IB Diploma · Biology B2.2
IB Biology B2.2: Org. & Compart. — Practice Questions & Answers
IB Biology B2.2 study notes: eukaryotic organelles, their functions, and how compartmentalization improves the efficiency of cell processes.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
Which of the following is considered an organelle?
- Nucleus
- Cytoplasm
- Cell wall
- Cytoskeleton
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WhyThe nucleus is a membrane-bound organelle housing the cell's DNA.
2
Multiple choice
What technological advancement significantly contributed to the study of individual organelle functions?
- Ultracentrifugation and cell fractionation
- Light microscopy
- Gel electrophoresis
- Polymerase chain reaction (PCR)
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WhyUltracentrifugation and cell fractionation separate organelles by density, allowing their individual functions to be studied.
3
Multiple choice
What is the primary advantage of separating the nucleus and cytoplasm into distinct compartments?
- Allows for post-transcriptional modification of mRNA before translation.
- Increases the rate of cellular respiration.
- Enhances the process of DNA replication.
- Facilitates simple diffusion.
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WhySeparating nucleus and cytoplasm lets mRNA be processed and modified before it reaches ribosomes for translation.
4
Multiple choice
Why is post-transcriptional modification of mRNA not possible in prokaryotes?
- Ribosomes can immediately bind to mRNA.
- Prokaryotes lack ribosomes.
- Prokaryotes lack mRNA.
- Prokaryotes have a nucleus.
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WhyLacking a nucleus, prokaryotes let ribosomes bind mRNA during transcription, leaving no time for processing.
5
Multiple choice
What is a key advantage of compartmentalization within the cytoplasm?
- Concentration of metabolites and enzymes
- It ensures all cellular reactions occur at the same rate and location
- Direct exposure of all cellular components to the external environment
- Elimination of protein synthesis
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WhyCompartments concentrate enzymes and their substrates together, speeding up metabolic reactions.
6
Multiple choice
Compartmentalization in the cytoplasm allows for:
- Separation of incompatible biochemical processes.
- Simultaneous execution of all cellular functions in one location.
- Decreased efficiency of metabolic pathways.
- Random distribution of enzymes.
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WhyCompartments isolate incompatible reactions so they can occur simultaneously without interfering.
7
Multiple choice
Which organelle is an example of cytoplasmic compartmentalization that separates digestive enzymes from the rest of the cell?
- Lysosome
- Endoplasmic reticulum
- Golgi apparatus
- Mitochondria
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WhyLysosomes enclose hydrolytic digestive enzymes, keeping them separated from the rest of the cell.
8
Multiple choice
What is the function of phagocytic vacuoles?
- To engulf and digest foreign particles or cellular debris
- To synthesize proteins
- To produce ATP
- To regulate the internal pH of the cytoplasm
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WhyPhagocytic vacuoles enclose engulfed particles or debris so they can be digested by fusing with lysosomes.
9
Multiple choice
How does compartmentalization contribute to cellular function?
- By creating specialized environments for specific processes
- By allowing for the free diffusion of all substances throughout the cell
- By eliminating the need for transport mechanisms
- By slowing down all biochemical reactions
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WhyCompartmentalization creates distinct microenvironments with the conditions optimal for particular reactions.
10
Multiple choice
Which of the following cellular components is considered an organelle despite not being membrane-bound?
- Ribosomes
- Cytoskeleton
- Cell wall
- Cytoplasm
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WhyRibosomes are counted as organelles even though they lack a surrounding membrane.
Key terms in Org. & Compart.
Compartmentalization: Division of a cell into membrane-bound compartments so that different processes occur in separate, optimised environments.
Organelle: A specialised structure within a cell that performs a particular function, usually membrane-bound in eukaryotes.
Cristae: Infoldings of the inner mitochondrial membrane that increase surface area for oxidative phosphorylation.
Thylakoid: A flattened membrane sac in a chloroplast that holds chlorophyll and is the site of the light-dependent reactions.
Endoplasmic reticulum: A network of membranes; the rough ER processes proteins and the smooth ER synthesises lipids.
Golgi apparatus: An organelle that modifies, sorts and packages proteins into vesicles for transport or secretion.
Lysosome: A vesicle containing hydrolytic enzymes for digesting materials, kept isolated to protect the cell.
Nucleoid: The region of a prokaryotic cell containing its circular DNA; not enclosed by a membrane.
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