Chapter 2 Flashcards
Molecular biology
Carbon
- forms basis of organic life due to its ability to form large and complex molecules via covalent bonding
- can form 4 covalent bonds w/ other carbon atoms or atoms of other elements
4 types of macromolecules
Carbon-based compounds found in living organisms
- lipids
- carbohydrates
- nucleic acids
- proteins
Macromolecules
Organic compounds that living organisms are made of
- build living cells
- take part in numerous biochemical reactions
- made up of smaller monomers, form larger structures called polymers
Carbohydrates
- contains carbon, hydrogen and oxygen atoms
- ratio of hydrogen to oxygen is 2:1
Function:
- source of energy
- also a short-term energy storage option
- important as a recognition molecule and as a structural component (part of RNA/DNA)
Lipids
- non-polar, hydrophobic molecule that come in a variety of forms
- are a major component of cell membranes (phospholipids and cholesterol)
- contains carbon, hydrogen and oxygen atoms
- phospholipids also contain phosphorus
Function:
- a long-term energy storage
- as a signalling molecule (steroids)
Nucleic acids
- contains carbon, hydrogen, nitrogen and oxygen atoms
- genetic material of all cells and determines the. inherited features of an organism
- consist of nucleotides, arranged in long chains
Proteins
- contains carbon, hydrogen, nitrogen and oxygen atoms (some may contain sulphur)
- consist of amino acids, arranged in long chains
Functions: - major regulatory molecules involved in catalysis (all enzymes are proteins)
- may also function as structural molecules or play a role in cellular signalling (transduction pathways)
Common carbohydrates and their functions
- Alpha-D glucose- used in production of ATP in cells
- Beta-D glucose- used to build cell walls in plants
- Starch- used as long-term storage in plants
- Ribose- used as a component of DNA and RNA
Common lipids and their functions
- Triglycerides- used as long-term storage in adipose tissue in animals
- Steroids- used as chemical messengers in the body, have a distinctive ring shape
- Phospholipids- major component of plasma membranes
Common proteins and their functions
- Structural proteins- proteins eg. keratin and collagen form structural framework of many parts of the body
- Enzymes- metabolic proteins that speed up chemical reactions in the body
- Polypeptides- a sequence of AA that may make up a protein, or a series of polypeptides can also make up a protein
Common nucleic acids and their functions
- DNA- used to store genetic information
2. RNA- used to create proteins at ribosomes using information stored in DNA
Monomers
Small recurring subunits that make up complex macromolecules
- monomeric subunits join together to form larger polymers
NB/ lipids don’t contain recurring monomers, but, certain types may be composed of distinct subunits
Functional groups of monomers
Amino acid:
- functional group -COOH (carboxyl group)
- functional group -NH2 (amine group)
Fatty acid:
- functional group -COOH attached to a long hydrocarbon chain
Sugar:
- when hydrogen: oxygen ratio is 2:1
- ribose = 5 carbons
- glucose = 6 carbons
Metabolism
web of all enzymatic reactions in a cell or organism
Metabolism = anabolism + catabolism
Anabolism
synthesis of complex molecules from simpler molecules, requires input of energy
- includes formation of macromolecules from monomers by condensation reactions
Catabolism
breakdown of complex molecules into simpler molecules- energy is released
- eg. hydrolysis of macromolecules into monomers
- eg. glycolysis, breakdown of fats to release energy
Hydrolysis reaction
breaking of chemical bonds by addition of water molecules
Condensation reaction
Reaction in which 2 smaller organic molecules combine to form a larger molecule w/ accompanied formation of water or some other simple molecule
Urea
- organic compound; formula- CO(NH2)2
- used by human body to excrete nitrogen as urea is non-toxic and highly soluble
- also widely used as a nitrogen fertiliser- this has led to its artificial synthesis on a large scale
Artificial synthesis of urea
- it was artificially synthesised accidentally by Wohler
- he demonstrated that a by-product of life could be artificially synthesised in a lab
- his experiment was the first to show that synthesis of an organic compound from 2 inorganic molecules was achievable
- later, he provided evidence that contradicted the theory of vitalism
Theory of vitalism
Organic compounds could only be synthesised by living organisms as they possessed an ‘element’ that non-living things didn’t have
- element has been referred to as divine principle
- hence, artificial synthesis of urea from inorganic chemicals in lab helped to falsify it
Water
- consists of 2 hydrogen atoms and 1 oxygen atom
- O is more electronegative than H atoms; O has greater pull on electron cloud between the atoms
- hence, O acquires slightly negative charge, leaving each H atom w/ slightly +ve charge
Water molecules
- polar due to their partial +ve and -ve charges
- allows formation of hydrogen bonds between water molecules
- partial +ve H atoms of one molecule are attracted to partial -ve O atoms of other water molecules
Hydrophilic compounds
Polarity of water molecules allows them to attract other polar/charged compounds and form hydrogen bonds w/ them
- this will cause polar compounds to dissolve in water
- such compounds are hydrophilic
eg. sugars and salts