1. The process of cellular respiration occurs in:
- Options:
a) Nucleus
b) Mitochondria
c) Ribosomes
d) Golgi apparatus - Answer: b) Mitochondria
- Explanation: Mitochondria are known as the “powerhouse of the cell” because they produce energy (ATP) through cellular respiration.
- Tip: Associate “mitochondria” with “energy production.”
2. The smooth endoplasmic reticulum (SER) is primarily involved in the synthesis of:
- Options:
a) Proteins
b) Lipids
c) Carbohydrates
d) Nucleic acids - Answer: b) Lipids
- Explanation: The SER is specialized in lipid synthesis and detoxification of harmful substances in cells.
- Tip: Think of “smooth” as “soft,” linked to fats (lipids).
3. Ribosomes are composed of:
- Options:
a) RNA and protein
b) DNA and protein
c) Carbohydrates and lipids
d) RNA and carbohydrates - Answer: a) RNA and protein
- Explanation: Ribosomes are made up of rRNA (ribosomal RNA) and proteins, enabling them to synthesize proteins.
- Tip: Remember “R” in ribosomes for “RNA.”
4. What is the primary function of ribosomes?
- Options:
a) Energy production
b) Protein synthesis
c) Lipid synthesis
d) DNA synthesis - Answer: b) Protein synthesis
- Explanation: Ribosomes assemble amino acids into proteins.
- Tip: Ribosomes are like “factories” for making proteins.
5. Which cell organelle is involved in packaging and modifying proteins?
- Options:
a) Nucleus
b) Mitochondria
c) Golgi apparatus
d) Endoplasmic reticulum - Answer: c) Golgi apparatus
- Explanation: The Golgi apparatus processes, modifies, and packages proteins for transport.
- Tip: Link “Golgi” with “gift wrap” for packaging.
6. Which cell organelle is responsible for breaking down waste materials?
- Options:
a) Golgi apparatus
b) Nucleus
c) Mitochondria
d) Lysosome - Answer: d) Lysosome
- Explanation: Lysosomes contain digestive enzymes to break down cellular waste and debris.
- Tip: Think “lyso-” as in “lysis” (breaking down).
7. Which of the following cell structures is involved in maintaining cell shape?
- Options:
a) Cytoskeleton
b) Centrioles
c) Nucleus
d) Lysosome - Answer: a) Cytoskeleton
- Explanation: The cytoskeleton provides structural support and maintains the shape of the cell.
- Tip: “Skeleton” in cytoskeleton helps recall “support.”
8. What is the main function of the smooth endoplasmic reticulum in a cell?
- Options:
a) Synthesis of proteins
b) Synthesis of lipids
c) Digestion of cellular waste
d) Storage of genetic material - Answer: b) Synthesis of lipids
- Explanation: The smooth ER specializes in lipid and steroid hormone synthesis.
- Tip: Recall that smooth ER handles “fats” (lipids), unlike rough ER, which synthesizes proteins.
9. Which specialized region of the nucleus is responsible for ribosome assembly?
- Options:
a) Nucleoplasm
b) Nucleolus
c) Chromatin
d) Chromatid - Answer: b) Nucleolus
- Explanation: The nucleolus is the site where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins.
- Tip: Think “nucleolus” for “ribosome production hub.”
10. What is the main function of the nuclear pores?
- Options:
a) Regulation of cell division
b) Control of pH of the cell
c) Protein synthesis
d) Control of transport of molecules - Answer: d) Control of transport of molecules
- Explanation: Nuclear pores allow selective transport of molecules (e.g., RNA and proteins) between the nucleus and cytoplasm.
- Tip: “Pores” indicate passage or transport.
11. Which of the following cellular structures is found in animal cells and helps in cell division?
- Options:
a) Cell membrane
b) Plasmodesma
c) Centriole
d) Vacuole - Answer: c) Centriole
- Explanation: Centrioles play a key role in the organization of spindle fibers during mitosis and meiosis in animal cells.
- Tip: Centrioles are specific to animal cells for cell division.
12. Which sub-cellular organelle plays a crucial role in energy production within the cell?
- Options:
a) Endoplasmic reticulum
b) Golgi apparatus
c) Mitochondria
d) Lysosomes - Answer: c) Mitochondria
- Explanation: Mitochondria are the site of ATP production via cellular respiration.
- Tip: Recall “powerhouse of the cell.”
13. In a multicellular plant, which cell type is responsible for the production of glucose?
- Options:
a) Xylem
b) Phloem
c) Epidermal
d) Mesophyll - Answer: d) Mesophyll
- Explanation: Mesophyll cells contain chloroplasts, where photosynthesis occurs to produce glucose.
- Tip: Link “mesophyll” with “middle” (the leaf tissue performing photosynthesis).
14. Which organelle can double its number by itself?
- Options:
a) Ribosomes
b) Lysosomes
c) Mitochondria
d) Golgi apparatus - Answer: c) Mitochondria
- Explanation: Mitochondria have their own DNA and replicate independently through binary fission.
- Tip: Mitochondria behave like “semi-autonomous” organelles.
15. Which of these are present on the surface of rough endoplasmic reticulum?
- Options:
a) Ribosomes
b) Lysosomes
c) Mitochondria
d) Vacuoles - Answer: a) Ribosomes
- Explanation: Ribosomes attached to the rough ER synthesize proteins, giving it a “rough” appearance.
- Tip: Remember “Rough ER” is rough due to ribosomes.
Section B: Short Answers
1. What are the main functions of the cell membrane?
- Answer:
- Regulates the entry and exit of substances (selective permeability).
- Protects the cell by providing structural support.
- Facilitates communication and signaling between cells.
2. What key role does the Golgi apparatus play in eukaryotic cells?
- Answer:
- Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
- Forms lysosomes and transports cellular materials.
3. How do lysosomes contribute to the cell’s functioning?
- Answer:
- Break down cellular waste and debris using digestive enzymes.
- Play a role in recycling cellular components (autophagy).
4. Which organelle detoxifies harmful substances and breaks down lipids?
- Answer: Smooth Endoplasmic Reticulum (SER).
- Explanation: SER is involved in lipid synthesis, detoxification of drugs, and storage of calcium ions.
5. What is the smooth endoplasmic reticulum responsible for?
- Answer:
- Synthesis of lipids and steroid hormones.
- Detoxification of harmful substances.
- Storage and release of calcium ions in muscle cells.
6. How do the vacuoles in plant cells differ from vacuoles in animal cells?
- Answer:
- Plant cells have large central vacuoles for storage of water, nutrients, and waste.
- Animal cells have smaller, temporary vacuoles, mainly for storage and transport.
7. What could happen if lysosomal enzymes stop working properly?
- Answer:
- Accumulation of waste materials and toxins within the cell.
- Possible cell death due to impaired autophagy and digestion.
8. Why are the cristae important for cellular respiration?
- Answer:
- Cristae increase the surface area of the inner mitochondrial membrane, allowing more space for the enzymes and proteins involved in ATP production during cellular respiration.
Here’s the detailed solution to the questions in the uploaded image:
Section B: Short Answers
9. How are chromatin and chromosomes related?
- Answer:
Chromatin is the uncoiled and relaxed form of DNA, combined with proteins (histones), found in the nucleus during interphase. During cell division, chromatin condenses and organizes into tightly coiled structures called chromosomes.
10. Which type of cell is responsible for sending nerve signals?
- Answer:
Neurons (nerve cells) are specialized cells that transmit electrical and chemical signals throughout the body.
11. What do mesophyll cells do in plant leaves?
- Answer:
Mesophyll cells in plant leaves perform photosynthesis. They contain chloroplasts that use sunlight, carbon dioxide, and water to produce glucose and oxygen.
12. How would you define a stem cell?
- Answer:
A stem cell is an undifferentiated cell capable of dividing and differentiating into specialized cell types. Stem cells also have the ability to self-renew.
13. Name the chemical compounds that make up:
- a) Cell membrane: Phospholipids, proteins, carbohydrates, and cholesterol.
- b) Fungal cell wall: Chitin and glucans.
- c) Plant cell wall: Cellulose, hemicellulose, and pectin.
- d) Bacterial cell wall: Peptidoglycan (murein).
- e) Ribosomes: rRNA (ribosomal RNA) and proteins.
- f) Chromosomes: DNA and proteins (histones).
14. Label the parts of these cell diagrams.
For the provided cell diagrams, the labels typically represent major cell organelles. Based on general diagrams:
- A: Nucleus
- B: Mitochondria
- C: Endoplasmic reticulum
- D: Golgi apparatus
- E: Cell membrane
- F: Lysosome
- G: Ribosome
Section C: Detailed Answers
1. Explain the fluid mosaic model of the cell membrane.
- The cell membrane is a phospholipid bilayer with embedded proteins.
- The “fluid” aspect refers to the flexible and dynamic nature of the bilayer, allowing lateral movement of lipids and proteins.
- The “mosaic” aspect describes the patchwork of proteins interspersed within the bilayer, performing various functions such as transport, signaling, and enzymatic activity.
2. Describe the structure and functions of the cell wall.
- Structure:
- Found in plants, fungi, and bacteria.
- Composed of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria).
- Functions:
- Provides structural support and protection.
- Maintains cell shape.
- Prevents excessive water uptake (osmotic regulation).
3. Discuss the components of the nucleus.
- Nuclear envelope: Double membrane with pores for transport.
- Nucleoplasm: Fluid containing ions, enzymes, and nucleotides.
- Nucleolus: Site of ribosome assembly.
- Chromatin: DNA and protein that form chromosomes during cell division.
4. Describe the structure and function of lysosomes and the endoplasmic reticulum.
- Lysosomes:
- Membrane-bound organelles containing digestive enzymes.
- Function: Breakdown of waste materials, cellular debris, and pathogens.
- Endoplasmic Reticulum (ER):
- Rough ER: Ribosomes on its surface; synthesizes proteins.
- Smooth ER: Synthesizes lipids and detoxifies harmful substances.
5. Describe the formation and function of the Golgi apparatus.
- Formation: Derived from vesicles from the ER.
- Function: Modifies, sorts, and packages proteins and lipids for secretion or delivery within the cell.
6. Describe the structure and functions of the chloroplast.
- Structure:
- Double membrane.
- Contains thylakoids stacked into grana, surrounded by stroma.
- Contains chlorophyll for capturing light energy.
- Function: Photosynthesis to convert light energy into glucose and oxygen.
7. How does turgor pressure develop in a plant cell?
- Turgor pressure develops due to water entering the cell via osmosis. The vacuole swells, pressing the plasma membrane against the cell wall, providing rigidity to the plant.
8. Write any four differences between a plant cell and an animal cell.
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell wall | Present (cellulose) | Absent |
| Chloroplasts | Present (photosynthesis) | Absent |
| Vacuoles | Large central vacuole | Small, temporary vacuoles |
| Centrioles | Absent | Present |
9. Describe the concept of division of labor and how it applies in multicellular organisms.
- Concept: Division of labor refers to specialization of cells, tissues, or organs to perform specific functions.
- Examples:
- Red blood cells transport oxygen.
- Neurons transmit nerve signals.
- Muscle cells contract to enable movement.
10. Write a note on cell specialization.
- Cell specialization is the process where generic cells develop into specific cell types to perform unique functions. For example:
- Muscle cells specialize in contraction.
- Xylem cells specialize in water transport.
- Specialized cells increase efficiency and allow multicellular organisms to perform complex tasks.
