I.
Cell Theory a.
The cell is the basic structural and functional unit of living organisms b.
The activity of an organism is dependent on both the individual and collective activities of its cells c.
The biochemical activities of cells are determined and made possible by the specific subcellular structures of cells d.
Continuity of life has a cellular basis
II.
Plasma membrane a.
Defines the boundaries of the cell b.
Fluid mosaic model – thin, stable structure with two layers of phospholipids and proteins dispersed throughout c.
Lipid bilayer – relatively impermeable to most water soluble molecules i.
Phospholipid – lollipop shape – head & tail
1.
Polar head – hydrophilic – interacts well with water
2.
Nonpolar tail – hydrophobic – avoids water & other polar molecules ii.
Sandwich like, two parallel sheets of phospholipids with the heads facing the water inward and outward iii.
Substantial amounts of cholesterol that help stabilize and keep the membrane fluid iv.
Integral proteins – inserted in the bilayer
1.
those that face the external environment serve as receptors for hormones
2.
Those that span the width of the membrane are both hydrophilic and hydrophobic – help with transport across the membrane v.
Peripheral proteins – not imbedded in the bilayer
1.
usually attached to integral proteins on the internal surface
2.
some act as enzymes, others help with mechanical functions like the cell shape
III.
Specializations a.
Microvilli i.
Minute finger-like extensions of plasma membrane ii.
Increase surface area iii.
Often found on absorptive cells b.
Membrane junctions i.
Three ways – adhesive glycoproteins, tongue/groove fit, and special membrane junctions ii.
Tight Junctions – protein molecules in adjacent membranes fuse together forming an impermeable junction around the cell iii.
Desmosomes – adhesive spots scattered along the cell membrane binding it to adjacent cells
1.
Button-like attachments, cells do not actually touch
2.
Thick filament extend in toward the center of the cell iv.
Gap junctions – allow direct passage of chemical substances between adjacent cells

1.
Cells are connected by hollow cylinders to allow ions, sugars, small molecules to pass from one cell to the next
2.
Usually found in electrically excitable cells – heart, smooth muscle
Mitochondria
Ribosomes
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Golgi apparatus
Lysosome
Peroxisomes
Microfilaments
Microtubules
Centrioles
Cilia
Flagella
Nuclear envelope
Nucleoli
Chromatin

IV.
Functions of the Plasma Membrane – Membrane Transport a.
Interstitial fluid – extracellular fluid derived from the blood i.
Contains different kinds of nutrients, chemicals, waste ii.
The cell must extract the exact amount needed at specific times b.
Selective permeability – cell membrane allows some substances to pass but not others i.
Characteristic of healthy cells, if cell membrane is damaged, substances flow into and out of the cell freely c.
Passive transport – substances penetrate the membrane without any energy required from the cell i.
Diffusion – tendency of molecules or ions to scatter evenly
1.
The energy source is from the molecules themselves which affects the rate of diffusion
2.
Molecules move from a high concentration to a lower area of concentration
– moving along the concentration gradient
3.
The greater the difference in the concentrations, the faster the diffusion
4.
Increase in temperature, increases the rate of diffusion
5.
Decrease in particle size, increases the rate of diffusion
6.
In a closed container – concentration will balance out
7.
Particles will pass if they: a.
Are lipid soluble b.
Small enough to pass through the membrane pores c.
Have help from a carrier molecule
8.
Simple diffusion a.
Substances that are nonpolar and lipid soluble that pass easily across the lipid bilayer b.
Substances that are polar but small enough to fit through the pores created by proteins
9.
Osmosis a.
The diffusion of a solvent through the membrane, usually water b.
Occurs when there is a large concentration gradient c.
If there is an unequal amount of solute on different sides of the membrane, there is an unequal amount of water i.
If solute increases, water decreases ii.
Depends on the number, not the type of molecules d.
Hydrostatic pressure – the back pressure by the water against the membrane e.
Osmotic pressure – tendency to resist further water entry i.
The higher the amount of nonpenetrable solute within the cell, the higher the osmotic pressure and the greater hydrostatic pressure needed to resist inflow ii.
In animal cells, osmotic pressure causes cells to shrink or swell iii.
Tonicity – ability of a solution to change the shape of cells by altering the internal water volume
1.
Isotonic – solutions with concentrations equal to that found in cells – cells maintain normal shape

2.
Hypertonic – solutions that have a higher concentration of solute than found in cells – cells shrink when placed in this solution
3.
Hypotonic – solutions that are more dilute (contain less solute) then the cells – cells swell and cold lyse (burst)
10.
Facilitated Diffusion a.
Combine with a protein molecule to carry it across the membrane b.
Highly selective which molecules are transported c.
Still passive transport because there is no ATP used ii.
Filtration
1.
The process by which water and solutes are forced out through a membrane by hydrostatic pressure
2.
Does not use a concentration gradient, Uses a pressure gradient a.
Solute is pushed from a high pressure to a low pressure across the membrane
3.
Not a selective process – only blood and proteins can not pass d.
Active processes – cells use ATP to move a substance from one side of the membrane to the other i.
Active Transport or Solute pumping – uses carrier proteins
1.
Different from facilitated diffusion because it goes against the gradient ii.
Bulk transport – large particles are transported through the membrane
1.
Uses ATP
2.
Exocytosis – mechanism that moves substances from the cell interior to the outside a.
Material is first enclosed in a vesicle (membranous sac) b.
Vesicle migrates to the membrane, binds to it and ruptures to the outside
3.
Endocytosis – means for large molecules to enter the cells a.
Substance is enclosed in a fold in the membrane creating a vesicle b.
Vesicle pinches off the membrane and enters the cytoplasm c.
Phagocytosis – cell eating i.
Parts of the membrane and cytoplasm protrude and flow around a piece of material and engulf it d.
Pinocytosis – cell drinking i.
A fold in the membrane engulfs a droplet e.
Receptor-mediated endocytosis i.
Very selective, proteins in the membrane bind with certain molecules

I.
Cell life cycle – time from formation to reproduction of self a.
Purpose i.
Increase number of cells b.
Interphase – growth phase, time when the cell is maintaining normal activity i.
Carrying on life-sustaining reactions ii.
Prepares cell for next cell division iii.
G1 phase – cells are metabolically active, synthesize proteins, grow
1.
ends as centrioles start to replicate iv.
S phase – DNA replicates itself v.
G2 phase – proteins and enzymes are synthesized and moved to proper sites
II.
DNA Replication a.
DNA must be replicated before a cell can divide b.
Helices are uncoiled with helicase – enzyme that untwists the double helix and separates in to two chains c.
Leading strand – where replication occurs following the movement of the separation d.
Nucleotide base pairs always match – A:T, G:C i.
After the DNA is unzipped, the base pairs match up creating identical new strands e.
Two new chromatin strands are formed f.
Chromatin strands condense into chromatids and united by a centromere g.
Semiconservative – each strand contains ½ the original
III.
Cell division a.
Cells that wear away easily – skin, intestinal lining reproduce quickly and frequently b.
Cells of the liver reproduce slowly c.
Nervous, skeletal, cardiac do not reproduce d.
Cell division control i.
Unsure of actual triggers, surface-volume relationship or MPF – protein concentrations e.
Mitosis – division of the nucleus i.
Series of events that distribute the copied DNA to daughter cells ii.
4 stages
1.
Prophase – longest phase a.
Chromatin threads begin to condense and coil into chromosomes b.
Centrioles begin to separate and migrate to opposite ends c.
Spindles extend from the centrioles and help push them apart d.
Nuclear membrane fragments, allows spindles to interact with the chromosomes
2.
Metaphase – Chromosomes line up at the equator of the cell a.
Centrioles are at the poles
3.
Anaphase – Shortest stage a.
Centromeres split, the chromatids become chromosomes of their own b.
Chromosomes are pulled toward the poles c.
Centrioles are pushed farther from each other, elongating the cell

4.
Telophase – begins when the chromosomes stop moving a.
At each pole, chromosomes begin to uncoil (threadlike) into chromatin b.
Nuclear membrane forms c.
Spindles break down and disappear d.
Cytoplasm divides f.
Cytokinesis – division of the cytoplasm i.
Begins during the late anaphase/early telphase ii.
The center of the cell is drawn in – cleavage furrow iii.
Cleavage furrow increases until the cell is pinched in two
Meiosis
Occurs only in sex cells – gametes
2 complete divisions
1. Reduction division
2. Separation division
End result – 4 haploid cells = ½ the DNA of the parent cells
Interphase - Begins by replicating DNA, roots lie in mitosis
Prophase I - Like prophase in mitosis
Metaphase I - Homologous chromosomes line up next to each other after synapse – finding each other
Crossing over occurs
Anaphase I - Whole chromosomes move apart
Telophase I - Divide cytoplasm
NOW two non-identical diploid cells
Interkinesis/Interphase II
Phophase II - Just like prophse in mitosis except with ½ the chromosomes
Metaphase II - Single line of chromosomes
Anaphase II - Like chromosomes separate
Telophase II - Division of cytoplasm, equal or unequal
RESULT – 4 haploid cells
Divisions
# Cells
# chromosomes
Mitosis
1
2
2N (diploid)
Synapsing
Chrom. Duplicate
Chrom. Reduction
Chromatids separate
Function
No
Interphase
No
Anaphase
Growth & repair
Meiosis
2
4
1N (haploid)
Yes
Interphase
Yes
Anaphase II
Gametes for reproduction

Protein Synthesis
Uses information from DNA
“Genes” codes for protein construction
Tells specific order of amino acids to assemble to make a given protein
Genetic traits
Protein absence or presence for a particular protein on DNA (chromosome)
Gene – specific length for DNA for a given protein
Arranged as 3 base units – codon
1 codon specifies 1 particular amino acid
Translate & Transcribe
DNA – partially unzip it
Duplicate it
½ strand makes up mRNA
RNA – new bases – uracil replaces thyamine mRNA read and followed by ribosomes
Alleles – alternate form of a gene
only two alleles per individual for any gene
only one allele per gamete
Dominate alleles – always expressed in phenotype if they are present in genotype of individual
Recessive allele – only visibly expressed in homozygous recessive state
Homozygous – having 2 identical alleles in an organism
Heterozygous – having 2 unlike alleles of a gene