CELL STRUCTURE & FUNCTIONS

IntroductionIntroduction Eucaryotic cell structureEucaryotic cell structure Procaryotic cell structureProcaryotic cell structure Differences between Procaryotic Differences between Procaryotic & &

Eukaryotic cells.Eukaryotic cells. Reproduction of organisms & Reproduction of organisms & their their

cells.cells. Gram stain Gram stain

OutlineOutline

Introduction- Cell is defined as the fundamental living unit of any

organism.

- Cell is important to produce energy for metabolism (all chemical reactions within a cell)

- Cell can mutate (change genetically) as a result of accidental changes in its genetic material (DNA).

- Some microrganisms are procaryotic, some are eucaryotic, & some are not cells at all (Viruses)

- Viruses are composed of only a few genes protected by a protien coat, & may contain few enzymes.

- Cytology: the study of the structure and functions of cells.

Eucaryotic cell structure

Eucaryotic cells: have a true nucleus, & the DNA is enclosed by a nuclear membrane.

They are 10 times larger than Procaryotic cells.

Cell membrane

It’s composed of large molecules of protiens & phospholipids (certain types of fats).

The cell membrane is seperating the contents of the cell from the outside world.

It has the property of selective permiability: only certain substances may enter & leave the cell

Cell Membrane

Phospholipid bi-layer that separates the cell from its environment.

Selectively permeable to allow substances to pass into and out of the cell.

Nucleus

Double membrane-control, & integrates the functions of the entire cell.

Consider the command center of the cell.

Separates the genetic material from the rest of the cell.

Parts of the nucleus:

Chromatin - genetic material of cell in its non-dividing state.

Nucleoplasm is the gelatenous matrix of the nucleus, like cytoplasm.

Nucleolus - dark-staining structure in the nucleus that plays a role in making ribosomes.

Nuclear envelope - double membrane structure that separates nucleus from cytoplasm.

Cytoplasm

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

Fluid around the organelles called cytosol.

Most of the cells metabolic reactions occur in the cytoplasm.

The Endoplasmic Reticulum

The endoplasmic reticulum (ER) Accounts for more than half the total

membranes in many eukaryotic cells The ER membrane: is continuous with the

nuclear envelope

There are two distinct regions of ER Smooth ER, which lacks ribosomes Rough ER, which contains ribosomes

Rough Endoplasmic Reticulum

Network of continuous sacs, studded with ribosomes.

Manufactures, pro-cesses, and transports proteins for export from cell (vesicles)

Continuous with nuclear envelope.

Smooth Endoplasmic Reticulum

Similar in appearance to rough ER, but without the ribosomes.

Involved in the production of lipids, carbohydrate metabolism, and detoxification of drugs and poisons.

Stores calcium.

Ribosomes Are the sites of protein synthesis.

Found attached to the Rough endoplasmic reticulum or free in the cytoplasm.

60% RNA and 40% protein.

Protein released from the ER are not mature, need further processing in Golgi complex before they are able to perform their function within or outside the cell.

Golgi Apparatus Modifies proteins and lipids

made by the ER and prepares them for export from the cell (exocytosis).

Encloses digestive enyzymes into membranes to form lysosomes.

Consists of flattened membranous sacs called cisternae

Lysosome

Single membrane bound structure.

Contains digestive enzymes that break down cellular waste and debris and nutrients for use by the cell.

Originate at the Golgi complex.

Are the

Lysosome

They contain lysozymes & other digestive enzymes that breakdown foreign material taken into the cell by phagocytosis (e.g Amebas, and certain types of WBCs “phagocyte”).

Also these enzymes may breakdown parts of the cell or destroy the entire cell by process called autolysis if the cell damaged or deteriorated.

They contain up to 40 enzymes for digestion

Peroxisomes

They are similar to lysosome but smaller. Peroxisomes contain the enzyme

catalase, which breakdown of hydrogen peroxide into water and oxygen.

Found mainly in liver and kidney cells Main function is detoxification of toxic

materials.

Mitochondrion

Membrane bound organelles that are the site of cellular respiration (ATP production)

Mitochondria are enclosed by two membranes A smooth outer membrane An inner membrane folded

into cristae

Chloroplast

Site of photosynthesis

Membrane bound structure.

Contains chlorophyll

Found only in plants

Cytoskeleton

The cytoskeleton Is a network of fibers extending throughout

the cytoplasmMicrotubule

0.25 µm Microfilaments

Roles of the Cytoskeleton: Support, Motility, and Regulation The cytoskeleton

Gives mechanical support to the cell Is involved in cell motility, which utilizes motor

proteins

Components of cytoskeleton: 1) Microfilaments

Solid rods of globular proteins.

Important component of cytoskeleton which offers support to cell structure.

Components of cytoskeleton: 2) Microtubules

Microtubules Shape the cell Guide movement of organelles Help separate the chromosome copies in

dividing cells

Components of cytoskeleton: 2) Microtubules

Centrosomes and Centrioles

The centrosome Is considered to be a “microtubule-

organizing center” Contains a pair of centrioles

Components of cytoskeleton: 2) Microtubules

Centrioles Found only in

animal cells. Self-replicating Made of bundles of

microtubules. Help in organizing

cell division.

Cell Wall

Protects and gives rigidity to plant cells

Formed from fibrils of cellulose molecules in a “matrix” of polysaccharides and glycoproteins.

Cilia and Flagella

External appendages from the cell membrane that aid in locomotion of the cell.

Cilia also help to move substance past the membrane.

Animal Cell vs. Plant Cell

Prokaryotic vs. Eukaryotic

Procaryotic cell strucure

Are about 10 times smaller than eucaryotic cells.

Reproduction of these cells by binary fission.

Binary fission: the simple division of one cell into two cells, following DNA replication, & the formation of a separating membrane & cell wall.

Procaryotic cell strucure

Cytoplasm is surrounded by a cell membrane, a cell wall (usually), & sometimes a capsule or slime layer.