Anatomy and Physiology 1: Chapter 3 - The Cellular Level of Organization

Overview

• Focuses on the cellular level of organization.
• Builds from atoms and molecules (Chapter 2) to organelles and cells.
• Cells are the fundamental units of life, performing all vital physiological functions.
• Cytology: the study of cells.
• Two main types of cells: Sex cells (germ cells) and somatic cells.

Cell Theory

• Cells are the building blocks of all organisms.
• All cells come from pre-existing cells.
• Cells perform all vital physiological functions to maintain homeostasis.

Cell Structure

Plasma/Cell Membrane

• Separates cytoplasm from extracellular fluid.
• Functions:
  • Isolates the cell from its environment.
  • Controls entry and exit of substances (ions, nutrients, waste).
  • Responds to environmental signals via receptors.
  • Offers structural support and helps in cell junctions.
• Made of a phospholipid bilayer.
• Phospholipids have hydrophilic heads and hydrophobic tails.

Cytoplasm

• Includes all cell materials except the nucleus.
• Contains cytosol and organelles.
• High in protein and potassium, low in carbohydrates, lipids, and sodium.

Organelles

• Non-membranous: cytoskeleton, centrioles, ribosomes, proteasomes, microvilli, cilia, flagella.
• Membranous: endoplasmic reticulum (ER), Golgi apparatus, lysosomes, peroxisomes, mitochondria.

Non-Membranous Organelles

Cytoskeleton

• Provides shape and support.
• Consists of microfilaments, intermediate filaments, and microtubules.

Microvilli

• Increase surface area for absorption, commonly found in the digestive tract.

Centrioles

• Form spindle apparatus for cell division.

Cilia and Flagella

• Cilia: Move fluids across cell surface.
• Flagella: Long tails for cell movement.

Ribosomes

• Sites of protein synthesis.
• Free ribosomes produce proteins for the cytosol.
• Fixed ribosomes are attached to rough ER.

Membranous Organelles

Endoplasmic Reticulum (ER)

• Smooth ER: Lipid synthesis and detoxification.
• Rough ER: Protein synthesis and processing.

Golgi Apparatus

• Modifies and packages proteins and lipids.
• Produces lysosomes.

Lysosomes

• Contain digestive enzymes for breaking down substances and recycling cellular components.

Peroxisomes

• Break down fatty acids.

Mitochondria

• Powerhouse of the cell, produces ATP from glucose.

Nucleus

• Control center of the cell.
• Contains DNA, nucleolus, and nuclear envelope.
• DNA organized into chromatin and chromosomes.

Protein Synthesis

Transcription

• RNA polymerase transcribes DNA into messenger RNA (mRNA) in the nucleus.
• mRNA exits through nuclear pores.

Translation

• Occurs in the cytoplasm at ribosomes.
• mRNA is translated into proteins by transfer RNA (tRNA).
• tRNA brings amino acids to form polypeptides.

Membrane Transport

Diffusion and Osmosis

• Diffusion: Movement from high to low concentration.
• Osmosis: Water movement across a semi-permeable membrane.

Tonicity

• Isotonic: No net water movement.
• Hypotonic: Water enters the cell, causing swelling.
• Hypertonic: Water leaves the cell, causing shrinkage.

Endocytosis and Exocytosis

• Endocytosis: Cell uptake of materials (phagocytosis for solids, pinocytosis for liquids).
• Exocytosis: Release of substances from the cell.

Membrane Potential

• Separation of charges across the cell membrane creates potential difference.
• Resting membrane potential ranges from -10 to -100 mV.

Cell Division

Mitosis

• Process of cell division producing two identical daughter cells.
• Phases: prophase, metaphase, anaphase, telophase.
• Followed by cytokinesis.

Tumors and Cancer

• Tumor: Abnormal cell growth; can be benign or malignant.
• Cancer involves uncontrolled cell growth, potentially spreading through metastasis.

Differentiation

• Process by which cells become specialized.
• Different types of cells perform specific functions.

This chapter concludes the general biology review, preparing for the study of tissues in Chapter 4.