Revision Lecture B30 Flashcards by Charlotte Smith

What is glycogenolysis

Breakdown of glycogen to form glucose

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What is gluconeogensis

Synthesis of glucose int he body form non carb precursors such as amino acids, lactic acid and glycerol

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When does gluconeogensis occur

During starvation

New glucose must be synthesised

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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

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Where does gluconeogensis occur

Mainly in the liver

Small in kidney

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Where does the energy for gluconeogensis come from

Oxidation of fatty acids released form adipose tissue

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What is gluconeogensis essentially

The reverse of glycolysis

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What are the three irreversible reactions involved in glycolysis

Hexokinase
Phosphofructokinase
Pyruvate kinase

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What are the reactions for bypass 1

1 - pyruvate + co2 + ATP + h2o –> oxaloacetate + ADP + Pi + 2h+

2- oxaloacetate + GTP –> phosphoenolpyruvate + GDP + co2

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What does bypass 1 require in terms of energy

1 ATP

1 GTP

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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

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Is pyruvate –> phosphoenolpyruvate reversible

No it is irreversible

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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)

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How is gluconeogensis energetically expensive

Atp hydrolysis drives unfavourable reaction
4 ATP
2 GTP

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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

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What does ketogenic mean

Ketone bodies or fatty acids

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What are some examples of ketogenic amino acids

Isoleucine 
Leucine 
Tryptophan 
Lysine 
Phenylalanine 
Tyrosine

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What are glycogenic amino acids

Conv to pyruvate of TCA intermediates

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If an amino acid is not ketogenic or glycogenic wht else can they be

A mixture of both

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What are some examples of glycogenic amino acids

Alanine 
Cysteine 
Glycine 
Serine 
Tryptophan 
Asparagine 
Aspartate 
Phenylalanine 
Valine

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What effect does glucagon have on phosphofructokinase-1

Negative effect

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What effect does insulin have on phosphofructokinase -1

Positive effect

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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