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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.
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 forbuilding polypeptidechains leave the nucleusand enter the cytoplasm.
The chains (green) areassembled on ribosomesin 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. 4.8a, 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
nucleolusnuclear envelope
NUCLEUS
plasma membrane
cell wall
Fig. 4.8b, p. 59
microfilaments
microtubules
components ofcytoskeleton
plasma membrane
mitochondrion
nuclear enevelope
nucleolus
DNA + nucleoplasm
NUCLEUS
vesicle
lysosome
rough ER
ribosomes(attached torough ERand free incytoplasm)
smooth ER
vesicle
Golgi body
pair ofcentrioles
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