The document provides an overview of structural biology and cell structure. It discusses the hierarchy of living systems from subcellular to multicellular organisms. It describes the basic structural and functional principles of cells, including the cell memory principle based on nucleic acids and proteins, the membrane principle involving various membranes, and the cytoskeletal principle involving microtubules, microfilaments and intermediate filaments. It compares the key differences between prokaryotic and eukaryotic cells as well as animal and plant cells.

1. MEDICAL BIOLOGY Lecture 1 Prof. MUDr. Roman Janisch, DrSc. Department of Biology [email_address] Structural Biology * Cell Structure and Functions of Prokaryotic and Eukaryotic Cell

2. Introduction into Medical Biology Why biology in medical studies? Characteristics of life Structural hierarchy of living systems Central position of the cell in biology Cell theory Cell structure Basic principles of functional structures of the cell Prokaryotic and eukaryotic cells Animal and plant cells Differentiation of a cell

3. Why biology in the medical studies? Medicine is a science dealing with the human body in health and disease. The human body is a living system and biology is concerned with general laws and principles governing living systems. Knowledge of the common characteristics of living systems will facilitate understanding of the very complex human organism with all special aspects and processes of human physiology. A good physician must know all about the human body and its functions and can achieve this only if they have good knowledge of basic natural laws.

4. Characteristics of life Differences between living and inanimate nature Chemical composition Cellular nature Metabolism Growth Reproduction Heredity Variation Movement Evolution Irritability Differentiation Regeneration Adaptation All these characteristics are required for the definition of a living system. The basic characteristic is chemical composition, all living systems a built up from organic biopolymers.

5. Structural hierarchy of living systems Subcellular organisms (acellular) - viruses, phages. 2. Unicellular organisms - bacteria, cyanobacteria, protozoa (Paramecium, Amoeba), algae (Chlamydomonas), fungi (yeast cells). 3. Cell colonies - algae (Volvox), slime mould (Physarum). 4. Multicellular organisms - animals, plants, fungi. 5. Animal societies - social insects (honeybee society, termites, etc.)

6. Building hierarchy in multicellular organisms Atoms (carbon, oxygen, hydrogen, nitrogen) Molecules (actin, tubulin, globulins, DNA, RNA) Supramolecular complexes (microtubules, membranes) Organelles (mitochondria, chloroplasts, lysozomes) Cells (neurones, muscle cells, leukocytes) Tissues (connective, epithelial, muscle, nervous tissues) Organs (stomach, salivary gland, brain, eye, heart) Systems of organs (digestive, respiratory, excretory) Organisms (human)

7. Cell theory Central position of the cell in biology . Mid-19th century Schleiden, Schwann, Purkinje . The cell is a basic structural and functional unit of all organisms. All forms of life are associated with cells. Except for viruses, all living systems are based on cells. All cells have a uniform principle of structure. The size range is 0.3 μ m - 3 mm. Cells are differentiated according to their structure and function. Examples of differentiated cells - yeast cell, infusorian, amoeba, alga, erythrocyte, leukocyte, neurone, fibroblast, chondrocyte, epithelial cell, smooth muscle cell, gland cell, gamete, receptor cell. Morphology of any differentiated cell depends on its function. Molecular biology confirmed cell theory principles by the discovery of universality of the genetic code.

8. Cell Structure The previous cytological view on the cell structure distinguished morphology from function of different cell components (organelles). Recent technologies have revealed new details of microscopic, submicroscopic and molecular structures. Findings in molecular biology eliminated the gap between morphology and function of cell structures. In the current concept of cell biology structure and function together are understood in terms of three basic structural and functional principles of the cell.

9. Cell Structures in Different Cell Types

10. Basic structural and functional principles of a cell Cell memory principle ( nucleic acids, proteins ,chromosomes, nucleosomes, ribosomes ) Membrane principle (biomembranes, plasma membrane,nuclear envelope, endoplasmic reticulum, vacuoles, Golgi apparatus, lysozomes, mitochondria, chloroplasts) Cytoskeletal principle ( microtubules, centrioles, kinetosomes, axonemes, microfilaments, intermediate filaments ) The cell is a complex hierarchical system. Molecular and cell biology, previously cytology, is a field of science dealing with cells.

11. Cell Memory Memory is ability to record and store information. Biological memory is based on storage of information in living systems and is therefore called genetic information. Genetic information is a complex system carrying complete data necessary for the existence of one’s own life and reproduction. Cell memory system has to be large, stabilised, permanent in time, fast in expression into traits, able to duplicate, change and develop. DNA is the main information medium in all living systems.

12. Biomembranes Cells need membranes to: compartmentalize and delineate the cell and its organelles regulate the flow of materials, energy and information mediate recognition of environmental factors mediate interaction between cells

13. Biomembranes

14. Historical Data o n Membrane Structure Research Presence of lipids (Overton 1890) Monolayer of phospholipids (1905) Bilayer of phospholipids (Gorter a Grendel 1925) Bilayer of phospholipids and protein layers (Dawson a Danielli 1935) Unite membrane (Roberton 1960) Fluid mosaic model (Singer and Nicolson 1972) Structure of membrane proteins (Unwin and Henderson (1972)

15. Molecular Structure of Biomembranes

16. The asymmetrical distribution of phospholipids and glycolipids in a plasma membrane lipid bilayer

17. Transmembrane proteins

18. Ways in which membrane proteins associate with the lipid bilayer

19. The cytoskeleton A skin cell (fibroblast) in culture has been fixed and stained with Coomassie blue, a general stain for proteins. Various filamentous structures extend throughout the cell. The dark body in the center is the n ucleus.

20. Basic Components of the Cytoskeleton Microtubules Microfilaments Intermediary filaments

21. Three types of cytoskeletal components

22. Three types of cytoskeletal components

23. Functions of the Cytoskeleton Maintenance of cell structure Movement Information medium

24. Prokaryotic and E ukaryotic C ells There are two categories of cells from the point of view of evolution and their structural arrangement - prokaryotic and eukaryotic cells. Differences: cell size membrane organelles type of DNA RNA and protein synthesis ribosomes cytoskeleton cell division

25. Differences between prokaryotic and eukaryotic cells: present only in plants and fungi present Cell wall mitosis binary cell division Cell reproduction present none Cytoskeleton large size small size Ribosomes multipl e and divers e minimun Membranel organelles more then one, linear single, circular Chromosomes present none Nuclear envelope Eukaryotic cell Prokaryotic cell Cell strctures

26. Structure of Prokaryotic and Eukaryotic Cell

27. Cell ’ s Evolution Tree The three major domains of the living world The tree is based on comparison of the nucleotide sequence of ribosomal RNA subunit in the difference species. The lengths of the lines represent the number of evolutionary changes that have occurred in this molecule in each lineage. Bacteria recently has been redefined to refer to eubacteria specifically.

28. Animal and P lant C ells Differences in structure There are three cell structures typical of plant cells: cell wall plastids vacuole

29. Animal C ell

30. Plant C ell

31. Differentiation of the C ell Differentiation during phylogenesis and ontogenesis. Specialisation in function. Regulation of differentiation - regulation of gene expression. Failure of regulation – congenital defects, cancerogenesis.

32. Glossary An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water. Chloroplast A structure in the cytoplasm of eukaryotic cells, consisting of two centrioles and pericentriolar matrix, important during cell division; also called microtubule-organising centre (MTOC). Centrosome An organelle having the same structure as a kinetosome (basal body); part of the microtubule-organising centre (MTOC). Centriole Structural and functional divergence of cells as they become specialized during the development of a multicellular organism; dependent on control by gene expression. Cellular differentiation Schleiden, Schwann, and Purkinje recognized in the 1850s that the cell is a basic structural and functional unit of all organisms, that all forms of life are associated with cells, and that the structure of a cell is organised by a uniform principle. Cell theory Biological memory is based on ability to record and store information in living systems; it is also called genetic information. Biological memory A type of cell division in prokaryotes; each dividing daughter cell receives a copy of the single parental chromosome. Binary fission A cylindrical structure at the base of a cilium or a flagellum consisting of nine sets of triplet microtubules from which the microtubules forming axonemes radiate; a synonym for kinetosome; a homologous structure for centriole. Basal body The domain name for achaebacteria. Archaea A photosynthetic, plant-like protist. Alga

33. A usually insoluble network consisting of glycosaminoglycans, collagen, and various adhesive proteins secreted by animal cells. Extracellular matrix A structural unit of the genetic material consisting of a single, linear double-stranded DNA molecule and associated proteins, particularly histones aggregated into nucleosomes. Eukaryotic chromosome A cell with a membrane-enclosed nucleus and membrane-enclosed organelles, comprising protists, plants, fungi, and animals (eukaryotes). Eukaryotic cell Organelles that arise from clathrin-coated vesicles that have lost their coat after endocytosis. Early endosomes The semifluid portion of cytoplasm. Cytosol A network of protein fibrils resistant to non-ionic detergent , i.e., microtubules, microfilaments and intermediate filaments that serve a variety of mechanical, motor and transport functions. Cytoskeleton A science dealing with cell structure and function. Cytology Photosynthetic, oxygen-producing bacteria (formerly known as blue-green algae). Cyanobacteria Transport vesicles surrounded by an outer protein cage composed primarily of the fibrous protein clathrin. Coated vesicles A membrane-enclosed locomotory structure extending from the surface of eukaryotic cells and composed of nine peripheral and one central doublets of microtubules called axonemes. Numbers of them cover the whole cell surface. See also flagellum. Cilium Aggregate mass of dispersed genetic material composed of DNA and protein, and observed between periods of cell division in eukaryotic cells. Chromatin

34. The membrane that encloses the nucleus, separating chromosomes from the cytoplasm, in eukaryotic cells. Nuclear envelope A membrane organelle in eukaryotic cells that serves as the site of cellular respiration. Mitochondrion One of many fine, finger-like projections of animal cells which increase their surface area. Microvillus A hollow rod of tubulin protein in the cytoplasm, flagella and cilia of eukaryotic cells. Microtubule A solid rod of actin protein in the cytoplasm of eukaryotic cells, part of the cytoskeleton acting with myosin to cause cell contraction. Microfilament A membrane-enclosed bag of hydrolytic enzymes present in the cytoplasm of eukaryotic cells. Lysosome A synonym for basal body and a homologous structure for centriole. Kinetosome A component of the cytoskeleton that includes all filaments intermediate in size between microtubules and microfilaments (mostly 10 – 16 nm) Intermediate filament An organelle in eukaryotic cells, consisting of stacks of membranes that modify, store, and route products of the endoplasmic reticulum. Golgi apparatus The process by which information encoded in a gene is converted into an observable phenotype (most commonly the production of protein). Gene expressibility The model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids. Fluid mosaic model A membrane-enclosed locomotory structure extending from the surface of eukaryotic cells and composed of nine peripheral and one central doublets of microtubules, called axonemes. One or several of them are attached to the cell pole. See also cilium. Flagellum

35. Major organelles found only in plants and algae, responsible for photosynthesis and storage of products like starch. Plastids Any of many minute strands of cytoplasm that extend through plant cell walls and connect adjoining cells Plasmodesma A membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the flow of molecules, energy and information. Plasma membrane Molecules that constitute the inner bilayer of biomembranes; they have a polar, hydrophilic end, and a non-polar, hydrophobic tail. Phospholipids A virus that infects bacteria; also called bacteriophage. Phage A vesicle-like organelle containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide. Peroxisome One of several structures with specialised functions, suspended in the cytoplasm of eukaryotic cells. Organelle The chromosome-containing organelle of a eukaryotic cell. Nucleus A basic bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histones. Nucleosome A specialized structure in the nucleus formed by parts of various chromosomes that is active in the synthesis of ribosomes. Nucleolus A protein-lined channel through the nuclear envelope that permits passage of RNA from the nucleus to the cytoplasm and transport of proteins in the opposite way. Nuclear pore A group of intermediate filament proteins that form a fibrous network on the inner surface of the nuclear envelope. Nuclear lamins

36. A unicellular fungus primarily reproducing asexually by simple cell division or by budding of a parent cell. Yeast A membrane enclosed sac taking up most of the interior of a mature plant cell and containing a variety of substances important in plant reproduction, growth, and development. Vacuole A membrane that encloses the central vacuole in a plant cell, separating the cytosol from the cell sap. Tonoplast An integrated group of cells with a common structure and function. Tissue The portion of endoplasmic reticulum free from ribosomes. Smooth endoplasmic reticulum The portion of endoplasmic reticulum studded with ribosomes. Rough endoplasmic reticulum A cell organelle arising in the nucleolus, consisting of two subunits and functioning as the site of protein synthesis in the cytoplasm. Ribosome A synonym for bacterial flagellum; its width is one tenth of that of an eukaryotic flagellum; it is not covered by a membrane and is composed of flagellin. Prokaryotic flagellum One double stranded DNA molecule arranged in a circle. Prokaryotic chromosome A cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Prokaryotic cell