WEEK 3 (chapter 2) Flashcards
What is distinguishable about carbon atoms?
They readily form bonds with each other and other atoms
What are the different carbon-containing backbones?
Linear
Branched
Cyclic
Define ‘Functional groups’
Particular groupings of atoms that often behave as a unit and give organic molecules their physical properties, chemical reactivity and solubility in aqueous solution
What are the different classes of biological molecules?
Macromolecules
Building blocks of macromolecules
Metabolic Intermediates (metabolites)
Molecules of miscellaneous function
What are the four major categories of macromolecules and how are they constructed?
Proteins, Nucleic acids, Polysaccharides and certain lipids.
Macromolecules are constructed from monomers by a process of polymerisation.
Describe the process of construction of a macromolecule
Each monomer is first activated by attachment to a carrier molecule that helps the monomer to chemically react with the end of the growing macromolecule. It is attached through polymerisation (a condensation reaction).
Describe the disassembling of a macromolecule
A macromolecule is disassembled by hydrolysis of the bonds that join the monomer together which is catalysed by specific enzymes
What are the building blocks of the different macromolecules?
Sugars = Polysaccharides
Fatty acids = Fats/lipids/membranes
Amino acids = Proteins
Nucleotides = Nucleic acids
What are ‘metabolic intermediates’?
Compounds formed along the pathways leading to the end products which have no function
What is the purpose of molecules with miscellaneous function?
They are materials to proteins
examples include: vitamins, steroid or amino acid hormones, ATP (energy storage), cyclic AMP (regulatory molecules) and urea (waste products)
What is cyclic AMP?
The second messenger that goes on to activate a cascade of enzymes that allow the mobilisation of glucose from glycogen
What are the properties of carbohydrates?
- Function primarily as stores of chemical energy and as durable building materials for biological construction
- General formula (CH2O)n
- Sugars of importance have values of n that range from 3 to 7
What bonds join sugars together?
Glycosidic bonds
Describe the mechanism of a glycosidic bond
Glycosidic bonds form between carbon atom C1 of one sugar and the hydroxyl group of another sugar, generating a -C-O-C- linkage between the two sugars
What forms when polysaccharide chains covalently bond to lipids and proteins?
Glycolipids and Glycoproteins
___________ are particularly important on the glycolipids and glycoproteins of the plasma membrane, where they project from the cell surface
Oligosaccharides
What were the findings of Claude Bernard?
Bernard found that glucose enters the blood from the liver; liver tissues contain an insoluble polymer of glucose he named “Glycogen”. He concluded that food is carried to the liver where they are chemically converted to glucose and stored as glycogen.
Define ‘Polysaccharide’
A polymer of sugar units joined by glycosidic bonds
What are the common properties of Lipids?
- Non-polar
- Ability to dissolve in organic solvents (e.g chloroform or benzene)
- Inability to dissolve in water
What is the structure of lipids?
The Glycerol moiety is linked by three ester bonds to the carboxyl groups of three fatty acids
What differentiates fat cells from carbohydrates?
- Fats are rich in chemical energy (contains twice the energy content as carbohydrates)
- Fat reserves store energy on a long-term basis whereas carbohydrates function as a short-term, rapidly available energy source
What are the properties of fats?
- Extremely insoluble in water
- Lack polar groups
- Stored in cells in the form of dry lipid droplets
- Stored in adipocytes whose cytoplasm is filled with one or a few large lipid droplets
fact: Adipocytes exhibit a remarkable ability to change their volume to accommodate varying quantities of fat
What is cholesterol?
A component of animal cell membranes and a precursor for the synthesis of a number of steroid hormones such as testosterone, progesterone and oestrogen
Describe the structure of steroids
Steroids are built around a characteristic four-ringed hydrocarbon skeleton
Describe the structure of Phospholipid phosphatidylcholine “Phospholipids”
- Consists of a glycerol backbone whose hydroxyl groups are covalently bonded to two fatty acids and a phosphate group.
- Negatively charged phosphate is bonded to a small, positively charge choline group
- Phosphorylcholine end hydrophilic whereas the fatty acid tail is hydrophobic
What are the different classes of protein and their function?
- Structural - provide structural components (e.g collagen and keratin)
- Contractile - movement of muscle (e.g myosin and actin)
- Transport - carry essential substances (e.g haemoglobin)
- Storage - store nutrients (e.g ferritin)
- Hormone - regulate body metabolism and nervous system (e.g insulin)
- Enzyme - catalyse biochemical reactions in the cells (e.g sucrase)
- Protection - recognise and destroy foreign substances (e.g immunoglobulins)
Describe the structure of amino acids and how a polypeptide is formed
Contain a carboxyl group, an amino group and a variable (R) group around a central carbon atom
Amino acids that make up a polypeptide chain are joined by peptide bonds that result from the linkage of the carboxyl group of one amino acid and to the amino group of its neighbour with the elimination of a water molecule (condensation)
How many different amino acids are there?
20
What are the classes of amino acids?
Essential amino acids
Nonessential amino acids
Conditional amino acids
What is the difference between nonessential and essential amino acids?
Essential amino acids cannot be synthesised by the human body so must be obtained by diet; Nonessential amino acids can be synthesised by the human body
What is Phenylketonuria (PKU)?
PKU is an inherited metabolic disease where the body cannot change Phenylalanine (an essential amino acid) into Tyrosine (another needed amino acid) since phenylalanine hydroxylase (PAH) cannot be formed. It is caused by a mutated PAH (Phenylalanine hydroxylase) gene on the long (q) arm of chromosome 12.
What are the symptoms of PKU?
- Light hair, eyes and skin
- Eczema-like rash
- Seizures
- Hyperactivity
- Unpleasant odour
- Mental retardation
- Phenylketones in urine
How is PKU diagnosed and how is it treated?
Main diagnostic is newborn screening
Treatment:
- Limited intake of protein their whole lives
- Special diet starting a few days after birth
- Babies must drink a special formula without phenylalanine
What are nucleic acids?
macromolecules constructed from nucleotides. There are two types, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Describe the structure of a nucleic acid
- a five-carbon sugar (deoxyribose/ribose)
- a nitrogenous base
- a phosphate group
What is the difference between the structures of DNA and RNA?
RNA nucleotides contain ribose (pentose sugar) which has a hydroxyl group bonded to the second carbon atom. DNA nucleotides contain deoxyribose which has a hydrogen atom attached to the second carbon atom.
What are the different nitrogenous bases of RNA and DNA?
- Guanine (Purine)
- Adenine (Purine)
- Cytosine (Pyrimidines)
- Thymine (Pyimidines)
- Uracil (Pyrimidines)
What is the difference between Pyrimidines and Purines?
Pyrimidines are smaller molecules consisting of a single ring and purines are larger consisting of two rings
RNA strands are single stranded whereas DNA strands are ______________ with _____________ base pairing
Double stranded
Complementary base pairing
In DNA, Uracil is replaced by _____________
Thymine
Despite the single-stranded structure of RNA, they often fold back on themselves to produce molecules with extensive __________ segments and complex _____________ structures
Double-stranded
Three-dimensional
What are Ribosomal RNAs?
Structural scaffolds where proteins of the ribosome can be attached and serve as elements that recognise and bind various soluble components required for protein synthesis.
One of the ribosomal RNAs of the large subunit acts as a catalyst for the reaction by which amino acids are covalently joined during protein synthesis (RNA catalysts are called RNA enzymes or ribozymes)
What are the different types of RNA and their functions?
mRNA (messenger) - translation (protein synthesis)
rRNA (ribosomal) - translation [CATALYTIC]
tRNA (transfer) - translation
hnRNA (heterogenous nuclear) - precursors & intermediates of mature mRNAs & other RNAs
scRNA (small cytoplasmic) - signal recognition particle & tRNA processing [CATALYTIC]
snRNA (small nuclear) - mRNA processing [CATALYTIC]
snoRNA (small nucleolar) - rRNA processing/maturation/methylation
regulatory RNAs (e.g siRNA and miRNA) - regulation of transcription and translation
Describe the structure of Adenosine Triphosphate (ATP)
- Adenine (nitrogenous base)
- Ribose
- Three terminal phosphate groups
Give two examples of important nucleotides, apart from nucleic acids, and their functions
- Adenosine Triphosphate (ATP) is where most of the cell’s energy is derived from
- Guanosine Triphosphate (GTP) binds to proteins (called G proteins) and activates them to do their activities
What is stated in Bernard’s hypothesis?
The balance between glycogen formation and glycogen breakdown in the liver was the prime determinant in maintaining the relatively homeostatic level of glucose in the blood
Why are there 20 different amino acids?
There are 20 different radicals
What is a free radical?
A naturally or artificially occurring substance that causes diseases if left unchecked
What is the most abundant RNA in the cell?
rRNA
Which amino acid is not a component of RNA?
Thymine
What is the composition of a nucleoside?
Base + Sugar
How many hydrogen bonds are between Adenine and Thymine?
2
__________ leads to the disruption of nucleosomal structure
Methylation
