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4 .3 PRO TEINS
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Elements in protein
Carb on, hyd rog en, oxy gen, nitrog en, sulphur &phosphorus
Basic unit: amino acids
Amino a cids a re joined to ea ch other in a p a rticula rseq uence to f orm poly p ep tide cha in or p rotein
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Forma tion and b rea kdown of
d ipeptides & polypeptides
+
condensation
hydrolysis
Peptide bond
+ H2O
Amino
acid
Amino
aciddipept ide
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+
condensation
hydrolysis
++ 2H2O
Aminoacid
Aminoacid
Aminoacid tripeptide
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condensation
hydrolysisA polypeptide chain
+ 9H2O
* 10 to 100 amino acids
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Protein Structures
Comp lete p rotein molecule is a simp le unb ra nchedcha in of amino a cids
3D protein structure is classified into 4 levels:
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Q ua ternary structure
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keratin silk
Enzymes, hormones, antibodies, haemoglobin
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Essentia l amino a cid s & Non essentia lamino acids
Essential:
Amino acid that required for protein synthesis, butcannot be synthesized in the human body
O btained f rom f ood we eat
Non essential:
Amino acid that is required for protein synthesis andcan be synthesized by humans
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LIPIDS
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LIPIDS
Consist of C,H and O
High hyd rog en to oxy gen ra tio
Non pola r hyd rop hob ic compounds Includ e FATS, O ILS, W AXES, PHO SPHO LIPIDS and
STERO IDS
Fats and oils similar chemically
At room tempera ture, fa ts a re solid a nd oils a reliquid
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Lipids Function
Trig lycerid es (fa ts & oils)
composed of a glycerol plus threefatty acids t rue fa ts
Serve a s a good energ y store
Stored under skin as insulatorTra nsport f at soluble vitamins
Phospholipids:Composed of a digly ceride that
bonded to p hospha te group
Most a bundant lip ids in p lasma
membrane
Control cell p ermeab ility
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Lipids Function
W a x e s Insoluble
Form a waterproof layer of cuticle on:
1 .Ep ider mis of p lants
2 .Exoskele ton of insects3 .Fea thers of b ird4.Fur of mammals
Steroidsa)Cholesterol
b)Sex hormones (testosterone, oestrogen,
progesterone)
c)Bile
Ma kes the p lasma membra ne more rig id& stab le
Control sexual development & body
physiology
Emulsifies fats
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Components of f a ts & oils
2 d if f erent kinds of org a nic molecules tha t join toma ke fa ts & oils a re:
Glycerol
Fatty acid
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Glycerol
Color less, odor less,sweet tasting sy rupyliquid
3 ca rbon and 3hyd roxy l g roup (O H)
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Fa tty acid
O rg anic acid
Molecular structure
Long hyd rocarb on ta ilwith carboxyl (-CO O H) a t one end
Diff erent f a tty acidshave dif f erent
hyd roca rbon tails
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Forma tion & b rea kdown of f a ts & oils
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Saturated fats vs unsaturated fats
Solid state at room tempera ture
Are in the liquid state (oil) at
room temperature
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Differences between saturated and unsaturated fats
Saturated fats Aspects that are different Unsaturated fats
All covalent b onds betweencarbon atoms are single
(C-C)
Type of chemical bond Ex istence of doublecovalent bonds betw een
car bon atom (C= C)Less reactive Reactivity Mor e rea ctive b ecause d ue
to the double bonds
More tig htly p ackedtogether
Packaging of the f atmolecule
Less tig htly p acked due tothe double bonds
Solid (fat) State of matter a t room
temperatureLiquid (oil)
Ma inly f rom animalproducts: red meat, chicken
skin, butter & coconut oil)
Source Mainly from plants:vegeta b le oils, pa lm oil,
corn oil and olive oil
Increase level of bad
cholesterol
Effects on blood cholesterol
level
Increa se levels of good
cholesterol
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