Chapter 2

Cytology (the study of cells)

Microscopy

Light microscope (LM)

Uses visible light to produce an image

Most often used

But, most limited in magnification

Term definitions

• Magnification - increase in viewable size

• Resolution - ability to reveal detail

The Cell Theory

• All organisms are made of cells

• All existing cells are produced by other living cells

• All existing cells are produced by other living cells

• The cell is the most basic unit of life

Plasma membrane

• Boundary of cell

• Cell membrane lipids

  • Phospholipids/lipid bilayer (75% of plasma membrane)

    • Hydrophobic tails

    • Hydrophilic heads

  • Arranged in what is called a lipid bilayer

  • Lipid Bilayer - 75%

  • Cholesterol - 20% (increases fluidity of the membrane)

  • Glycolipids - 5%

  • Glucose (sugar) + phospholipid for cell signaling and recognition

Membrane Proteins

• Pass through membrane

  • Integral (transmembrane) proteins

  • Glycoproteins

• Adhere to either face of membrane

  • Peripheral proteins

Glycocalyx

• dense, gel-like meshwork that surrounds the cell, constituting a physical barrier for any object to enter the cell

Cell surface extensions

• Villi & Microvilli

  • Plasma membrane extensions 

  • Increase surface area

  • Brush border

• Cilia - motile microtubules

• Flagella - propels sperm cells

Cellular Junctions (AKA attachments)

• Apical: lines the lumen of sac- and tube-shaped organs and the inner surfaces of the body cavities

• Lateral: contains proteins for cell-cell adhesion, intercellular signaling, and cell-cell communication

• Basal:  the innermost layer of the epidermis

• Tight junction - sealant

• Desmosomes - resist stress

• Gap junction - communication

Cell cytoskeleton

• Composed of:

  • Microfilaments and terminal web

  • Intermediate filaments

  • Microtubules

• Cell Functions:

  • Support cell

  • Determine shape

  • Organize contents

  • Move substances

  • Move cell

• The Cell Cytoskeleton Components

  • Microfilaments (smallest)

  • Mostly made of the protein actin

  • Support the plasma membrane and play a role in cell movement

• Intermediate filaments

  • Thicker and give strength to cells and tissues

• Microtubules (largest)

  • Small strands that hold organelles in place

  • Guide organelles and macromolecules to destinations within the cell 

  • Involved in cell division

  • Form cilia on cells

Organelles (Identify and know their function - i.e., nucleus, mitochondria, ribosomes, etc.)

• Endoplasmic Reticulum

  • Rough endoplasmic reticulum (RER)

    • Studded with ribosomes

    • Produces phospholipids and proteins of plasma membrane

  • Produces proteins for secretion and for lysosomes

    • Smooth endoplasmic reticulum (SER)

    • Cells that detoxify

    • Cells that synthesize steroids

• Ribosomes

  • Reads messenger RNA→ assemble amino acids into proteins

  • Locations of Ribosomes

  • Cytosol

  • Rough endoplasmic reticulum

  • Nuclear envelope

  • Nucleoli

  • Mitochondria

• Golgi Complex/Apparatus

  • Composed of cisterns

  • Transport vesicles from RER to Golgi complex

  • Golgi vesicles - packaged proteins

    • Insertion into plasma membrane

    • Lysosomes

    • Secretory vesicles

• Cell Degraders/Recyclers - Lysosomes

  • Enzymes (a type of protein that breaks up cell “garbage”) that are contained in a membrane

  • Some actions that these perform

    • Autophagy - breaks down organelles

    • Apoptosis - programmed cell death

• Cell Degraders/Recyclers - Proteasomes

  • Cylindrical organelles that break down proteins

  • Cell marks “old” proteins for disposal by proteasomes

  • Degrade 80% of a cell’s proteins

• Mitochondria

  • Specialized for aerobic respiration

  • Make most of body’s ATP (the cells energy molecule)

  • Outer membrane

  • Inner membrane

    • Contains cristae

  • Mitochondrial matrix

  • Mitochondrial DNA (mtDNA)

• Centrioles/Centrosomes

  • Centrioles - made of microtubules arranged in 9 groups of 3

  • Centrosome - cytoplasm that contains the perpendicular pairs

  • Active during cellular division (mitosis)

• Nucleus

  • Largest organelle

  • Contains chromosomes 

  • Genetic control center

  • Nuclear envelope

  • Nuclear pores

  • Nucleoplasm - contains chromosomes

  • Nucleolus/nucleoli - produces ribosomes

The Cell Cycle

• Interphase - preparation for dividing

• Mitotic (M) phase - dividing; PMAT

• Cytokinesis

  • Division of cytoplasm

  • Cleavage furrow develops end of anaphase/beginning of telophase

  • Ultimately, cell pinches into 2 identical daughter cells

Mitosis

• Mitotic Phase (M) - Actual division of nuclear material

• Prophase

  • Chromatin condenses

  • Nuclear envelope breaks down

  • Nucleolus disappears

  • Spindle fibers form to connect to kinetochore

• Metaphase

  • Chromosomes align at center of cell

• Anaphase

  • Daughter chromosomes move to opposite poles

• Telophase

  • Chromatids at each pole decondense

  • Surrounded by new nuclear membrane

  • Nucleoli reformed