TIS

Chapter 1
Geriatrics: Section II - Cells and Cell Division


I. CELL CHEMISTRY

A. Elements: (def: basic chemical substance)

-- Oxygen, Carbon, Hydrogen, etc.

B. Compounds:

1) Organic Compounds (contain carbon):

a) Proteins

* consist of amino acids
* functions:

** contribute to tissue structure (ex: collagen)
** they form enzymes
** form some hormones
** some help regulate materials entering and leaving cell

b) Carbohydrates (Starches & Sugars)

* contain Carbon, Hydrogen, & Oxygen
* major energy source for body

c) Lipids (Fats)

* insoluble in water
* functions:

** energy source
** insulation

* some kinds of lipids:

1) triglycerides: (fat and oil)
2) phospholipids: help form cell membrane
3) steroids: secreted byadrenal cortex and gonads

2) Inorganic Compounds(don't contain carbon)

a) Water

* functions:

** solvent
** maintains constant body temperature


II. BASIC CELL COMPOSITION

A. Cell Membrane (Plasma Membrane, Plasmalemma) - surrounds cell, gives it form

B. Cytoplasm and Organelles

* Cytoplasm: gel-like substance containing tiny organs (organelles)

C. Nucleus - contains DNA


III. CELL MEMBRANE

-- Structure: double layer of phospolipids

* proteins "float" in membrane

-- it is selectively permeable

-- Specializations of cell membrane:

1) microvilli:

* help increase surface area

2) cilia:

* help move materials along

-- Transportation across cell membrane:

1) endocytosis: process where materials are brought INTO the cell

* cell membrane encircles material, fuses, and becomes a vesicle (small sac) w/in cytoplasm

2) Exocytosis: process where cellular materials EXIT the cell

* materials packaged w/in vesicles
* vesicles fuse w/cell membrane and release contents outside of cell


IV. CYTOPLASM & ORGANELLES

A. Ribosomes - involved in protein synthesis

B. Endoplasmic Reticulum (ER) - a network of tubules that transports & synthesizes (produces) materials

1) Smooth ER - no ribosomes on walls
* synthesizes lipids

2) Rough ER - has ribosomes on walls
* synthesizes proteins

C. Golgi Apparatus - oval ends of ER

* packages materials for secretion
* forms lysosomes

D. Mitochondria - oval-shaped, has cristae

* makes ATP (adenosine triphosphate)
* contains its own DNA

E. Lysosomes - contain digestive enzymes

F. Centrioles - pair of rodlike structures

* positioned at right angles to each other


V. NUCLEUS

A. Nuclear Membrane - has inner and outer membrane

* nuclear pores

B. Nucleolus - contains protein and RNA

C. Chromatin - coiled mass of DNA


VI. DNA COMPOSITION/REPLICATION

-- DNA is deoxyribonucleic acid

-- formed from nucleotides (which consist of a phosphate, sugar and base)

-- Shape: double helix (spiral ladder)

-- Replication: DNA "unzips" to form two half-ladders + free nucleotides attach to rungs, forming two identical DNA strands


VI. CELL CYCLE

-- cells divided into two groups:

1) Sex cells (sperm and ova)

2) Somatic cells (all other cells)

-- cell cycle subdivided into 2 phases:

1) Interphase

2) Mitosis (for somatic cells) or Meiosis (for sex cells)

Interphase: cell is not dividing

* DNA duplicated during this time

Mitosis: cell division for somatic cells

Meiosis: cell division for sex cells


VII. MITOSIS

-- 4 stages:

1) Prophase ("Puffy")

* DNA in form of chromosomes (def: structure that houses 1 or several DNA molecules)

* duplicated chromosomes consist of 2 chromatids joined at a centromere

** (chromatid = each half of the duplicated chromosome)

* spindle fibers extend from centrioles to chromatids

* dissolution of nuclear membrane

2) Metaphase ("Middle"

* chromosomes along center of cell

3) Anaphase ("Apart")

* chromatids split apart at centromere
* each set of chromatids pulled to opposite ends of cell

4) Telophase ("Two")

* nuclear membrane forms
* nucleolus reappears
* cleavage furrow develops
* cytokinesis occurs

-- Cell now re-enters interphase


VIII. MEIOSIS - Def: cell division where gametes (haploid sperm cells or ova) are formed

-- Differences between mitosis and meiosis:

1) Mitosis produces 2 cells containing 46 chromosomes (23 pairs)

* daughter cells identical to original cell
* cells are diploid: have 2 of each chromosome

2) Meiosis produces 4 cells containing only 23 chromosomes

* there are 2 cell divisions
* cells have a haploid number of chromosomes (only 1 of each chromosome)

-- Start off with sex cell that has 23 pairs of chromosomes

* one set of chromosomes came from MOTHER, the other from FATHER

-- Interphase: DNA is duplicated

-- 1st meiotic prophase: homologous chromosomes pair up

** you have mom chromosome duplicates (23 pairs) and dad chromosome duplicates (23 pairs)

--Crossing Over: process where genetic material is exchanged between homologous chromosomes

-- cell finishes 1st meiotic division, producing 2 daughter cells

* daughter cells each have 23 chromosomes (each chromosome contains 2 chromatids)

-- cells go through 2nd meiotic division

* 4 cells produced, each with 23 chromosomes (each chromosome has only 1 chromatid now)

* these cells are gametes

 


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