Cell biology for nurse practitioners.
The study of cells
Typical size of 7 um
Fixation
* rapid killing and preservation of tissue.
* prevent autolysis and exolysis.
* liquid nitrogen, acetic acid, alcohol, mercuric chlorides
Embedding
* mechanical support to allow thin sectioning, 5 - 10 um
* paraffin way or epoxy resins
* dehydration must be carried out before waxing, using ethanol
Sectioning
Light microscopy 1-20 um
Electron microscopy 50-100 nm (use a microtone)
Mounting - glass for light copper mesh for electron
Staining
Cells are often transparent
Light - eg. toluidine blue, haematoxylin, eosis
Electron - differential electron density, eg. lead, uranium, osmium
Microscopes
Light wavelength = 0.5 x 10 -6
Electron wavelength = 5 x 10 -12
ie. electron is 105 smaller
Interpretation of images
Reality or artifact
Cell composition
Cells are largely composed of macro-molecules
These exist because of structural hierarchy and weak bonding
primary structure - the order of the units in the covalently linked chain
secondary structure - portions of the chain fold into a regular structure
tertiary structure - the overall shape of the molecule, the irregular but precise folding pattern adapted by the whole molecule
quanternary structure - a multimeric complex, the combining units may be the same or different
Cell Anatomy and physiology
Types of cell
* eukaryotic, (compartmentalized cells)
- recognizable nucleus and nuclear membrane
- mitochondria
- chloroplasts
* prokaryotic
- no recognizable nucleus and nuclear membrane
- no mitochondria
Prokaryotic cell walls often contain peptidoglycan
Light microscopy
* Cell membrane, cytoplasm, cytoplasmic granules, (cell organelles), nucleus.
* Overall cell morphology
Electron microscopy
Cell Membranes
* regulates the internal cellular environment
* 7.5 - 10 nm thick
* lipid bilayer, the fluid mosaic model
* proteins float in the lipid layer, transmembrane proteins have a gateing function.
* gateing
The nucleus
* Membrane in two layers so often called the nuclear envelope
* Connections to the cytoplasm are via nuclear pores
* Dark area called the nucleolus, rich in RNA
* contains chromosomes
Endoplasmic reticulum
* Flattened sacks form an extensive intracellular network
* Enzymes are found in the reticulum
* Function probably varies depending on the cell type
* Internal transport
* Smooth and rough due to ribosomes
* Ribosomes are rich in ribonucleic acid (RNA), sites of protein synthesis
Golgi apparatus
* A number of flattened cisternae stacked on top of one another
* Formed from the ER
* Packaging of cell products for export
* Extensively developed in secretory cells
* Adds carbohydrate components to proteins synthesized in the ribosomes, ie. glycoproteins, a form of exocytosis
Lysosomes
* Membrane bound vesicles
* Rich in proteolytic enzymes such as lysosome
* Breakdown of cell contents and foreign material
* 15% of synthesized proteins probably contain errors and are digested.
Mitochondria
0.7 x 7 um sausage shaped organelles
Composed of a two layered membrane the inner one being highly infolded forming cristae.
Contain enzymes involved in the TCA cycle, fatty acid oxidation, and oxidative phosphorylation
Frequent in metabolically active tissues.
Adenosine triphosphate production
Can synthesise 5 -10% of their own structural protein from their own DNA.
Centrioles
Two pairs in most cells
Composed of 9 sets of microtubules, made of tubulin, (9+0)
Spindle formation
Cilia
Protrude out from cells into lumen
Waft to and fro
(9+2) arrangement
Microtubules
Exist in the cytoplasm and form an "internal scaffolding"
Cytosol
Cell contents not part of organelles
Cell functions
* Form tissues
* Secretory - intracellular matrix
- transmitters and hormones
* Body growth and repair
* Carry genetic instructions
* Energy production
* Receive messages
* House enzymic reactions
* Endocytosis and exocytosis, eg phagocytosis and digestive enzymes)
Cell Requirements
* Oxygen
* Carbohydrates, amino acids, fatty acids, vitamins, minerals
* To be free of waste products, eg carbon dioxide
* Adequate blood supply and venous drainage
* Messages from other cells eg. nervous, endocrine
* Constant level of pH and temperature
Cell division
Replication of the genetic material and cell contents
* mitosis - conservation
* meiosis - reduction
Growth and repair
Hypertrophy or hyperplasia
Chromosomes
Lit - coloured bodies
46 structures found in the nucleus
Composed of histone proteins and deoxyribonucleic acid
Genes
The amount of DNA that codes for one protein polypeptide or one protein
The amount of DNA to code for a length of RNA
A length of DNA which starts or stops the activity of other lengths of DNA, (control genes)
The DNA for one gene is not always adjacent on the DNA molecule.
The effect of genes may be single, (eg. eye or hair colour) or polygenetic, (eg height or intelligence).
Cell biochemistry
Enzymes increase the rate of reactions by 109 to 1012 times
Enzymes have high specificity re. conditions and chemicals catalysed
Some vitamins are co-enzymes
Isoenzymes
Metabolic pathways
1 2 3 4 5
Glucose ------- A ------- B ------- C ------- D ------- X
* Substrate
* Cofactors
* Activators
* Inhibitors
Primary and secondary messenger systems
Primary - an endocrine molecule
Secondary - an intra cellular messenger, eg. Cyclic Adenosine monophosphate (cAMP)
Binding of the primary to a receptor molecule initiates the secondary messenger.
Protein synthesis
The genetic code in the DNA contains all of the instructions for the organism.
This code is transferred to mRNA by the process of transcription using the enzyme transcriptase
The mRNA diffuses out to the ribosomes
mRNA transfers genetic code to tRNA, this polyribonucleotide codes for strings of amino acids by the process of translation.
Amino acids interact to form polymers
Mutation
A mistake in the process of cell division
An abnormality in the structure of a gene or chromosome
Causes of mutation
Cell ageing
* limited number of divisions possible
* mistakes in the division process - mutations
- cancers
Inheritance
Determination of gender
Monozygotic conception
Dizygotic conception
Inheritance may be:
* autosomal
* gametosomal
Cellular differentiation from the zygote
Cell components
cell organelle
cell membrane
nuclear membrane
chromosomes
genes
mitochondria
endoplasmic reticulum
ribosomes
centrosomes
cytoplasm
nucleus
lysosomes
golgi
mitosis
meiosis