biochemistry, study of the chemical substances and processes that occur in plants, animals, and microorganisms and of the changes they undergo during development and life. It deals with the chemistry of life, and as such it draws on the techniques of analytical, organic, and physical chemistry,...
Cell structure
1. T h e cell is th e functional basic unit o f all living organism s
2. Hum ans have = 1 0 14 cells
3. T h e re a re 2 types o f cell ( B o x 5 .1 )
• Prokaryotic
• Eukaryotic
B ox 5.1 Types o f cells
P ro k a ry o tic cells
A re mainly bacteria
■J ' E u k a ry o tic cells
A re mainly protista, fungi, plants, and animals
• ti
Size = 1-10 pm Size = 10-100 pm
D o n ot contain membrane-bound organelles Contain membrane-bound organelles
Lack nucleus Have a nucleus
Nuclear material lies in the cytoplasm C hrom osom e is usually a linear molecule w ith
Chrom osome is usually a circular molecule histone proteins
Gan carry plasmids C ell wall may o r may n o t be present
Most have cell wall (except fo r mycoplasma and Usually contain m itochondria
thermoplasma) Cell division occurs via mitosis o r meiosis
Lack m itochondria
Cell division occurs via binary fission
4- All eu k ary otic cells have
• Plasma m em brane
i. Made o f a phospholipid bilayer
ii. It is sem i-perm eable
iii. Contains re cep to r proteins
, 178 C h a p te rs Biochemistry ___________________ :
• Cytoplasm
i. Provides cellular shape and integrity Microtubules
ii. Contains cytoskeletons (i.e. responsible fo r cytokinesis and and
endocytosis) Microfilaments
iii. Contains organelles
• Nucleus
i. Is spherical
ii. Is th e largest cellular organelle
iii. Surrounded by a nuclear envelope (i.e. a double m em brane)
iv. Contains th e nucleolus (that synthesizes ribosom al RNA) Q
v. Contains genetic material
5. O rg a n elles w ithin an eu k ary otic cell
Endoplasmic reticulum (ER) - th ere are tw o types
i. Sm ooth ER
o
ii. Rough ER (con tains ribosom es on its surface)
Golgi apparatus
M itochondria
o
i. A re th e pow er house o f th e cell double layer memb
ii. Contain genetic material inherited maternally
iii. A re self-replicating organelles
» Lysosom es and peroxisom es
i. A re rich in digestive enzymes
ii. Lysosom es internal pH value is
o
Cell s ig n a llin g (Communication between cells)
1. Signal transd u ctio n
* Is th e p rocess by which an external stimulus to a cell is converted to a specific cellular
response, which includes
. Activation o f genes
i. M etabolic alterations
ii. Proliferation o f th e cell
• Can take milliseconds (for ion influx) to days (for gene
expression)
• Intracellular signal transduction is via second m essengers -------
2. Signalling m olecu les
* Can be classified in to 6 groups
H orm ones
i. G row th factors
ii. Cytokines
iv. Chem okines Chemotactic Cytokines
v. N eurotransm itters
vi. Extracellular matrix com ponents (e.g. fibronectin)
A ct on cellular receptors, which can be divided into tw o classes
i. Cell surface receptors
ii. Intracellular receptors o
T h e re a re 3 types o f extra cellu lar cell signalling
® Endocrine action (via bloodstream )
• Paracrine action (acts locally on neighbouring cells)
• A utocrine action (acts on cell producing th e horm one)
, Cell 179
C ell su rfa ce re cep to r s
1 . T h e r e a re 3 main classes o f cell su rface re c e p to rs
• lon-channel-tinked recep to rs - consist o f 2 types
i. Voltage gated Action potential
ii. Ligand gated
• Enzyme-linked receptors
i. C onsist o f 6 types
ii. A ctivate tyrosine protein kinase
iii. A re receptors for growth factors
• G protein-coupled recep to rs
i. Also known as th e 'seven transm em brane domain recep to rs’ o r serpentine receptors
ii. A ctivate G proteins (guanine nucleotide-binding proteins)
iii. Have 3 subunits ( a , p, y)
iv. Found only in eukaryotes
2. Exam ples o f cell su rface re c e p to r s (Box 5 .2 )
B o x 5.2
lon -ch a nn e t re ce p to rs Enzym e lin k e d re c e p to rs p ro te in -c o u p le d re c e p to rs
3. Exam ples o f G protein -cou p led re c e p to r subclasses (Box 5.3)
A drenergic receptors
1. A d renergic re c e p to rs (Table 5 . 1)
• A re m em bers o f the G protein-coupled recep to r superfamity
• P rom ote glycogenolysis and gluconeogenesis from adipose tissue and liver
• T h ere are 2 adrenergic re c e p to r subgroups: a and P
2. P-antagonists (Box 5.4)
3. P -b lo ck ers w ith intrinsic sy m p ath o m im etic activity (ISA)
• Have agonist and antagonist activity
• Include
i. O xprenolol
ii. Pindolol
4- a-an tag on ists
• Used in
i. Benign prostatic hypertrophy (BPH)
ii. Hypertension
• a,-antagonists include
i. Tamsulosin
ii. Prazosin
iii. Phentolamine
iv. Doxazosin Q
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