Unit 3: Cells

Unit 3: Cells

The Cell Theory

(1) All living things are made up of cells;

(2) Cells: basic structure and function in living things;

(3) New cells created from existing cells

Prokaryotes and Eukaryotes

Prokaryotes:

-cells do not enclose DNA in nuclei

-do not separate their genetic material w/in nucleus

-smaller & simpler than eukaryotes

-carry out every activity

-grow, reproduce, respond to environment

-known as bacteria

Eukaryotes:

-cells that enclose their DNA in nuclei

-the nucleus separates the genetic material from rest of cell

-larger & more complex

-dozens of structures & internal membranes; specialized

-unicellular or multicellular

Cell Organization

-Eukaryotic cell divided into two major parts: the nucleus and the cytoplasm.-

-Prokaryotes have cytoplasm too, but not a nucleus.

-Nucleus: large membrane enclosed structure containing genetic material, DNA, & controls cell's activities.

-Cytoplasm: portion of cell outside nucleus.

The Nucleus

The Control Center of the Cell:

(1) Contains nearly all of the cell's DNA, and

(2) Coded instructions for making proteins and other molecules.

-Nuclear Envelope: dotted w/nuclear pores allowing material to move in & out of nucleus: messages, instructions, and blueprints, proteins, RNA, and other molecules.

-Chromosomes, found in nucleus, carries cell's genetic info; spread out in form of chromatin-complex DNA bound proteins.

-Cell divides=visible under microscope

-Nucleolus: where assembly of ribosomes begins.

Organelles: outside nucleus of eukaryotic cell have specific functions:

(1) Vacuoles and Vesicles: (storage space)

-Vacuoles: large, saclike, membrane-enclosed structure

-store materials: water, salts, proteins, and carbohydrates.

-Pressure of liquid in vacuoles makes plants rigid, allowing it to hold up stems, leaves, flowers.

-Vesicles: store and move materials between cell organelles, as well as to and from cell surface.

(2) Lysosomes: break down large molecules into smaller one that can be used by cell; break down organelles that outlived usefulness

-Function: (1) break down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell; (2) breaking down organelles that outlived usefulness.

-Removes junk that clutter cell

-found in animal, and some plant cells

The Cytoskeleton (support structure)

-Function: allow eukaryotic cells to maintain shape, and internal organization

-Protein filaments in eukaryotic cell that gives cells its shape and internal organization.

-Also involved in transport btwn different parts of cell.

The two principal protein filaments that make up cytoskeleton:

(1) Microfilaments: threadlike, made of actin-produces tough, flexible framework supports cell; also helps cells move.

(2) Microtubules: (a) hollow, made of tubulins-maintains cell shape; forms mitotic spindle to separate chromosomes (cell division); (b) centrioles-organelle in animal cells, located near nucleus, help to organize cell division-not in plant cells; (c) Microtubules build cilia & flagella: enables cells to swim rapidly through liquid: "9+2" Pattern

Organelles: Make & Transport Proteins

(1) Ribosomes: proteins produced; coded instructions from DNA

(2) Endoplasmic Reticulum: protein synthesizes completed; export proteins to cell membrane complete assembly on ribosomes bound to rough ER that produces large amounts of protein for export.

(3) proteins transported from rough ER to Golgi apparatus in vesicles.

(4) Golgi apparatus modifies, (sorts, and packages from rough ER for storage in cell or release) proteins before sorting/packaging in membrane-bound vesicles; "proteins shipped"

*ribosomes, endoplasmic reticulum, and Golgi apparatus synthesize, modify, package and ship proteins.

Organelles: Capture & Release Energy

Chloroplasts: capture the energy from sunlight, converts into food that contains chemical energy, photosynthesis.

Mitochondria: convert chemical energy stored in food into compounds that are more convenient for cell to use.

-comes from mom

-defects can cause deafness, blindness, and diseases that affect muscles and nerves

-cells depend on on energy released by chemical reactions

Cellular Boundaries

Cell membrane: (1) regulates what enters and leaves the cells, and (2) protects and supports cell.

-fluid mosaic

-Permeable: substances able to cross membrane

-Impermeable: substances cannot pass

Cell wall: supporting layer around the membrane;

-support, shape, and protect cell

-animals do not have cell walls

-outside cell membrane

-porous