Biochemistry Flashcards
Phosphorylation & De-phosphorylation
Addition/Deletion of a phosphate group [PO4-]
Describe Acylation
Addition of acyl group to compound
Explain carboxylation…
a chemical reaction in which a carboxylic acid group is introduced in a substrate
Describe esterification
2 products come together (alcohol and carboxylic acid) to form an ester
describe a hydrolysis reaction
water is used to break a polymer onto two smaller monomers
name the 5 oxidation states of carbon
alkane > alcohol > aldehyde > Carboxylic acid > CO2
what is the first law of thermodynamics?
Energy is neither created or destroyed
what is the second law of thermodynamics
when energy is convwrted from one form to another, some of it becomes unavailable to do work ( as reactions are not 100% efficient)
What is an exergonic reaction
reactions in which the total free energy of the products is less than the total free energy of the reactants
.: ΔG = -ve
Reaction can occur spontaneously and the energy released can be used to do work
What is an endergonic reaction?
Reactions in which the total free energy of the product(s) is more than the total free energy of the reactant(s)
.: ΔG = +ve
Such reactions cannot occur spontaneously and they need an input of energy to proceed
What is ATP
- 𝑨𝑻𝑷 + 𝑯𝟐𝑶 → 𝑨𝑫𝑷 + 𝑷(𝒊) + 𝑯!
- Many reactions occur in the body by coupling unfavourable reactions (∆𝐺 = +ve) with the above
hydrolysis.
- ATP is thus used as a universal energy currency.
What is catabolism?
breaking down complex molecules into smaller ones and releasing
energy (exergonic – oxidation)
what is anabolism
is synthesizing complex molecules out of smaller ones in energy- consuming reactions (endergonic – reduction)
What is a micelle?
The formation of a micelle is a response to the amphipathic nature of fatty acids, meaning that they contain both hydrophilic regions (polar head groups) as well as hydrophobic regions (the long hydrophobic chain).
What is special about the amino acid GLYCINE?
it has no stereoisomers
Name the 4 sub groups of amino acids…
1) Non-Polar, Hydrophobic Amino Acids
2) Polar, Uncharged Amino Acids
3) Acidic Amino Acids
4) Basic amino acids
What is the direction of a peptide bond?
You have a repeating chain of
- alpha-carbon -> carboxy- carbon -> amino nitrogen
what is a zwitterion?
Amino acids without charged side groups (no net charge)
(will have to PKa values)
What is a Nucleoside
have a 5-carbon sugar + a base
What is a nucleotide
5-carbon sugar + a base + one or more phosphate groups
What is transfer RNA?
tRNA
Transfer RNA become covalently linked to amino acids.
They act as transducter molecules to bring amino acids to growing protein chain (and ribosome)
Name the three types of eukaryotic ploymerase?
- Pol I
- Pol I
- Pol III
How can polymerases be distinguisged?
By their sensitivity to toxins like α-amanitin (which is derived
from a fungus) – inhibits Pol II but doesn’t inhibit Pol I or Pol III
What happens in cells that cannot divide
Still produce gene products via gene expression
Whats is the function of primase?
Synthesizes short RNA sequences that are complementary to a single-stranded piece of DNA, which serves as its template.
Whats is a promoter?
- Is a very specific sequence of nucleotides within the DNA (which act as a binding site for very specific proteins and for RNA Polymerase)
What is a tata box?
Is found in all promoters that are recognised by RNA Pol II. It tells the Pol II where to start transcribing and in which direction.
What needs to happen to mRNA before translation can occur?
- SPLICING
- Processing the ends of the mRNA
What happens during splicing?
he process through which the non-coding regions (introns) of the mRNA are removed, leaving only the coding regions (exons).
What happens during the processing of ends of mRNA?
- Addition of poly(A) tail
- Addition of 5’ cap
What is a polysome?
- a complex of a mRNA molecule and two or more ribosomes that is formed during active translation.
Ribosomes in the cytosol make proteins destined for…..
— Cytosol
— Nucleus
— Mitochondria
Bound ribosomes on the RER make proteins destined for…
— Plasma membrane
— ER
— Golgi apparatus
— Secretion
When does DNA replication occur??
S phase
What is a polymorphism
•Any variation in the human genome that does not cause a disease in its own right. It may however, predispose to a common disease
Unbalanced chromosome rearrangement
Extra or missing chromosomal material. Usually 1 or 3 copies of some of the genome.
What diease is caused by TRISOMY 18
Edward Syndrome
45 X
Turner Syndrome
47 xxy
Klinefelter syndrome
Describe microfilaments
are composed of the protein actin
Describe Intermediate filaments
are composed of six main proteins, which vary in different cell types.
Describe Microtubules
are composed of two tubulin proteins.
What is the perinuclear cisterna
the space separating the inner from the outer nuclear membrane.
Describe type 1 diabetes
Little/no insulin secretion
Defect in Beta cell function
Ketosis develops (if untreated)
Insulin injections for treatment
Symptoms develop rapidly
Describe type 2 diabetes
Insulin secretion may be normal (or exceed normal)
Defect in insulin sensitivity
Ketosis rare
Diet/exercise and oral drugs for treatment
Symptoms develop slowly
Describe the genetics of twins
Monozygotic twins share all their genes
Dizygotic twins share 50% of their genes
Name some models of Non-medelian inheritance patterns
- Epigenetic Modifaction of DNA
- Mitochondrail Inheritance
- Somatic Mosaicism
What is DNA methylation?
- Usually occurs on cytosine bases just before guanine bases
- DNa methylation leads to modification of histones this represses transcription
PREVENTS TRANSCRIPTION
Every cancer methlates genes
List 5 hormones that influence [glucose]p.
- Insulin
- Glucagon
- Adrenaline
- Cortisol
- Growth Hormone
Explain the changes in plasma glucose,
insulin and glucagon concentrations
with time after a meal.
Glucose and Insulin both rise after a meal whilst glucagon levels drop.
Describe the major physiological actions of insulin
INSULIN:
Favours anabolism.
Stimulates conversion
of glucose into glycogen,
fatty acids into triglycerides
and amino acids into protein.
Insulin is the hormone of the fed-state.
Explain how insulin lowers [glucose]p.
- Stimulating the uptake of glucose
from the blood into muscle and fat cells.
- Activating the enzymes in liver
and muscle which convert glucose into glycogen.
- Insulin also promotes the incorporation
of amino acids into protein
in muscle and promotes lipogenesis in - adipose tissue
Explain how diabetes mellitus may be detected
ORAL GLUCOSE TOLERANCE TEST
Know what stimulates glucagon release from pancreatic alpha cells.
STIMULATION:
Decreased blood glucose
Amino acids
Sympathetic nerve activity
Know what inhibits glucagon release from pancreatic alpha cells.
INHIBITION:
Raised blood glucose
Insulin
Explain how glucagon raises [glucose]p.
GLUCAGON RAISES [GLUCOSE]p by:
Increasing liver glycogenolysis.
Inhibiting liver glycogen synthesis.
Promoting liver gluconeogenesis.
also promotes lipolysis in liver and adipose tissue.
Explain the role of growth hormone in providing glucose during prolonged fasting.
Not normally important in control of [glucose]p
BUT in response to starvation,
growth hormone:
Decreases glucose uptake by muscle – “glucose sparing” action
Mobilises glucose from liver
also promotes lipolysis in fat cells
What is the Nucleus tractus solitarius
- is site of 1st synapse for all CVS afferents in the medulla
- relays information to other regions in the brain e.g. medulla, hypothalamus, cerebellum
Generates vagal outflow to heart
What is special about succinate dehydrogenase in the TCA cycle?
It is located in the mitochondrial membrane NOT the matrix!
Control point in gycolysis.
Name 3 enzymes catalysing irreversible reactions.
Hexokinase – substrate entry .
Phosphofructokinase – rate of flow
Pyruvate Kinase – product exit
What is the warburg effect?
Cancer cells produce energy by high rate of glucose metabolism to lactate
What enzyme catalyzes
Glucose-6-phosphate –> Glucose-1-phosphate
Phosphoglucomutase
What is DNA replication catalysed by?
DNA Polymerase
What enzyme unwinds DNA ?
Helicase
What are the 3 ways treating cancer by targeting gycolsis?
- 2-deoxy-glucose block further metabolism of g6p
- 3 bromopyruvate competitive inhibitor
- Di-chloroacetate stops cells from growinng
