The size range of cells - Most cells are smaller than 0.1 mm - The smallest cells (some bacteria) - are similar in size to large viruses (0.1 µm) Mycoplasma cells attached to erythrocytes
Juicy pieces of a citrus fruit are separate gigant cells
General Biology: Cell structure and function
General Biology: Cell structure and function
Electron microscopy reached sub Ångstrom (Å) resolution in year 2000 by resolving the 0.89Å spacing between carbon atoms of diamond (1Å =10-10 m)
General Biology: Cell structure and function
Centrifugation makes it possible to separate cell components
General Biology: Cell structure and function
Composition of a prokaryotic cell
In a prokaryotic cell, the content (cytoplasm) is not separated into compartments. DNA and rybosomes are freely floating in the cytoplasm.
General Biology: Cell structure and function
Prokaryotic cells can have two types of cell wall:
Hans Christian Gram (1853 - 1938)
Gram (+):
Gram (-):
- thick layer of murein (peptidoglycan) - no second (outer) membrane
- thin layer of murein (peptidoglycan) - there is a second (outer) membrane
General Biology: Cell structure and function
Bacterial flagella rotation It is the only example of ’’a wheel principle’’ in nature
General Biology: Cell structure and function
Animal and fungal cells
General Biology: Cell structure and function
Plant and protistan cells
General Biology: Cell structure and function
Nucleus
General Biology: Cell structure and function
Endoplasmic reticulum (ER) 200 nm
Smooth ER: - synthesis of lipids - metabolism of carbohydrates - detoxification of drugs and poisons - storage of Ca2+ ions Rough ER: - synthesis of glycoproteins - (carbohydrate + protein) - production of secretory vesicles - membrane factory (phospholipids)
General Biology: Cell structure and function
Ribosomes
Protein synthesis in three locationes: - cytosol (free ribosomes) - rough ER - nuclear envelope
General Biology: Cell structure and function
Ribosomes
Prokaryotes: 30S and 50S subunits Eukaryotes: 40S and 60S subunits Svedberg (S): measure of sedimentation speed. Sedimentation = movement towards the bottom of a centrifuge tube. Ribosome 30S subunits sediment with speed of 30 µm/s under the force of 106 g. Sedimentation speed depends on: (1) weight, (2) shape, (3) temperature, (4) medium. Svedberg units are not additive! Prokaryote ribosomes: 30S and 50S subunits together have speed of 70S (not 80S).
General Biology: Cell structure and function
The Golgi Apparatus: shipping, receiving and manufacturing center
General Biology: Cell structure and function
The Golgi Apparatus: shipping, receiving and manufacturing center
Functions: - modification of polysaccharides, glycoproteins, phospholipids - synthesis of many secretory products - sorting and shipping to various locations (like a post office)
General Biology: Cell structure and function
Lisosomes: digestive organelles
General Biology: Cell structure and function
Vacuoles Types of vacuoles: - central vacuole (plants) - food vacuoles - contractile vacuoles (protista)
General Biology: Cell structure and function
Mitochondria and chloroplasts The ednosymbiont theory: mitochondria and chloroplasts derive from ancient prokaryotes captured by an eukaryotic cell - have their own DNA - devide independently - have ribosomes of - bacterial type (70S)
General Biology: Cell structure and function
Mitochondria µ
µ
- Mitochondrial matrix and inner membrane contain enzymes involved in - respiration and production of ATP (energy) - 1 to 1000s mitochondria per cell, depending on metabolic ativity of the cell - mitochondria can change their shape - in metabolically active cells, mitochondria form a network of tubes
General Biology: Cell structure and function
Chloroplasts
µ
µ
- chloroplasts contain enzymes involved in photosynthesis - chloroplasts can change their shape - fatty acid biosynthesis - amino acid biosynthesis - plant immune response
General Biology: Cell structure and function
Chloroplast is one of the eight types of plastids
General Biology: Cell structure and function
Peroxisomes
- contain enzymes that remove hydrogen atoms and transfer them to O2 - (hydrogen peroxyde H2O2 is a by-product → name ’’peroxysome’’) - convertion of fatty acids to smaller molecules for use as fuel in mitochondria - detoxification of alchohol and other poisons in liver cells - thought to have endosymbiotic origin
General Biology: Cell structure and function
Cytosceleton
µ
µ
The cytosceleton is a network of fibers that organize structures and activities in the cell.
General Biology: Cell structure and function
Cytosceleton
µ
µ
µ
General Biology: Cell structure and function
Cytosceleton Centrosome is the place of microtubule self-assembly in animal cells. In plant and fungal cells other structures fulfil such function.
µ
General Biology: Cell structure and function
Cytosceleton: motive instuments of a cell
µ
µ
General Biology: Cell structure and function
Cytosceleton: structure of flagellum or motile cilium µ
µ
µ
General Biology: Cell structure and function
Cytosceleton: principle of movement Movement without cross-linking proteins
Effect of cross-linking proteins
General Biology: Cell structure and function
Cytosceleton: examples of movement
µ
µ
µ
General Biology: Cell structure and function
Cytosceleton: structural function of microfilaments
Microvilli of nutrient-absorbing intestinal cells are kept in shape by microfilaments (actin)
µ
General Biology: Cell structure and function
Extracellular components of a plant cell - Primary cell wall (cellulose)
Extracellular matrix (ECM) of animal cells helps get information about outside conditions and transfer it to the nucleus. Collagen – 40% of human protein. Fibronectin and integrins – mechanical signalling in cooperation with cytosceleton. Integrins are receptors – integration of changes outside and inside of the cell.