Q1: What is the primary function of the mitochondria in a cell? (a) Protein synthesis (b) Energy production through cellular respiration (c) Photosynthesis (d) DNA replication
Solution:
Ans: (b) Explanation: The mitochondria are known as the powerhouse of the cell because they produce ATP (adenosine triphosphate) through cellular respiration. Option (a) is incorrect because protein synthesis occurs at ribosomes. Option (c) is incorrect because photosynthesis occurs in chloroplasts in plant cells. Option (d) is incorrect because DNA replication occurs in the nucleus.
Q2: Which organelle is responsible for packaging and modifying proteins before they are sent to their final destination? (a) Rough endoplasmic reticulum (b) Smooth endoplasmic reticulum (c) Golgi apparatus (d) Lysosome
Solution:
Ans: (c) Explanation: The Golgi apparatus modifies, sorts, and packages proteins received from the endoplasmic reticulum for transport to other parts of the cell or for secretion. Option (a) is incorrect because the rough ER synthesizes proteins but doesn't package them for final distribution. Option (b) is incorrect because the smooth ER is involved in lipid synthesis. Option (d) is incorrect because lysosomes break down waste materials.
Q3: What structure controls what enters and exits the cell? (a) Cell wall (b) Cytoplasm (c) Cell membrane (d) Nuclear envelope
Solution:
Ans: (c) Explanation: The cell membrane (also called the plasma membrane) is selectively permeable, meaning it controls the movement of substances in and out of the cell. Option (a) is incorrect because the cell wall provides structural support but is not selectively permeable. Option (b) is incorrect because cytoplasm is the gel-like substance inside the cell. Option (d) is incorrect because the nuclear envelope surrounds only the nucleus, not the entire cell.
Q4: In plant cells, which organelle is responsible for photosynthesis? (a) Mitochondria (b) Chloroplast (c) Vacuole (d) Ribosome
Solution:
Ans: (b) Explanation:Chloroplasts contain the green pigment chlorophyll and are the site of photosynthesis, where light energy is converted into chemical energy (glucose). Option (a) is incorrect because mitochondria produce energy through cellular respiration, not photosynthesis. Option (c) is incorrect because vacuoles store water and nutrients. Option (d) is incorrect because ribosomes synthesize proteins.
Q5: Which of the following is found in plant cells but NOT in animal cells? (a) Mitochondria (b) Cell wall (c) Ribosomes (d) Cell membrane
Solution:
Ans: (b) Explanation:Cell walls are rigid structures made of cellulose that provide support and protection to plant cells. Animal cells do not have cell walls. Options (a), (c), and (d) are all found in both plant and animal cells.
Q6: What is the function of ribosomes in a cell? (a) Breaking down cellular waste (b) Storing genetic information (c) Synthesizing proteins (d) Producing lipids
Solution:
Ans: (c) Explanation:Ribosomes are the site of protein synthesis, where amino acids are assembled into proteins based on instructions from mRNA. Option (a) is incorrect because lysosomes break down waste. Option (b) is incorrect because the nucleus stores genetic information. Option (d) is incorrect because the smooth ER produces lipids.
Q7: The nucleus of a cell contains which important molecule? (a) ATP (b) DNA (c) Glucose (d) Cellulose
Solution:
Ans: (b) Explanation: The nucleus contains DNA (deoxyribonucleic acid), which stores the genetic information necessary for cell function and reproduction. Option (a) is incorrect because ATP is produced in mitochondria. Option (c) is incorrect because glucose is a sugar used for energy. Option (d) is incorrect because cellulose is found in plant cell walls.
Q8: Which organelle contains digestive enzymes that break down waste materials and cellular debris? (a) Vacuole (b) Lysosome (c) Peroxisome (d) Golgi apparatus
Solution:
Ans: (b) Explanation:Lysosomes contain digestive enzymes that break down waste materials, old organelles, and foreign substances in the cell. Option (a) is incorrect because vacuoles primarily store materials. Option (c) is incorrect because peroxisomes break down fatty acids and detoxify harmful substances. Option (d) is incorrect because the Golgi apparatus packages proteins.
Section B: Fill in the Blanks
Q9: The __________ is a network of membranes that synthesizes proteins and is studded with ribosomes.
Solution:
Ans: rough endoplasmic reticulum (or rough ER) Explanation: The rough endoplasmic reticulum has ribosomes attached to its surface, giving it a "rough" appearance, and is responsible for synthesizing proteins that will be secreted or sent to other organelles.
Q10: The jelly-like substance that fills the cell and surrounds the organelles is called __________.
Solution:
Ans: cytoplasm Explanation:Cytoplasm is the gel-like material inside the cell membrane that contains water, salts, and organic molecules, and provides a medium for chemical reactions and organelle movement.
Q11: Plant cells have a large central __________ that stores water, nutrients, and waste products.
Solution:
Ans: vacuole Explanation: The central vacuole in plant cells can occupy up to 90% of the cell's volume and helps maintain turgor pressure, which keeps the plant rigid and upright.
Q12: The __________ is the control center of the cell and contains the cell's genetic material.
Solution:
Ans: nucleus Explanation: The nucleus regulates cell activities by controlling gene expression and contains chromosomes made of DNA that carry hereditary information.
Q13: The process by which cells convert glucose and oxygen into energy, carbon dioxide, and water is called __________.
Solution:
Ans: cellular respiration Explanation:Cellular respiration occurs primarily in the mitochondria and produces ATP, the energy currency of the cell. The equation is: \(\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}\).
Q14: The __________ endoplasmic reticulum lacks ribosomes and is involved in lipid synthesis and detoxification.
Solution:
Ans: smooth Explanation: The smooth endoplasmic reticulum (smooth ER) synthesizes lipids, phospholipids, and steroids, and also detoxifies drugs and poisons in liver cells.
Section C: Word Problems
Q15: A scientist observes a cell under a microscope and notices it has a cell wall, chloroplasts, and a large central vacuole. Based on these observations, is this cell from a plant or an animal? Explain your reasoning by identifying at least two structures that led to your conclusion.
Solution:
Ans: Final Answer: This is a plant cell. The presence of a cell wall, chloroplasts, and a large central vacuole are characteristic structures found only in plant cells, not in animal cells.
Q16: Maria is studying cells and learns that mitochondria produce ATP through cellular respiration. If a cell has 50 mitochondria and each mitochondrion produces an average of 30 ATP molecules per minute, how many ATP molecules does the cell produce in 5 minutes?
Solution:
Ans: ATP per minute = 50 mitochondria × 30 ATP/mitochondrion = 1,500 ATP/minute ATP in 5 minutes = 1,500 ATP/minute × 5 minutes = 7,500 ATP Final Answer: 7,500 ATP molecules
Q17: A student compares two cells. Cell A has many ribosomes and a well-developed rough endoplasmic reticulum, while Cell B has few ribosomes and minimal rough ER. Which cell is likely producing more proteins? Explain why using your knowledge of cell organelles.
Solution:
Ans: Final Answer: Cell A is likely producing more proteins. Ribosomes are the sites of protein synthesis, and the rough endoplasmic reticulum is studded with ribosomes to synthesize proteins. A cell with many ribosomes and well-developed rough ER is specialized for high protein production.
Q18: During photosynthesis, a chloroplast in a leaf cell converts light energy into chemical energy stored in glucose. If a single chloroplast produces 12 glucose molecules in one hour, how many glucose molecules would 8 chloroplasts in the same cell produce in 3 hours under the same conditions?
Solution:
Ans: Glucose per chloroplast in 3 hours = 12 molecules/hour × 3 hours = 36 molecules Total glucose from 8 chloroplasts = 8 × 36 = 288 molecules Final Answer: 288 glucose molecules
Q19: A biologist notices that a particular cell type has an unusually high number of lysosomes. Based on this observation, what might be the specialized function of this cell? Provide a specific example of where such a cell might be found in the body.
Solution:
Ans: Final Answer: A cell with many lysosomes is likely specialized for breaking down and digesting materials. Such cells are found in the immune system, specifically white blood cells (such as macrophages), which engulf and digest bacteria, viruses, and cellular debris.
Q20: A plant cell and an animal cell are both placed in distilled water. The plant cell swells but does not burst, while the animal cell swells and eventually bursts. Explain why the plant cell does not burst, identifying the specific cell structure responsible for this difference.
Solution:
Ans: Final Answer: The plant cell does not burst because it has a rigid cell wall made of cellulose that prevents excessive swelling by providing structural support. The turgor pressure builds up inside the cell, but the cell wall limits expansion. Animal cells lack a cell wall and only have a flexible cell membrane, so they burst when too much water enters by osmosis.
The document Worksheet (with Solutions): Exponents Intro and Order of Operations is a part of Grade 7 category.
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