General Biology: Cell structure and function

Cell structure and function

General Biology: Cell structure and function

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

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- 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

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- 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

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The cytosceleton is a network of fibers that organize structures and activities in the cell.

General Biology: Cell structure and function

Cytosceleton

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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.

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General Biology: Cell structure and function

Cytosceleton: motive instuments of a cell

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General Biology: Cell structure and function

Cytosceleton: structure of flagellum or motile cilium µ

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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

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General Biology: Cell structure and function

Cytosceleton: structural function of microfilaments

Microvilli of nutrient-absorbing intestinal cells are kept in shape by microfilaments (actin)

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General Biology: Cell structure and function

Extracellular components of a plant cell - Primary cell wall (cellulose)

- Middle lamella (pectin)

- Secondary cell wall - (cellulose + proteins + lignin)

General Biology: Cell structure and function

Extracellular components of an animal cell

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.

General Biology: Cell structure and function

Time to go for lunch!!!