Revision Lecture B30 Flashcards
What is glycogenolysis
Breakdown of glycogen to form glucose
What is gluconeogensis
Synthesis of glucose int he body form non carb precursors such as amino acids, lactic acid and glycerol
When does gluconeogensis occur
During starvation
New glucose must be synthesised
What are some precursors used for gluconeogensis
Lactate - syn by skeletal muscles in anaerobic conds
Glycogenic amino acids - derived form mucle protein by Proteolysis
Glycerol - derived form TAGs by lipolysis in adipose tissue
Where does gluconeogensis occur
Mainly in the liver
Small in kidney
Where does the energy for gluconeogensis come from
Oxidation of fatty acids released form adipose tissue
What is gluconeogensis essentially
The reverse of glycolysis
What are the three irreversible reactions involved in glycolysis
Hexokinase
Phosphofructokinase
Pyruvate kinase
What are the reactions for bypass 1
1 - pyruvate + co2 + ATP + h2o –> oxaloacetate + ADP + Pi + 2h+
2- oxaloacetate + GTP –> phosphoenolpyruvate + GDP + co2
What does bypass 1 require in terms of energy
1 ATP
1 GTP
Where do the steps of bypass 1 occur and what are the steps catalysed by
1) catalysed by pyruvate carboxylase in the mito
2) catalysed by phosphoenolpyruvate carboxykinase in cyto
Is pyruvate –> phosphoenolpyruvate reversible
No it is irreversible
What is bypass 2 and 3
2) fructose - 1,6 - biphosphate + water –> fructose - 6 - phosphate + Pi
This occurs in the cytoplasm and is irreversible
3) glucose - 6 - phosphate + water –> GLUCOSE + Pi
This occurs in the endoplasmic reticulum
In (liver and kidney)
How is gluconeogensis energetically expensive
Atp hydrolysis drives unfavourable reaction
4 ATP
2 GTP
What is the cori cycle
Lactate - precursor for gluconeogensis
Lactate prod in muscles anaerobic glycolysis
In blood to liver
Liver converts lactate to pyruvate then back to glucose via gluconeogensis
This I then recirculated as glucose which relieves statin on muscle to pro energy onto other organs
What does ketogenic mean
Ketone bodies or fatty acids
What are some examples of ketogenic amino acids
Isoleucine Leucine Tryptophan Lysine Phenylalanine Tyrosine
What are glycogenic amino acids
Conv to pyruvate of TCA intermediates
If an amino acid is not ketogenic or glycogenic wht else can they be
A mixture of both
What are some examples of glycogenic amino acids
Alanine Cysteine Glycine Serine Tryptophan Asparagine Aspartate Phenylalanine Valine
What effect does glucagon have on phosphofructokinase-1
Negative effect
What effect does insulin have on phosphofructokinase -1
Positive effect
What does insulin have a negative effect on in glycogenesis reactions
Negative effect on fructose -1,6- biphosphate
What does glucagon have a positive effect on in glycogenesis reactions
Fructose-1,6-biphosphate
What enzyme is used to conv glucose to g-6-p
Hexokinase
What enzyme is used to conv F-6-P to fructose -1,6-biphosphate
Phosphofructokinase-1
What enzyme is used to conv G-6-P to glucose
Glucose - 6 - phosphate
What is protein primary structure
Linear sequence (order) of amino acid residues, joined by peptide bonds
What si the sencondary protein structure
Localised conformation of the polypeptide backbone (alpha helix or beta sheets)
What si tertiary protein structure
The 3D structure of an entire polypeptide, including its side chains
What si the quarteneary proetin structure
Spatial arrangement of polypeptide chains in a protein with multiple subunits
What si a peptide bonds
Carboxyl group of one amino acid reacts with the amino group of another
Condensation reaction releasing water
A covalent bond v strong
What si the direction of peptides
Form the N terminus to the C terminus –> primary structure
What are some examples of a protein secondary structure
Alpha helix or beta sheets
What does the sencondary structure determined by
Hydrogen bonds between the carbonyl oxygen group of one peptide and the amide hydrogen of another
What is an alpha helix
Rod like
One polypeptide chain, tightly coiled, side chains extended out
What are beta sheets
Polypeptide backbone almost completely extended
Hydrogen bonds between polypeptide chains
Can involve more than one polypeptide
May be parallel or antiparallel
Turns between strands ( glycine and proline)
What si phosphoglycerate kinase
Enzyme involved in glycolysis
What are the two types of tertiary structure
Fibrous
Globular
Give some examples of fibrous proteins
Collagen
Fibroin
Keratin
Give some examples of globular proteins
Albumin
Myoglobin
Hb
What is a globular protein
Proteins which are folded to a more soherical shape
Sol in water and salt solution
Polar side chains on the outside and non polar inside
What are fibrous proteins
Polypeptide chains organised approximately parallel
Long fibres, large sheets
Mechanically strong
Insoluble in water and dilute salt solutions
What are some forces stabilising tertiary structure
Disulphide bonds - Covalent
Hydrogen bonds
Salt bridges - ion pairs
Hydrophobic interactions
What determines tertiary structure
Interactions between side chain and functional groups
What are disulphide bods
Covalent bon between two cysteine side chains
Involves oxidation reaction
Explain myoglobin structure and purpose
Structure - globular protien, 8 alpha helical regions, has haem group (iron prosthetic group)
Purpose - haem group = iron and protoporphyrin
- binds one oxygen molecule per molecule of myoglobin
N. - stores oxygen in muscle
What is myoglobin - haem called
APOPROTEIN
What are quarteneary protiens
Contain more than one polypeptide chains
Dimer - trimer etc
What are Quartensry structures held together by
Electrostatic interactions
Hydrogen bonds
Hydrophobic interactions
Explain the structure and purpose of Hb
Strutre - 4 subunits - 2 alpha and 2 beta, each contain haem group and each subunit can bind one oxygen
Purpose - transports oxygen in blood
What is positve cooperativity
Binding of one oxygen molecule increases the affinity of the other subunits to oxygen
What happens in sickle cell anaemia at cellular level
In the coding sequnce of the beta subunit of Hb a single nucleotide changed (GAG -> GTG )
What happens because of this change in sickle cell anaemia
During translation a glutamate residue to be substituted by a valine
Glutamic acid is negatively charged and can form bonds with water and ions
However valine is hydrophobic and interacts with other hydrophobic amino acid
What are the consequences of sickle cell anaemia
The Hb behaves normally until exposed to low oxygen tensions where it forms large fibrous aggregated districting erythrocyte to sickle shape
This alters the flow properties of the cells whic may block blood flow in vessels and capillaries
Red cells are fragile leading to haemolysis and aneamia
What is glycogenesis
Synthesis of glycogen from glucose
