Cell Biology
Microscopes
Light wavelength
= 0.5 x 10 -6
Electron wavelength
= 5 x 10 -12
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 Anatomy and physiology
Types of cell
* Eukaryotic,
(compartmentalised cells)
* Prokaryotic
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 may act as gates.
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 synthesised in the ribosomes, ie.
glycoproteins,
a form of
exocytosis
Lysosomes
* Membrane bound vesicles
* Rich in protolytic enzymes such as lysozyme
* Breakdown of cell contents and foreign material
(15% of
synthesised 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"
Chromosomes
* Literally -
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).
Cytosol
* Cell contents
not part of organelles
Cell division
Replication of the genetic material and cell contents
* mitosis -
conservation
* meiosis -
reduction
Growth and repair
Hypertrophy or hyperplaysia
Inheritance
Determination of gender
Monozygotic conception
Dizygotic conception
Inheritance may be:
* autosomal (dominant or recessive)
*
gametosomal (nearly always
recessive)
Cellular differentiation from the zygote
Cell functions
* Form tissues
* Secretory - intracellular matrix
- transmitters, hormones, export
products
* Body growth and
repair
* Carry genetic
instructions
* Energy
production
* Receive
messages
* House enzymic
reactions
* Endocytosis and
exocytosis, eg. phagocytosis and digestive enzymes)
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
Cell composition
Cells are largely composed of macromolecules
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
Primary and secondary messenger systems
Primary - an
endocrine molecule
Secondary - an
intra cellular messenger, eg. Cyclic Adenosine monophosphate (cAMP)
Binding of the primary messenger 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
* reduced capacity for repair
* slower
function/metabolic rates