1. Lecture Outline Cell Structure and Function 3 Chapter
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2. 3.1 Cellular Organization
3 main parts of a cell
Plasma membrane
Nucleus
Cytoplasm
Organelles are scattered throughout the cytoplasm and have various functions
The cytoskeleton maintains cell shape and allows the cell and its content to move

4. Cellular Organization
Plasma Membrane
Separates the inside of the cell (cytoplasm) from the outside
Phospholipid bilayer
Attached peripheral and integral proteins
Receptors
Channels
Carriers
Cholesterol molecules stabilize the membrane
Glycoproteins and glycolipids attached to outer surface of some protein and lipid molecules mark cells as belonging to a particular individual

6. Cellular Organization
The Nucleus
Stores genetic information
Chromatin
Contains DNA, protein, and some RNA
Coils into rodlike structures called chromosomes before the cell divides
Nucleoli
Contains rRNA
Site where ribosomes are formed
Nuclear envelope separates nucleus from cytoplasm

8. Cellular Organization
Ribosomes
Composed of subunits containing proteins and rRNA
Can be found free within the cytoplasm
sometimes in groups called polysomes
Also found attached to the endoplasmic reticulum
Produce proteins that carry out various functions within the cell

9. Cellular Organization
Endomembrane System
Nuclear envelope
Endoplasmic reticulum (ER)
Continuous with the outer membrane of the nuclear envelope
Rough ER
Has attached ribosomes
Processes proteins produced by attached ribosomes
Smooth ER synthesizes phospholipids

11. Cellular Organization
Endomembrane System
Golgi apparatus
Processes, packages, and secretes various substances
Receives protein and/or lipid-filled vesicles from ER
Contains enzymes that modify proteins and lipids
Produces lysosomes

13. Cellular Organization
Endomembrane System
Lysosomes
Contain hydrolytic digestive enzymes
Autodigestion responsible for cell rejuvenation and development
Vesicles – tiny membranous sacs

14. Cellular Organization
Peroxisomes and Vacuoles
Peroxisomes
Enzyme-containing vesicles, similar to lysosomes
Detoxify drugs, alcohol, and other toxins
Large numbers found in liver and kidney
Break down fatty acids from fats
Vacuoles isolate substances captured inside the cell

15. Cellular Organization
Mitochondria
Bound by a double membrane
Site of ATP production
Undergo cellular respiration (use up oxygen and release carbon dioxide)
The Cytoskeleton
Helps maintain the cell’s shape and anchors or assists the movement of organelles
Includes microtubules, intermediate filaments, and actin filaments

17. Cellular Organization
Centrioles
Composed of microtubules
A pair of centrioles are found near the nucleus of every cell
Involved in cell division
Form basal body (anchor point) for each cilium or flagellum
Cilia and flagella are projections of cells
Allow for movement of cell or movement of material along the cell surface

19. 3.2 Crossing the Plasma Membrane
Simple Diffusion
Movement of atoms or molecules from an area of higher concentration to an area of lower concentration
Movement of atoms or molecules occur until they are equally distributed
Only certain types of molecules can enter and exit a cell by simple diffusion
No cellular energy is required

21. Crossing the Plasma Membrane
Osmosis
Diffusion of water across a plasma membrane
Occurs when there is an unequal distribution of water on either side of a selectively permeable membrane
Osmotic pressure – force exerted on a selectively permeable membrane

22. Crossing the Plasma Membrane
Tonicity – concentration of solute versus the concentration of water
Isotonic – equal concentration of solutes (dissolved substances) and solvent (water) inside and outside cell; cell shape is maintained
Hypotonic – higher concentration of water (lower concentration of solutes) outside cell; water moves into cell causing it to swell and eventually lyse
Hypertonic – lower concentration of water (higher concentration of solutes) outside cell; water moves out of cell causing it to shrink or crenate

24. Crossing the Plasma Membrane
Filtration is the movement of liquid from high pressure to low pressure
Transport by Carriers
Facilitated diffusion
Solutes are transported by means of a protein carrier
Movement from area of higher concentration to area of lower concentration (no energy required)

25. Crossing the Plasma Membrane
Transport by Carriers
Active transport
Solutes move up their concentration gradient
Requires a protein carrier (often called pumps)
Requires the use of cellular energy

27. Crossing the Plasma Membrane
Endocytosis and Exocytosis
In endocytosis the plasma membrane envelopes a substance and forms an intracellular vesicle
Phagocytosis (“cell eating”) – cell ingests solid particles
Pinocytosis (“cell drinking”) – cell consumes solutions
In exocytosis a vesicle fuses with the plasma membrane as secretion occurs

28. 3.3 The Cell Cycle
Set of stages that take place between the time a cell divides and the time the daughter cell divides
Apoptosis (cell death) occurs at the restriction checkpoint if the cell did not complete mitosis and is abnormal
Some specialized cells no longer go through the cell cycle
Muscle cells
Nerve cells

29. The Cell Cycle Cell Cycle Stages Interphase
Cell is not dividing, but is preparing to divide
The cell carries on regular activities
Three phases
G1 phase – cell doubles number of organelles and accumulates materials used for DNA synthesis
S phase – “synthesis” phase; DNA replication occurs
G2 phase – cell synthesizes proteins that will assist cell division

31. The Cell Cycle Major events during interphase Replication of DNA
Before replication, the two strands of DNA are hydrogen bonded together
Parental DNA strands unwind (hydrogen bonds are broken)
New complimentary nucleotides pair with nucleotides in the parental DNA strands and DNA polymerase joins the new nucleotides
When replication is complete, two identical double helix molecules have been formed
Each strand of this double helix is equivalent to a chromatid

34. The Cell Cycle Protein synthesis
DNA also serves as a template for RNA formation and protein construction
Two steps involved in protein synthesis are:
Transcription – formation of mRNA
Translation – involves mRNA, tRNA, and rRNA; specifies the order of amino acids in a polypeptide

36. The Cell Cycle Mitotic stage
Mitosis – cell division stage divided into 4 phases
Prophase
The centrioles near nucleus begin moving towards opposite ends of nucleus
Spindle fibers appear
Nuclear envelope begins to fragment
Nucleolus begins to disappear
Metaphase
Spindle is fully formed
Chromosomes are aligned at the equator

37. The Cell Cycle Cytokinesis – division of the cytoplasm and organelles
Anaphase
Sister chromatids separate (now called chromosomes)
Chromosomes move toward opposite poles of the spindle
Telophase
Chromosomes become chromatin
Spindle disappears and nucleoli appear
Nuclear envelope reassembles and two daughter cell nuclei can be observed
Cytokinesis – division of the cytoplasm and organelles

40. The Cell Cycle Importance of Mitosis Meiosis: Reduction-Division
Each cell in our body is genetically identical
Important to the growth and repair of multicellular organisms
Meiosis: Reduction-Division
Produces gametes (sex cells)
Stages of mitoses are repeated twice
Gametes (sperm or ova) that results have half the normal number of chromosomes