All Free Biology MCQs with Answers

• A. Cell wall
• B. Plasma membrane
• C. Nuclear membrane
• D. Vacuole

Explanation: Selectively permeable means only substances that are needed in the cell are allowed to pass throughOption A: Cell wall is fully permeableOption B: Plasma membrane (cell membrane) is partially permeable and allows only those substances to pass through which are required by the cellOption C: It is the membrane of the nucleus and allows only required substances to pass through to the nucleus Option D: A vacuole is a membrane-bound cell organelle. In animal cells, vacuoles are generally small and help sequester waste products. In plant cells, vacuoles help maintain water balance. Sometimes a single vacuole can take up most of the interior space of the plant cell

• A. M
• B. K
• C. C
• D. D
• E. E

Explanation: The alphabet D represents the mitochondria, which is also known as the cell's powerhouse due to its role in producing energy in the form of ATP (adenosine triphosphate) through cellular respiration. The mitochondria have a unique double membrane structure and their DNA, which is inherited maternally. They are found in most eukaryotic cells, and their number and size can vary depending on the cell's energy needs.

• A. Magnification
• B. Image
• C. Match
• D. Contrast

Explanation: Staining is used to enhance contrast in microscopic samples, making it easier to distinguish between different structures and components within the sample. By increasing contrast, stains help highlight specific features that might otherwise be difficult to see. The other options are unrelated to the purpose of using dyes: magnification is achieved by the microscope's lenses, images are the visual outcomes, and matching is a comparison process, not related to the dye's function.

• A. Sieve tube cells
• B. Bacteria
• C. Red blood cells
• D. All of the above

Explanation: The correct answer is 'All of the above'. Sieve tube cells, bacteria, and red blood cells all lack a nucleus. Sieve tube cells, part of the plant's phloem, lose their nucleus to allow efficient nutrient transport. Bacteria, as prokaryotes, naturally lack a defined nucleus and instead have their genetic material dispersed in the cytoplasm. Red blood cells in mammals extrude their nucleus during development to create more space for hemoglobin, thereby enhancing their oxygen-carrying capacity. Each of these cell types has adapted to function without a nucleus for efficiency in its specific role.

• A. Robert Brown
• B. Camillo Golgi
• C. Christian de Duve
• D. Robert Hooke

Explanation: The Golgi complex, also referred to as the Golgi apparatus, was discovered by Camillo Golgi in 1898, and it bears his name. This is why he is the correct choice. Robert Brown's significant contribution was identifying the cell nucleus. Christian de Duve discovered lysosomes, an entirely different organelle. Robert Hooke was a pioneer in cell biology, known for introducing the term 'cell' but not for discovering the Golgi complex.

• A. Golgi complex, plastids, mitochondria
• B. Plastids, mitochondria, endoplasmic reticulum
• C. Golgi complex, endoplasmic reticulum, centrioles
• D. Mitochondria, endoplasmic reticulum, ribosomes

Explanation: The correct answer is Option D: Mitochondria, endoplasmic reticulum, ribosomes. These organelles are essential and found in both plant and animal cells. Mitochondria generate energy, the endoplasmic reticulum facilitates protein and lipid synthesis, and ribosomes are critical for protein production. In contrast, plastids (Options A and B) are specific to plant cells, and centrioles (Option C) are primarily found in animal cells, making these options incorrect for both cell types.

• A. Carbohydrates
• B. Nucleic acids
• C. Proteins
• D. Lipids

Explanation: The correct answer is Lipids. The smooth endoplasmic reticulum (SER) is primarily responsible for lipid metabolism, including the synthesis of phospholipids and steroids. It also plays a significant role in detoxifying harmful substances within the cell. Although the SER can be involved in carbohydrate metabolism, particularly in the liver, its main function is lipid metabolism.Carbohydrates are not the primary focus of the SER, Nucleic acids are metabolized in the nucleus, mitochondria, and chloroplasts, and Proteins are synthesized by ribosomes and the rough endoplasmic reticulum.

• A. Leeuwenhoek
• B. Robert Hooke
• C. Flemming
• D. Robert Brown

Explanation: The origins of the word 'cell' in the 1660s, Robert Hooke looked through a primitive microscope at a thinly cut piece of cork. He saw a series of walled boxes that reminded him of the tiny rooms, or cellula, occupied by monks.

• A. Cytoplasm
• B. Nucleus
• C. Chromosomes
• D. Nucleolus

Explanation: The centrosome is found in the cytoplasm of animal cells. The centrosome is a small organelle that plays a crucial role in cell division (mitosis) and is involved in organizing the microtubules of the cell's cytoskeleton. It consists of two centrioles, which are cylindrical structures composed of microtubules. The centrosome is located near the nucleus in the cytoplasm and serves as the main microtubule organizing center (MTOC) in animal cells.

• A. Integral proteins of the plasma membrane
• B. Proteins that bind to ion gated channels in plasma membrane
• C. Proteins which randomly bind to lipids of membrane
• D. Peripheral proteins of membrane

Explanation: GPI-anchored proteins can indeed be considered a specific type of peripheral membrane protein. The term "GPI-anchored" refers to the method by which these proteins are attached to the lipid bilayer. They are linked to the membrane via a glycosylphosphatidylinositol (GPI) anchor, which allows them to be peripherally associated with the membrane surface. On the other hand, the rest of the options are incorrect.