Lecture 1 - Biology Chapter: Key Molecules of Life

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Questions and Answers

Which statement correctly describes the differences between prokaryote and eukaryote cells?

Prokaryote cells have organelles, eukaryote cells do not.

Both prokaryote and eukaryote cells have cell walls.

Eukaryote cells have a nucleus, prokaryote cells do not. (correct)

Prokaryote cells are always larger than eukaryote cells.

What is the relationship between phenotype and genotype?

Genotype is solely determined by environmental factors.

Genotype affects phenotype, which is the observable traits. (correct)

Phenotype and genotype are the same concepts.

Phenotype is the genetic makeup, while genotype refers to observable traits.

What role does phospholipase play in biological membranes?

It stores glucose for energy metabolism.

It catalyzes the formation of proteins.

It hydrolyzes phospholipids, impacting membrane structure. (correct)

It aids in the synthesis of nucleic acids.

What distinguishes saturated fatty acids from unsaturated fatty acids?

Unsaturated fatty acids contain double bonds, while saturated ones do not. Signup and view all the answers

How do estrogen and progesterone function differently despite their chemical differences?

The chemical elements attached to them alter their function and timing. Signup and view all the answers

Which of the following correctly describes the structure of amino acids?

Amino acids have an amino group on one end and a carboxyl group on the other. Signup and view all the answers

What happens to glucose when it is in solution form?

It is composed of approximately 36% alpha-glucose and 64% beta-glucose. Signup and view all the answers

What is the significance of the hydrophilic and hydrophobic components of phospholipids in membrane formation?

They create a double layer, with hydrophobic tails sheltered from water. Signup and view all the answers

Which statement about glucose is correct?

b) In solution, glucose exists as ~36% α-glucose and ~64% β-glucose. Signup and view all the answers

What is the composition of a nucleotide?

Sugar attached to phosphate and nitrogenous bases Signup and view all the answers

What is the directionality of nucleic acid reading during transcription?

5’ to 3’ Signup and view all the answers

What determines the hydrophilic or hydrophobic nature of an amino acid?

The R group attached to the amino acid Signup and view all the answers

What is a unique feature of phospholipids in the cell membrane?

Their hydrophilic heads interact with water, and hydrophobic tails avoid water. Signup and view all the answers

What makes proteins have polarity in their structure?

The directionality of the amino and carboxyl ends Signup and view all the answers

Which of the following is true about sickle cell anemia?

It is due to a change in the shape of hemoglobin. Signup and view all the answers

Which of the following statements is true about amino acids?

Serine is hydrophilic due to its hydroxyl group. Signup and view all the answers

Which of the following correctly describes nucleic acids?

Nucleotides polymerize to form nucleic acids, which are read from 5’ to 3’. Signup and view all the answers

What is the functional role of phospholipase?

It is an enzyme that breaks down phospholipids. Signup and view all the answers

What is the main difference between the hydrophobic and hydrophilic parts of a molecule?

Hydrophobic parts avoid water, while hydrophilic parts interact with water. Signup and view all the answers

Study Notes

Key Molecules of Life

Prokaryotic cells lack a nucleus (bacteria, archaea)
Eukaryotic cells contain a nucleus (plants, fungi, animals)
Plant cells have cell walls and chloroplasts
Fungi cells have cell walls but no chloroplasts
Animal cells lack cell walls and chloroplasts

Links Between Molecules, Cells, and Organisms

Molecules determine phenotypes
Mutant hemoglobin: Brain cell death, holes in adult brains
Missing hormone leptin: Loss of cell signaling pathway
Examples: Sickle cell anemia, Swiss cheese phenotype, obese mouse

Phenotype vs. Genotype

Phenotype: Observable traits (height, eye color, blood type)
Genotype: Genetic makeup
Example: Change in hemoglobin shape causes sickle cell anemia
Example: Phospholipase is an enzyme

Life's Molecular Building Blocks

Life is composed of the same molecules in all organisms
Small molecules form larger molecules
Building Blocks: Sugars, fatty acids, amino acids, nucleotides
Larger Molecules and Structures: Polysaccharides, lipids, proteins, nucleic acids

Carbohydrates: Energy and Structure

Monosaccharides (e.g., glucose): Energy source for cells
Formula: (CH₂O)ₙ (where n = 3 or more)
Glucose (n=6), hexose sugar
α-glucose and β-glucose isomers—interchangeable
Examples: Glycogen (energy storage in animals, fungi, bacteria), Cellulose (cell walls in plants, algae)

Lipids: Definition and Roles

Lipids are water-insoluble, but highly soluble in organic solvents
Diverse structure and functions
Functions: Energy storage, structure (membrane lipids), signaling (steroid hormones)
Example: Fatty acids (palmitate), membrane lipids (phospholipids), steroidal hormones (estrogen)

Fatty Acids: Energy Source

Structure: Carboxylic acid group at one end, methyl group at the other; saturated or unsaturated hydrocarbon chain
Saturated vs. unsaturated: Differences relate to bonding
Energy Value: Fatty acids have more energy per gram than glucose

Membrane Lipids: Phospholipids, Glycolipids, and Cholesterol

Structural components of cell membranes
Phospholipids have hydrophilic heads and hydrophobic tails
Phospholipids create a boundary; hydrophobic tails face inward

Steroid Hormones: Signaling

Function: Control of various bodily functions.
Examples: Estrogen and progesterone regulate the menstrual cycle
Steroids have different chemical structures, binding to different receptors, resulting in changes in bodily functions.

Amino Acids

20 common amino acids form proteins
Structure: Central alpha carbon, amino group, carboxyl group, side chain (R group)
R group variations: Determine the properties of each amino acid
Examples: Serine (hydrophilic), Valine (hydrophobic)

Proteins: Functions

Functions: Catalysts (enzymes), communication (receptors), defence (antibodies), transport (hemoglobin), structure (cytoskeleton), control (transcription factors, chaperones)

Nucleotides and Nucleic Acids

Nucleotides form nucleic acids
Types of Nucleotides: Adenine, guanine, cytosine, thymine
Structure: Sugar-phosphate backbone with nitrogenous bases attached.
The order of bases stores genetic information.

Gene Sequences

Gene sequences are conserved—shared—across different organisms
This similarity reflects shared ancestry.
Implications: The conservation of gene sequences provides evidence of evolutionary relationships

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Description

Test your knowledge on the key molecules that form the basis of life and the differences between prokaryotic and eukaryotic cells. Explore phenotypes and genotypes and understand how molecular structures influence cellular function. This quiz includes examples of diseases related to molecular mutations.