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Biological molecules
A wide range of molecules essential for life, including various types of proteins, nucleic acids, carbohydrates, and lipids.
Monomers
The smaller units from which larger molecules are made, such as monosaccharides, amino acids, and nucleotides.
Polymers
Molecules made from a large number of monomers joined together through chemical bonding.
Hydrolysis
The reaction where a chemical bond is broken apart with the addition of a water molecule. It is essential for breaking down carbohydrates and glycosidic bonds.
Condensation
The reaction that joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water. This reaction always releases water.
Carbohydrates
A group of macromolecules that includes sugars, starches, and cellulose, and serves as a major source of energy for living organisms.
Monosaccharides
The monomers from which larger carbohydrates are made, such as glucose, galactose, and fructose. They have the formula CH2On where n is between 3 and 7.
Disaccharides
Carbohydrates formed by the condensation of two monosaccharides. Examples include maltose (glucose + glucose), sucrose (glucose + fructose), and lactose (glucose + galactose).
Polysaccharides
Complex carbohydrates formed by the condensation of many glucose units. Examples include glycogen, starch, and cellulose.
Glycosidic bond
A covalent bond formed between two monosaccharides through a condensation reaction. It is broken through hydrolysis reactions.
Alpha glucose
A type of glucose unit in which the hydrogen on the first carbon is below the plane of the ring, commonly found in starch and glycogen.
Beta glucose
A type of glucose unit in which the hydrogen on the first carbon is above the plane of the ring, commonly found in cellulose.
Glycogen
A polysaccharide that serves as a storage form of glucose in the liver and muscle cells. It is synthesized from glucose when blood glucose levels are high.
Starch
A polysaccharide made up of glucose monomers, commonly found in plant cells and serves as a storage form of energy.
Cellulose
A polysaccharide that makes up the cell walls of plants and provides structural support. It is an important component of dietary fiber.
What is Glycogen?
Glycogen is a polysaccharide found mainly in muscle and liver cells, synthesized from glucose when blood glucose levels are high, and serves as a ready source of glucose for tissues throughout the body when blood glucose levels decline.
Where is Glycogen found?
Glycogen is found mainly in muscle and liver cells.
What activates the enzymes involved in glycogen synthesis in liver cells?
Insulin activates the enzymes involved in glycogen synthesis in liver cells when blood glucose levels rise.
What is the process called when glycogen chains are elongated as glucose molecules are added to them?
The process is called gluconeogenesis.
What hormones stimulate glycogen breakdown in muscle cells?
Cortisol, epinephrine, and norepinephrine stimulate glycogen breakdown in muscle cells, along with glucagon.
What is the structure of glycogen?
Glycogen is a polysaccharide made of alpha glucose monomers with 1,4 and 1,6 glycosidic bonds between glucose. The 1,6 glycosidic bonds allow the glycogen to be branched, occurring every 10 to 15 units.
What is Starch used for in plants?
Starch is used as a storage of glucose for the plant.
How can starch be tested for presence in a fruit or vegetable?
Starch can be tested by applying a drop of iodine to a cut surface of a fruit or vegetable. If starch is present, the iodine will change color from dark brown to dark bluish purple or black.
What happens to iodine when it comes into contact with a cut surface of a fruit or vegetable that contains starch?
Iodine changes color from dark brown to dark bluish purple or black.
What process can be used to test if starch is present in a cell?
Boiling the leaf, which removes chlorophyll and some membranes.
Why is glucose stored as starch in plants?
1. Glucose requires sunlight for production, so on days without sunlight, starch can be broken down and used as a source of glucose. 2. Glucose is soluble in water and can cause an osmotic potential across the cell membrane, whereas starch is not soluble and does not affect water potential.
What is the structure of amylose, and how does it contribute to energy storage?
Amylose is a long chain of alpha glucose monomers joined by 1,4 glycosidic bonds, coiling in a spiral shape held together by hydrogen bonds. This structure allows for compact energy storage and makes it insoluble in water, unlike glucose.
What is the structure of amylopectin, and how does it provide energy for plants?
Amylopectin consists of branched chains of alpha glucose monomers joined by 1,4 and 1,6 glycosidic bonds, forming branches every 20-30 glucose units. The branching allows for easy access to glucose molecules for rapid energy release through hydrolysis.
What is the ratio of amylose to amylopectin in starch and why?
Starch is approximately 20% amylose and 80% amylopectin, allowing for both compact storage and rapid release of glucose due to the branching structure of amylopectin.
What purpose does cellulose serve in plant cells?
Cellulose provides rigidity to plant cells, contributing to their structural integrity and support.
Storage
Starch is not only good for storage but also for carrying the hydrolysis reaction faster due to a larger surface area in contrast to the tight protected amylose.
Cellulose Structure
Cellulose is made up of thousands of b-glucose subunits linked via beta-1,4 glycosidic bonds. Every alternate glucose molecule in cellulose is inverted. It is an unbranched molecule with linear polymeric chains arranged in a parallel pattern. It forms cellulose microfibrils that are firm and strong due to hydrogen bonds.
Function of Cellulose
Cellulose provides rigidity to plant cells and ensures that they do not burst in a hypotonic solution, remaining turgid. It is an important dietary source of carbohydrates in herbivores and is used in various industrial applications such as paper production, textile industry, electrical insulation, biofuel, gunpowder, and pharmaceuticals.
Insolubility
Cellulose is insoluble in water but soluble in organic solvents. It has high tensile strength due to hydrogen bonds between chains, providing a strength comparable to that of steel.
Biological Function
Cellulose is the most abundant carbohydrate present in nature and is used in biological labs as a stationary phase for chromatography. It also acts as a stabilizer in different drugs and is used to make biofuel.
Alkaline solution used to test for the presence of the aldehyde functional group CHO
Benedict's solution
Procedure for testing the presence of aldehyde functional group CHO using Benedict's solution
1. Place 1 mL of sample in a clean test tube 2. Add 2 mL (10 drops) of Benedict's reagent (CuSO4) to the test tube 3. Heat the solution in a boiling water bath for 3-5 minutes 4. Observe for color change or precipitate formation
Result interpretation of Benedict's test
If the color changes to green: 0.1-0.5% sugar If the color changes to yellow: 0.5-1% sugar If the color changes to orange: 1-1.5% sugar If the color changes to red: 1.5-2% sugar
Iodine Test for Starch (Solid)
Peel off the skin of the vegetable, take a sample, add iodine solution, and note any color changes. Brown means no starch, blue-black means starch is present.
Iodine Test for Starch (Liquid)
Add 10cm3 of the liquid sample to a test tube, add iodine solution, and note any color changes. Brown means no starch, blue-black means starch is present.
Lipids
Lipids are made up of fatty acids and glycerol, they contain carbon, hydrogen, and less oxygen than carbohydrates, are nonpolar, insoluble in water, and can be stored in large quantities in animals without increasing mass.
Fatty Acids
Long chains of carbon and hydrogen atoms with a carboxyl group at one end, can be saturated (no double bonds), monounsaturated (one double bond), or polyunsaturated (multiple double bonds).
Saturated Fatty Acids
Straight shape with tightly packed molecules, solid at room temperature (fats).
Unsaturated Fatty Acids
Kink where double bonds are, less straight, liquid at room temperature (oils).
Triglycerides
A type of lipid that includes fats and oils.
What are the two key types of lipids?
Triglycerides (fats and oils) and phospholipids in cell membranes.
How are triglycerides formed?
By the condensation of one molecule of glycerol and three molecules of fatty acid. This reaction occurs between the carboxyl group (COOH) of the fatty acid and the hydroxyl group (OH) of the glycerol, releasing water and forming ester bonds.
What is the function of triglyceride lipids?
Triglycerides are an energy storage due to the large ratio of energy-storing carbon-hydrogen bonds compared to the number of carbon atoms. They can also act as a metabolic water source.
What are phospholipids formed of?
One glycerol, two fatty acids, and a phosphate-containing group. One of the fatty acids in the triglycerides is substituted by this group.
Describe the nature of the heads and tails in a phospholipid.
The phosphate molecule (the hydrophilic head) can interact with water as it is charged and repels other fats. The fatty acids (the hydrophobic tails) are not charged, repel water, and will mix with fats. This makes a phospholipid a polar molecule.
What structure does the phospholipid bilayer form?
The phospholipid bilayer forms the plasma membrane around cells. The arrangement of heads and tails enables carbohydrates to attach and form important receptors on the membrane (glycolipids).
What is the emulsion test used for?
The emulsion test is used to check for the presence of lipids.
Plasma Membrane
The nature of the lipids in the plasma membrane enables it to form a bilayer arrangement.
Glycolipids
Carbohydrates attach to the plasma membrane to form important receptors through glycolipids.
Emulsion Test
The emulsion test checks for the presence of lipids by dissolving fats and oils in ethanol and observing the formation of a milky white emulsion.
Proteins
Proteins are formed from amino acid monomers that combine to form polypeptides and eventually proteins. There are 20 naturally occurring amino acids with around 80 synthetic amino acids.
Amino Acids
The basic monomer units of proteins, made of a central carbon atom, amino group (NH2), carboxyl group (COOH), and R side group that varies among different amino acids.
Peptide Bond
Formed between amino acid monomers in a condensation reaction, resulting in a dipeptide and the release of a water molecule. It can be broken through hydrolysis.
What is the process that results in the linking of two amino acids by a peptide bond?
Condensation reaction, which results in the removal of a water molecule from the carboxyl group of one amino acid and the hydrogen from the amino group of another.
What can break a peptide bond?
Hydrolysis, which involves the addition of a water molecule to break the peptide bond.
What is the primary structure of proteins?
It is the sequence of amino acids in a polypeptide chain, which determines the shape and function of the protein.
What is the secondary structure of proteins?
It is the twisting of the polypeptide chain into a 3D shape known as an alpha helix, caused by the formation of hydrogen bonds between NH and CO groups.
What is the tertiary structure of proteins?
It is the complex and specific 3D structure of each protein, maintained by bonds including disulfide bridges, ionic bonds, and hydrogen bonds.
What is the quaternary structure of proteins?
It is the structure of larger proteins containing multiple polypeptides linked together in various ways, and may also involve nonprotein prosthetic groups.
What are the types of bonds involved in the tertiary structure of proteins?
Disulfide bridges, ionic bonds, and hydrogen bonds.
What is the test used to detect proteins?
The biuret test, which detects the presence of peptide bonds.
What determines the 3D shape of proteins in their primary structure?
The sequence of amino acids
What test is used to test for proteins?
The biuret test
How is the biuret test performed?
Place a sample of solution in a test tube and add an equal volume of sodium hydroxide solution at room temperature
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Flashcard Deck: Biological molecules, monomers, polymers, hydrolysis, condensation, carbohydrates, lipids, proteins.
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