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• Cells are the building blocks of all plants and animals
• Cells are produced by the division of preexisting cells
• Cells are the smallest units that perform all vital physiological functions
• Each cell maintains homeostasis at the cellular level– Homeostasis at higher levels reflects combined,
coordinated action of many cells
The Cell Theory States:
Figure 3.2 The Anatomy of a Representative Model Cell
Figure 3.2
• Physical isolation• Regulation of
exchange with the environment
• Sensitivity to the environment
• Structural support
Cell membrane functions include:
• The cell membrane is a phospholipid bilayer with proteins, lipids and carbohydrates.
Figure 3.3 The Cell Membrane
Figure 3.3
• Phospholipids: composed of glycerol and fatty acid tails linked by a phosphate group.
• Acts as a selective physical barrier between cell and extracellular environment
• Cholesterol and other lipids are also part of the membrane structure.
Membrane Lipids:
• Anchoring proteins: attach to other structures to stabilize cell position
• Recognition proteins: Identifies cell as “self”, nonself, normal, or abnormal
• Receptor proteins: trigger changes in cell activity based materials in extracellualr environment that bind to them
• Carrier proteins: bind and transport materials across cell membrane
• Channel proteins: pores in cell membrane which allows solutes to diffuse in and out of cell
• Enzymes: catalyze reactions in and out of cell.
Membrane Proteins Include:
Cell Membrane Proteins
• Movement of a substance from an area of high concentration to low
• Continues until concentration gradient is eliminated
Diffusion
Figure 3.4 Diffusion
Figure 3.5 Diffusion across the Cell Membrane
• Diffusion of water across a semipermeable membrane in response to solute differences
• Osmosis occurs across a selectively permeable membrane that is permeable to water but NOT freely permeable to solutes
• In osmosis, water flows across a membrane toward the solution that has the HIGHER concentration of SOLUTES because that is where the concentration of WATER molecules is LOWER
Osmosis
• OP = the force of water into a solution as a result of different solute concentrations.
• Isotonic = no net gain or loss of water• Hypotonic = net gain of water into cell–Hemolysis (swelling or bursting of cell)
• Hypertonic = net water flow out of cell–Crenation (shrinking of cell)
Osmotic Pressure
Figure 3.7 Osmotic flow across a cell membrane (RBC)
• Carrier mediated transport– Proteins bind and transport specific ions or organic
molecules and transport them across the cell membrane• Cotransport: 2 substances move together• Counter-transport: 2 substances move in opposite
directions
– Passive Transport: no ATP required– Active Transport: ATP dependent
Transport Mechanisms
• Facilitated diffusion (passive)– Compounds to be transported bind to a receptor site
on a carrier protein– Not totally dependent on concentration of solutes
• Active transport (active)– Consumes ATP– Independent of concentration gradients– Types of active transport include• Ion pumps• Exchange pumps
Carrier Mediated Transport
Facilitated Diffusion
Figure 3.8
Figure 3.9
The Sodium Potassium Exchange Pump
• Material moves into or out of cells in membranous sacs • Endocytosis is movement of materials into the cell– Receptor-mediated endocytosis (coated vesicles)– Pinocytosis: cell drinking– Phagocytosis: cell eating (pseudopodia)
• Exocytosis is ejection of materials from the cell– Hormones– Mucus– Waste products
Vesicular transport
Figure 3.10 Receptor-Mediated Endocytosis
Figure 3.10
Figure 3.11 Pinocytosis and Phagocytosis
• Cell division is the reproduction of cells
• Apoptosis is the genetically controlled death of cells
• Mitosis is the nuclear division of somatic cells
• Meiosis produces sex cells
Cell Division
• Most somatic cells spend the majority of their lives in this phase
• Interphase includes– G1– S – G2
Interphase
• Prophase• Metaphase• Anaphase• Telophase
Mitosis, or nuclear division, has four phases
During cytokinesis, the cytoplasm divides and cell division ends
The Cell Life Cycle
Interphase, Mitosis, and Cytokinesis
Interphase, Mitosis, and Cytokinesis
• Generally, the longer the life expectancy of the cell, the slower the mitotic rate– Stem cells undergo frequent mitoses –Growth factors can stimulate cell division–Abnormal cell division produces tumors
(neoplasms)• Benign•Malignant (invasive, and cancerous)–Spread via metastasis–Oncogenes
Mitotic rate and cancer
• Process of specialization• Results from
inactivation of particular genes
• Produces populations of cells with limited capabilities
• Differentiated cells form tissues
Cell Differentiation