Cell Anatomy and Physiology

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Independence

• Rule #1: Be Proactive

Objectives

• Functions of 3 main parts of cell
• Plasma membrane, exchanges w extracellular space
• Transport into and out of a cell
• Components of cytoplasm

Objectives (2)

• Structures and function of cytosol, organelles
• Protein synthesis, transcription, translation
• Structure and function of nucleus

Objectives (3)

• Structure and function of nucleus
• Sequence of events in protein synthesis
• Somatic vs. reproductive cell division
• Case study

Your Homework

• Read Jenkins Chapter 3 for today, Chapter 4 for next week
• Read Allen Exercise 6 for next week

Cellular Level of Organization

• Over 200 types of cells
• Each cell type has its own job
• Similarities of structures and functions

Principal Parts of Cells

• Plasma membrane
• Cytoplasm
• Nucleus

Plasma Membrane

• Flexible, sturdy barrier
• Fluid mosaic model
• Membrane made up of proteins, lipids
• Allow or prevent entry or exit of substances

Plasma Membrane - Lipid Bilayer

• Two layers of 3 types of lipids
• Mostly phospholipids - lipid that contains phosphate
• Cholesterol (small amount)
• Glycolipids - lipids with attached carbohydrate groups

Arrangement of Lipids

• Hydrophilic "heads" face outwards
• Hydrophobic "tails" face inwards
• Results in 2 layers that face watery environments

Proteins in Cell Walls

• Form ion channels
• Act as carriers
• Act as receptors
• Provide enzymes
• Act as linkers
• Act as cell identity markers

Cell Wall Controls Transport

• One type of control is passive transport
• Simple diffusion
• Dependent on concentration gradient, temperature, particle size, surface area, distance

Cell Wall Transport

• Simple diffusion - passive process
• Facilitated diffusion - membrane protein allows substance through the wall
• Carrier-mediated facilitated diffusion - carrier presents substance to membrane protein

Osmosis

• Solvent moves through selectively permeable membrane
• Water moves by osmosis from higher water concentration to lower water concentration

Osmotic pressure
See diagram on page 71

Tonicity

• Relative water content on either side of membrane
• Isotonic - same amount of water
• Hypertonic - higher amount of solute, less water
• Hypotonic - lower amount of solute, more water

Tonicity - Effect on Water

• Hypertonic solution - water flows in to dilute it
• Expands container
• Hypotonic solution - water flows out to concentrate it
• Contracts container

Cell Wall Transport

• Active transport
• Some solutes have to move uphill, require an active process to carry them
• Na+/K+ pump

Vesicles

• Small blister or sac on membrane
• Vesicles pick up substances and pull them into cell
• Can also eject substances from cell

Vesicle Transport

• Receptor-mediated endocytosis (page 74)
• Phagocytosis (page 75)
• Phagocytes eat up worn-out cells, bacteria, viruses

Vesicle Transport

• Exocytosis - releases materials from cells
• Enzymes, hormones, mucus, cellular wast

Cytoplasm

• Everything inside cell wall except nucleus
• Cytosol - fluid portion
• Water plus glucose, ions, proteins, lipids, ATP
• Can contain storage molecules

Organelles

• Specialized structures within cell
• Have specific functions to perform
• Compartmentalized specialized factories

Organelles

• Cytoskeleton provides structure, shape
• Centrosome important in cell division
• Cilia, flagella sit on surface of cell, provide movement

Organelles

• Ribosomes - sites of protein synthesis
• Endoplasmic reticulum creates glycoproteins, phospholipids, fatty acids, steroids
• ER also detoxifies drugs, harmful substances

Organelles

• Golgi complex modifies, sorts, packages, transports proteins from ER
• Also forms membrane vesicles

Organelles

• Lysosomes - contain powerful enzymes to break down molecules
• Peroxisomes, proteasomes

Organelles

• Mitochondria - power plants of the cell
• Site of most ATP production
• Can self-replicate if needed
• Very important in pharmacology

Nucleus

• Zero to many per cell
• Contains nucleoli, genes
• Nucleolus is clump of DNA, RNA, proteins
• Genes arranged in chromosomes

Protein Synthesis

• Cells make proteins according to instructions from DNA
• Information from DNA transcribed onto RNA
• RNA attaches to ribosome which translates information to create protein
• Human cells have 46 chromosomes, 23 from each parent

Cell Division

• Cells divide to replace old cells, create new ones
• Somatic cells (any cell other than reproductive cells) divide to make identical twins
• Process called mitosis and cytokinesis

Somatic Cell Division Phases

• Interphase - cell replicates its DNA
• Mitosis - nucleus divides, nuclear walls develop, cytoplasm divides, cell walls form

Reproductive Cell Division

• End result is cell with 23 chromosomes
• Occurs in gonads
• Meiosis produces gametes with half the number of chromosomes

Reproductive Cell Division

• Interphase - DNA is replicated
• Meiosis I - nuclear envelope and nucleoli disappear
• Chromosomes intermingle then realign, different from before
• Meiosis II - chromosomes divide

The End!

• For next week, read chapter 4 (Jenkins) and exercise 6 (allen