Biology Chapter 1: Molecules of Life

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Questions and Answers

What process joins two monosaccharides to form a disaccharide?

Condensation process

What is the name of the bond formed between two monosaccharides?

Glycosidic bond

What happens during the hydrolysis process of a disaccharide?

Water is added and the glycosidic bond is broken down.

What are the three components of a nucleotide?

A pentose ring sugar, a nitrogenous base, and a phosphate group. Signup and view all the answers

What are the pentose sugars found in RNA and DNA?

Ribose in RNA and deoxyribose in DNA. Signup and view all the answers

Which two molecules combine to form maltose?

Two molecules of α-glucose Signup and view all the answers

What is maltose also known as?

Malt sugar Signup and view all the answers

Match the following nitrogenous bases with their type:

Cytosine = Pyrimidine Uracil = Pyrimidine Thymine = Pyrimidine Adenine = Purine Guanine = Purine Signup and view all the answers

What is the structure of DNA based on the Watson and Crick model?

DNA consists of two polynucleotide chains twisted to form a double helix. Signup and view all the answers

What is the process called that release separate monomer units from maltose?

Hydrolysis process Signup and view all the answers

The two polynucleotide chains in DNA are arranged in ________ direction.

opposite (antiparallel) Signup and view all the answers

Which of the following is NOT a general property of polysaccharides?

Sweet in taste Signup and view all the answers

Match the following polysaccharides with their functions:

Starch = Energy source in plants Glycogen = Energy source in animals Cellulose = Main component of cell walls Signup and view all the answers

How many base pairs are there per full turn of a DNA double helix?

10 base pairs. Signup and view all the answers

What type of bond links the monomers in starch?

α-1,4 glycosidic bond Signup and view all the answers

Which types of RNA are there?

All of the above Signup and view all the answers

What is the function of mRNA?

Carries genetic information copied from DNA which acts as a template for protein synthesis. Signup and view all the answers

What are the two types of starch?

Amylose and amylopectin Signup and view all the answers

What is glycogen primarily used for?

Energy storage in animals Signup and view all the answers

What does rRNA do?

Forms ribosomal subunits (together with proteins). Signup and view all the answers

What is formed when 1 glycerol combines with 3 fatty acids?

1 triglyceride + 3 water Signup and view all the answers

What is the breakdown process of triglycerides called?

Hydrolysis Signup and view all the answers

What is the function of tRNA?

Transfers specific amino acids to the ribosome during protein synthesis. Signup and view all the answers

What type of glucose makes up cellulose?

β-glucose Signup and view all the answers

Humans can digest cellulose.

False Signup and view all the answers

Which functional groups are contained in an amino acid?

Carboxyl group (-COOH) Signup and view all the answers

What type of lipid consists of three fatty acids linked to one glycerol molecule?

Triglycerides Signup and view all the answers

How are amino acids classified?

Based on R group Signup and view all the answers

Dipeptides consist of a single amino acid linked by a peptide bond.

False Signup and view all the answers

What are two types of fatty acids?

Saturated and unsaturated fatty acids Signup and view all the answers

What does the primary structure of a protein consist of?

Linear chain of amino acids Signup and view all the answers

What is the molecular formula of glycerol?

C3H8O3 Signup and view all the answers

Match the following protein structures with their descriptions:

Primary structure = Linear chain of amino acids Secondary structure = Regions stabilized by hydrogen bonds Tertiary structure = Three-dimensional shape stabilized by side chain interactions Quaternary structure = Association of multiple polypeptide chains Signup and view all the answers

What type of reaction occurs to form triglycerides?

Condensation process Signup and view all the answers

What can cause denaturation of proteins?

Changes in pH and temperature Signup and view all the answers

What is a characteristic of fibrous proteins?

Stable and tough structure Signup and view all the answers

What is the effect of high temperature on protein structure?

Denaturation of protein Signup and view all the answers

What is the structure of a water molecule?

A water molecule consists of one oxygen atom and two hydrogen atoms, connected by covalent bonds. Signup and view all the answers

What angle do the two covalent bonds in a water molecule spread apart?

104.5 degrees Signup and view all the answers

A water molecule has a net charge.

False Signup and view all the answers

What is a polar molecule?

A polar molecule is one where the opposite ends have opposite charges. Signup and view all the answers

What kind of bond forms between two water molecules?

Hydrogen bond Signup and view all the answers

Which of the following is NOT a property of water?

Inert and non-reactive Signup and view all the answers

What happens to salt when it is dissolved in water?

Salt crystals separate into Na+ ions and Cl- ions. Signup and view all the answers

What is the term for water acting as a dissolving agent?

Solvent Signup and view all the answers

What does high specific heat capacity of water enable?

It allows temperatures in cells to remain relatively constant. Signup and view all the answers

Cohesion refers to water molecules' attraction to different substances.

False Signup and view all the answers

Ice is less dense than water.

True Signup and view all the answers

What are the classes of carbohydrates?

Monosaccharides, disaccharides, polysaccharides Signup and view all the answers

What are disaccharides formed from?

Two monosaccharides joined together by a glycosidic linkage. Signup and view all the answers

Which of the following is a disaccharide?

Maltose Signup and view all the answers

Study Notes

Molecules of Life

Properties of Water

Water is made of one oxygen atom and two hydrogen atoms, forming covalent bonds.
The water molecule's structure is V-shaped, with an angle of 104.5° between the hydrogen atoms.
Oxygen is more electronegative than hydrogen, resulting in a polar molecule with partially positive (δ+) hydrogen atoms and a partially negative (δ-) oxygen atom.
Hydrogen bonds form between the positive hydrogen atoms of one water molecule and the negative oxygen atoms of neighboring molecules, creating cohesion.
Each water molecule can form up to four hydrogen bonds with adjacent water molecules.
Water’s polarity allows it to interact with other polar substances (hydrophilic) and repel non-polar substances (hydrophobic).

Importance of Water Properties

Universal Solvent: Water dissolves many substances, allowing for vital biological reactions (e.g., sodium and chloride ions).
High Specific Heat Capacity: Requires significant energy to change temperature, stabilizing environments (e.g., oceans, cellular temperature).
Latent Heat of Vaporization: Absorbs high energy for vaporization, allowing cooling mechanisms in organisms (e.g., sweating).
Cohesion and Surface Tension: Water molecules bond with each other, allowing capillary action and surface tension, essential for plant water transport.
Density Maximum at 4°C: Water is most dense at this temperature, allowing ice to float and insulate aquatic environments, supporting life beneath.

Classes of Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio (general formula: (CH2O)n).
Divided into three classes:
- Monosaccharides: Simple sugars (e.g., glucose); sweet, soluble, crystallizable; building blocks for larger carbohydrates.
- Disaccharides: Formed by two monosaccharides via glycosidic bonds through condensation; examples include maltose (α-glucose + α-glucose), sucrose (α-glucose + β-fructose), and lactose (β-galactose + α-glucose).
- Polysaccharides: Complex carbohydrates made of many monosaccharides; include starch, glycogen, and cellulose.

Monosaccharides

Simple sugars characterized by a carbonyl group and multiple hydroxyl groups; classified as aldoses or ketoses based on the location of the carbonyl group.
Pentoses (5C): Include ribose (RNA component) and deoxyribose (DNA component).
Hexoses (6C): Examples include glucose (primary energy source) and fructose (found in fruits), both capable of ring formation.
Isomers of glucose exhibit different ring structures (α and β forms).

Disaccharides Formation and Breakdown

Formed through condensation, creating glycosidic bonds with the removal of water.
Broken down via hydrolysis, which requires water to split the disaccharide into monosaccharides.
Example: Maltose is created from two α-glucose molecules, linked by an α-1,4 glycosidic bond.

Nutritional Importance

Monosaccharides serve as energy sources and structural components of cell membranes, while disaccharides and polysaccharides are used in energy storage and supply.### Polysaccharides
Polysaccharides are polymers formed from the condensation of many monosaccharides, linked by glycosidic bonds.
Chains may be branched or unbranched.

General Properties of Polysaccharides

Insoluble in water
Can form colloids in water
Not sweet in taste
Cannot crystallize

Functions of Polysaccharides

Energy source: starch and glycogen
Structural component: cellulose in plant cell walls
Protection and immunization: heparin in mammalian blood prevents blood clotting, produced by basophils.

Starch

A polymer of α-glucose linked by α-1,4 glycosidic bonds.
Two types of starch:
- Amylose: Simple and unbranched, composed of 200-1500 α-glucose molecules.
- Amylopectin: Complex and branched, made of 2000 to 200000 α-glucose molecules, branching occurs every 25-30 units with α-1,6 bonds.

Glycogen

Composed of short, highly branched chains of α-glucose.
Found in muscle and liver cells.
Characteristics: Not sweet, insoluble in water, cannot crystallize, compact structure.

Cellulose

A polymer of β-glucose forming the main component of plant cell walls.
Linked by β-1,4 glycosidic bonds, stabilized by hydrogen bonds for rigidity.

Comparison of Amylose and Cellulose

Amylose: Monomer (α-glucose), α-1,4 glycosidic bond, function in starch storage in plants.
Cellulose: Monomer (β-glucose), β-1,4 glycosidic bond, function as structural component of cell wall.

Digestion of Cellulose

Ruminant/herbivorous animals rely on symbiotic bacteria or protozoa to digest cellulose, as they lack cellulase.
Humans cannot digest cellulose due to the absence of necessary enzymes.

Types of Lipids

Main types: triglycerides (fat and oil), phospholipids, steroids.
Lipids are large biological molecules consisting of carbon, hydrogen, and oxygen; they are hydrophobic due to nonpolar C-H bonds.

Importance of Lipids

Energy storage, cellular membrane components, insulation (e.g., blubber), carriers for flavor and odor compounds, transport of fat-soluble vitamins.

Triglycerides

Composed of three fatty acid molecules linked to one glycerol molecule via ester bonds.
Types: fats (solid at room temperature) and oils (liquid at room temperature).

Phospholipids

Key components of cell membranes, forming a bilayer with hydrophilic heads and hydrophobic tails.

Steroids

Organic compounds with a four fused carbon ring structure, with variable side chains.

Fatty Acids

Long, unbranched hydrocarbon chains with a carboxyl group (-COOH) at one end.
Amphiphilic nature: hydrophilic carboxyl group versus hydrophobic hydrocarbon tail.

Saturated vs. Unsaturated Fatty Acids

Saturated fatty acids: only single bonds, solid at room temperature (e.g., stearic acid).
Unsaturated fatty acids: one or more double bonds, liquid at room temperature (e.g., oleic acid).

Glycerol

An alcohol consisting of three carbon atoms, each bearing a hydroxyl group (-OH), forming ester bonds with fatty acids.

Formation and Breakdown of Triglycerides

Formation: Through condensation, one glycerol molecule combines with three fatty acids, yielding a triglyceride and three water molecules.
Breakdown: Hydrolysis reaction, reversible process yielding glycerol and three fatty acids from triglycerides.

Structure of Amino Acids

Composed of an amino group (-NH2), carboxyl group (-COOH), one hydrogen atom, and an R group (side chain).
Zwitterionic form at cellular pH (~7.4) due to simultaneous positive and negative charges.

Grouping Amino Acids

Classified based on R group/side chain properties, primarily into non-polar (hydrophobic) and polar types.

This summary captures the essential concepts concerning polysaccharides, lipids, and proteins, focusing on their structures, functions, and classifications.### Amino Acid Grouping

Amino acids are categorized based on their R group/side chain.
Polar amino acids: Characterized by hydrophilic R groups.
Acidic amino acids: Contain a carboxyl group (-COOH) in their R group.
Basic amino acids: Contain an amino group (-NH2) in their R group.

Levels of Protein Structure

Primary structure (1°): Linear sequence of amino acids linked by peptide bonds.
Secondary structure (2°): Includes regions stabilized by hydrogen bonds, forming structures like α-helices and β-pleated sheets.
Tertiary structure (3°): Three-dimensional shape formed by interactions between side chains. Stabilized by hydrogen bonds, hydrophobic interactions, ionic bonds, and disulfide bridges.
Quaternary structure (4°): Formed from the association of multiple polypeptide chains (subunits) into a functional protein.

Secondary Structure Details

α-helix: Coiled structure held by hydrogen bonds (e.g., keratin in hair and feathers).
β-pleated sheet: Parallel polypeptide regions held together by hydrogen bonds, foundational in many globular proteins (e.g., fibroin in silk).

Tertiary Structure Specifics

Stabilization comes from multiple types of interactions including hydrophobic interactions and ionic bonds.
Example: Myoglobin, responsible for oxygen storage in muscle tissue.

Quaternary Structure Examples

Collagen: Fibrous protein with three intertwined helical polypeptides, provides strength in connective tissues.
Hemoglobin: Composed of four polypeptide chains, involved in oxygen transport.

Effects of pH and Temperature on Protein Structure

Denaturation: Loss of original conformation due to changes in temperature or pH, resulting in biological inactivity.
High temperatures disrupt hydrogen bonds, ionic bonds, and disulfide bridges, leading to denaturation.
Extreme pH also breaks ionic and hydrogen bonds.

Dipeptide Formation and Breakdown

Dipeptides consist of two amino acids linked by a peptide bond, formed through condensation.
The carboxyl group of one amino acid bonds with the amino group of another, releasing a water molecule.

Classification of Proteins

Fibrous proteins: Long, stable structure suitable for support (e.g., keratin, collagen). Generally insoluble in water.
Globular proteins: Spherical shape with flexible structure, generally soluble in water, and play roles as enzymes and hormones (e.g., antibodies, insulin).
Conjugated proteins: Composed of amino acids and non-protein components (e.g., heme in hemoglobin).

Nucleotide Structure in Nucleic Acids

Nucleotides consist of a pentose sugar, a nitrogenous base, and a phosphate group.
Pentose sugars: Ribose in RNA; deoxyribose in DNA, differing by one oxygen atom.
Nitrogenous bases: Two categories—pyrimidines (C, U, T) and purines (G, A).

DNA Structure

Composed of two intertwined polynucleotide chains forming a double helix, joined by phosphodiester linkages.
Antiparallel arrangement: One strand has a 3' hydroxyl group; the other has a 5' phosphate group.
Base pairing rules: A pairs with T (2 hydrogen bonds) and C pairs with G (3 hydrogen bonds).

RNA Structure

RNA consists of a shorter, single polynucleotide strand with ribose sugar.
Contains nitrogenous bases: A, U, C, G.

Types of RNA

RNA is a single-stranded polynucleotide that plays various roles in genetic expression and protein synthesis.

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Description

This quiz covers Chapter 1 on the Molecules of Life, focusing on essential topics such as water, carbohydrates, lipids, proteins, and nucleic acids. Test your understanding of the structure and function of these vital biomolecules and their importance in biological systems.