Proteins, Polysaccharides and Lipids Flashcards by Heather McAinsh

What is the primary structure of a protein?

Amino Acid chain linked together by peptide bonds

How well did you know this?

Not at all

Perfectly

What are the 3 types of secondary protein structures?

-Alpha Helix
-Beta Sheet
-Triple Helix

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

Give examples of alpha helix secondary proteins

Haemoglobin, Myoglobin, Keratins, Fibrins, Myosin

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

What repeating structure does each chain have in triple helix secondary proteins?

X- Pro- Gly

X- Hyp- Gly

How well did you know this?

Not at all

Perfectly

What repeating structure does each chain have in triple helix secondary proteins?

X- Pro- Gly

X- Hyp- Gly

How well did you know this?

Not at all

Perfectly

By what bonds are the three strands in triple helix secondary proteins held together by?

Hydrogen bonds by HYP and Hydroxylysine residues

How well did you know this?

Not at all

Perfectly

By what bonds are the three strands in triple helix secondary proteins held together by?

Hydrogen bonds by HYP and Hydroxylysine residues

How well did you know this?

Not at all

Perfectly

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 well did you know this?

Not at all

Perfectly

How is the triple helix intra and intermolecularly cross linked?

By covalent bonds between Lys and His

How well did you know this?

Not at all

Perfectly

Describe fibrous proteins.

Insoluble, Metabolically unreactive

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

What does the interior of myoglobin contain?

Entirely non-polar residues except for two polar His residues (attachment and function of Haem group)

How well did you know this?

Not at all

Perfectly

What is myoglobin used for?

Oxygen storage in muscle

How well did you know this?

Not at all

Perfectly

What type of protein is myoglobin and what structures is it associated with?

Globular, associated with 3º structures

How well did you know this?

Not at all

Perfectly

How Many chains does myoglobin have?

Single chain (153 aa)

How well did you know this?

Not at all

Perfectly

How Many chains does myoglobin have?

Single chain (153 aa)

How well did you know this?

Not at all

Perfectly

How many helical regions in myoglobin

8 (75% of all aa)

How well did you know this?

Not at all

Perfectly

Is there beta pleated sheet regions in myoglobin?

How well did you know this?

Not at all

Perfectly

How are the helical segments of myoglobin joined?

Regions of random coiling where chain makes major directional change

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

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

1. Influence rate of synthesis of enzymes and other proteins 2. Affect rate of enzymatic catalysis 3. 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