Chapter 4: Cell Structure and Function I. Cell Theory: 1. Every living thing is composed of one or more cells. 2. The cell is the smallest/simplest unit of life. 3. Under current conditions, all cells come from preexisting cells.

II. Prokaryotic Cells A. Prokaryotic cells do contain DNA and ribosomes, but no membrane-bound organelles or nuclear membrane. B. Include bacteria and archea (all unicellular). C. Single strand of DNA.

Fig. 4.27a, p. 74 ribosomes In cytoplasm Prokaryotic Cell (Label)

III. Eukaryotic Cells Eukaryotic cells are characterized by the presence of membrane-bound organelles and a defined nucleus. Include animals, plants, fungi, and ‘protists.’ Organelles: Discrete structures within eukaryotic cells with specific functions.

Nucleus Brain of Cell. The nucleus is surrounded by two lipid bilayers, forming the nuclear envelope. The nuclear envelope has numerous pores, allowing certain items to leave the nucleus. The pores are not large enough to allow DNA to leave the nucleus. Also, the nucleus holds the nucleolus, which is responsible for making the components of the ribosomes.

Ribosomes Construction Crew of Cell. Made of two pieces of RNA, the ribsomes read DNA and assemble amino acids into proteins. +

Endoplasmic Reticulum The UPS of the cell. Rough ER contains ribosomes, so rough ER modifies proteins. Smooth ER is involved with the modification of lipids rather than proteins.

Golgi Bodies UPS/related to ER. Hollow tubes that are involved with processing of lipids and proteins. Golgi bodies produce vesicles (membrane-bound sacs) for shipment to specific locations within a cell.

Fig. 4.13, p. 64 DNA instructions for building polypeptide chains leave the nucleus and enter the cytoplasm. The chains (green) are assembled on ribosomes in the cytoplasm.

Important Vesicles Lysosomes: Loaded with enzymes to digest cell components, or even entire cells. Peroxisomes: Loaded with enzymes to break down fats and proteins.

Mitochondrion Powerhouse. The mitochondrion is an organelle with a double membrane that functions to convert stored energy such as sugar into useable energy, ATP. Interestingly, the mitochondrion contains its own distinct DNA. Glucose to ATP.

Chloroplast Solar Panel. The inner membrane hold pigments (such as chlorophyll) that collect light and the conversion to stored energy occurs within the membrane system. Solar energy is converted to stored chemical energy (glucose).

Plasma Membrane The tails are fatty acid chains (hydrophobic) and the heads contain phosphate groups (hydrophilic). The basic function of the plasma membrane is to keep the contents within the membrane separate from the contents outside of the membrane. A B C

Cytoskeleton Made of microtubles (hollow tubes made of protein) and microfilaments (thin ‘ropes’ of twisting two polypeptide chains together).

Fig. 4.19, p. 69 tubulin subunit 37 nm 25 nm actin subunit one polypeptide chain 8-12 nm

Fig. 4.8a, p. 59 microtubules (components of cytoplasm) Golgi body vesicle microfilaments (components of cytoskeleton) mitochondrion chloroplast central vacuole rough endoplasm reticulum (rough ER) ribosomes (attached to rough ER) ribosomes (free in cytoplasm) smooth endoplasmic reticulum (smooth ER) DNA + nucleoplasm nucleolus nuclear envelope NUCLEUS plasma membrane cell wall

Three Organelles Unique to Plants:

Fig. 4.8b, p. 59 microfilaments microtubules components of cytoskeleton plasma membrane mitochondrion nuclear enevelope nucleolus DNA + nucleoplasm NUCLEUS vesicle lysosome rough ER ribosomes (attached to rough ER and free in cytoplasm) smooth ER vesicle Golgi body pair of centrioles

IV. Cell Movement A.Cytoskeleton can add/remove amino acids (important in mitosis). B.Many extentions = cilia C.Few extentions = flagellum

V. Cell Junctions A. Tight Junction: Cell connections don’t allow materials to flow past a surface. Proteins extend from the cell membranes of the neighboring cells, acting to bring the two cells close together

V. Cell Junctions B. Adhering Junctions- Muscles cells are connected but also must be able to flex and stretch. They are connected with adhering junctions. C. Gap Junctions - The nerve cells of your brain/nervous system have small gaps between connecting cells.