Biology Chapter 5: Carbohydrates and DNA Structure
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Questions and Answers

What type of reaction occurs when monomers are joined together to form polymers?

  • Redox reaction
  • Condensation reaction (correct)
  • Hydrolysis reaction
  • Dehydration synthesis

Which of the following correctly describes monosaccharides?

  • They consist of long chains of sugar units.
  • They contain only carbon and oxygen atoms.
  • They are primarily structural molecules in plants.
  • They can be combined to form disaccharides. (correct)

Which disaccharide is formed from two glucose molecules?

  • Maltose (correct)
  • Fructose
  • Lactose
  • Sucrose

What type of bond is formed between two monosaccharides during a condensation reaction?

<p>Glycosidic bond (B)</p> Signup and view all the answers

What type of glucose is used to form cellulose?

<p>Beta glucose (B)</p> Signup and view all the answers

Which polysaccharide is primarily utilized for energy storage in animals?

<p>Glycogen (D)</p> Signup and view all the answers

Which of the following statements about hydrolysis is correct?

<p>It breaks chemical bonds by adding water. (B)</p> Signup and view all the answers

What is the general formula for common monosaccharides?

<p>(CH2O)n (B)</p> Signup and view all the answers

What effect do competitive reversible inhibitors have on the rate of reaction?

<p>They decrease the rate of reaction by temporarily blocking active sites. (D)</p> Signup and view all the answers

Which component is NOT part of a DNA nucleotide?

<p>Ribose sugar (B)</p> Signup and view all the answers

How do non-competitive reversible inhibitors affect enzyme activity?

<p>They alter the shape of the enzyme but not the active site. (A)</p> Signup and view all the answers

What is the structure of DNA in terms of its composition?

<p>A double helix made of two polynucleotides with hydrogen bonds between bases. (C)</p> Signup and view all the answers

Which base pairing is correct for DNA structure?

<p>Adenine pairs with Thymine. (D)</p> Signup and view all the answers

What is the significance of semi-conservative replication in DNA?

<p>It produces two new DNA strands from one original strand. (C)</p> Signup and view all the answers

Which factor contributes to the stability of DNA?

<p>The phosphodiester backbone protecting the nitrogenous bases. (D)</p> Signup and view all the answers

What role does RNA play in relation to DNA?

<p>It transfers genetic information from DNA to ribosomes for protein synthesis. (C)</p> Signup and view all the answers

What characteristic of unsaturated fats allows them to remain liquid at room temperature?

<p>Presence of carbon-carbon double bonds (A)</p> Signup and view all the answers

Which property of triglycerides makes them excellent energy storage molecules?

<p>They possess a high ratio of energy storing carbon-hydrogen bonds. (C)</p> Signup and view all the answers

What does the hydrophilic nature of the heads in phospholipids allow them to do in an aqueous environment?

<p>Hold at the surface of the cell membrane (C)</p> Signup and view all the answers

What is the primary purpose of the emulsion test?

<p>To identify the presence of lipids (B)</p> Signup and view all the answers

Which of the following statements is true regarding the storage of triglycerides?

<p>They release water when oxidized, providing moisture in dry environments. (A)</p> Signup and view all the answers

What is created when a triglyceride's fatty acid is replaced by a phosphate-containing group?

<p>Phospholipid (B)</p> Signup and view all the answers

What role do glycolipids play in relation to phospholipids?

<p>They are important for cell recognition on the cell surface. (A)</p> Signup and view all the answers

Why are non-polar lipids advantageous for storage in cells?

<p>They do not affect the water potential of cells. (B)</p> Signup and view all the answers

What is the significance of water's large latent heat of vaporisation?

<p>It aids in cooling with minimal water loss. (A)</p> Signup and view all the answers

What indicates the presence of a peptide bond in a solution?

<p>A purple coloration (D)</p> Signup and view all the answers

How do hydrogen ions affect pH levels in a solution?

<p>Higher concentrations of hydrogen ions lower the pH. (C)</p> Signup and view all the answers

Which factor affects the rate of enzyme-controlled reactions by altering the enzyme's tertiary structure?

<p>Hydrogen ion concentration (pH) (B)</p> Signup and view all the answers

What happens to the rate of reaction when the temperature exceeds the optimum temperature for an enzyme?

<p>It decreases as the enzyme becomes denatured (A)</p> Signup and view all the answers

Which ion is a crucial component of haemoglobin?

<p>Iron ions (A)</p> Signup and view all the answers

How does enzyme concentration affect the rate of reaction beyond a certain point?

<p>Plateaus as substrate concentration becomes limiting (D)</p> Signup and view all the answers

What role do sodium ions play in cellular processes?

<p>They are involved in the co-transport of glucose and amino acids. (B)</p> Signup and view all the answers

What model describes how an enzyme's active site adapts to fit a substrate?

<p>Induced fit model (B)</p> Signup and view all the answers

What effect does water's strong cohesion have in plants?

<p>It allows for effective transport of water in xylem. (B)</p> Signup and view all the answers

Which enzyme is known to function best in very acidic conditions?

<p>Pepsin (B)</p> Signup and view all the answers

What is the primary role of enzymes in biochemical reactions?

<p>To lower the activation energy of the reaction (B)</p> Signup and view all the answers

What formula is used to calculate the pH of a solution?

<p>pH = -log10[H+] (A)</p> Signup and view all the answers

What are amino acids primarily composed of?

<p>An amino group, carboxylic acid group, and a variable R group (C)</p> Signup and view all the answers

Which type of bond forms between amino acids during a condensation reaction?

<p>Peptide bond (C)</p> Signup and view all the answers

What determines the primary structure of a protein?

<p>The order and number of amino acids (B)</p> Signup and view all the answers

Which structure of a protein is characterized by alpha helices and beta pleated sheets?

<p>Secondary structure (A)</p> Signup and view all the answers

Which type of bond is the strongest in maintaining protein structure?

<p>Disulfide bridges (A)</p> Signup and view all the answers

What is the purpose of the Biuret test?

<p>To test for the presence of peptide bonds in a protein (B)</p> Signup and view all the answers

Which of the following describes a globular protein?

<p>Compact and folded into a spherical shape (C)</p> Signup and view all the answers

Which structure of a protein involves multiple polypeptides coming together?

<p>Quaternary structure (D)</p> Signup and view all the answers

Flashcards

Monomers

Small units that join to form larger molecules, such as monosaccharides, amino acids, and nucleotides.

Polymers

Large molecules made from many monomers joined together, formed by condensation reactions.

Condensation reaction

A chemical reaction that joins two molecules together, releasing a water molecule.

Hydrolysis

The process of breaking a chemical bond between two molecules by adding a water molecule.

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Monosaccharide

A type of carbohydrate that consists of a single sugar unit, such as glucose, fructose, or galactose.

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Disaccharide

A type of carbohydrate formed by two monosaccharides joined together by a glycosidic bond, such as maltose, sucrose, or lactose.

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Polysaccharide

A type of carbohydrate formed from many monosaccharides joined together by glycosidic bonds.

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Glycogen

The main energy storage molecule in animals, formed from many alpha glucose units joined by 1,4 and 1,6 glycosidic bonds.

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Unsaturated Lipids

Lipids that contain at least one carbon-carbon double bond, making them bendable and liquid at room temperature.

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Triglyceride

A type of lipid that stores energy, composed of glycerol and three fatty acid chains.

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Energy Storage Ratio

The ratio of carbon-hydrogen bonds to carbon atoms in a molecule, important for energy storage.

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Mass to Energy Ratio

The ratio of mass to energy stored in a molecule, which affects efficiency of energy storage.

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Phospholipid

A lipid with a phosphate-containing group attached, forming a hydrophilic head and hydrophobic tails.

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Phospholipid Bilayer

A structure formed by phospholipids in an aqueous environment, with hydrophilic heads facing outward and hydrophobic tails facing inward.

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Emulsion Test

A test used to detect the presence of lipids in a sample.

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Glycolipids

Carbohydrates attached to lipids, found on cell surfaces and important for cell recognition.

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Semi-conservative DNA replication

The process of copying a DNA molecule, where each new molecule contains one original strand and one newly synthesized strand.

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Competitive reversible inhibitors

The concentration of these inhibitors influences the rate of reaction. They can bind to the active site, preventing the substrate from binding.

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Non-competitive reversible inhibitors

These inhibitors affect the enzyme shape. The substrate can still bind to the active site, but the enzyme is changed and may not work as well.

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Nucleotide

A molecule consisting of a pentose sugar (5-carbon sugar), a phosphate group, and a nitrogen-containing base.

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Phosphodiester bonds

These bonds form a chain of nucleotides. The phosphate group of one nucleotide forms a bond with the sugar of the next nucleotide.

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Deoxyribose

The sugar in DNA, with a hydrogen atom on the 2' carbon atom.

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Ribose

The sugar in RNA, with a hydroxyl group on the 2' carbon atom.

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Base pairing in DNA

The base pairing rules in DNA are: Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C)

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Water's High Specific Heat Capacity

Water molecules stick together through hydrogen bonds, requiring lots of energy to break. This stabilizes temperature in organisms, acting as a buffer against fluctuations.

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Water Cohesion and Transport

Strong cohesion between water molecules allows efficient transport in plants. It supports columns of water in structures like xylem.

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High Latent Heat of Vaporization

The evaporation of 1 gram of water requires a lot of energy due to hydrogen bonds. This makes water a good coolant, as evaporation removes heat with little water loss.

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pH

A measure of the concentration of hydrogen ions (H+) in a solution.

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Role of Iron Ions

Iron ions are a crucial component of hemoglobin, the oxygen-carrying molecule found in red blood cells.

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Primary Structure

The specific sequence of amino acids in a protein chain. This sequence determines the protein's overall structure and function.

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Tertiary Structure

The three-dimensional shape of a protein, formed by the folding and twisting of the polypeptide chain. This structure is stabilized by various bonds, like hydrogen bonds, ionic bonds, and disulfide bridges.

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Quaternary Structure

The arrangement of multiple polypeptide chains into a single protein. It involves the interactions between different polypeptide units.

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Secondary Structure

The specific shape formed by the polypeptide chain, either α-helix or β-pleated sheet. This shape is stabilized by hydrogen bonds.

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Peptide Bond

A chemical bond formed between two amino acids, linking them together in a polypeptide chain. It involves the removal of a water molecule.

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Enzyme

A protein that speeds up chemical reactions without being consumed in the process.

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Biuret Test

A test that detects the presence of proteins in a sample by detecting peptide bonds. It involves a color change reaction.

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Fibrous Protein

A type of protein that forms long fibers. It has a structural function, like providing strength or flexibility.

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What are enzymes?

Enzymes are biological catalysts that speed up chemical reactions in living organisms by lowering the activation energy required for the reaction to occur. They are highly specific, meaning they only work on specific substrates, and are not consumed in the reaction.

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What is the active site of an enzyme?

The active site of an enzyme is a specific three-dimensional region that binds to the substrate molecule. It is formed by a specific arrangement of amino acid residues, creating a unique shape complementary to the substrate.

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What is the induced fit model?

The induced fit model describes how the active site of an enzyme changes shape slightly to accommodate the substrate molecule when it binds. This interaction optimizes the fit between the enzyme and substrate, facilitating the reaction.

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How does temperature affect enzyme activity?

Temperature affects enzyme activity by influencing the kinetic energy of the enzyme molecules. At optimal temperatures, the enzyme works at its maximum rate. However, extreme temperatures can denature the enzyme, causing it to lose its shape and function.

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How does pH affect enzyme activity?

pH, a measure of acidity or alkalinity, affects enzyme activity by influencing the ionization state of amino acids in the active site. Each enzyme has an optimal pH at which it functions best. Deviating from this pH can alter the shape of the active site and hinder enzyme activity.

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What is the effect of enzyme concentration on reaction rate?

Increasing enzyme concentration leads to an increased rate of reaction, as more active sites are available to bind with substrates. However, beyond a certain point, increasing enzyme concentration has no further effect because substrate concentration becomes the limiting factor.

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What is the effect of substrate concentration on reaction rate?

Increasing substrate concentration initially increases the rate of reaction as more enzyme-substrate complexes are formed. However, beyond a certain point, the rate of reaction levels off as all active sites are saturated with substrate and the enzyme becomes the limiting factor.

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What are inhibitors and how do they affect enzymes?

Enzymes are affected by inhibitors, which can bind to the enzyme and decrease its activity. Competitive inhibitors bind to the active site, preventing substrate binding, while non-competitive inhibitors bind to a different site, changing the enzyme's shape and reducing its efficiency.

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Study Notes

Biological Molecules

  • Monomers are small units forming larger molecules (e.g., monosaccharides, amino acids, nucleotides).
  • Polymers are large molecules made from many monomers joined together.
  • Condensation reactions join monomers, eliminating a water molecule.
  • Hydrolysis breaks down polymers, adding a water molecule.

Carbohydrates

  • Carbohydrates are made of carbon, hydrogen, and oxygen.
  • Monosaccharides are single sugar units (e.g., glucose).
  • Disaccharides are two monosaccharides joined (e.g., maltose).
  • Polysaccharides are many monosaccharides joined (e.g., glycogen, starch, cellulose).
  • Glycosidic bonds link monosaccharides in condensation reactions.
  • Glucose has alpha and beta isomers.
  • Common monosaccharides include glucose, galactose, and fructose.

Disaccharides

  • Formed by condensation of two monosaccharides.
  • Examples include maltose (glucose + glucose), sucrose (glucose + fructose), and lactose (glucose + galactose).
  • A glycosidic bond is formed in a condensation reaction.

Polysaccharides

  • Formed from many glucose units joined together.
  • Glycogen is the main energy storage molecule in animals.
  • Starch is an energy storage molecule in plants, composed of amylose and amylopectin.
  • Amylose is unbranched.
  • Amylopectin is branched.
  • Cellulose forms plant cell walls.
  • It consists of beta glucose linked together by 1,4 and 1,6 glycosidic bonds.

Biochemical Tests

  • Benedict's reagent: used to test for reducing sugars.
    • Reducing sugars reduce Cu2+ to Cu+ forming a brick-red precipitate.
  • Hydrochloric acid and sodium hydrogencarbonate are used to test for non-reducing sugars; HCl hydrolyzes the disaccharides into monosaccharides.
  • Iodine/potassium iodide: used to detect starch.
    • A positive result is a blue-black colour change from an orange-brown colour.

Lipids

  • Lipids are made of carbon, hydrogen, and oxygen, insoluble in water.
  • Triglycerides are made of one glycerol molecule and three fatty acids.
  • Fatty acids can be saturated (no C=C double bonds) or unsaturated (one or more C=C double bonds).
  • Phospholipids have a hydrophilic head and hydrophobic tails, crucial for cell membranes.

Proteins

  • Proteins are made from amino acids linked by peptide bonds.
  • The primary structure of a protein is the sequence of amino acids.
  • Secondary structures include alpha helices and beta pleated sheets.
  • Tertiary structure is the overall 3D shape of a protein.
  • Proteins contain peptide bonds.
  • The Biuret test is used to detect proteins.

Enzymes

  • Enzymes are proteins that catalyse biochemical reactions.
  • Enzymes have an active site that binds to a substrate, forming an enzyme-substrate complex.
  • The induced fit model describes how the enzyme's active site changes shape to bind the substrate more effectively.
  • Enzymes lower activation energy.

Factors Affecting Enzyme Activity

  • Temperature: Optimum temperature exists for enzyme activity. Beyond this, enzymes denature.
  • pH: Enzymes have an optimum pH range.
  • Substrate concentration: Increasing substrate concentration increases the rate until the enzyme is saturated.
  • Enzyme concentration: Increasing enzyme concentration increases the rate until the substrate becomes limiting.
  • Inhibitors: Competitive and non-competitive inhibitors can reduce enzyme activity.

Nucleic Acids

  • DNA and RNA are nucleic acids; polymers of nucleotides.
  • Nucleotides consist of a pentose sugar, a nitrogenous base, and a phosphate group.
  • DNA is a double helix; RNA is a single strand.
  • DNA stores genetic information; RNA transfers information from DNA to ribosomes for protein synthesis.
  • DNA nucleotides contain deoxyribose; RNA nucleotides contain ribose.

ATP

  • Adenosine triphosphate (ATP) is a nucleotide derivative, a source of readily available energy in cells.
  • ATP releases energy when hydrolysed to ADP and phosphate.
  • ATP is crucial for various metabolic activities.
  • ATP synthase catalyses the formation of ATP.

Water

  • Water is a polar molecule.
  • Water has high specific heat capacity and high latent heat of vaporization.
  • Water is a good solvent for polar and charged molecules.
  • Water is essential for many biological processes.
  • Water is involved in various transport processes.
  • Water is crucial for regulating temperature.

Inorganic Ions

  • Inorganic ions play critical roles in biological processes.
  • Examples include hydrogen ions (affect pH), iron (part of haemoglobin), sodium (co-transport), and phosphate (part of DNA, ATP).

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Description

Test your knowledge on carbohydrates, including the formation of polymers from monomers and the characteristics of monosaccharides and disaccharides. Additionally, this quiz explores key concepts of DNA structure and the roles of RNA in genetic processes. Perfect for students studying biology at an advanced level.

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