Unit 3 - Cells

I. Cytology - The study of cellsA. Cell Theory

1. Cells are the basic unit of structural units of all plants and animals.

2. Cells are the smallest functioning units of life.

3. Cells are produced by the division of pre-existing cells.

4. Each cell maintains homeostasis.

B. Ways we visualize cells:

1. Light microscopes – 1000X, thin sections

2. Electron microscopes – 1oo,oooX

b. Scanning = 3-D, surface, plasma membrane

a. Transmission – very thin sections, show detail of internal cellular structures

C. The typical cell – The cell membrane separates:

1. Extracellular (Interstitial) fluid – Watery medium surrounding the cell

2. Cytoplasm – cell contents made up of:

a. CYTOSOL – fluid inside

b. ORGANELLES – “little organs”, structures that perform specific functions

D. Membrane Transport - Selectively permeableAllows some materials to pass, prevents others (based on size, electrical charge, molecular shape, lipid solubility, or combination.)

1. PASSIVE - Move ions or molecules without an energy input, through the lipid portion of the membrane or through a channel protein.

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1101

a. Diffusion - Net movement from an area of high concentration (many collisions) to an area of low concentration (few collisions)

CONCENTRATION GRADIENT

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1903

EX: Osmosis - Diffusion of water across a selectively permeable membrane toward a solution that has the highest solute concentration (due to substances dissolved, etc. in solution)

Osmotic pressure – the amount of pressure required to stop osmosis across a membrane.

http://www.ac-creteil.fr/biotechnologies/doc_osmosis.htm

*ISOTONIC - “equal tension” – equlibrium exists, no net movement into or out of the cell., 0.9% NaCl = isotonic for RBC

*HYPOTONIC - “below” – solute concentration is higher inside the cell, water moves into the cell. Cell may swell, rupture.

*HYPERTONIC - “above” – solute concentration is higher outside the cell, water moves out and the cell shrivels.

RBC = HEMOLYSIS

RBC = CRENATION

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

b. Facilitated Diffusion - Large and lipid soluble substances move across the membrane with the help of carrier proteins.

Glucose and Aquaporins

http://www.wisc-online.com/objects/index_tj.asp?objID=AP11103

c. Filtration - Use of gravity or mechanical pressure to move substances across a selectively permeable membrane

Capillaries, kidneys

2. ACTIVE TRANSPORT - Cell requires energy in the form of ATP to move substances across a membrane against the concentration gradient

EX: Cytosis – Vesicular transport

a. Endocytosis - Large particles/molecules are surrounded by plasma membrane and brought into the cell.

http://programs.northlandcollege.edu/biology/Biology1111/animations/transport1.html

PHAGOCYTOSIS – Projections of cytoplasm surround and engulf cell, “cell eating”.

PINOCYTOSIS – engulfed material is liquid – a droplet of liquid is attracted to the membrane surface which folds inward and forms a pinocytic vesicle.

RECEPTOR-MEDIATED – recognition sites that attach to specific molecules such as hormones, nutrients, antibodies, neurotransomitters

http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitosis.swf

E. Protein Synthesis - Cells are protein factories – produce a large # of proteins, some structural, others regulatory (hormones), antibodies, enzymes

1. The genetic code -

DNA – Holds the instructions (genes) to produce a protein.

a. Made up of nucleotides that are in turn made up of a nitrogen base, phosphate, and deoxyribose sugar.

b. Exocytosis – elimination of undigestible particles.

b. Located in the nucleus of eukaryotic cells, cannot leave

c. Double-stranded molecule that is kept together by H-bonds between complementary base pairs.

2. Transcription - Instructions are copied from DNA.

a. From double-stranded DNA, which cannot leave the nucleus, the protein instructions are copied as complementary base pairs into single-stranded messenger RNA (mRNA). b. The mRNA leaves the nucleus through the nuclear pores to reach protein factories – WHICH ORGANELLE? WHERE LOCATED?

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a2.html

3. Translation - mRNA provides the template for a protein to be made.

a. mRNA attaches to the small subunit of a ribosome (one protein is made per ribosome) and the large subunit then attaches.

b. tRNA (transfer RNA) brings the specific amino acid (20 different) with the complementary triplet code (anticodon) to mRNA (tRNA – UAC, mRNA – AUG)

c. The next tRNA brings another amino acid to the next mRNA codon and these amino acids are joined by a peptide bond.

d. Amino acids are attached one-by-one until the protein is formed – this process is stopped by a “stop codon”.

e. The protein is released from the ribosome.

b. & c.a. d.

http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html

GENE – A group of nucleotides on a DNA molecule that serves as a set of instructions for a protein. Average 100 nucleotide pairs in length.

F. Cell Cycle – Somatic cells1. Why? Heal wounds, growth, surface area to

volume, limited capability of nucleus2. Two divisions:

a. Nuclearb. Cytokinesis

3. Phases - Nuclear

a.

b. c.

c. Prometaphase

b. Prophase

a. Interphase -Nondividing period (90% of cycle), separated into three phases = G1, S, G2. During S DNA is replicated.

-chromatin shortens into chromosomes-nuclear membrane begins to disappear-centrosomes move to poles

-Spindle fibers attach to centromeres

d. e.

f.

d. Metaphase-

e. Anaphase

f. Telophase

chromosomes line up on the equatorial plate

-duplicated halves of each chromosome separate and move to opposite poles

-Nuclear membrane reforms-Chromosomes re-condense into chromatin

4. Cytokinesis -

http://www.cellsalive.com/mitosis.htm

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120073/bio14.swf::Mitosis%20and%20Cytokinesis

Division of the cytoplasm

5. Cancer – cells duplicate without control•Tissue is called tumor, growth, neoplasm•Oncology – The study of•Cancerous is called malignant•Non-cancerous is benign – does not spread to other parts and may be removed

•Hyperplasia – increase in frequency of cell division

a. Malignant tumors – duplicate continuously, quickly and without control

•Hyperplasia

•Metastasis - Spread to other parts, cancer cells secrete AMF (autocrine motility factor) – a protein which allows them to metastasize – hard to detect and eliminate

•Often this invasion kills the normal tissues by starving it out•Then they invade adjacent tissues and establish secondary tumors

b. Causes •CARCINOGEN - Chemical or environmental agent

that causes cancer (60-90% of human cancers) 90% of all lung cancers caused by smoking, UV radiation

•VIRUSES - Mostly in animals

•ONCOGENESIS - Genes found in human cells that trigger cancerous growth when inappropriately activated

•ANTIONCOGENESIS

c. Treatment

•Chemotherapy

•Radiation