2.1 Molecules to metabolism Flashcards
Organic compounds
- Living organisms contain a vast range of chemical substances, the majority of which are carbon-containing compounds such as glucose, fats and proteins.
- These are collectively known as organic compounds.
- However, it is worth noting that there are a few carbon compounds that are not considered to be organic, such as carbon dioxide, carbon monoxide, carbonates and hydrogen carbonates.
Carbon
- Carbon is an element. It has the atomic number 6, which means that it has 4 electrons in its outer shell.
- These can form four covalent bonds with other carbon atoms or atoms of other elements.
- This allows a diversity of stable carbon compounds to exist.
Structure of methane
Methane consists of a single carbon atom and four hydrogen atoms.
Diagram of carbon atom in a methane molecule
Diagram showing carbon chain and ring structures (Carbon is able to react with many other atoms and form stable arrangements)
Examples of carbon-based compounds found in living organisms
- lipids
- carbohydrates
- nucleic acids
- proteins.
Carbon can form a diversity of stable compounds due to ___
Its ability to form covalent bonds with atoms of carbon or other elements.
Living organisms are made of organic compounds called ___
Macromolecules
What are the four types of macromolecules?
- carbohydrates
- lipids
- proteins
- nucleic acids
- All of them contain carbon, hydrogen and oxygen atoms. Other elements are also present. Nitrogen appears in proteins and nucleic acids, phosphorus in some lipids (phospholipids).
Function of macromolecules
They build living cells and take part in numerous biochemical reactions.
What elements are carbohydrates composed of?
- Carbon
- Hydrogen
- Oxygen
What is the ratio of hydrogen to oxygen in carbohydrates?
2:1
Lipids are a very diverse group of ___
Organic compounds.
Examples of lipids
- Steroids (e.g. cholesterol)
- Waxes
- Phospholipids
- Triglyceries
Proteins consist of ___
Amino acids that re arranged in long chains.
Nucleic acids are chains just like proteins, but formed by ___
Nucleotides
What are macromolecules made up of?
- Smaller monomers
- Monomers join together to form larger structures called polymers
Examples of carbohydrates
- Alpha-D-glucose
- Beta-D-glucose
- Starch
- Ribose
Function of Alpha-D-glucose
Used in the production of ATP in cells.
Function of Beta-D-glucose
Used to build cell walls in plants.
Function of starch
Used as long-term storage in plants.
Function of ribose
Used as a component of DNA and RNA.
Examples of lipids
- Triglycerides
- Steroids
- Phospholipids
Function of triglycerides
Used as long-term storage in adipose tissue in animals.
Function of steroids
Used as chemical messengers in the body, have a distinctive ring shape.
Function of phospholipids
Major component of plasma membranes.
Examples of proteins
- Structural proteins
- Enzymes
- Polypeptides
Function of structural proteins
Proteins such as keratin and collagen form the structural framework of many parts of the body.
Function of enzymes
Metabolic proteins that speed up chemical reactions in the body.
Function of polypeptides
A sequence of amino acids that may make up a protein, or a series of polypeptides can also make up a protein.
Examples of nucleic acids
- DNA
- RNA
Function of DNA
Used to store genetic information.
Function of RNA
Used to create proteins at ribosomes using the information stored in DNA.
Structure of Alpha-D-glucose
Structure of Beta-D-glucose
Structure of amino acid
Diagram showing the structure of fatty acid
.
Structure of ribose
How to tell if a monomer is an amino acid or a fatty acid
Check the functional groups:
- Presence of -COOH, also called a carboxyl group and -NH2, also called an amine group, implies the monomer is an amino acid.
- Presence of -COOH attached to a long hydrocarbon chain implies the monomer is a fatty acid.
How to draw a carbohydrate
- When you have to draw a carbohydrate, such as alpha-D-glucose, start by drawing a hexagon with the oxygen atom at the top.
- Then there should be 5 carbon atoms clockwise, where the last C atom (number 6) is a CH2OH group attached to carbon atom number 5.
- Then, draw the -OH groups in their correct positions.
- The difference between alpha and beta-D-glucose is that in beta-D-glucose the hydroxyl group is above the plane of the ring.
- You may draw a saturated fatty acid simply as CH3(CH2)16COOH. Keep the total number of carbon atoms in the molecule between 8 and 12.
How can starch be detected?
- Using iodine solution.
- It turns blue-black in presence of starch in food.
How can protein be detected?
- Using a Biuret test
- The liquid in the Biuret turns a purple colour if protein is detected
How can some carbohydrates, such a glucose, fructose, and maltose be detected?
- Using Benedict’s solution
- They are called reducing sugars.
- Benedict’s solution gradually changes from blue to orange or brick red when heated with a reducing sugar.
What type of molecule is this? CH3(CH2)xCOOH
- Fatty acid
- The presence of the functional group -COOH attached to the hydrocarbon chain confirms that it is a fatty acid.
Metabolism
Metabolism is all of the enzymatic reactions that take place inside a living organism.
Anabolism
- Anabolism is the synthesis of complex molecules from simpler molecules; it is a process that requires the input of energy.
- Anabolism includes the formation of macromolecules from monomers by condensation reactions.
- For instance, protein and starch are made from amino acids and glucose units, respectively.
Catabolism
- Catabolism is the breakdown of complex molecules into simpler molecules and includes the hydrolysis of macromolecules into monomers.
- The breakdown of sugars (including glycolysis) or fats to release energy are all examples of catabolic reactions.
- Catabolism is a process during which energy is released.
Hydrolysis reaction
The breaking of chemical bonds by the addition of water molecules.
Condensation reaction
The reaction in which two smaller organic molecules combine to form a larger molecule with the accompanied formation of water or some other simple molecule.
Define metabolism
The sum of all the enzymatic reactions in a cell or organism.
Define anabolism
The synthesis of more complex molecules from simpler precursor molecules.
Define catabolism
The breakdown of complex molecules into simpler molecules.
Metabolism =
Anabolism + catabolism
Anabolism =
The opposite of catabolism
Example of a catabolic reaction
Breakdown of glucose during cellular respiration
What is urea?
- An organic compound with the formula CO(NH2)2.
- It is used by the human body to excrete nitrogen because urea is non-toxic and highly soluble.
- Urea is also widely used as a nitrogen fertilizer.
- This application of urea has led to its artificial synthesis on a large scale.
Artificial synthesis of urea
- Urea was artificially synthesised accidentally by a German chemist named Friedrich Wöhler in 1828.
- He demonstrated that a by-product of life could be artificially synthesised in a laboratory.
- Additionally, his experiment was the first one to show that the synthesis of an organic compound from two inorganic molecules was achievable.
- Hence, he provided evidence that contradicted the theory of vitalism.
According to the theory of vitalism, ___
- Organic compounds could only be synthesised by living organisms as they possessed an ‘element’ that non-living things did not have.
- That element has been referred to as the divine principle or the life spark by some.
- Thus, the artificial synthesis of urea from inorganic chemicals in the laboratory helped to falsify the theory of vitalism.
Diagram of urea
In 1828, Friedrich Wöhler artificially produced urea (organic compound) by an internal rearrangement of the atoms of ammonium cyanate (inorganic compound). What important principle did this experiment show?
That organic compounds can be synthesized without the need for a vital force.
How to tell if a compound is organic
An organic compound is a compound that contains carbon and is found in living things
Exceptions include carbides (e.g. CaC2), carbonates (CO32–), oxides of carbon (CO, CO2) and cyanides (CN–)
What is the theory of vitalism?
- Vitalism was a doctrine that dictated that organic molecules could only be synthesised by living systems
- It was believed that living things possessed a certain “vital force” needed to make organic molecules
- Hence organic compounds were thought to possess a non-physical element lacking from inorganic molecules
Describe how the theory of vitalism was disproved
- Vitalism as a theory has since been disproven with the discovery that organic molecules can be artificially synthesised
- In 1828, Frederick Woehler heated an inorganic salt (ammonium cyanate) and produced urea
- Urea is a waste product of nitrogen metabolism and is eliminated by the kidneys in mammals
- The artificial synthesis of urea demonstrates that organic molecules are not fundamentally different to inorganic molecules
What is the formula of urea?
CH₄N₂O
