Biomolecule
Found in living organisms and contain carbon atoms
- The structure of the carbon atom allows it to form a large variety of complex molecules with other atoms, including hydrogen, oxygen and nitrogen.
Biomolecules are made up of smaller molecules that bond together to form a larger substance
Several monomers join together to form a large polymer
Carbohydrates
Made up of carbon, hydrogen and oxygen (1:2:1) (2 Hydrogen atoms for every carbon and oxygen atom)
Are a form of short-term energy storage molecules for out cells
Three Major Groups:
- Monosaccharides - simpel sugars (glucose, fructose, galactose)
- Disaccharides - formed when two monosaccharides bind together (e.g. 2 glucose -> maltose)
- Polysaccharides - Formed when several monosaccharides bind together. e.g. glycogen (several glucoses)
Lipids
Lipids are non-polar molecules that are insoluble in water
They are long term energy storage for our cells
Also insulates the body and cushions major organs against shock
Mostly made up of carbon and hydrogen sometimes oxygen
Five Classes -
- Triglycerides
- Phospholipids
- Eicosanoids
- Steroids
- Ketones
Nucleotides & Nucleic Acids
Nucleic acids are chains of nucleotides and store our genetic information
Deoxyribonucleic acid (DNA) found in the nucleus as a double helix of nucleotides
Ribonucleic acid (RNA) found in both the nucleus and cytoplasm as a single strand of nucleotides.
Amino Acids & Proteins
Amino acids will form peptide bonds with each other to form polypeptides.
Proteins are typically > 50 amino acids in length but most have 300 or more.
Triglycerides (Lipids)
Sub Classes:
Several Subtypes (Depending on bonds between fatty acid chains)
Saturated e.g. increase levels of ‘bad’ cholesterol in blood → heart disease
Unsaturated
Monounsaturated
Polyunsaturated
Different types have different effect on human health.
Metabolism +Main Purposes
The set of life-sustaining chemical reactions in organisms
These enzyme-catalysed reactions allow our cells to maintain homeostasis
Three Main Purposes
The conversion of food into energy to run cellular processes
The conversion of food to building blocks for proteins, lipids, nucleic acids and some carbohydrates.
The elimination of nitrogenous wastes.
Role of Enzymes
Enzymes: Proteins that bind substrates at an active site. The reaction occurs while bound to the enzyme, and the products are then released.
Each individual reaction consists of substrates that are transformed into products
A + B substrates —> C + D products
Substrates often need to be activated before a reaction will take place
Reactions in living things are catalysed (induced and sped up) by enzymes.
Enzymes work by lowering the energy required for activation of a reaction
Enzymes are not used up in the reaction and are free to catalyse more reactions.
Metabolic Reactions
Catabolic Reactions: Involve the breakdown of larger molecules into smaller ones
Anabolic Reactions: Involve the production of larger molecules from smaller ones.
Enzyme Activity (6)
Temperature: Enzymes have optimum temperatures that vary according to the enzyme and the organism that contains
the enzyme. Extreme temperatures denature (degrade) the enzyme
pH: Each enzyme has an optimum pH at which it functions best, suited to the environment it operates in. Denaturation of the protein occurs at non-optimal pH.
Substrate Concentration: Generation of product increases with increasing substrate concentration
Enzyme concentration: Increased availability of active enzyme increases generation of product
Cofactors: Many enzymes require vitamin-based coenzymes or metal ions to function
Inhibitors: Molecules that bind to the enzyme inhibit activity. Inhibition may be reversible or irreversible (poisoning)
ATP
A major role of metabolic reactions is to provide our body with energy necessary for survival
This energy is synthesised into a temporary form of energy storage called ATP. (in cells)
ATP: A complex organic chemical that provides energy to drive many processes into living cells. e.g. muscle contraction, nerve impulse propagation, cell division
ATP is synthesised by combining ADP (Adenosine diphosphate), inorganic phosphate and energy.
Energy is stored in the ATP molecules as potential energy.
When needed, ATP is broken down into ADP and inorganic phosphate, and energy is released.
ATP & Mitochrondria
Most of the cell’s ATP is generated in the mitochondria (the ‘powerhouse’ of the cell)
Energy to make ATP is supplied by glucose and other nutrient molecules through specific reactions
Inner mitochondrial membrane forms folds called cristae, which is where ATP synthesis occurs
Inner membrane also contains the electron transport chain and ATP synthase, which are critical during ATP synthesis
Within the matrix are also important molecules involved in ATP synthesis
Cellular Respiration
Cellular Respiration: A type of metabolic reaction where biomolecules (carbohydrates, lipids, proteins) are broken down to synthesise ATP.
Glucose is the primary biomolecule broken down via cellular respiration.
Aerobic Respiration
Aerobic Respiration:
Uses oxygen and occurs mostly in the mitochondria (but can occur in cytoplasm)
A single glucose molecule can produce 30-32 ATP molecules
Will also produce carbon dioxide and water as by-products
Involves the interaction of glucose with oxygen, through a process called glucose oxidation, to produce energy.
Oxygen is obtained from our respiratory system when we breath and carbon dioxide is expelled as a waste product.
Anaerobic Respiration
Does not use oxygen and occurs only in the cytoplasm
A single glucose molecule can produce 2 ATP molecules
Will also produce lactic acid as a by product.
Occurs when the cell’s metabolic demand is too high that not enough oxygen can be supplied to the cell for glucose oxidation to occur. e.g. muscle cells during intense exercise.
Anaerobic respiration can be divided into two main stages:
- Glycolysis
- Pyruvate Fermentation
Examples of Anaerobic Respiration
Intense exercise: Body’s demand for ATP can exceed oxygen supply, especially in hardworking muscle cells. When oxygen supply is insufficient for demands of aerobic respiration — cells switch to anaerobic.
High-Altitude Conditions: At high altitudes, oxygen level is lower than at sea level — resulting in less oxygen available for aerobic respiration. People not acclimatised go through anaerobic exasperation → fatigued quicker
Medical Conditions: Certain conditions can impair oxygen delivery to tissue and lead to increased anaerobic respiration. e.g. respiratory diseases such as chronic obstructive pulmonary disease (COPD) or severe astham that limits oxygen intake.
Leigh Syndrome
Caused by mutations in the proteins that make up the electron transport chain.
Electron transport chain: Located in the inner membrane of mitochondria and is involved in the process of oxidative phosphorylation (where ATP is mainly produced)
Mutations in mtDNA or nuclear genes encoding mitochondrial proteins can impair energy production
Affects organs that have high energy demand e.g. brain, muscle. Symptoms include:
Poor muscle tone
Movement disorders
Severe developmental delays
Seizures
Respiratory distress
Cardiac arrhythmias
DNA
DNA is made up of four nucleotide bases
Adenine
Thymine
Guanine
Cytosine
Bases pair up and form strong hydrogen bonds to form the double helix structure of DNA.
A pairs with T
G pairs with C
Template Strand
Template strand: Gene that codes for a specific protein
The template strand is used during transcription to synthesise RNA.
Complementary Strand
Complementary strand: Opposite to the template strand
Transcription
A process occurring in the nucleus where RNA is synthesised from DNA.
Controlled by an enzyme called RNA polymerase, which ‘reads’ the template strand of DNA and synthesises a single strand of RNA
Gene Structure
Promoter region: The start of the gene where RNA polymerase binds to and begins transcription
Coding region: A sequence of nucleotides that are transcribed into the RNA strand.
Termination sequence: Terminates the transcription process
Transcription Steps (3)
Unzipping DNA
RNA polymerase binds to the promoter region of gene on the template strand
RNA polymerase causes the double-stranded DNA to ‘unzip’ (breaks hydrogen bonds’
RNA synthesis
RNA polymerase reads the template strand builds the RNA strand using free-floating nucleotides
Adenine (A) pairs with Uracil (U) — no thymine in RNA
Cytosine (C) with Guanine (G)
Termination
RNA polymerase reaches the termination sequence and the RNA is released as a single strand
Types of RNA
messenger RNA (mRNA): A transcribed copy of the nucleotide sequence of a single gene for a specific protein.
ribosomal RNA (rRNA): Is a structural RNA that forms the ribosome, upon which proteins are synthesised.
transfer RNA (tRNA): A structural RNA involved in translation and protein synthesis
