Cell Theory was proposed by Schleiden and Schwann in 1838 to 1839. Which is NOT part of Cell Theory?
Viruses are non-cellular: the major exception to cell theory. Cell theory states all organisms are made of cells; cells are the basic unit of life; all cells arise from pre-existing cells (Virchow, 1855).
Question 2 of 20
The powerhouse of the cell is the:
Mitochondria produce ATP through cellular respiration: hence powerhouse. They have own DNA and double membrane (semi-autonomous). Most numerous in high-energy cells like muscle and liver.
Question 3 of 20
Which organelle is called the suicidal bag of the cell?
Lysosomes contain about 40 hydrolytic enzymes. If ruptured they digest the cell itself: hence suicidal bag. They also digest worn-out organelles and foreign particles. Formed by the Golgi apparatus.
Question 4 of 20
Prokaryotic cells differ from eukaryotic cells because they:
Prokaryotes have no membrane-bound nucleus: DNA lies freely in the cytoplasm (nucleoid). They have 70S ribosomes (eukaryotes have 80S). Examples: bacteria, Mycoplasma.
Question 5 of 20
The post office of the cell, responsible for packaging and secreting proteins, is the:
Golgi apparatus receives proteins from the ER, modifies and packages them, then dispatches to destination. Also forms lysosomes.
Question 6 of 20
In mitosis, how many daughter cells are produced and what is their chromosome number?
Mitosis = equational division: 2 daughter cells, genetically identical to parent, diploid (2n). Used for growth and repair. Meiosis = reductional division: 4 haploid (n) gametes.
Question 7 of 20
Ribosomes in eukaryotic cells are:
Eukaryotic ribosomes are 80S (prokaryotic = 70S). Not membrane-bound: made of rRNA and protein. Present in both prokaryotes and eukaryotes. Sites of protein synthesis.
Question 8 of 20
Which organelle is found ONLY in plant cells and performs photosynthesis?
Chloroplasts are found only in plant cells and photosynthetic algae. Contain chlorophyll; site of photosynthesis. Like mitochondria: double membranes, own DNA (semi-autonomous).
During meiosis, genetic variation is primarily created by:
Crossing over during meiosis I (prophase I) exchanges DNA segments between homologous chromosomes, creating new gene combinations. Primary source of genetic variation in sexual reproduction.
Question 11 of 20
The nucleus controls cell activity because it contains:
Nucleus contains DNA: the genetic blueprint controlling which proteins are made and all cellular activities. Surrounded by nuclear envelope; contains nucleolus which makes rRNA.
Question 12 of 20
Which of the following is a membrane-LESS organelle?
Ribosomes have NO membrane. All others are membrane-bound. Present in both prokaryotes (70S) and eukaryotes (80S). Sites of protein synthesis.
Question 13 of 20
The total number of chromosomes in a normal human body cell is:
Normal human somatic cells are diploid: 2n = 46 (23 pairs: 22 autosomes + 1 sex chromosome pair). Gametes are haploid: n = 23. Down syndrome has 47 (trisomy 21).
Question 14 of 20
Cellular respiration to produce ATP occurs primarily in the:
ATP is produced in mitochondria through cellular respiration. The inner mitochondrial membrane contains the electron transport chain. Most numerous in high-energy cells.
Question 15 of 20
Cell theory states that all cells arise from:
Rudolf Virchow (1855): Omnis cellula e cellula: all cells arise from pre-existing cells. This disproved spontaneous generation (life arising from non-living matter spontaneously). CORRECTED: Q15 answer is B.
Question 16 of 20
The endoplasmic reticulum with ribosomes on its surface is called:
Rough ER (RER) has ribosomes and is involved in protein synthesis and transport. Smooth ER (SER) has no ribosomes and handles lipid/steroid synthesis and detoxification.
Question 17 of 20
Programmed cell death involving lysosomes is called:
Autolysis: lysosomes rupture and release digestive enzymes, destroying the cell. Part of programmed cell death (apoptosis), important in development (loss of tadpole tail) and removal of damaged cells.
Question 18 of 20
Which statement about the cell membrane is correct?
Cell membrane = fluid mosaic model: phospholipid bilayer with embedded proteins. Selectively permeable. Present in ALL cells; plant cells also have a cell wall outside it.
Question 19 of 20
Vacuoles in plant cells primarily function to:
Plant cells have a large central vacuole (tonoplast membrane) storing water, sap, salts, and pigments. Maintains turgidity (rigidity) of the cell. Animal cells have small temporary vacuoles.
Question 20 of 20
Which phase of mitosis involves alignment of chromosomes at the cell equator?
Metaphase: chromosomes align at the metaphase plate (cell equator): most clearly visible and counted here. Mnemonic P-MAT: Prophase (condense), Metaphase (middle), Anaphase (apart), Telophase (two cells).