Lesson 2. Cytology

Hans and Zacharias Janssen

Dutch lens grinders; father and son produced the first compound microscope (2 lenses) in 1595

Robert Hooke

first discovered cells from cork slices in 1665; published Micrographia.

Francis Crick and James Watson

Discovery of DNA published in March 7, 1953 the helical structure of the DNA that earned them the Nobel Prize in 1962

Types of Cells

Prokaryote; Eukaryote

Prokaryote

cells with no nucleus or organelles with membranes; Blue Green algae; Bacteria

Eukaryote

cells that contain nucleus and organelles surrounded by membranes (animals, plants, fungi, protozoa)

Germ cells

able to produce gametes (haploid daughter cells) (sperm, ova)

Somatic cells

able to produce other somatic cells (diploid daughter cells)

Similarities of prokaryote and eukaryote

DNA as their genetic material; Ribosomes; similar basic metabolism; amazingly diverse in forms.

Differences of Prokaryote and Eukaryote

Size; DNA; Nucleus and Nuclear envelope; Histones; Organelle; Cytoskeleton; Metabolism; Size of ribosome; Reproduction

Organization of the Cell

Nucleus; Cytoplasm

Nucleus

control center

Cytoplasm

refers to the part of cell bounded by cell membrane includes both fluids and particulate matter

Cytosol

refers to the cytoplasmic matrix more specifically its fluid portion

Water, Ions/electrolytes, Proteins, Lipids

CarbohydratesProtoplasm composed of five basic substances

Water

principle fluid medium comprising 70-85% of the cell (except for fat cells)

Ions/electrolytes

Potassium; Magnesium; Phosphate; Sulfate; Bicarbonate; smaller amounts Sodium; Chloride; Calcium

Structural proteins

present in the cell mainly in the form of long filaments

Functional proteins

composed of combinations of a few molecules in tubular-globular form, mobile in the cell fluid; enzymes of the cell

Lipids

2% of the total cell mass, insoluble in water; Phospholipids; cholesterol

Carbohydrates

for nutrition of the cell, 1-3% of total cell mass (6% in the liver); Glycogen

Membrane bound organelles

Nucleus; Endoplasmic Reticulum; Golgi Apparatus; Lysosomes; Peroxisomes; Mitochondria; Secretory vesicles

Non-membrane bound organelles

Cytoskeleton; Ribosomes

Biomembrane functions

Selective permeability and transport; Synthesis and detoxification; Energy transduction; Cell to cell adhesion; Cell movement; Site of receptors; Insulation; Intercellular communication between adjacent cell; Compartmentalization; Conduction of electrical impulse

Membrane composition

Lipid bilayer; Integral proteins; Peripheral proteins

Integral proteins

Carrier proteins; receptors

Peripheral proteins

function almost entirely as enzymes or as controllers of transport of substances through the cell membrane

Membrane Protein Functions

Transport; Enzymatic Activity; Signal Transduction; Cell to Cell Recognition

Glycocalyx

loose carbohydrate coat of the entire outside surface of the cell

Granular endoplasmic reticulum

for protein synthesis

Agranular ER

for lipid synthesis

Golgi Apparatus

receives substances from the ER; repackaging; sending the substances to new location in the cell

Golgi secretory products

Integral proteins; Lysosomes; Mucopolysaccharide (hyaluronic acid and chondrointin sulfate); Hormones/neurotransmitters

Lysosomes functions

Provide nutrition via cellular autophagy; Lysis of organelles during cellular differentiation and metamorphosis; Destruction of aged RBC or dead cells; Dissolution of blood clot or thrombi; Bone resorption; Defense against invading organism

Peroxisome

Derived from SER; Contains oxidases and forms hydrogen peroxide; Contains catalase in large quantities to oxidize poisonous substances

Mitochondria

powerhouses of the cell; self-replicative; contains DNA

ATP

cell currency produced by mitochondria from breakdown of CHO, fats and proteins

Nucleus

Contains large quantities of DNA (genes); Genes determine the characteristics of the cell’s proteins; Genes control and promote reproduction of the cell.

Nucleolus

Rich in RNA and proteins and is the source of ribosomal rRNA; No limiting membrane

Ribosome

protein synthesizing machines of the cell

Cytoskeleton

System of filaments or fibers present in the cytoplasm of eukaryotic cells

Function of MT

Mechanical or structural function; Morphogenesis; Cellular motility; Transport of macromolecular transport within cell

Function of MF

Cell structure; Cell motility; Muscle contraction; Cytokinesis; Cytoplasmic streaming; Endocytosis and exocytosis; Cell integrity

Summary

The two types of cell are differentiated primarily by the presence of nuclear membrane; Cell organelles may be grouped into membranous and non-membranous types; Cell membranes are composed of varying proportions of lipids and proteins; Microtubules, microfilaments and intermediate filaments comprise the cytoskeleton; Each organelle has their specific function