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Histology and cells
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Cells, tissues and histology introduction
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HISTOLOGY:The Cell:
Smallest unit of life and a basic building block of life.
- 38 trillion cells make up the human (estimation)
- Over 200 different cell types which make up our organs
- From this we have developed drugs due to identifying diseases which affect cells
- Counting number of cells can also see if someone has an infection (e.g. checking
White blood cell count in specimen)
The cell is an extremely complex mechanism due to processes and reactions
Things are broken down and rebuilt all the time.
- Acts like a machine sends signals and proteins which
can impact other cells too.
Organelles:
- Is a specialised subunit within a cell which has a specific
Function
- Job is unique to them
- They are wrapped up in a lipid bilayer which is very fluid
and controls what occurs within the organelle.
THE NUCLEUS:
The nucleus contains the blueprint for all cell activity as
CHROMATIN
Chromatin is DNA complex which winds around proteins called
HISTONES.
Histone can give the protein a UNIQUE SHAPE making the DNA
have a different function.
The winding shape can activate and deactivate the genes in the DNA
- Switch on and off parts of genetic sequence (called EPIGENETICS)
GENE TRANSCRIPTION Converting DNA to RNA.
2 types of chromatin (darker and paler) – Euchromatin and
Heterochromatin
Nucleus has a double membrane NUCLEAR membrane
Membrane has small holes called the NUCLEAR ENVELOPE which allows movement of
molecules in and out of the nucleus. – they control the movement
Nuclear import sequence: process of entering the nucleus
Nuclear export sequence: process of getting out of nucleus
THE NUCLEAR ENVELOPE
Made up of two lipid bilayer membranes
, The inner membrane is lined with a network of fibrous proteins which form a structure
called the nuclear LAMINA.
Outer external membrane is surrounded by continuous rough endoplasmic reticulum.
Electron light stuff Euchromatin lightly packed. Active so can be transcribed and turned
into genetic sequences (genes)
Electron dark stuff Heterochromatin tightly packed. Inactive sequences because they are
wrapped extremely tightly so are inactive when it comes to transcription and replication.
Nuclear Laminar (INNER MEMBRANE of nucleus)
THE NUCLEOLUS:
Round body found inside of the nucleus of a eukaryotic cell.
Makes ribosomal RNA (produces ribosomes)
Nucleolus is made of proteins, DNA and RNA
- Assembly of ribosomes important for converting DNA TO RNA which gets
converted into proteins.
Transported out via nuclear pores
- Important role in cell response to stress manufactures things the cell needs
THE NUCLEUS AND DISEASE:
Inner nuclear membrane (nuclear lamina) may be defective due to
being misfolded.
Disease is inherited called Laminopathies.
e.g. Hutchinson Gilford progeria (premature ageing)
- lamina is defective and mis-shaped.
First year – normal as cells divide normally by mitosis
Over time nuclear lamina weakens meaning it limits the ability to divide.
THE ENDOPLASMIC
RETICULUM AND
GOLGI APPARATUS:
RER: covered in ribosomes
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