Classes of Molecules Found in Cells,.pdf

Ged science notes on Classes of Molecules Found in Cells

1. CLASSES OF MOLECULES FOUND IN CELLS
GED Science: Life Science
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2. Lipids
Lipids
Definition and Structure:
Long chains of carbon and hydrogen: Lipids are primarily composed of long hydrocarbon chains or rings, making them nonpolar and hydrophobic.
Hydrophobic (water-fearing) nature: Due to their nonpolar nature, lipids do not mix well with water.
Types of Lipids:
Fats:
Usually solid at room temperature.
Composed of glycerol and three fatty acids (triglycerides).
Oils:
Usually liquid at room temperature.
Similar to fats but with unsaturated fatty acids.
Phospholipids:
Contain a glycerol backbone, two fatty acids, and a phosphate group.
Major component of cell membranes.
Steroids:
Composed of four fused carbon rings.
Includes hormones like testosterone and cholesterol.
Functions:
Energy storage: Lipids store energy efficiently due to their high caloric content.
Cell membrane structure: Phospholipids form the bilayer of cell membranes, providing structural integrity and fluidity.
Hormonal roles: Steroid hormones regulate various physiological processes.
Examples:
Triglycerides: Primary form of stored fat in animals.
Cholesterol: Essential component of cell membranes and precursor for steroid hormones.
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3. Proteins
Definition and Structure:
Made up of amino acids: Proteins are polymers of amino acids linked by peptide bonds.
Primary structure: Sequence of amino acids in a polypeptide chain.
Secondary structure: Local folding into alpha helices and beta sheets.
Tertiary structure: Overall 3D shape of a single polypeptide.
Quaternary structure: Arrangement of multiple polypeptide subunits.
Types of Proteins:
Enzymes: Catalysts for biochemical reactions.
Structural proteins: Provide support and shape to cells and tissues (e.g., collagen).
Transport proteins: Move molecules across cell membranes (e.g., hemoglobin).
Antibodies: Part of the immune system, recognizing and neutralizing pathogens.
Functions:
Catalyzing biochemical reactions: Enzymes accelerate chemical reactions in the body.
Structural support: Proteins like collagen provide strength and support to tissues.
Transporting molecules: Hemoglobin transports oxygen in the blood.
Defense against pathogens: Antibodies identify and neutralize foreign objects like bacteria and viruses.
Examples:
Hemoglobin: Transports oxygen in the blood.
Insulin: Regulates blood sugar levels.
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4. Carbohydrates
Definition and Structure:
Made up of carbon, hydrogen, and oxygen: Typically in a ratio of 1:2:1 (CH2O)n.
Monosaccharides: Single sugar molecules (e.g., glucose).
Disaccharides: Two monosaccharides linked together (e.g., sucrose).
Polysaccharides: Long chains of monosaccharide units (e.g., starch, glycogen, cellulose).
Types of Carbohydrates:
Simple sugars: Include monosaccharides (glucose, fructose) and disaccharides (sucrose).
Complex carbohydrates: Include polysaccharides like starch (energy storage in plants), glycogen (energy storage in animals), and cellulose (structural component in plants).
Functions:
Primary energy source: Glucose is a major energy source for cellular activities.
Energy storage: Starch and glycogen store energy for later use.
Structural components: Cellulose provides structural support in plant cell walls.
Examples:
Glucose: A key energy source for cells.
Sucrose: Common table sugar.
Cellulose: Provides rigidity to plant cell walls.
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5. DNA (Deoxyribonucleic Acid)
Definition and Structure:
Double-stranded helix: DNA consists of two strands that form a double helix.
Composed of nucleotides: Each nucleotide includes a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, guanine).
Functions:
Storage of genetic information: DNA contains the instructions for building and maintaining an organism.
Transmission of genetic information: DNA passes genetic information from one generation to the next.
Processes:
DNA replication: The process by which DNA makes a copy of itself during cell division.
Transcription: The process of making RNA from a DNA template.
Importance in Heredity:
Genetic inheritance: DNA carries genetic information that determines traits.
Mutations and their effects: Changes in DNA sequence can lead to variations in traits or cause genetic disorders.
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6. RNA (Ribonucleic Acid)
Definition and Structure:
Single-stranded molecule: Unlike DNA, RNA is typically single-stranded.
Composed of nucleotides: Each nucleotide includes a sugar (ribose), a phosphate group, and a nitrogenous base (adenine, uracil, cytosine, guanine).
Types of RNA:
Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes for protein synthesis.
Transfer RNA (tRNA): Brings amino acids to ribosomes during protein synthesis.
Ribosomal RNA (rRNA): A structural component of ribosomes.
Functions:
Protein synthesis (translation): mRNA, tRNA, and rRNA work together to translate genetic information into proteins.
Gene regulation: RNA molecules can regulate gene expression and play roles in various cellular processes.
Processes:
Transcription: The synthesis of RNA from a DNA template.
Translation: The synthesis of proteins from an mRNA template.
Examples:
mRNA: Conveys genetic information from DNA to the ribosome.
tRNA: Transfers specific amino acids to the growing polypeptide chain.
rRNA: Combines with proteins to form ribosomes.
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7. Questions and Answers
Lipids
Q: What are lipids primarily composed of? A: Long chains of carbon and hydrogen.1.
Q: Are lipids hydrophilic or hydrophobic? A: Hydrophobic (water-fearing).2.
Q: Name the four types of lipids. A: Fats, oils, phospholipids, and steroids.3.
Q: What is the primary function of fats in the body? A: Energy storage.4.
Q: What role do phospholipids play in cells? A: They are a major component of cell
membranes.
5.
Q: Which type of lipid serves as hormones in the body? A: Steroids.6.
Q: Give an example of a triglyceride. A: Common animal fats and oils.7.
Q: What is cholesterol's role in the body? A: It is a component of cell membranes and a
precursor for steroid hormones.
8.
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8. Questions and Answers
Proteins
Q: What are the building blocks of proteins? A: Amino acids.1.
Q: What are the four levels of protein structure? A: Primary, secondary, tertiary, and
quaternary structures.
2.
Q: What type of protein acts as a catalyst for biochemical reactions? A: Enzymes.3.
Q: Name a structural protein found in the human body. A: Collagen.4.
Q: What protein transports oxygen in the blood? A: Hemoglobin.5.
Q: What type of proteins are antibodies? A: Defense proteins.6.
Q: Give an example of a transport protein. A: Hemoglobin.7.
Q: What protein regulates blood sugar levels? A: Insulin.8.
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9. Questions and Answers
Carbohydrates
Q: What three elements make up carbohydrates? A: Carbon, hydrogen, and oxygen.1.
Q: What is the simplest form of carbohydrate? A: Monosaccharides.2.
Q: Name two common monosaccharides. A: Glucose and fructose.3.
Q: What is a disaccharide? A: A carbohydrate composed of two monosaccharides.4.
Q: Give an example of a disaccharide. A: Sucrose.5.
Q: What are polysaccharides? A: Long chains of monosaccharides.6.
Q: Name two storage forms of polysaccharides. A: Starch and glycogen.7.
Q: What polysaccharide is a major component of plant cell walls? A: Cellulose.8.
Q: What is the primary function of glucose in cells? A: To provide energy.9.
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10. Questions and Answers
DNA (Deoxyribonucleic Acid)
Q: What is the structure of DNA? A: A double-stranded helix.1.
Q: What are the four nucleotide bases in DNA? A: Adenine, thymine, cytosine, and guanine.2.
Q: What is the function of DNA? A: To store and transmit genetic information.3.
Q: What process copies DNA during cell division? A: DNA replication.4.
Q: What process makes RNA from DNA? A: Transcription.5.
Q: How is genetic information inherited? A: Through the DNA passed from parents to
offspring.
6.
Q: What can mutations in DNA cause? A: Genetic variations and sometimes disorders.7.
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11. Questions and Answers
RNA (Ribonucleic Acid)
Q: How does RNA differ structurally from DNA? A: RNA is single-stranded, while DNA is
double-stranded.
1.
Q: What nucleotide base is found in RNA but not in DNA? A: Uracil.2.
Q: Name the three types of RNA. A: Messenger RNA (mRNA), transfer RNA (tRNA), and
ribosomal RNA (rRNA).
3.
Q: What is the function of mRNA? A: To carry genetic information from DNA to the
ribosome for protein synthesis.
4.
Q: What does tRNA do during protein synthesis? A: It transfers amino acids to the
ribosome.
5.
Q: What is the role of rRNA? A: It is a component of ribosomes, which are the sites of
protein synthesis.
6.
Q: What process synthesizes RNA from a DNA template? A: Transcription.7.
Q: What process uses mRNA to synthesize proteins? A: Translation.8.

12. Questions and Answers
General Questions
Q: What are the primary functions of lipids in biological systems? A: Energy storage, cell membrane structure, and hormonal roles.1.
Q: How do enzymes speed up biochemical reactions? A: By lowering the activation energy required for the reaction.2.
Q: What is the significance of the tertiary structure of proteins? A: It determines the protein’s overall shape and function.3.
Q: Why are carbohydrates important for cellular function? A: They provide a primary source of energy and structural components.4.
Q: What is the role of DNA in genetic inheritance? A: DNA carries the genetic instructions used in growth, development, functioning,
and reproduction.
5.
Q: How does RNA differ in function from DNA? A: RNA is involved in protein synthesis and gene regulation, while DNA stores genetic
information.
6.
Q: What is the main purpose of glycolysis in cellular respiration? A: To break down glucose into pyruvate, producing ATP and NADH.7.
Q: How do phospholipids contribute to cell membrane structure? A: They form a bilayer that serves as a barrier to protect the cell and
control what enters and exits.
8.
Q: What is the primary function of hemoglobin in the blood? A: To transport oxygen from the lungs to the rest of the body and return
carbon dioxide to the lungs for exhalation.
9.
Q: Why is it important for mutations to occur in DNA? A: Mutations create genetic diversity, which is essential for evolution and
adaptation.
10.
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13. End
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