Topic 2A: Cell structure and division Flashcards
What is a eukaryotic cell?
A cell that has a nucleus and membrane-bound organelles.
Name three types of eukaryotic cells.
Animal cells, plant cells, and fungal cells.
What is the function of the nucleus?
It contains DNA and controls the cell’s activities.
What is the function of mitochondria?
They produce ATP via aerobic respiration.
What is the function of ribosomes?
They synthesize proteins.
What is the role of the Golgi apparatus?
It processes, modifies, and packages proteins and lipids.
How are plant cells different from animal cells?
Plant cells have a cell wall, chloroplasts, and a large central vacuole, which animal cells do not.
What is the function of lysosomes?
They contain digestive enzymes that break down waste and unwanted materials in the cell.
How do prokaryotic cells differ from eukaryotic cells?
They lack a nucleus and membrane-bound organelles.
What is the function of plasmids in prokaryotic cells?
They contain small loops of DNA that may carry advantageous genes (e.g., antibiotic resistance).
What is the function of the prokaryotic cell wall?
It provides structural support and is made of murein (a glycoprotein).
How do prokaryotes store their DNA?
As a single circular DNA molecule that floats freely in the cytoplasm.
What are viruses made of?
A protein coat (capsid), genetic material (DNA or RNA), and attachment proteins.
How do viruses reproduce?
They infect host cells and use the host’s machinery to replicate.
What is cell fractionation?
A process used to separate different organelles from a cell.
What are the three stages of cell fractionation?
Homogenisation, filtration, and ultracentrifugation.
Why must the solution in cell fractionation be cold, isotonic, and buffered?
~Cold: Reduces enzyme activity that might break down organelles.
~Isotonic: Prevents osmotic damage to organelles.
~Buffered: Maintains pH to prevent protein denaturation.
In ultracentrifugation, which organelle is separated first?
The nucleus (as it is the heaviest/densest).
What is an optical (light) microscope used for?
Viewing living cells in color, but with a lower resolution than electron microscopes.
How do transmission electron microscopes (TEMs) work?
They pass electrons through a specimen, producing high-resolution 2D images.
How do scanning electron microscopes (SEMs) work?
They scan a beam of electrons across a specimen, producing a 3D image.
What is the purpose of mitosis?
To produce two genetically identical daughter cells for growth and repair.
What are the four main stages of mitosis?
- Prophase: Chromosomes condense; spindle fibers form; nuclear envelope breaks down.
- Metaphase: Chromosomes align at the equator.
- Anaphase: Sister chromatids are pulled apart to opposite poles.
- Telophase: Nuclear envelopes reform; cytokinesis follows, splitting the cytoplasm.
What is interphase?
The stage before mitosis where the cell grows and DNA is replicated.
What happens during the G1 phase of interphase?
The cell grows, new organelles and proteins are made.
What happens during the S phase of interphase?
DNA replication occurs, so each chromosome consists of two sister chromatids.
What happens during the G2 phase of interphase?
The cell continues to grow, and proteins needed for mitosis are synthesized.
What is the role of spindle fibers in mitosis?
They attach to centromeres and pull sister chromatids apart during anaphase.
What happens during cytokinesis?
The cytoplasm divides, producing two separate daughter cells.
How does mitosis ensure genetic consistency?
It produces daughter cells that are genetically identical to the parent cell.
What happens if the cell cycle is uncontrolled?
It can lead to cancer, as cells divide uncontrollably and form tumors.
How can the mitotic index be calculated?
Mitotic index = (Number of cells in mitosis / Total number of cells) × 100
What stain is commonly used to observe mitosis in root tip cells?
Acetic orcein or toluidine blue, which stains DNA.
Why are root tips used to observe mitosis?
They contain a high number of actively dividing cells in the meristem.
How is a root tip squash prepared for microscopy?
The root tip is softened in acid, stained, and gently squashed under a coverslip to spread the cells out.
Why is a thin layer of tissue used when preparing a slide for mitosis observation?
To allow light to pass through for clearer visibility of the chromosomes.
How can you identify different stages of mitosis under a microscope?
~Prophase: Chromosomes condense and become visible.
~Metaphase: Chromosomes align in the center.
~Anaphase: Chromatids are pulled to opposite poles.
~Telophase: Two nuclei form.
Why is hydrochloric acid used in root tip mitosis experiments?
It softens the cell walls, making it easier to squash the tissue and spread the cells.
What is a Prokaryotic cell?
A cell that lacks a nucleus and membrane-bound organelles.
What is an Organelle?
A specialized structure within a cell that performs a specific function.
What is a plasmid?
A small circular DNA molecule found in prokaryotic cells.
What is a capsid?
The protein coat surrounding a virus.
What is Cell fractionation?
A process to separate organelles from a cell.
What is Ultracentrifugation?
The spinning of a cell homogenates at high speeds to separate organelles by density.
What is Mitosis?
A type of cell division that produces two genetically identical daughter cells.
What is interphase?
The phase of the cell cycle where the cell grows and DNA is replicated.
What is a Centromere?
The region where two sister chromatids are joined.
What are Spindle fibers?
Protein structures that pull chromatids apart during mitosis.
What is Cytokinesis?
The division of the cytoplasm following mitosis.
What is mitotic index?
The proportion of cells in a tissue sample undergoing mitosis.
What is a meristem?
A region in plants where rapid cell division occurs.
What is cancer?
Uncontrolled cell division leading to tumor formation.
