Chapter 1 part B Flashcards
Define protein
Proteins are large, complex molecules that play a variety of critical roles in biological systems. They are essential for the structure, function, and regulation of the body’s cells, tissues, and organs. Proteins are involved in almost every cellular process, including enzymatic reactions, immune responses, and signal transmission.
What are proteins made of?
What Are Proteins Made Of?
Proteins are made up of smaller units called amino acids. There are 20 different amino acids that can be combined in various sequences to form proteins. The sequence of amino acids determines the protein’s structure and function.
List the four level of protein structure
Primary, Secondary, Tertiary and Quaternary protein structures.
What is primary protein structure?
This is the sequence of amino acids in a polypeptide chain. It is determined by the gene encoding the protein.
What is secondary protein structure
Secondary Structure:
The polypeptide chain can fold into specific shapes such as alpha helices and beta-pleated sheets, stabilized by hydrogen bonds.
What is tertiary protein structure?
Tertiary Structure:
The three-dimensional shape of the entire polypeptide chain is formed. This shape is stabilised by various bonds and interactions, such as hydrogen bonds, disulfide bonds, ionic bonds, and hydrophobic interactions.
What is quaternary protein structure?
Quaternary Structure (not all proteins have this):
Some proteins are composed of multiple polypeptide chains that come together to form a functional protein. Examples include haemoglobin, which consists of four polypeptide chains.
What do amino acids consist of?
Amino Acids:
Amino acids consist of:
An amino group (-NH₂)
A carboxyl group (-COOH)
A side chain (or R group), which is different for each amino acid and determines its properties.
What are ester bonds?
Ester bonds are a type of chemical bond that forms between a carboxyl group (-COOH) of a fatty acid and a hydroxyl group (-OH) of an alcohol, such as glycerol in lipids. This bond is formed through a condensation reaction, where a molecule of water (H₂O) is released.
Formation of Ester Bonds:
When a fatty acid and an alcohol like glycerol react, the hydroxyl group (-OH) from the alcohol and the carboxyl group (-COOH) from the fatty acid combine to form an ester bond (-COO-) and release a water molecule.
Example (formation of ester bond in triglycerides):
Glycerol (alcohol) + Fatty acid → Ester bond + Water
Test for proteins
Testing for protein (RAP)
To test for the presence of protein, add Biuret
reagent (ready-mixed 5% (w/v) sodium hydroxide)
solution and 1% (w/v) copper sulphate solution). A
purple colour indicates the presence of protein
(see fig G).
What affects the shape of proteins, and what happens when these factors affect proteins?
Factors That Affect the Shape of Proteins
The shape of a protein is critical for its function, and it is influenced by several factors. Changes in these factors can disrupt the protein’s structure, leading to loss of function, a process called denaturation.
- pH
Effect: Changes in pH can alter the charge of amino acid side chains, disrupting ionic bonds and hydrogen bonds that stabilise the protein’s structure.
Consequence: Extreme pH changes can cause proteins to unfold or denature, leading to loss of biological function. For example, digestive enzymes like pepsin only work in acidic conditions. - Temperature
Effect: High temperatures provide energy that can break weak bonds, such as hydrogen bonds, within the protein.
Consequence: When the temperature exceeds a certain threshold, the protein denatures and loses its functional shape. For example, cooking denatures proteins in egg whites, causing them to solidify.
Step-by-step process of formation of triglycerides.
- Start with the reactants:
Glycerol: A molecule with three hydroxyl (-OH) groups.
(propane-1,2,3-triol).
Fatty acids: Long-chain carboxylic acids with a carboxyl (-COOH) group at one end. For example, palmitic acid (COOH). - Reaction mechanism:
Step 1: One hydroxyl (-OH) group from the glycerol reacts with the carboxyl (-COOH) group of a fatty acid.
Step 2: During this reaction, a molecule of water (H₂O) is removed as the hydroxyl (-OH) from glycerol and a hydrogen (H) from the fatty acid’s carboxyl group combine. This forms an ester bond (-COO-).
Step 3: The process repeats for the other two hydroxyl groups of glycerol, with each reacting with another fatty acid. - Products formed:
Triglyceride: This is a molecule where glycerol is bonded to three fatty acid chains via ester bonds. Its general structure is:
Here, R₁, R₂, and R₃ represent the hydrocarbon chains of the fatty acids.
Water: Three water molecules (H₂O) are produced as byproducts, one for each ester bond formed.
Define physically unreactive
Physically Unreactive
A substance is physically unreactive when it does not undergo noticeable changes in its physical state or properties under normal conditions.
Examples:
Not melting, boiling, or changing shape easily.
Remaining unaffected by changes in pressure or temperature (within a certain range).
Example: Noble gases like helium are physically unreactive because they remain gaseous and inert under standard conditions.
Define chemically unreactive
Chemically Unreactive
A substance is chemically unreactive when it does not readily undergo chemical reactions with other substances.
This is often due to having a stable electron configuration, meaning the atoms do not easily gain, lose, or share electrons.
Example: Noble gases like neon or argon are chemically unreactive because their outer electron shells are full, making them stable and resistant to bonding with other elements.
What is Amylose?
Amylose is a type of polysaccharide and one of the two main components of starch (the other being amylopectin). It is a long, unbranched chain of alpha-glucose molecules.
Structure: Amylose forms a helical structure due to the way the glucose units are connected.
Function: It serves as a storage molecule for energy in plants, providing glucose when broken down.
