Section 1: Structure and Function of Cells

Slide 5-8: Cell Composition and Plasma Membrane

• Cell Size and Shape

  • Human cells vary in size but are all microscopic.

  • Cells have different shapes based on their function (e.g., round, elongated, flattened).

  • Examples: Red blood cells are biconcave to enhance gas exchange; nerve cells have long extensions to transmit signals.

• Cytoplasm

  • Internal living material of the cell, primarily composed of water, dissolved nutrients, and organelles.

  • Cytosol: The fluid portion of the cytoplasm that provides the medium for chemical reactions.

  • Cytoskeleton: Network of protein filaments that provide structural support, enable cell movement, and assist in intracellular transport.

• Plasma Membrane

  • Structure: Thin, double-layered membrane composed of phospholipids, cholesterol, and proteins.

  • Phospholipid Bilayer: Hydrophilic (water-attracting) heads face outward, and hydrophobic (water-repelling) tails face inward, creating a barrier.

  • Function: Acts as a selectively permeable barrier, maintaining homeostasis by regulating what enters and exits the cell.

  • Role of proteins: Serve as receptors, channels, or carriers for substances.

  • Glycoproteins and Glycolipids: Involved in cell recognition and communication, forming part of the glycocalyx.

Slide 9-12: Organelles Overview

• Ribosomes: Sites of protein synthesis; found free in cytoplasm or attached to the rough endoplasmic reticulum (ER).

  • Rough ER: Has ribosomes on its surface; involved in protein production and transport.

  • Smooth ER: No ribosomes; synthesizes lipids and helps in detoxification processes.

  • Function in Muscle Cells: Sarcoplasmic reticulum, a type of smooth ER, stores calcium ions essential for muscle contraction.

• Golgi Apparatus

  • Composed of stacks of membrane-bound sacs near the nucleus.

  • Functions as a packaging center: Modifies, sorts, and ships proteins produced by the ER.

  • Vesicle Formation: Packages proteins into vesicles for transport within the cell or for secretion outside the cell.

• Mitochondria

  • Known as the powerhouse of the cell due to their role in ATP (energy) production.

  • Double-membrane structure with the inner membrane forming folds called cristae, which increase surface area for chemical reactions.

  • Matrix: The innermost compartment that contains enzymes for the Krebs cycle.

  • Contain their own DNA, which is inherited maternally.

  • Role in Apoptosis: Mitochondria release cytochrome c to trigger programmed cell death.

Slide 13-15: Lysosomes and Centrosome

• Lysosomes

  • Vesicles containing digestive enzymes; break down unwanted or harmful materials within cells.

  • Have a protective role by digesting invading pathogens (e.g., bacteria).

  • Autophagy: Process by which lysosomes break down damaged organelles to recycle cellular components.

• Centrosome

  • Located near the nucleus; contains two centrioles that play a role in cell division by organizing the mitotic spindle.

  • Microtubules: Protein filaments that form the spindle fibers essential for chromosome movement during mitosis.

Slide 16-18: Cell Extensions

• Microvilli

  • Small, fingerlike extensions of the plasma membrane that increase the surface area, enhancing absorption (e.g., in intestinal cells).

  • Actin Filaments: Provide structural support to microvilli, aiding in stability.

• Cilia

  • Hairlike projections capable of coordinated movement; help move substances along surfaces (e.g., respiratory tract).

  • Primary Cilia: Non-motile cilia that act as sensory organelles, detecting environmental signals.

• Flagella

  • Long, whip-like extensions used for cell motility; the only example in humans is the sperm cell tail.

  • Structure: Composed of microtubules arranged in a 9+2 pattern, driven by the motor protein dynein.

Section 2: The Nucleus

Slide 23-25: Nucleus Overview

• Nuclear Envelope

  • Double membrane surrounding the nucleus, contains nuclear pores that allow exchange of substances with the cytoplasm.

  • Nuclear Pores: Permit the movement of RNA and ribosomal subunits out of the nucleus.

• Nucleolus

  • Dense, spherical body within the nucleus where ribosomal RNA (rRNA) is synthesized.

  • Ribosome Assembly: Site where ribosomal subunits are assembled before being transported to the cytoplasm.

• Chromatin and Chromosomes

  • Chromatin is a complex of DNA and proteins that condenses to form chromosomes during cell division.

  • Histones: Proteins that help package DNA into chromatin, regulating gene expression.

  • Human cells contain 46 chromosomes; the genetic material determines cell function and characteristics.

Slide 26-27: Cell Functions

• Cells have specific functions based on their organelles; specialization includes secretion, transport, protection, and synthesis.

  • Example: Pancreatic cells have abundant rough ER and Golgi apparatus for protein secretion (e.g., insulin).

  • Hepatocytes: Liver cells that contain many smooth ER and peroxisomes to aid in detoxification.

Section 3: Transport Processes in Cells

Slide 28-31: Passive Transport

• Diffusion

  • Movement of molecules from an area of high concentration to an area of low concentration without energy expenditure.

  • Important for gas exchange (e.g., oxygen and carbon dioxide in the lungs).

  • Factors Affecting Diffusion: Temperature, concentration gradient, and molecule size.

• Osmosis

  • Special type of diffusion where water moves across a selectively permeable membrane in response to solute concentration.

  • Maintains cellular hydration and electrolyte balance.

  • Osmotic Pressure: The pressure exerted by the movement of water during osmosis.

• Dialysis

  • Separation of small molecules from large ones through a selectively permeable membrane (e.g., artificial kidney).

  • Used in medical treatments to remove waste products from the blood.

Slide 32-33: Filtration

• Movement of water and solutes driven by hydrostatic pressure (e.g., blood pressure); crucial for kidney function and urine formation.

  • Capillary Filtration: Movement of fluid and solutes from the blood into the interstitial space, influenced by blood pressure and osmotic pressure.

Slide 34-36: Active Transport

• Ion Pumps

  • ATP-driven protein pumps that move ions across the cell membrane against their concentration gradient (e.g., sodium-potassium pump).

  • Electrochemical Gradient: The difference in charge and chemical concentration across the membrane, crucial for nerve impulse transmission.

• Phagocytosis

  • Cell engulfs large particles or pathogens, forming a vesicle that fuses with lysosomes for digestion.

  • Immune Function: White blood cells use phagocytosis to destroy bacteria and foreign particles.

• Pinocytosis

  • Similar to phagocytosis, but involves engulfing fluid and dissolved substances into vesicles.

  • Nutrient Absorption: Common in cells lining the small intestine.

Section 4: Cell Transport and Disease

Slide 37-39: Examples of Cell Transport in Disease

• Cystic Fibrosis: Genetic disorder caused by malfunction in chloride ion transport, leading to thick mucus in the lungs and digestive tract.

  • CFTR Protein: Defective chloride channel protein that disrupts water movement, causing mucus buildup.

• Cholera: Bacterial toxin triggers chloride and water efflux from intestinal cells, leading to severe dehydration and diarrhea.

  • Mechanism: Toxin activates adenylate cyclase, increasing cAMP levels and causing ion and water loss.

Section 5: Cell Reproduction and Genetics

Slide 40-42: DNA and RNA

• DNA Structure

  • Double-helix structure made of nucleotide pairs (adenine with thymine, cytosine with guanine).

  • Sugar-Phosphate Backbone: Forms the structural framework of DNA, holding the base pairs together.

• Genes

  • Specific DNA sequences that encode proteins, which determine cell characteristics.

  • Gene Expression: The process by which information from a gene is used to synthesize a functional product, often a protein.

Slide 43-45: RNA and Protein Synthesis

• Transcription

  • DNA strands unwind to form messenger RNA (mRNA) that carries genetic code to ribosomes in the cytoplasm.

  • RNA Polymerase: Enzyme that catalyzes the synthesis of mRNA from DNA.

• Translation

  • Ribosomes read mRNA sequences and synthesize proteins using transfer RNA (tRNA) to add amino acids.

  • Codons: Three-nucleotide sequences on mRNA that specify particular amino acids.

  • Anticodon: A sequence of three bases on tRNA that is complementary to an mRNA codon.

Slide 46: Protein Synthesis and Disease

• Abnormalities in DNA or RNA can lead to genetic disorders or cancers; mutations may be caused by environmental factors such as radiation.

  • Point Mutations: Single nucleotide changes that can alter protein function (e.g., sickle cell anemia).

  • Frameshift Mutations: Insertions or deletions that change the reading frame, leading to dysfunctional proteins.

Slide 47-49: Cell Life Cycle

• Interphase: Period of growth and DNA replication between cell divisions.

  • G1, S, G2 Phases: Cell grows, duplicates DNA, and prepares for division.

• Mitosis: Division of the nucleus into two genetically identical daughter nuclei.

  • Cytokinesis: Division of the cytoplasm, resulting in two separate daughter cells.

Slide 50-53: Mitosis Phases

• Prophase: Chromatin condenses into chromosomes; nuclear envelope dissolves.

  • Mitotic Spindle: Microtubules form spindle fibers that attach to chromosomes.

• Metaphase: Chromosomes align at the cell's equator; spindle fibers attach.

  • Metaphase Plate: The imaginary line where chromosomes align during metaphase.

• Anaphase: Chromatids are pulled apart to opposite poles of the cell.

  • Centromere Division: Allows sister chromatids to separate and move to opposite poles.

• Telophase: Nuclear envelope re-forms; cytoplasm divides (cytokinesis), creating two daughter cells.

  • Nucleolus Reappears: Indicates the end of mitosis and the beginning of the interphase in daughter cells.

Section 6: Changes in Cell Growth and Reproduction

Slide 54-55: Hypertrophy and Atrophy

• Hypertrophy: Increase in cell size, resulting in larger tissue (e.g., muscle cells with exercise).

  • Physiological vs. Pathological: Exercise-induced hypertrophy vs. cardiac hypertrophy due to hypertension.

• Atrophy: Decrease in cell size, resulting in tissue shrinkage (e.g., muscle wasting).

  • Causes: Disuse, denervation, reduced blood supply, inadequate nutrition.

Slide 56: Hyperplasia and Anaplasia

• Hyperplasia: Increase in cell number leading to tissue enlargement (e.g., callus formation).

  • Hormonal Hyperplasia: Breast tissue growth during pregnancy.

• Anaplasia: Loss of cellular differentiation, typically seen in cancerous tissues.

  • Characteristics: Irregular cell shapes, large nuclei, increased mitotic activity.

Slide 57: Cancer

• Cancer: Uncontrolled cell growth resulting from mutations affecting cell cycle regulation.

  • Common factors: Radiation, chemical exposure, viral infections, and genetic predisposition.

  • Oncogenes and Tumor Suppressor Genes: Genes that, when mutated, promote or fail to inhibit uncontrolled growth.