Cell Structure

A. There are three basic structures of all types of cells: 1. Cell membrane a. Contains a bilayer of lipids b. Is selectively permeable (allows only certain molecules through protein carriers) 2. Nucleus 3. Cytoplasm

Plasma Membrane Separates intracellular fluids from extracellular fluids Allows certain substances in and out Glycocalyx is a glycoprotein are biological markers by which cells recognize one another

Cell walls and membranes video

Fluid Mosaic Model Double bilayer of lipids with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids Glycolipids are lipids with bound carbohydrate Phospholipids have hydrophobic and hydrophilic bipoles

Functions of Membrane Proteins Transport Enzymatic activity Receptors for signal transduction

Functions of Membrane Proteins Intercellular adhesion Cell-cell recognition Attachment to cytoskeleton and extracellular matrix

Membrane Junctions Tight junction – impermeable junction that encircles the cell Desmosome – anchoring junction scattered along the sides of cells Gap junction – a nexus that allows chemical substances to pass between cells

Membrane Junctions: Tight Junction

Membrane Junctions: Desmosome

Membrane Junctions: Gap Junction

Diffusion

Facilitated Diffusion

Osmosis

Isotonic – solutions with the same solute concentration as that of the cytosol Hypertonic – solutions having greater solute concentration than that of the cytosol Hypotonic – solutions having lesser solute concentration than that of the cytosol

Sodium Potassium Pump

Active Transport

Transport of large particles and macromolecules across plasma membranes Exocytosis – moves substance from the cell interior to the extracellular space Endocytosis – enables large particles and macromolecules to enter the cell Phagocytosis – pseudopods engulf solids and bring them into the cell’s interior

Ex. Of Endocytosis

Generation and Maintenance of Membrane Potential

B. Differences between animal and plant cells, plant cells have: 1. Chloroplasts a. Contain pigments that absorb sunlight. 2. Vacuoles a. Large containers that store water. 3. Cell walls a. Rigid structure(contain cellulose) surrounding the cell.

1. Nucleus a. “Boss” of the cell. b. Contains the genetic material of an organism=chromosomes. c. Surrounded by a nuclear envelope with pores (openings). d. Contains the nucleolus which makes ribosomes.

e. Cells or organisms with a nucleus (area that contains the DNA with a surrounding nuclear envelope) are called eukaryotic. f. Cells or organisms without a nucleus (DNA not contained within a nuclear envelope) are called prokaryotic. 1. Ex. bacteria

Nuclear Envelope Selectively permeable double membrane barrier containing pores Outer membrane is continuous with the rough ER and is studded with ribosomes Pores regulate transport of large molecules into and out of the nucleus

The Nucleus Video

Nucleoli Dark-staining spherical bodies within the nucleus Site of ribosome production Acts like the “assistant to the boss”

Chromatin Threadlike strands of DNA and histones Arranged in fundamental units called nucleosomes Form condensed, barlike bodies of chromosomes when the nucleus starts to divide

Cell Cycle Interphase Growth (G 1 ), synthesis (S), growth (G 2 ) Mitotic phase Mitosis and cytokinesis

Interphase G 1 (gap 1) – metabolic activity and vigorous growth G 0 – cells that permanently cease dividing S (synthetic) – DNA replication G 2 (gap 2) – preparation for division

2. Cytoplasm a. The area between the nucleus and the cell membrane. b. Holds all the organelles in place. c. Gives shape to the cell.

3. Centrioles a. Structures that aid in cell division. b. Found in the nucleus.

Centrioles Video

4. Mitochondria a. Known as the “power house” of the cell. b. Converts food into ATP to be used as energy. c. ATP= Adenosine Triphosphate (Adenine plus three phosphate molecules.)

5. Ribosomes a. Sites of protein synthesis (making).

6. Endoplasmic Reticulum=E.R. a. Passageway that transports materials throughout the cell. b. Rough E.R. is studded with ribosomes. c. Smooth E.R. is not studded with ribosomes.

7. Golgi apparatus a. Passageway that modifies and packages proteins as they pass through. b. Stacked and flattened membranous sacs (stack of pancakes) c. Functions in modification, concentration, and packaging of proteins

8. Lysosome a. Round organelle that rids the cell of unwanted waste. b. Digest ingested bacteria, viruses, and toxins c. Degrade nonfunctional organelles

Lysosomes video

9. Peroxisomes a. Detoxify harmful or toxic substances b. Neutralize dangerous free radicals

10. Vacuole a. Containers that hold water and food for the cell.

Vacuole video

11. Cytoskeleton a. Contain microtubules and filaments to add structure to the cell.

Cytoskeleton

Microtubules Dynamic, hollow tubes made of the spherical protein tubulin Determine the overall shape of the cell and distribution of organelles

Microfilaments Dynamic strands of the protein actin Attached to the cytoplasmic side of the plasma membrane Braces and strengthens the cell surface Attach to CAMs and function in endocytosis and exocytosis

Intermediate Filaments Tough, insoluble protein fibers with high tensile strength Resist pulling forces on the cell and help form desmosomes

Motor Molecules Protein complexes that function in motility Powered by ATP Attach to receptors on organelles

Motor Molecules

12. Cilia and flagella a. Hair-like projections that help move some types of cells. Cilia act like oars

Flagella act like a whip to move the cell:

Ciliary Action