THE CELL

The cell is one of the most basic units of life.  There are millions of different types of cells.  All Organisms are built from cell.

There are cells that are organisms onto themselves, such as microscopic amoeba and bacteria cells. 

And there are cells that only function when part of a larger organism, such as the cells that make up your body.

Plant cell

The cell is the smallest unit of life in our bodies.  In the body, there are brain cells, skin cells, liver cells, stomach cells, and the list goes on.

Modern Cell theory can be divided into the following Fundamental statements . . .

• Cells make up all living matter

• All Cells arise from other cells

• The genetic information (required during maintenance and production) passes from one generation to the other next generation

• The Chemical Reactions of an Organism takes place in the Cell

Major Complex Biomolecules of CellsBio Molecule Building Block Major Function

1. Protein Amino acids Fundamental basis of Structure & Functions of the cell

2. DNA Deoxyribo-nucleotides

Repository of Hereditary information

3. RNA Ribonucleotides Required for Protein Synthesis

4. Polysaccharides (glycogen)

Monosaccharides (glucose)

Energy storage formto meet short term demand

5. Lipids Fatty Acids, Glycerol

Energy storage formto meet long term demandStructural components of membranes.

Types of Cells:The cells of the living kingdom may be divided into two categories…

• Prokaryotes(Pro-before; karyon-nucleus)

Lack a well defined nucleolusAnd possess relatively simple structure

• Eukaryotes (eu-True; karyon-nucleus)Possess well defined nucleusmore complex in their structure and function.

Prokaryotic CellsProkaryotic Cells

Prokaryotic Cells

• Believed to be the first cells to evolve.

• Lack a membrane bound nucleus and organelles.

• Genetic material is naked in the cytoplasm

• Ribosomes are only organelle.

Cell Wall

• Rigid peptidoglycan - polysaccharide coat that gives the cell shape and surround the cytoplasmic mem-brane. Offers protection from environment.

Prokaryotic Cells

Prokaryotic CellsPlasma Membrane

• Layer of phospho-lipids and proteins that separates cytoplasm from external environment.

• Regulates flow of material in and out of cell

Prokaryotic CellsCytoplasm

• Also known as proto-plasm is location of growth, metabolism, and replication.

• Is a gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains cell structures.

Prokaryotic CellsRibosomes

• Translate the genetic code into proteins.

• Free-standing and

distributed throughout the cytoplasm.

Prokaryotic CellsNucleoid

• Region of the cytoplasm where chromosomal DNA is located.

• Usually a singular, circular chromosome.

• Smaller circles of DNA called plasmids are also located in cytoplasm.

Mesosome

• Infolding of cell membrane.

• Possible role in cell division.

• Increases surface area.

• Photosynthetic pigments or respiratory chains here.

Prokaryotic Cells

Eukaryotic Cells

Eukaryotic Cells

• “True nucleus”; contained in a membrane bound structure.

• Membrane bound organelles.

• Thought to have evolved from prokaryotic cells.

Eukaryotic Cells

• Has a considerable degree of internal structure with a large

number of distinctive membrane enclosed having specific functions.

• Nucleus is the site for informational components collectively called Chromatin

Eukaryotic Cells

• Sexual reproduction involves both mitosis & meiosis

• The respiratory site is the Mitochondria

• In the plant cell the site of conservation of radiant energy to chemical energy is the Chloroplast

Plant Cells

Plant Cells • Central vacuole

– often found in the center of a plant, and serves as a storage facility for water and other materials

• Cell wall

– primary walls – laid down while cell is growing

– middle lamella – glues cells together

– secondary walls – inside the primary cell walls after growth

Differences between Prokaryotic & Eukaryotic cells

Prokaryotic Cell Eukaryotic Cell1. Smaller in Size 1 to 10µm 1. Large in size 10 to100µm or more

2. Mainly unicellular 2. Mainly multicellular(with few exception)

3. Single membrane, surrounded

by rigid cell wall

3. Lipid bilayer membrane with protein

4. Anaerobic or aerobic 4. Aerobic

5. Not well defined nucleus, only a nuclear zone with DNA

5. Nucleus well defined, 4 to 6µm in diameter, contains DNA and surrounded by a nuclear membrane

6. No nuclei 6. Nucleolus present, rich in RNA

7. Cytoplasm contains no cell organelles

7. Membrane bound cell organelles are present

DifferencesProkaryotic Cell Eukaryotic Cell

08. Ribosomes present free in cytoplasm

08. Ribosomes present on outer surface of endoplasmic reticulum

09. Mitochondria absent 09. Mitochondria present “Power House” of the Cell

10. Enzymes bound to membrane

10. Enzymes are located in Mitochondria

11. Golgi apparatus absent 11. Golgi apparatus present

12. Lysosomes, Cytoskeleton absent

12. Lysosomes, Cytoskeleton present

13. Cell division by usually by fission, No mitosis

13. Cell division by mitosis

14. RNA & Protein synthesis in same compartment

14. RNA synthesized and processed in nucleus.

15. Eg: Bacteria, rickettsii 15. Eg: Fungi, Plant & Animal cells