Biology Chapter: Water and Organic Molecules

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Questions and Answers

What is the primary reason for the Earth's habitability?

The existence of a strong magnetic field.

The abundance of liquid water. (correct)

The presence of a thick atmosphere.

The presence of a large moon.

What is the primary chemical component of most cells?

Water. (correct)

Proteins.

Carbohydrates.

Lipids.

Which of the following is NOT an emergent property of water?

Ability to form covalent bonds. (correct)

Expansion upon freezing.

Cohesion/Adhesion.

Moderation of Temperature.

What is the chemical symbol for the most abundant element in the universe?

H (B) Signup and view all the answers

Which of these molecules is NOT a carbon-based compound?

Water (A) Signup and view all the answers

What is the chemical formula for aspartic acid?

C4H7NO4 (B) Signup and view all the answers

What is the most important factor determining the properties of water?

Its polarity. (B) Signup and view all the answers

Which of the following is NOT a characteristic of carbon that makes it essential for life?

Ability to form ionic bonds with other elements. (D) Signup and view all the answers

What is the process called when a water molecule is removed to form a new bond between monomers, creating a polymer?

Dehydration synthesis (B) Signup and view all the answers

What is the role of water in the breakdown of a polymer?

Water is required to break the bonds between monomers. (B) Signup and view all the answers

Which of the following is NOT a biological macromolecule?

Water (C) Signup and view all the answers

What is the monomer subunit of carbohydrates?

Simple sugars (A) Signup and view all the answers

What is the chemical formula that represents the ratio of carbon, hydrogen, and oxygen in simple sugars?

CH2O (C) Signup and view all the answers

Which of the following is a characteristic of simple sugars?

They are often used as fuel by organisms. (B) Signup and view all the answers

What is the general name for simple sugars?

Monosaccharides (A) Signup and view all the answers

What is the main difference between dehydration synthesis and hydrolysis?

Dehydration synthesis removes a water molecule, while hydrolysis adds one. (A) Signup and view all the answers

What is the defining characteristic of lipids?

They are hydrophobic. (A) Signup and view all the answers

Which of these molecules is NOT a type of lipid?

Glucose (B) Signup and view all the answers

Which of the following is a function of steroids?

Components of hormones (B) Signup and view all the answers

What are the subunits that make up nucleic acids?

Nucleotides (A) Signup and view all the answers

What type of bond connects the subunits of nucleic acids?

Phosphodiester Bonds (D) Signup and view all the answers

Which of the following carbohydrates is a ketose?

Fructose (B) Signup and view all the answers

What is the chemical formula for a hexose sugar?

C6H12O6 (D) Signup and view all the answers

How many carbons are present in a triose sugar?

3 (C) Signup and view all the answers

Which of the following is formed when glucose converts from its linear to its ring form?

An ether (C) Signup and view all the answers

Which of the following best describes the process of glucose converting from its linear to its ring form?

Cyclization (D) Signup and view all the answers

What functional group is present in the linear form of an aldose sugar?

Aldehyde (A) Signup and view all the answers

Which of the following statements is true about the conversion of glucose from its linear to its ring form?

The conversion is in dynamic equilibrium. (C) Signup and view all the answers

Which carbon in a hexose sugar, when numbered according to convention, is involved in the formation of the ring?

1 (D) Signup and view all the answers

What type of molecule is the repeating unit in a polymer?

Monomer (A) Signup and view all the answers

Which of the following biological macromolecules is NOT a polymer?

Lipids (B) Signup and view all the answers

What is the primary function of proteins in biological systems?

Providing structural support and acting as catalysts (D) Signup and view all the answers

What is the primary function of carbohydrates in biological systems?

Providing a source of energy and making up cell walls (A) Signup and view all the answers

Which of the following is a type of bond that connects monomers together in a polymer?

Covalent bond (A) Signup and view all the answers

What type of linkage is responsible for the bonding between two monosaccharides, forming a disaccharide?

Glycosidic bond (A) Signup and view all the answers

Which of the following is an example of a monomer?

Amino acid (D) Signup and view all the answers

What is the structural polysaccharide found in plants?

Cellulose (D) Signup and view all the answers

Which of the following best describes the role of nucleic acids in living organisms?

Storing and transmitting genetic information (C) Signup and view all the answers

What is the primary role of glycogen in animals and fungi?

Energy storage (A) Signup and view all the answers

Which type of molecule is responsible for storing energy in cells?

Lipids (A) Signup and view all the answers

Which of the following sugars is a transport sugar found in plants?

Sucrose (B) Signup and view all the answers

Where does the plant store starch?

Chloroplasts (B) Signup and view all the answers

What is the primary difference between amylose and amylopectin?

Amylose is linear, while amylopectin is branched. (B) Signup and view all the answers

What is the main structural component of the exoskeleton of insects and crustaceans?

Chitin (A) Signup and view all the answers

Which of the following is an example of a disaccharide?

Maltose (D) Signup and view all the answers

Study Notes

Biology 1 - Cells, Molecular Biology and Genetics (Biol 1000)

Course offered by Dr. Michael Cardinal-Aucoin in Winter 2025 at York University
Course covers cells, molecular biology, and genetics

Building Blocks of Life

Chemistry of Life is a fundamental concept in the course.
Biological macromolecules are crucial elements.
Polymers, carbohydrates, lipids, proteins, and nucleic acids are discussed as key biological macromolecules.

Review Chapter 2

Matter, elements, and atoms are building blocks.
Atoms consist of protons, neutrons and electrons.
Atomic mass and number are important concepts.
Isotopes have different neutron numbers.
Valence electrons and ions are described.
Ionic and covalent bonds are discussed.
Non-polar, polar covalent bonds, and electronegativity are explored.
Hydrogen and Van der Waals forces are introduced.
Chemical reactions include reactants, products, reversible reactions, equilibrium, and specificity.
Water properties – polarity, cohesion, adhesion, high specific heat are discussed.
Functional groups are covered.

The Molecules of Life

All cells comprise four main biological macromolecules—carbohydrates, lipids, nucleic acids, and proteins.
These molecules share a carbon backbone.
The diversity of ways these molecules are built and combined is explored.

The Chemistry of Life

20-25% of the 92 elements are essential for life.
Carbon, hydrogen, oxygen, and nitrogen together account for 96% of all living matter.
Other important elements like calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium make up the remaining 4%.

Table 2.1 Elements in the Human Body

A table detailing the percentage of each element present in the human body, including the percentage of water.

Water and Life

Water is the fundamental biological medium on Earth, where life originated.
All living organisms rely on water more than any other substance.
Most cells comprise 70-95% of water.
Water is vital for dissolved molecules in cells.
Water's abundance on Earth contributes to its habitability.

Summary (Water)

Water’s key properties result from polarity and hydrogen bonding.
Expansion upon freezing, cohesion/adhesion, moderation of temperature, and versatility as a solvent are discussed.
pH of water is tightly regulated by living organisms.

Water

Polarity, simplicity and complexity, and the importance of water as the birthplace of life are addressed.
Hydrogen as a fundamental element is discussed.
Oxygen's significance as the most abundant component of water.

The Backbone of Life

All living organisms primarily consist of carbon-based molecules.
Carbon's ability to form complex, large molecules.
The vast abundance of carbon in the cosmos is noted.
Proteins, DNA, and carbohydrates fundamentally distinguish living matter.

A Note about Formulae

Aspartic acid, a building block of proteins, is detailed.
Chemical and condensed structural formulae and the Lewis diagram for the molecule are presented.
The various chemical bonds in the molecule are described.

Diversity of chemical functional groups

Chemical functional groups constructed with carbon are diverse.

The Molecules of Life (Summary)

Key functions of carbohydrates, lipids, nucleic acids, and proteins are described.

Polymers

Polymers are formed from repeating monomer units joined by covalent bonds.
Proteins consist of amino acid subunits.

Building polymers

Polymer formation occurs via dehydration synthesis (condensation).
Dehydration removes a water molecule to form a bond.

Breaking down polymers

Polymer breakdown occurs through hydrolysis.
Hydrolysis adds a water molecule to break a bond.

Polymers (Summary)

Biological macromolecules, such as carbohydrates, lipids, proteins, and nucleic acids, are generally polymers made from monomer subunits.

Carbohydrates

Carbohydrates are used as sources of energy by organisms.
Carbohydrates are essential structural components of some organisms.
Carbohydrates consist of chains of simple monosaccharides.

Simple sugars (carbohydrates)

Simple sugars contain a 1:2:1 ratio of C, H and O.
Simple sugars are called monosaccharides, ending in '-ose', and are named based on the number of carbons

Carbohydrates (Simple sugars)

Monosaccharides are categorized by the number of carbons in the carbohydrate skeleton (e.g., triose, tetrose, pentose, or hexose).
They are classified based on the location of the carbonyl group (aldehyde or ketone).

Carbohydrates (Glucose - chain to ring)

Glucose often depicted as a linear chain in diagrams, but actually forms a ring structure in solution.
Functional groups, like aldehyde and alcohol can be involved in forming the reactive ring structures.

Carbohydrates (Glycosidic bonds)

Disaccharides and polysaccharides are formed when monosaccharides are linked together via glycosidic bonds.
Glycosidic bonds occur between the carbon-1 of one monosaccharide and a hydroxyl group on another monosaccharide.

Sugars (carbohydrates - Disaccharides)

Disaccharides are composed of two monosaccharides bound together—examples include sucrose, lactose, and maltose.
They vary in their glycosidic linkage (alpha vs. beta), which impact their function.

Carbohydrates (Polysaccharides)

Polysaccharides are lengthy chains of monosaccharides linked by glycosidic bonds.
Examples include starches (i.e., amylose, amylopectin) used for energy storage in plants, and glycogen for energy storage in animals.
Structural polysaccharides such as cellulose in plants and chitin in fungi.

Carbohydrates (Energy storage in plants)

Plants store starch in chloroplasts.
Starch consists of amylose and amylopectin (branched).
A 1-4 glycosidic bond forms the linear amylose component.

Lipids

Lipids are significant biological macromolecules that are not derived from repeating monomers.
Lipids are distinguished by their hydrophobic property, defined by their chemical structure.
Principal categories include neutral fats, phospholipids, and steroids.

Lipids (Neutral Fats)

Neutral Fats, like triglycerides, have crucial roles in biological systems, such as energy storage.
They are crucial for insulation from cold temperatures and protecting internal organs.

Lipids (Phospholipids)

Phospholipids are constituents of cell membranes.
These lipids exhibit both hydrophilic and hydrophobic properties.
These properties lead to the formation of a bilayer structure in biological membranes.

Lipids (Steroids)

Steroids are components of cell membranes, vitamins and hormones.
Examples include cholesterol and hormones like cortisol.

Nucleic Acids

Nucleic acids are constructed from nucleotides, which then comprise nitrogenous bases, pentose sugars, and phosphate groups.
These biomolecules have prominent roles in information storage, including DNA and RNA.

DNA

In cells, DNA is typically a double helix composed of two nucleotide strands.

The "Central Dogma"

DNA acts as a blueprint for protein synthesis.
The process of transcription translates DNA sequences into mRNA.
mRNA carries instructions to build proteins, which then involves the process of translation.

Proteins

Proteins are complex polymers designed from amino acid subunits.
Proteins are essential components of living organisms performing numerous life functions.

Proteins (Enzymatic proteins)

Enzymatic proteins accelerate chemical reactions.
Examples include digestive enzymes.

Proteins (Defensive proteins)

Antibodies fight against diseases.

Proteins (Storage proteins)

Storage proteins, such as casein and ovalbumin are responsible for storing amino acids.

Proteins (Transport proteins)

Proteins known as transport proteins carry substances throughout the body.
Examples include hemoglobin that carries oxygen in blood.

Proteins (Hormonal proteins)

Hormones, such as insulin, coordinate bodily functions regulating glucose concentrations and other bodily processes, such as blood sugar levels.

Proteins (Receptor proteins)

Receptors respond to chemical signals.
Receptors may be membrane bound molecules that initiate cellular responses in response to molecules such as growth hormones.

Proteins (Contractile proteins)

Example is actin and myosin that facilitates cellular movement.

Proteins (Structural proteins)

Proteins that form the structural component of hair, feathers, and other external appendages.

Proteins (Amino acid substitution)

Genetic mutations in the DNA sequences change the amino acid sequence in the resultant protein molecules.
This has an impact on the proteins' function.

Proteins (Quaternary structure)

Proteins' quaternary structure occurs when two or more polypeptide chains come together to form larger functional complexes.
Examples of such proteins are hemoglobin that carries oxygen in the circulation system.

Protein: Form and Function

Structure determines protein function.
Different levels of protein structure (primary, secondary, tertiary, and quaternary) contribute to protein function

Proteins (Denaturation)

Tertiary structure is crucial for protein function.
Denaturation disrupts bonds causing proteins to lose function.

Proteins (Types of R-Groups)

Hydrophobic and hydrophilic types of amino acid R-groups exist.
These properties determine how specific segments of the protein interact
These interactions are also crucial for how various levels of protein structure form.

Proteins (Special amino acids)

Specific amino acids may contain specific reactive groups.
For instance, glycine is very small and proline creates a bend in the protein chain.
Cysteine residues can bind via a disulfide bond to create strong and stable bridges in the three dimensional conformation of the protein molecules.

Proteins (Essential amino acids)

Some amino acids need to be obtained via external sources because they cannot be produced by the body.

Proteins (Peptide bonds)

Peptide bonds connect amino acids to create polypeptide chains.
These bonds are formed by dehydration synthesis.

Proteins (Polypeptide chain)

Polypeptide chains have directionality (polarity) with an amino terminus and a carboxyl terminus.

Proteins (Primary structure)

The sequence of amino acids is the primary structure of a protein.
The primary structure is unique for each specific protein.

Proteins (Secondary structure)

Interactions influence alpha-helices and beta-sheets.
Secondary structures form parts of larger protein structures via interactions between amino acids.

Proteins (Tertiary structure)

The tertiary structure is the three-dimensional arrangement of a peptide chain.
R-Group interactions, and chemical bonds (i.e. hydrogen bonds, disulfide bridges, ionic bonds, Van der Waals forces, and hydrophobic interactions) contribute to the protein’s unique three dimensional form.