1. Vaccines work by stimulating the immune system to develop memory without causing full-blown illness. What type of molecule in a vaccine typically triggers the immune response?

A. Toxins produced by the pathogen
B. Live, attenuated (weakened) forms of the pathogen
C. Inactivated (dead) forms of the pathogen
D. Antigens (specific molecules) from the pathogen

Correct answer: D

Rationale: The correct answer is D: Antigens (specific molecules) from the pathogen. Vaccines contain antigens, which are specific molecules from the pathogen that trigger the immune response without causing the full-blown illness. By presenting these antigens to the immune system, vaccines stimulate the production of memory cells that can recognize and combat the pathogen in the future. Options A, B, and C are incorrect because vaccines typically do not contain toxins, live attenuated forms, or inactivated forms of the pathogen. Instead, they contain specific antigens to induce an immune response without causing the actual disease.

2. What are the three main types of RNA?

A. Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
B. DNA, RNA, and protein
C. Adenine, guanine, cytosine, and thymine
D. Deoxyribose, ribose, and phosphate

Correct answer: A

Rationale: Rationale: - Messenger RNA (mRNA) carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm for protein synthesis. - Ribosomal RNA (rRNA) is a structural component of ribosomes, which are the cellular machinery responsible for protein synthesis. - Transfer RNA (tRNA) is responsible for bringing amino acids to the ribosome during protein synthesis. Options B, C, and D are incorrect: - Option B lists DNA, RNA, and protein, which are biomolecules but not the three main types of RNA. - Option C lists nitrogenous bases (adenine, guanine, cytosine, and thymine) found in DNA, not types of RNA. - Option D lists components of nucleotides (deoxyribose, ribose, and phosphate), which are building blocks of nucleic

3. The main function of the nephrons is to:

A. Store urine
B. Filter blood and remove waste products
C. Produce hormones
D. Control blood pressure

Correct answer: B

Rationale: The correct answer is B: 'Filter blood and remove waste products.' Nephrons are the functional units of the kidneys responsible for filtering blood to remove waste products, excess ions, and water, while reabsorbing essential substances like glucose and amino acids. This process forms urine, which is stored in the bladder before being excreted. Options A, C, and D are incorrect because nephrons do not store urine, produce hormones, or directly control blood pressure; although the kidneys do play a role in long-term blood pressure regulation through mechanisms like the renin-angiotensin-aldosterone system.

4. Which of the following is the main function of the small intestine?

A. To store food and break it down into smaller pieces
B. To absorb nutrients into the bloodstream
C. To produce enzymes that help digest food
D. To eliminate waste products from the body

Correct answer: B

Rationale: Rationale: The small intestine is a crucial part of the digestive system where the majority of nutrient absorption takes place. It is lined with tiny finger-like projections called villi that increase the surface area for absorption. The small intestine absorbs nutrients such as carbohydrates, proteins, fats, vitamins, and minerals from the digested food into the bloodstream to be transported to cells throughout the body for energy, growth, and repair. Options A, C, and D do not accurately describe the main function of the small intestine.

5. Which sentence uses comma splices incorrectly?

A. The baker kneaded the dough, flour dusted her apron, and the oven warmed up.
B. The mountains, shrouded in mist, seemed to disappear into the clouds.
C. He arrived late, having forgotten his keys, and the meeting had already started.
D. The movie, despite its flaws, was surprisingly enjoyable.

Correct answer: C

Rationale: Option (c) incorrectly combines two independent clauses with only a comma. A semicolon or conjunction is needed

6. Lysosomes are known as "suicide bags" of the cell. What enzymes do they contain?

A. Hydrolytic enzymes
B. Ligases (bonding enzymes)
C. Transferases (molecule transfer)
D. Oxidoreductases (redox reactions)

Correct answer: A

Rationale: Lysosomes are membrane-bound organelles containing hydrolytic enzymes responsible for breaking down various macromolecules, cellular waste, and foreign substances. These enzymes perform hydrolysis, a process where water molecules are used to break down larger molecules into smaller components. This function earned lysosomes the nickname 'suicide bags' as they can initiate cell death (apoptosis) by releasing their enzymes when needed. Ligases, transferases, and oxidoreductases are enzymes with different functions such as forming bonds, transferring molecules, and catalyzing redox reactions, respectively, which are not typically found in lysosomes. Therefore, the correct answer is A: 'Hydrolytic enzymes.'