Biochem Flashcards
Types of proteins
Fibrous and globular
Properties of fibrous proteins
Insoluble in water
Important structural proteins
Types of fibrous proteins (7)
Collagens
Keratin
Fibrin
Elastins
Myosin
Actin
Fibroin
Properties of collagen (2)
25-35% total protein in mammals
Major component of connective tissues
Properties of keratin (2)
Composed of a helix structure
Basic unit of structure is the protofibril
Properties of globular proteins (2)
Roughly spherical in shape
More soluble than fibrous proteins
Types of globular proteins (6)
Enzymes
Peptide hormone
Haemoglobin
Myoglobin
Albumin
Antibodies
What is a conjugated protein?
Contains a protein component associated with a non-protein component
Types of conjugated proteins (4)
Lipoproteins
Glycoproteins
Nucleoproteins
Metalloproteins
Properties of aliphatic amino acids (3)
C atoms in side chain are arranged in chains
Non-polar covalent bonds
Weak hydrophobic
Properties of hydroxy amino acids (3)
OH groups in side chains
Make polar bonds
Hydrophilic
Properties of sulphur-containing amino acids (3)
Aliphatic side chains
Thiol or thioether groups
Hydrophobic
Properties of aromatic amino acids (2)
Side chains contain benzene skeleton
Hydrophobic
Properties of heterocyclic amino acids (3)
Histine
Ring structure is not composed of one atom
Hydrophilic
Properties of basic amino acids (2)
Positively charged at a neutral pH
Hydrophilic
Properties of acidic amino acids (4)
Negatively charged at a neutral pH
Secondary carboxylate acid group
Amide group of CONH2
Hydrophilic
Properties of imino acids (2)
Aliphatic side chain
Hydrophobic
What are amino acids joined by?
Peptide bonds
What are all 20 amino acids used for?
To synthesise proteins
What is primary structure?
The sequence of amino acids of a polypeptide
What are the other levels of protein structure? (4)
Secondary structure
Tertiary structure
Quarternary structure
Process of amino acids polymerised into peptides and polypeptides
Catalysed by peptidyl transferase enzymes
Requires a template
Is a dehydration reaction
Via peptide bonds
When is a peptide bond formed?
When the a-carbonyl group of the first amino acid convalently links the a-amino group of the second amino acid
What is an oligopeptide?
A chain of amino acids residues linked by peptide bonds
What is the primary structure of bovine ribonuclease?
124 amino acids
4 disulphide bonds
Properties of a secondary structure
Certain arrangements that stabilises the protein
3D structure
Included alpha helix and beta pleated sheet
Structure of alpha helix
Cylinder shape
Held together by hydrogen bonds
Turns clockwise
What is an imino acid (proline)?
Helix breaker
Has a side chain which neighbouring residue can join
Properties of a beta pleated sheets
Extended polypeptide chains
Stabilised by hydrogen bonding with amino acids in other strands
Can link different regions with a single polypeptide
May be parallel or anti-parallel
Properties of tertiary structure
3D structure of an entire globular protein in its biologically active shape
Normally stabilised by non-covalent interactions between side chains
Compactly folded regions called domains
Types of dietary lipids (3)
Triglycerides
Chloesterol
Phospholipids
Types of triglycerides (4)
SFAs
Trans FAs
MUFAs
PUFAs
What does cholesterol make? (4)
Bile acids
Vitamin D
Steroid hormones
Cell membranes
What are dietary proteins for?
To build and repair tissue
Growth and development
Building blocks
What does excessive protein do to the body?
Kidney damage
Increased cancer risk
Possible dehydration
Constipation
What can excessive lipid do to the body?
Raised chloesterol
Increased risk of heart disease
What is an acid?
A molecule that acts as a proton donor
What is a base?
A molecule that acts as a proton acceptor
Alpha amino groups
NH2 or NH3+
Alpha carboxyl group
COO- or COOH
Side chains (7)
Asp, glu, lys, arg, his, cys, tyr
What are properties of amino acids that influence 3D structure (3)?
Aromatic stacking
Hydrogen bonding
Binding of metallic cations
What structure will denature an enzyme is disrupted?
Tertiary
What is a mutation?
A change in the DNA sequence of the gene encoding a protein.
How are peptide bonds broken?
Hydrolysis
What are the different types of proteins? (5)
Lipoproteins
Glycoproteins
Phosphoproteins
Hemoproteins
Metalloproteins
Oligomeric proteins
What are lipoproteins?
Proteins with fats attached to them.
What are glycoproteins?
Proteins with sugar attached to them.
What are phosphoproteins?
Proteins with phosphate groups attached to them.
What are hemoproteins?
Proteins with co-factors attached to them.
What are metalloproteins?
Proteins with metal ions attached to them.
What are oligomeric proteins?
Proteins consisting of more than one subunit.
What are the properties of lipids?
They are all insoluble in water and soluble in organic solvents.
What are the functions of lipids? (3)
They are structural components of biological membranes
They are energy reserves (mainly in the form of triacylglycerols)
Serves as vitamins and hormones
Types of lipids (7)
Fatty acids
Triacylglycerols
Phospholipids
Glycolipids
Prostaglandins
Terpenes
Steroids
What is the difference between saturated and unsaturated fatty acids?
Unsaturated have a cis double bonds and saturated have a trans double bond.
How does chain length affect fatty acids?
The longer the fatty acid, the higher the melting point.
How does saturation affect fatty acids?
The more saturated, the higher the melting point.
Why are triacylglycerols important?
They serve as insulation and cushioning from mechanical injury and stored as adipose tissue.
What are triacylglycerols?
3 fatty acids and 1 molecule of glycerol.
Properties of triacylglycerols?
Oxidised by atmospheric oxygen
Hydrolysed by atmospheric water
How is soap made?
Hydrolysis of triacylglycerols.
How do phospholipids help the body?
Important constituents of all biological membranes.
What are phospholipids constructed from?
Fatty acids
Platform to which fatty acids are attached
Phosphate group
Alcohol attached to phosphate group
Why are phospholipids amphipathic?
They have 2 long hydrophobic tails and a hydrophilic head.
How do glycolipids help the body?
They are important components of cell membrane.
Glycolipid structure
Contain one or more sugars
How do protstaglandins help the body?
They act as local hormones.
Roles of prostaglandins (6)
Stimulate inflammation
Stimulate smooth muscle contraction
Regulate blood flow to particular organs
Affect platelet aggregation
Modulate synaptic transmission
Induce sleep
Why are terpenes important?
They are videos occurring in nature and some are pungent.
Structure of terpenes
Same 5 car in building block.
What do steroids have roles in? (5)
Solubilisation of dietary lipids
Preparation and maintenance of pregnancy
Stress response
Sexual characteristics
Regulation of membrane fluidity
Structure of steroids.
6 isoprene units
Tetracycline ring structure
What do living things require a continual I put of free energy for?
Synthesis and maintenance
Performance of mechanical work
Active transport of substances into and out cells
Where is the energy derived from?
Chemotrophs (chemicals)
Phototrophs (light)
Processes that release energy are…
Favoured
Processes that require energy is…
Not favoured
Burning of coal equation.
C + O2 -> CO2 + heat
Production of energy equation.
C6H12O6 + 6O2 -> 6CO2 + 6H2O + free ENERGY
What is substrate level phosphorylation?
Direct transfer of phosphate gp from metabolites to ADP producing ATP.
What is oxidative phosphorylation?
ATP formed indirectly from oxidation of carbon atoms in fuel molecules.
What does the electron transport chain do?
Couples energy release from oxidation to energy requiring H+ pumping across inner membrane into inter membrane space.
What is the immediate source of energy?
Glucose.
What else can be used for energy?
Glycogen
Fats
Proteins
What is the biggest energy storage?
Fats
What is the major site of fat accumulation?
Adipose tissue.
Beta oxidation reaction
Oranges Have an Orangey Taste
1st oxidation
Hydration
2nd oxidation
Thiolysis
What does coenzyme A do?
Pick up, carry and drop metabolites and funnel them into whatever pathways are needed.
Also bind to FAs and break them down aerobically for energy
1st oxidation
Saturated acyl CoA is oxidised to an unsaturated trans-acyl CoA (enoyl CoA) containing a double bonds at its beta-carbon atom.
Hydration
Enoyl CoA double bond is hydrated so saturated hydroxyacyl CoA forms
Catalysed by enoyl CoA hydratase
2nd oxidation
The beta carbon of hydroxylacyl CoAs hydroxyl group is oxydysed by a keto group forming unsaturated 3-Ketoacyl CoA
Thiolysis
Thiol group of a 2nd CoA molecule attacks the c bond of 3-ketoacyl CoA causing cleavage of this bond and liberations a 2-carbon unit binding to CoA and forms acetyl CoA
Catalysed by beta-keto thiolase
Ketogenesis
A different way fat can be broken down in the liver when the balance between carbohydrates and fat metabolism shifts towards fat breakdown.
Formation of ketone bodies.
Ketone bodies diffuse out of the mitochondria and out of the hepatocytes
Enter the circulation and are taken up as a fuel source by non-hepatic tissues.
Protein/amino acid catabolism
Proteins are degraded to amino acids
Amino acids are degraded to amino croups and carbon skeleton
Carbon skeletons can be used catabollically as fuel
Excretion of excess nitrogen
Functions of carbohydrates (3)
Storage of energy
Structural
Specialised roles when modified or complexed with other macromolecules
Types of unmodified carbohydrates (4)
Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides
What are monosaccharides?
Simple sugars
Colourless or white crystalline solids
Water soluble
Open chain and ring structures
What are disaccharides?
2 linked monosaccharides
What are oligosaccharides?
Short chains (less than 20 residues)
What are polysaccharides?
100s or 1000s of units
Properties of aldoses.
Carbonyl at the end of chain = aldehyde
Reducing sugars
Asymmetric chiral centres at C2, C3, C4 and C5
Properties of ketoses.
Carbonyl group at C2 position = ketone
Non-reducing sugar
Asymmetric chiral centres at C3, C4 and C5
What are aldehydes acting as when oxidised?
Reducing agents.
Can ketones be oxidised?
No, only reduced to form alcohols.
Where do we get carbohydrates?
Hydrolysis of starch
Where is a glycosidic bond present?
Between C1 of one sugar and an -OH group at any position on the other sugar.
What reaction is glycosidic bond formation?
A condensation reaction.
Glucose disaccharides (3).
Trehalose
Maltose
Cellobiose
Functions of polysaccharides.
Storage of energy
Structural
2 important polysaccharides.
Glycogen and starch.
Where is glycogen stored?
Skeletal muscle
Liver
What is required for glycogen synthesis?
Glycogen synthase
Primer
Branching enzyme
What is maltodextrin?
A polysaccharides which is a preservative.
What are beta glucans good for?
Lowering cholesterol
Slows passage of food (making u full for longer)
Decreases inflammation
