bilayer and they act as an excellent barrier for the cell.
Water is inside and outside the cell. So, the hydrophilic heads will line up along both sides, near water. The hydrophobic layer in the middle will act as a barrier to anything soluble in water.
The cell membrane is also “equipped” with protein channels that regulate the passage of molecules in and out of the cell.

27. Conclusions
In this chapter we have covered the basic components of the human cell, which is the smallest living thing. Because our bodies are made up of millions of cells, it is important to thoroughly understand their physiology. The cell’s organelles work together to make sure the cell has everything it needs to survive.