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Biochemistry > Revision Lecture B30 > Flashcards

Revision Lecture B30 Flashcards

1
Q

What is glycogenolysis

A

Breakdown of glycogen to form glucose

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2
Q

What is gluconeogensis

A

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

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3
Q

When does gluconeogensis occur

A

During starvation

New glucose must be synthesised

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4
Q

What are some precursors used for gluconeogensis

A

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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5
Q

Where does gluconeogensis occur

A

Mainly in the liver

Small in kidney

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6
Q

Where does the energy for gluconeogensis come from

A

Oxidation of fatty acids released form adipose tissue

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7
Q

What is gluconeogensis essentially

A

The reverse of glycolysis

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8
Q

What are the three irreversible reactions involved in glycolysis

A

Hexokinase
Phosphofructokinase
Pyruvate kinase

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9
Q

What are the reactions for bypass 1

A

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

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

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10
Q

What does bypass 1 require in terms of energy

A

1 ATP

1 GTP

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11
Q

Where do the steps of bypass 1 occur and what are the steps catalysed by

A

1) catalysed by pyruvate carboxylase in the mito

2) catalysed by phosphoenolpyruvate carboxykinase in cyto

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12
Q

Is pyruvate –> phosphoenolpyruvate reversible

A

No it is irreversible

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13
Q

What is bypass 2 and 3

A

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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14
Q

How is gluconeogensis energetically expensive

A

Atp hydrolysis drives unfavourable reaction
4 ATP
2 GTP

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15
Q

What is the cori cycle

A

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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16
Q

What does ketogenic mean

A

Ketone bodies or fatty acids

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17
Q

What are some examples of ketogenic amino acids

A 
Isoleucine 
Leucine 
Tryptophan 
Lysine 
Phenylalanine 
Tyrosine
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18
Q

What are glycogenic amino acids

A

Conv to pyruvate of TCA intermediates

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19
Q

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

A

A mixture of both

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20
Q

What are some examples of glycogenic amino acids

A 
Alanine 
Cysteine 
Glycine 
Serine 
Tryptophan 
Asparagine 
Aspartate 
Phenylalanine 
Valine
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21
Q

What effect does glucagon have on phosphofructokinase-1

A

Negative effect

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22
Q

What effect does insulin have on phosphofructokinase -1

A

Positive effect

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23
Q

What does insulin have a negative effect on in glycogenesis reactions

A

Negative effect on fructose -1,6- biphosphate

24
Q

What does glucagon have a positive effect on in glycogenesis reactions

A

Fructose-1,6-biphosphate

25
Q

What enzyme is used to conv glucose to g-6-p

A

Hexokinase

26
Q

What enzyme is used to conv F-6-P to fructose -1,6-biphosphate

A

Phosphofructokinase-1

27
Q

What enzyme is used to conv G-6-P to glucose

A

Glucose - 6 - phosphate

28
Q

What is protein primary structure

A

Linear sequence (order) of amino acid residues, joined by peptide bonds

29
Q

What si the sencondary protein structure

A

Localised conformation of the polypeptide backbone (alpha helix or beta sheets)

30
Q

What si tertiary protein structure

A

The 3D structure of an entire polypeptide, including its side chains

31
Q

What si the quarteneary proetin structure

A

Spatial arrangement of polypeptide chains in a protein with multiple subunits

32
Q

What si a peptide bonds

A

Carboxyl group of one amino acid reacts with the amino group of another
Condensation reaction releasing water
A covalent bond v strong

33
Q

What si the direction of peptides

A

Form the N terminus to the C terminus –> primary structure

34
Q

What are some examples of a protein secondary structure

A

Alpha helix or beta sheets

35
Q

What does the sencondary structure determined by

A

Hydrogen bonds between the carbonyl oxygen group of one peptide and the amide hydrogen of another

36
Q

What is an alpha helix

A

Rod like

One polypeptide chain, tightly coiled, side chains extended out

37
Q

What are beta sheets

A

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)

38
Q

What si phosphoglycerate kinase

A

Enzyme involved in glycolysis

39
Q

What are the two types of tertiary structure

A

Fibrous

Globular

40
Q

Give some examples of fibrous proteins

A

Collagen
Fibroin
Keratin

41
Q

Give some examples of globular proteins

A

Albumin
Myoglobin
Hb

42
Q

What is a globular protein

A

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

43
Q

What are fibrous proteins

A

Polypeptide chains organised approximately parallel

Long fibres, large sheets

Mechanically strong

Insoluble in water and dilute salt solutions

44
Q

What are some forces stabilising tertiary structure

A

Disulphide bonds - Covalent
Hydrogen bonds
Salt bridges - ion pairs
Hydrophobic interactions

45
Q

What determines tertiary structure

A

Interactions between side chain and functional groups

46
Q

What are disulphide bods

A

Covalent bon between two cysteine side chains

Involves oxidation reaction

47
Q

Explain myoglobin structure and purpose

A

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

48
Q

What is myoglobin - haem called

A

APOPROTEIN

49
Q

What are quarteneary protiens

A

Contain more than one polypeptide chains

Dimer - trimer etc

50
Q

What are Quartensry structures held together by

A

Electrostatic interactions
Hydrogen bonds
Hydrophobic interactions

51
Q

Explain the structure and purpose of Hb

A

Strutre - 4 subunits - 2 alpha and 2 beta, each contain haem group and each subunit can bind one oxygen

Purpose - transports oxygen in blood

52
Q

What is positve cooperativity

A

Binding of one oxygen molecule increases the affinity of the other subunits to oxygen

53
Q

What happens in sickle cell anaemia at cellular level

A

In the coding sequnce of the beta subunit of Hb a single nucleotide changed (GAG -> GTG )

54
Q

What happens because of this change in sickle cell anaemia

A

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

55
Q

What are the consequences of sickle cell anaemia

A

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

56
Q

What is glycogenesis

A

Synthesis of glycogen from glucose

Biochemistry (13 decks)

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