Chapter 3: Biological molecules Flashcards
Macromolecules vs. Micromolecules
Macromolecules (large, complex molecules like carbohydrates, proteins, lipids, and nucleic acids) and Micromolecules (smaller, simpler molecules like water and inorganic salts).
Carbohydrates
Carbohydrates are a fundamental group of biological molecules that play a vital role in living organisms.
Structure of Carbohydrates
Made up of carbon (C), hydrogen (H), and oxygen (O) atoms, often in a ratio close to 1:2:1 (although some variations exist).
Basic unit: Simple sugars called monosaccharides (e.g., glucose, fructose).
More complex carbohydrates are formed by linking monosaccharides together:
Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).
Functions of Carbohydrates
Energy source, Storage, Structural support and Cell signalling and recognition
Energy source
Simple sugars like glucose are broken down by cells to provide energy for cellular processes.
Storage
Complex carbohydrates like starch and glycogen store energy for later use.
Structural support
Cellulose in plant cell walls provides rigidity and support.
Cell signalling and recognition
Certain carbohydrates on cell surfaces can be involved in cell communication and recognition.
Types of Carbohydrates
Monosaccharides, Disaccharides and Polysaccharides.
Monosaccharides
Simple sugars with the most basic structure (e.g., glucose, fructose, galactose).
Disaccharides
Two monosaccharides joined together (e.g., sucrose, lactose, maltose).
Polysaccharides
Long chains of monosaccharides with various functions:
Starch: Storage carbohydrates in plants.
Glycogen: Storage carbohydrates in animals.
Cellulose: Structural component of plant cell walls.
Chitin: Structural component of insect exoskeletons and fungal cell walls.
Proteins
Proteins are another crucial group of biological molecules with diverse functions in living organisms.
Structure of Proteins
Made up of chains of amino acids linked together by peptide bonds.
Amino acids: These are the building blocks of proteins, with 20 different types found in living things. Each amino acid has a central carbon atom bonded to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H), and a side chain (R group) that varies between different amino acids.
Functions of Proteins
Enzymes, Structural support, Transport, Signalling and regulation, Movement, Immune system.
Enzymes
These are biological catalysts that speed up chemical reactions in cells. They are highly specific proteins with a defined shape that allows them to bind to specific molecules (substrates).
Structural support
Proteins like keratin (in hair and nails) and collagen (in bones and connective tissues) provide structural support to cells and tissues.
Transport
Proteins like haemoglobin in red blood cells transport molecules like oxygen throughout the body.
Signalling and regulation
Proteins on cell surfaces can be involved in cell communication and signalling pathways.
Movement
Proteins like actin and myosin are essential for muscle contraction and movement.
Immune system
Antibodies are proteins that help the immune system fight off pathogens.
Importance of having proteins
Proteins are vital for virtually all biological processes. They are the workhorses of the cell, carrying out a vast array of functions that ensure proper cell and organism function.
Lipids
Lipids, often referred to as fats and oils, are a diverse group of biological molecules with a wide range of functions in living organisms.
Structure of Lipids
Unlike carbohydrates and proteins, lipids don’t have a well-defined ratio of elements. They are primarily composed of carbon (C), hydrogen (H), and oxygen (O), but the proportions can vary depending on the specific type of lipid.
There are two main categories of lipids:
Simple lipids and Complex lipids
Simple lipids
These include fats and oils, which are esters formed by glycerol (a 3-carbon alcohol) bonded to fatty acids (chains of hydrocarbons with a carboxyl group). The type and length of the fatty acid chains determine the properties of the lipid (e.g., saturated vs. unsaturated fats).
Complex lipids
These include molecules like phospholipids and steroids. Phospholipids have a glycerol backbone, fatty acids, and a phosphate group, making them amphipathic (having both hydrophobic and hydrophilic regions). This allows them to form bilayers, which are essential components of cell membranes. Steroids, like cholesterol, have a four-ringed carbon structure and play various roles, including hormone production and membrane stability.
Functions of lipids
Energy storage, Insulation, Protection, Cell membrane structure, Hormone production and Signalling.
Energy storage
Lipids are a major energy storage molecule in living things. They store more energy per gram compared to carbohydrates.
Insulation
Lipids, particularly subcutaneous fat, provide insulation for animals, helping them maintain body temperature.
Protection
Lipids can provide cushioning and protection for organs.
Cell membrane structure
Phospholipids are a major component of cell membranes, regulating what enters and leaves the cell.
Hormone production
Cholesterol is a precursor for various steroid hormones.
Signalling
Some lipids are involved in cell signalling pathways.
Importance of lipids
Lipids play a crucial role in various biological processes. They provide a concentrated energy source, insulation, and protection. A balanced intake of different types of lipids is important for maintaining good health.
Nucleic Acids
Nucleic acids are the crown jewels of biological molecules, carrying the genetic information that governs the structure, function, and inheritance of living things.
Structure of Nucleic Acids
Made up of chains of nucleotides linked together by phosphodiester bonds.
Meaning and Types of Nucleotides
These are the building blocks of nucleic acids, consisting of three main components: Sugar, Phosphate group and Nitrogenous base.
Sugar
Either ribose (in RNA) or deoxyribose (in DNA).
Phosphate Group
Plays a role in energy transfer and gives nucleic acids a negative charge.
Nitrogenous base
This is the key component that determines the type of nucleic acid and carries the genetic information.
There are two main types:
Purines: Adenine (A) and Guanine (G).
Pyrimidines: Cytosine (C), Thymine (T) in DNA, and Uracil (U) in RNA.
Types of Nucleic acids
Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA)
Deoxyribonucleic Acid (DNA)
This is the genetic material found in the nucleus of cells and carries the instructions for building and maintaining an organism. The double-helix structure of DNA is formed by two complementary strands held together by hydrogen bonds between specific nitrogenous bases (A-T and C-G).
Ribonucleic Acid (RNA)
There are several types of RNA molecules involved in protein synthesis and other cellular functions. RNA is typically single-stranded and plays a vital role in translating the genetic information encoded in DNA into proteins.
Functions of Nucleic acids
DNA (Replication and Transcription)
RNA (Messenger RNA (mRNA), Ribosomal RNA (rRNA) and Transfer RNA (tRNA)).
DNA and its types
Stores and transmits genetic information from generation to generation.
Replication: DNA can make copies of itself during cell division to ensure each new cell has a complete set of genetic instructions.
Transcription: DNA serves as a template for RNA synthesis, where specific DNA sequences are copied into RNA molecules.
RNA and its types
Plays a crucial role in protein synthesis:
Messenger RNA (mRNA): Carries the genetic code from DNA to ribosomes, where proteins are assembled.
Ribosomal RNA (rRNA): Forms part of the ribosome structure, essential for protein synthesis.
Transfer RNA (tRNA): Transports amino acids to the ribosomes during protein synthesis.
Importance of Nucleic acid
Nucleic acids are the foundation of life. DNA provides the blueprint for an organism’s development and function, while RNA plays a critical role in translating that information into proteins, the workhorses of the cell. Understanding nucleic acids is essential in various fields, including genetics, medicine, and biotechnology.
List the chemical elements that make:
– carbohydrates
– fats
– proteins
Carbohydrates:
Main elements: Carbon (C), Hydrogen (H), and Oxygen (O)
Fats (Lipids):
Main elements: Carbon (C), Hydrogen (H), and Oxygen (O) Plus: Phosphorus (P) (often present)
Proteins:
Main elements: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N)
Building Blocks of Life
Starch and Glycogen
Proteins
Fats and Oils
Starch and Glycogen
These complex carbohydrates are built from large chains of simpler sugar molecules called glucose.
Proteins
These essential molecules are constructed from smaller units called amino acids linked together in specific sequences.
Fats and Oils
These energy-storing molecules are formed by combining fatty acids with glycerol.
What test is done for:
– Starch
– Reducing sugars
– Proteins
– Fats and oils
– Starch - Iodine solution
– Reducing sugars - Benedict’s solution
– Proteins - Biuret test
– Fats and oils - ethanol emulsion test
Describe the use of iodine solution to test for starch
Iodine Solution for Starch:
Function: Detects the presence of starch.
Process: A drop of iodine solution is added to the sample.
Result:
Positive: If starch is present, the solution turns a blue-black colour.
Negative: The solution remains its original brown colour if no starch is present.
Describe the use of Benedict’s solution to test for reducing
sugars
Benedict’s Solution for Reducing Sugars:
Function: Detects the presence of reducing sugars (simple sugars like glucose that can donate electrons in a chemical reaction).
Process: Benedict’s solution (a blue copper sulfate complex) is heated with the sample.
Result:
Positive: The solution changes colour from blue to green, yellow, or orange precipitate depending on the sugar concentration.
Negative: The solution remains blue if no reducing sugars are present.
Describe the use of the biuret test for proteins
Biuret Test for Proteins:
Function: Detects the presence of proteins.
Process: Biuret reagent (containing copper sulfate in an alkaline solution) is added to the sample.
Result:
Positive: A violet-purple colour develops if protein is present due to a reaction with peptide bonds.
Negative: The solution remains blue or greenish if no protein is present.
Describe the use of ethanol emulsion test for fats and oils
Ethanol Emulsion Test for Fats and Oils:
Function: Detects the presence of fats and oils (lipids).
Process:
The sample is mixed with ethanol (alcohol) and then water is added.
The mixture is shaken vigorously.
Result:
Positive: If fats or oils are present, a milky white emulsion forms due to the immiscibility of fats with water.
Negative: The solution remains clear if no fats or oils are present.
State that water is important as a solvent
Water is essential for life because it acts as the universal solvent, dissolving a wide range of substances. This allows for crucial chemical reactions and the transport of molecules within cells and throughout organisms.
