Cell Biology Quiz: Chromosome Numbers

Plant Cytology

•  Plant cytology is the study of plant cells, including their structure, function, molecular organization, morphology, physiology, growth, reproduction, and genetics.
•  The term "cytology" comes from the Greek words kytos or cytos, meaning hollow space or cell.

Cytology

•  Cytology is the biological science that examines the detailed structure, function, molecular organisation, morphology, physiology, growth, reproduction and genetics of cells.
• The internal ultrastructure of a plant cell is a complex system.

Plant Body Structure

•  A plant's body is structured hierarchically, from cells to tissues to organs to organ systems.
• Cells make up tissues, tissues make up organs, and organs make up organ systems (shoot system and root system)

Robert Hooke

•  Robert Hooke, a 17th-century English physicist, used a compound microscope to observe cork and coined the term "cell."
• Hooke observed compartments or boxes (dead cells with only cell walls remaining).
•  His observations marked the discovery of cells.

Methods to Study Cells

•  The invention of the microscope was a major step in the advancement of cell biology.
•  Early microscopes had blurry images.
•  Anton van Leeuwenhoek improved lens grinding techniques, enabling detailed, clear images, and discovering various microorganisms.
•  Microscopes continued to improve in the 19th century, enabling biologists to observe organelles.
•  Biologists discovered organelles perform roles analogous to organs in a multicellular organism, with each carrying out particular functions.
• Robert Brown identified and named the nucleus (an organelle that acts as the control center of the cell) in 1830.

Cell Theory

•  By the 1830s, biologists had concluded that all organisms are made of cells and that cells are the basic structural unit of life.
•  Matthias Schleiden and Theodor Schwann presented the foundation of cell theory through their separate papers in 1838 and 1839 respectively.
• The cell theory states that cells are the basic unit of life, all living things are composed of cells, and all cells come from pre-existing cells.

Cell Theory Points

•  The basic unit of life is the cell (Hooke).
•  All living things are composed of 1 or more cells (Schleiden & Schwann).
•  The cell is the unit of structure and function of all living things.
•  All cells come from pre-existing cells.

Exceptions to Cell Theory

•  Viruses are an exception to the cell theory as they lack a cellular structure.
•  Certain other organisms (like the protozoan Paramecium, the fungus Rhizopus, and the alga Vaucheria) also present challenges to the view of the cell as the basic unit of structure, having a protoplasmic mass that lacks organization like a cell.

Cell Membrane

•  The outermost layer of the protoplast is the plasma membrane.
•  It is a thin, non-rigid structure made of proteins and lipids.
•  It controls interactions between the cell and its environment.
•  It is selectively permeable, allowing only certain substances to enter or leave the cell.
•  It is composed of 3 layers, the outer and inner layers are formed of proteins, and the middle layer is a phospholipid bilayer.
•  The Fluid mosaic model explains the molecular structure of plasma membranes.
• The model views membranes as a two-dimensional mosaic of phospholipids and protein molecules in which membrane proteins move laterally like icebergs.

Membrane Proteins

•  Membrane proteins are embedded in the lipid bilayer.
•  There are extrinsic/peripheral proteins that attach to one side of the bilayer
•  There are intrinsic/integral proteins that penetrate the bilayer wholly or partially.

Membrane protein functions

•  Transport.
•  Enzymatic activity.
•  Signal transduction.

Membrane Protein and Lipid Synthesis

•  Membrane proteins and lipids are synthesized in the endoplasmic reticulum and Golgi apparatus.

Cytoplasm

•  The cytoplasm is a transparent, gel-like substance.
•  It contains several organelles and organic/inorganic substances and membranes.

Mitochondria

•  Mitochondria are organelles that carry out cell respiration.
•  They are often sausage-shaped but also appear as granular, filamentous, rod-shaped, and spherical structures.
•  Cell respiration produces ATP, which is the energy currency of the cell.
•  Mitochondria are surrounded by an outer membrane and an inner membrane that has folds called cristae to increase surface area.

Plastids

•  A group of dynamic organelles performing multiple functions, including photosynthesis in chloroplasts.
•  Diverse metabolic functions in other plastids include the formation of colors in flowers and fruits; specialized lipid molecule synthesis and storage; and carbohydrate and iron storage.

Ribosomes

•  Ribosomes are small, subspherical, granular particles, free in the cytoplasm or attached to the endoplasmic reticulum.
•  They are composed of ribonucleoproteins.
•  They are the site of protein synthesis.
• Ribosomes are of two types – 70S and 80S

Endoplasmic Reticulum

•  A system of narrow membrane tubules and sheets throughout the cytoplasm.
• Two types of endoplasmic reticulum include rough ER (RER) and smooth ER (SER)
• RER is studded with ribosomes, which produce proteins.
• SER has no ribosomes and plays a role in lipid production.

Golgi Apparatus

•  A factory for processing and packaging proteins and polysaccharides.
•  It is made of stacks of flattened sacs called cisternae.
•  Vesicles transport materials to the plasma membrane, to other organelles, or to the cell's exterior.
•  The Golgi apparatus collects and processes materials to be exported from the cell.
•  In plant cells, part of the cell wall is produced by the Golgi.

Microbodies

•  Spherical organelles bound by a single membrane.
•  Their exact function depends on the type of enzymes within them.
•  Peroxisomes oxidize certain molecules.
•  Glyoxysomes are involved in fat metabolism.

Spherosomes

•  Also known as plant lysosomes.
•  They originate from the endoplasmic reticulum in plants and possess hydrolytic enzymes.
•  They are involved in lipid storage and synthesis.

Nucleus & Nucleolus

•  The nucleus is a membrane-bound organelle containing DNA.
• Contains nucleolus, which is a structure of rRNA and proteins involved in ribosome synthesis.
• The nucleus controls cell growth and reproduction.
• Two types of chromatin exist: Heterochromatin and Euchromatin
• Heterochromatin is densely packed DNA (inert).
• Euchromatin is lightly stained DNA (active).
• Nucleoli are spherical, colloidal, acidophilic bodies.

Chromosomes

•  Chromosomes are thread-like structures of DNA and protein, visible during cell division.
•  Each chromosome has a distinct attachment point for microtubules.
•  The centromere is a constricted region, allowing spindle microtubules to attach.
•  Four classes of chromosomes based on the position of the centromere: metacentric, submetacentric, acrocentric, and telocentric.

Chromosome Number

•  The number of chromosomes is constant for a particular species.
•  The gametic cells contain half the number of chromosomes as the somatic cells.
•  The diploid number is the chromosome in somatic cells (2n).
• The polyploid contain more than the diploid number.

Cell Cycle

•  The cycle of cyclical changes that a cell undergoes from one cell division to the next.
•  Phases of the cycle include G1, S, G2, and M.

Mitosis

•  A process of nuclear division resulting in two identical daughter nuclei.
• The sequence of phases include Prophase, metaphase, anaphase, telophase.
• This process is needed for growth, repair, and asexual reproduction.

Cytokinesis

•  Cytokinesis refers to the division of a cell's cytoplasm in the process of mitosis and meiosis.

Meiosis

•  Meiosis is a type of cell division that results in four genetically unique haploid cells. These cells are also known as gametes, like sperm and eggs).
•  Meiosis involves two steps.
•  Meiosis one.
•  Meiosis two.
•  Meiosis I and II are both characterized by phases in prophase, metaphase, anaphase, and telophase.
• Meiosis is essential for sexual reproduction in eukaryotes.

Structural Changes

•  Deficiency or deletion.
• Duplication.
• Inversion.
• Translocation.

Changes in Chromosome Number

Polyploidy

• Polyploidy is a condition in which an organism has more than two complete sets of chromosomes.
•  There are autopolyploids and allopolyploids.

Aneuploidy

•  A numerical change in a part of the genome.
•  Forms include monosomy (with only one copy), trisomy (with three copies) and hypoploidy, and hyperploidy.

Test your knowledge on chromosome numbers, cellular division processes, and the distinctions between haploid and diploid cells. This quiz covers concepts such as karyokinesis, cytokinesis, and the characteristics of cytoplasm. Enhance your understanding of cell biology with these questions.