Proteins, Polysaccharides and Lipids Flashcards
What is the primary structure of a protein?
Amino Acid chain linked together by peptide bonds
What are the 3 types of secondary protein structures?
-Alpha Helix
-Beta Sheet
-Triple Helix
Describe the alpha helix structure of a secondary protein
Structure?
Where are they found?
What are they stabilised by?
The Co of each amino acid is bonded to what?
How many residues per turn
-Rod like, right handed
- Found in strong, extensible proteins
-Stabilised by Hydrogen Bonds
-CO of each amino acid is H bonded to NH of amino acid four residues ahead in sequence
-3.6 Residues per helix/ turn
Give examples of alpha helix secondary proteins
Haemoglobin, Myoglobin, Keratins, Fibrins, Myosin
Describe the Beta Pleated sheet structure of secondary proteins and where are they found
-Zigzag chains
-Place several chains side by side, CO and NH groups align, H-bonding occurs → sheet-like structure
-Parallel: chains run in same direction
-Anti-parallel: chains run in opposite
directions
-Found in proteins where flexibility needed eg. silk fibroin (anti-parallel arrangement
Describe the triple helix structures of secondary proteins
-Collagen only
-Major component of connective tissue (skin, bone, tendon)
-Very strong, water-insoluble fibres
-Three chains wound round each other (rope) → tropocollagen
-~ 1000 amino acids per chain
-No H bonds in each chain
What repeating structure does each chain have in triple helix secondary proteins?
X- Pro- Gly
OR
X- Hyp- Gly
What repeating structure does each chain have in triple helix secondary proteins?
X- Pro- Gly
OR
X- Hyp- Gly
By what bonds are the three strands in triple helix secondary proteins held together by?
Hydrogen bonds by HYP and Hydroxylysine residues
By what bonds are the three strands in triple helix secondary proteins held together by?
Hydrogen bonds by HYP and Hydroxylysine residues
What sits inside the helix and what projects out of the helix of triple helix secondary proteins?
-Small Gly residues sit inside helix
-BulkyR groups either side of Gly project outwards
How is the triple helix intra and intermolecularly cross linked?
By covalent bonds between Lys and His
Describe fibrous proteins.
Insoluble, Metabolically unreactive
What are fibrous proteins mainly? Give examples.
Structural Proteins;
-collagen
-keratin (skin, hair, nails, fur, wool)
-fibrin (bloot clots)
-elastin (elastic fibres of connective tissue eg. arterial walls)
-myosin (muscle)
Describe globular proteins
Spherical
Backbone folds on itself
Water-soluble, compact structures
Usually have 3º and 4º structures eg. myoglobin and actin (3º), haemoglobin (4º)
What does the interior of myoglobin contain?
Entirely non-polar residues except for two polar His residues (attachment and function of Haem group)
What is myoglobin used for?
Oxygen storage in muscle
What type of protein is myoglobin and what structures is it associated with?
Globular, associated with 3º structures
How Many chains does myoglobin have?
Single chain (153 aa)
How Many chains does myoglobin have?
Single chain (153 aa)
How many helical regions in myoglobin
8 (75% of all aa)
Is there beta pleated sheet regions in myoglobin?
No
How are the helical segments of myoglobin joined?
Regions of random coiling where chain makes major directional change
What group does myoglobin contain and how is it bound/ where is it?
in hydrophobic pocket, held in position by hydrophobic interactions between haem porphyrin ring and non-polar side chains of aa in surrounding helical segments
What happens to myoglobin if harm group is absent
apoprotein, not as tightly folded
Haemoglobin function?
oxygen Transport
What structures is haemoglobin associated with?
Quaternary Structures
How many polypeptide chains are in haemoglobin and what do they look like?
Two pairs of polypeptide chains ( 2 Alpha 2 beta) folded into a similar shape to myoglobin
Shape of haemoglobin molecule?
Spheroidal Molecule
How many ham groups in haemoglobin and where do they lie in the molecule?
Four Haem groups, lie on surface of molecule in individual pockets, far apart
How many amino acids on alpha chains of haemoglobin?
How many amino acids on beta chains of haemoglobin?
- Alpha- 141
- Beta- 146
What is each alpha unit in contact with in haemoglobin?
Both Beta Chains
Describe the structure of each chain and what forms when they are fitted together
α1β1 and α2β2 half-molecules irregular in shape → central open channel when fitted together
What are peripheral membrane proteins located?
Lie on membrane surface
Where are integral membrane proteins located?
Within Lipid Bilayer
What do channel proteins do?
Form a channel in membranes and facilitate movement of small molecules across the membrane (simple diffusion)
What do carrier proteins do?
Bind to transported molecules (facilitated diffusion)
Give an example of messenger proteins
Hormones
What is the function of hormones?
Allows cells to communicate with each other
Give 3 modes of action of hormones
- Influence rate of synthesis of enzymes and other proteins
- Affect rate of enzymatic catalysis
- Alter permeability of cell membranes
What does each hormone have?
Its own corresponding receptor
Describe the action of hormones binding to receptors?
Hormone binds receptor → message relayed to inside of cell → cascade of events → cellular action
Give examples of hormones
Insulin
Glucagon
Human Growth Hormone
What is the function of insulin?
Sugar uptake by cells from bloodstream
What is the function of Glucagon
Sugar release by cells into bloodstream
Hormones can be what?
-Protein/Polypetide
-Amino Acid Derivatives
-Steroid
Describe Enzymes;
What are they?
Protein Type?
Function?
Specificity?
-Biological Catalysts
-Globular Proteins
-Increase reaction rates up to 10^20
-Highly Specific (reaction, substrate)
Give examples of muscular contraction messenger proteins ? and their type
- Myosin- fibrous
- Actin- globular
Give examples of messenger proteins used in immune protection
-Cytokines
-Antibodies
What are the monomers of polysaccharides?
Monosaccharides
What are two functions of polysaccharides?
-Storage
-Structure
Give examples of two storage polysaccharides
Glycogen, Strarch
Give examples of three Structure Polysaccharides
Cellulose, Chondroitin, Sulphate, Peptidoglycan
What are two types of monosaccharides?
-Aldoses
-Ketoses
What are aldoses?
Monosaccharides that contain the aldehyde (CHO) group
What are ketoses?
Monosaccharides that contain the ketone (CO) group
What are monosaccharides?
The building blocks of complex carbohydrates
give a example of a monosaccharide
GLUCOSE
Formation of Disaccharides?
Dehydration reactions of monosaccharide units form complex carbohydrates
Breakdown of Disaccharides?
Hydrolysis reactions of monosaccharide units catabolise complex carbohydrates
What are polysaccharides
Isomers of monosaccharides give rise to a huge variety of polysaccharides
what are the monomers of lipids?
Fatty acids
What are the main types of lipids?
Triglycerides
Diglycerides
Sterols
Give 2 functions of lipids
-Storage
-Membrane Structure
What are glycerides based on
Glycerol
What are
-Glycerides
-Diglycerides
-Triglycerides
made up of
GLYCEROL FATTY ACID
1 1
1 2
1 3
Glyceride structure diagram;
Give an example of a diglyceride and its function
phosphoatidylcholine- a major phospholipid of membranes
What are triglycerides role?
Storage compounds
What are diacylglycerides used for?
Major components of biological membranes
The degree of saturation of fatty acids (acyl lipids) affects what?
-Van der Waals forces
-Changes lipid physical properties
Sterols function?
some have essential biological activity
Others are important constituents of biological membranes
