cell structure Flashcards
What are eukaryotic cells?
Large, complex cells with a nucleus and membrane-bound organelles; DNA is wrapped around histone proteins.
What are prokaryotic cells?
Small, simple cells with no nucleus or membrane-bound organelles. DNA is in a loop (nucleoid) and not associated with histones.
Key differences between prokaryotic and eukaryotic cells?
Eukaryotes: nucleus, larger, complex organelles
Prokaryotes: no nucleus, smaller, may have plasmids, flagella, capsule.
What is the function of the nucleus?
Contains DNA (in chromosomes), controls cell activities, and contains a nucleolus.
What is the mitochondrion for?
Site of aerobic respiration; the matrix contains enzymes for respiration.
What is the function of chloroplasts?
Site of photosynthesis; some parts occur in the grana, others in the stroma.
What is the Golgi apparatus?
Modifies, processes, and packages proteins and lipids; makes lysosomes.
What is a Golgi vesicle?
A transport vesicle for lipids and proteins from the Golgi.
What is a lysosome?
A vesicle containing digestive enzymes (lysozymes) for breaking down waste or pathogens.
What is a ribosome?
Site of protein synthesis; can float free or be attached to the RER; not membrane-bound.
Function of rough endoplasmic reticulum (RER)?
Folds and processes proteins made by ribosomes.
Function of smooth endoplasmic reticulum (SER)?
Synthesises and processes lipids.
What does the vacuole do?
Contains cell sap; helps maintain turgor pressure in plant cells; surrounded by a tonoplast.
What are epithelial cells specialised for?
Absorption — have villi, microvilli, and many mitochondria for active transport.
What is murein?
A glycoprotein that makes up the cell wall in prokaryotes.
What is a slime capsule?
A protective outer layer that helps evade the immune system.
What are plasmids?
Small circular DNA molecules, often carrying genes like antibiotic resistance.
What is a flagellum?
A tail-like structure used for movement.
Are viruses living?
No — they are non-living particles.
What is the structure of a virus?
Genetic material (DNA or RNA), capsid (protein coat), and attachment proteins.
How do viruses replicate?
Use attachment proteins to bind to host cell → inject genetic material → host replicates virus.
What is binary fission?
A method of asexual reproduction in prokaryotes.
DNA and plasmids replicate; cell enlarges; cytoplasm divides; two daughter cells produced (may have different numbers of plasmids).
What is magnification?
Image size ÷ Actual size.
What is resolution?
The ability to distinguish between two separate points.
Features of a light microscope?
Uses light; Max resolution: 0.2 µm; Max magnification: x1500; Cannot view small organelles (e.g. ribosomes).
Features of an electron microscope?
Uses electrons; Higher resolution: 0.0002 µm; Max magnification: x1,500,000.
What is a transmission electron microscope (TEM)?
Electrons pass through thin sample; provides high resolution internal images; only thin specimens.
What is a scanning electron microscope (SEM)?
Electrons scan surface; produces 3D surface images; lower resolution than TEM; can be used on thick specimens.
What is the purpose of cell fractionation?
To separate different organelles from a cell.
Steps of cell fractionation?
Homogenisation: grind cells, ice-cold, isotonic, buffered solution; Filtration: remove large debris; Ultracentrifugation: spin at different speeds to separate organelles (nuclei → mitochondria → lysosomes → ER → ribosomes).
What is mitosis?
Division of a parent cell into 2 genetically identical daughter cells — used for growth and repair.
What are the 4 stages of the cell cycle?
G₁: cell growth, new proteins/organelles; S: DNA replication; G₂: further growth, protein synthesis; M: mitosis.
What happens during interphase?
DNA replicates, organelles double, ATP levels increase — cell prepares for division.
What happens during prophase?
Chromosomes condense; centrioles move; spindle forms; nuclear envelope breaks down.
What happens during metaphase?
Chromosomes line up; spindle fibres attach to centromeres.
What happens during anaphase?
Centromeres divide; chromatids pulled to poles; appear V-shaped.
What happens during telophase + cytokinesis?
Chromatids uncoil; nuclear envelope reforms; cytoplasm divides → 2 cells.
What causes cancer?
Uncontrolled cell division forming tumours.
How do cancer treatments target the cell cycle?
Prevent DNA replication (G1); Damage DNA (S) so cell self-destructs; Prevent formation of spindle (M).
Why do these treatments affect healthy cells?
They target all rapidly dividing cells (e.g. hair, gut lining), but cancer cells divide more frequently so are affected more.
What is the mitotic index?
Mitotic index = Number of cells in mitosis ÷ Total number of cells.
What are artefacts in microscopy?
Things seen under the microscope not part of the specimen (e.g. dust, air bubbles) — common in EM due to sample prep.
