Cells are the basic unit of life

The cell: the smallest unit of life


1 The cell: the smallest unit of life Oliver Zierau Dresden, July 5th, 2015

2 The book slide 2 of 60

3 History of the Cell The Age of Biology? 1) Despite the tremendous achievements that have been made in the fields of physics and chemistry, in the decades since 1953 when James Watson, Francis Crick and Maurice Wilkins discovered DNA, biology has inexorably gained a key position in cell biology in particular a fundamental importance for the bio / life sciences to Cell research forms the basis on which the entire modern biology (including biotechnology) is built Slide 3 of 60

4 The cell basic unit of life Just as the atom is the basic unit of chemistry, the cell is the building block of life 2) The cell theory is based on 3 central statements: 3) Cells are the basic units of life All organisms are made up of cells All cells are made up of already existing cells slide 4 of 60

5 The cell Cells contain water molecules and a multitude of small and large molecules In every cell there are at least different types of molecules (sometimes multiple) These molecules are used for converting matter into energy Communication with the environment Reproduction 3b) Slide 5 of 60

6 The cell It follows that: 1. The principles of the cell are the same 4) Bacterium 5) 60 trillion cells in our body Slide 6 of 60

7 The cell It follows: 2. Cells exist continuously 6) 7) Slide 7 of 60

8 The Cell It follows: 3. Life began with the first cell 8) Slide 8 of 60

9 Cell scale The scale of life. This scale shows the relative size of molecules, cells and multicellular organisms. Slide 9 of 60

10 Size of cells Cells are (in general) tiny volumes of cells range from 1 to 1000 µm 3 exceptions: bird, reptile eggs, some algae and bacterial species Why is the cell size limited? Slide 10 of 60

11 Cell size Why is the cell size limited? Cell volume limits chemical activity per time Cell surface limits uptake and release »Grow cells therefore require more resources and waste production than exchange surface» Limits cell growth Multicellular organisms therefore have huge cavities inside Slide 11 of 60

12 Plasma membrane On the outside, cells are bounded by a plasma membrane> A closed compartment 8) Phospholipid bilayer film 12 of 60

13 Plasma membrane The cell membrane or plasma membrane, also called plasmalemma, is a biomembrane that surrounds the living cell and enables it to maintain the inner milieu. It consists of a lipid bilayer and is about 6 to 10 nm thick (maximum visible under light microscopy as a line) A cell membrane is the demarcation of a cell. In addition, there is an exchange of substances on the cell membrane 9) Slide 13 of 60

14 Plasma proteins Cells identify themselves to the outside with the help of their peripheral proteins (see surface antigen) These membrane proteins lie or float on or in the membrane according to the fluid mosaic model. In addition, short-chain, partially branched carbohydrate compounds on the proteins and on the outside often protrude the lipids (the so-called glycoproteins or glycolipids) 9) Slide 14 of 60

15 Plasma membrane These structures of the cell membrane have, among other things, receptor, transport or stabilizing functions. Furthermore, the cell membrane absorbs molecules bound by endocytosis by indenting and constricting cell membrane sections. Liquids are trapped by pinocytosis Slide 15 of 60 10)

16 Plasma Membrane Most plasma membranes are semi-permeable and therefore the cells have a membrane potential (there is a potential difference between inside and outside) Primarily through ion channels, different material and charge distributions occur> electrochemical gradient On the outside of the cell membrane there can be cell extensions, as is the case with animals Cell membranes the microvilli (pseudopodia-like protuberances) as surface enlargement 11) Slide 16 of 60

17 The eukaryotic cell Eukaryotic cells are also known as eucytes.The main difference to prokaryotic cells is the existence of a cell nucleus with a nuclear envelope around which DNA is organized in chromosomes. Eukaryotic cells are much more differentiated.They generally have to fulfill very different functions 12) Slide 17 from 60

18 What are eukaryotes? The Eukaryotic Cell 12) Slide 18 of 60 13)

19 What are eukaryotes? Crenarchaeota Nanoarchaeota Animals Fungi Slime molds Plants Algae Protozoa / Urtierchen Euryarchaeota Gram-positive Chlamydia Green non-sulfur bacteria Actinobacteria Planctomycetes Spirochetes Fusobacteria Cyanobacteria (blue-green algae) Thermophilic sulfur reducers Acidobacteria Proteobacteria Slide 19 of 60

20 The cell slide 20 of 60

21 The Eukaryotic Cell Slide 21 of 60 (3rd

22 the cell (14 slide 22 of 60 (15

23 Compartmentalization (16 The essential thing about eukaryotic cell functions is the compartmentalization (17 Slide 23 of 60

24 The essential thing about the eukaryotic cell functions is the compartmentalization: - parts produce substances, - other energy and compartmentalization - again others store substances cell organelles or organelles Slide 24 of 60 (14

25 Cell organelles The cell nucleus is a mostly rounded organelle which contains most of the genetic material (DNA) The genetic material is in the form of several chromosomes Most cells contain exactly one nucleus (exceptions e.g. myoblasts, mature mammalian erythrocytes) (17 Slide 25 of 60

26 Cell organelles The genetic material is duplicated in the cell nucleus Location of the genetic control of cell activity The nucleolus is also where the ribosome subunits are assembled from specific proteins and RNA molecules Slide 26 of 60

27 Cell organelles The mitochondrion (plural mitochondria) is an organelle enclosed by a double membrane with its own genetic material Mitochondria are found in the cells of almost all eukaryotes Mitochondria serve as energy power stations and form the high-energy molecule adenosine triphosphate (ATP) (17 slide 27 of 60

28 Cell organelles Mitochondria have other essential functions for the cell. A particularly large number of M. are in cells with high energy consumption (muscle cells, nerve cells, sensory cells and egg cells). Mitochondria are only inherited from the mother via the plasma of the egg cell Symbiosis of aerobic bacteria with the precursors of today's eukaryotes emerged (18 slide 28 of 60

29 Cell organelles functions of the mitochondria - citric acid cycle - respiratory chain - apoptosis (programmed cell death) - calcium storage - synthesis of iron-sulfur clusters - parts of the urea cycle (19 slide 29 of 60

30 Cell Organelles The endoplasmic reticulum (ER) is a richly branched canal system of flat cavities, which is enclosed by membranes. The ER is found in all eukaryotic cells; depending on the cell type, it is differently developed (with the exception of mature erythrocytes) (17 Slide 30 of 60

31 Cell organelles The ER is a branched membrane network of tubes, vesicles and cisterns. ER membrane closes the interior (ER lumen) from the cytosol. The ER membrane labyrinth makes up over half of the total amount of membrane in the cell. The ER membrane is direct into the nuclear envelope of the cell nucleus. In rough ER, their membrane surfaces are covered with ribosomes; with smooth ER they are ribosome-free and therefore smooth. Rough and smooth ER differ in their function. Slide 31 from 60

32 Cell organelle functions of the rough ER - Translation, protein folding, protein quality control, post-translational protein modification, protein transport and protein secretion take place on and in the ER - nuclear membrane production - calcium storage (20 slide 32 of 60

33 Cell organelles The smooth ER plays an important role in several metabolic processes - synthesis of lipids, fatty acids and steroids - carbohydrate metabolism - detoxification of the cell (e.g. liver cells) (21 slide 33 of 60

34 Cell Organelles The rough ER has two functions: - protein biosynthesis - membrane production It is increasingly found in the cells of exocrine glands and the liver as well as in nerve and embryonic cells (22 slide 34 of 60

35 Cell organelles The Golgi apparatus is a membrane-enclosed reaction space within the cell Golgi apparatus is involved in secretion formation and other tasks of cell metabolism (17 slide 35 of 60

36 cell organelles The Golgi apparatus consists of 4 to 6 membrane-enclosed, mostly flat cavities (cisterns). Cisterns form stacks with a diameter of approx. 1 µm (dictyosome). The GA contains one to several hundred dictyosomes for each cell type. The extension of the G-A depends on their activity and function - may vary temporarily (23 slide 36 of 60

37 Cell organelles Lysosomes are vesicles with an acidic pH value enclosed by a simple biomembrane.They contain digestive enzymes and are partially formed in the Golgi apparatus.The function of the lysosomes is to break down biopolymers into their monomers (17 Slide 37 of 60

38 Cell organelles Lysosomes contain (for intracellular digestion) a number of different hydrolyzing enzymes such as: Proteases, nucleases and lipases For the hydrolysis of proteins, polysaccharides, nucleic acids and lipids (24 Slide 38 of 60

39 Cell organelles The hydrolyzing enzyme in the lysosomes only reaches a high activity with a pH of 4.5 5 This serves to protect the cell (why?) Thus an example of the importance of compartmentalization within the cell. The membrane proteins are on the inside for protection Heavily glycosylated before self-digestion (25 slide 39 of 60

40 Cell organelles Vacuoles are built similar to vesicles but are much larger spaces enclosed by a membrane. as food vacuoles (formed by phagocytosis from parts of the cell membrane) (17 slide 40 of 60

41 Cell organelles Vacuoles can have the following tasks: The turgor creates a firm state of the cell, which stores proteins, organic compounds and ions, i.e. substances that are toxic or could disrupt the metabolism Digestion of macromolecules (26 Slide 41 of 60

42 Cell organelles Ribosomes are macromolecular complexes of proteins and ribonucleic acids (RNA) that occur in the cytoplasm, in the mitochondria. Proteins are synthesized on them - according to the base sequence of the DNA / RNA, which is transcribed into the amino acid sequence of the protein (27 slide 42 of 60

43 Cell organelles The conversion of the information stored in the mrna into a sequence of linked amino acids is called translation (Latin for translation) The translation of the mrna is a central component of protein biosynthesis and occurs in all living things (17 slide 43 of 60

44 The cytoskeleton The cytoskeleton is a network in the cytoplasm of eukaryotic cells made up of proteins.It consists of thin, thread-like cell structures (filaments) that can be dynamically built up and degraded.It is responsible for the mechanical stabilization of the cell and its external shape, for the active locomotion of the cell as well as for movements and transports within the cell (17 slide 44 of 60

45 The name of the cytoskeleton is misleading because the cytoskeleton is not a rigid skeleton or framework, but rather a dynamic network of structures. The cytoskeleton is not only necessary for mechanical stability, but also for sensory functions such as signal transmission between cells (28 Slide 45 from 60

46 The cytoskeleton In the eukaryotic cell, a distinction is made between three classes of cytoskeletal filaments, each formed by different proteins, possessing specific accompanying proteins and each having a different role actin filaments, intermediate filaments, and microtubules (29 slide 46 of 60

47 The cytoskeleton are fibers with a diameter of 7 nm in network-like arrangements below the plasma membrane and in membrane bulges (microvilli, pseudopodia) they stabilize the outer shape of the cell can be dynamically built up and broken down (30 Slide 47 of 60

48 The cytoskeleton Intermediate filaments are structures made of proteins in the cytoplasm of a cell and serve to increase the mechanical stability of the cell. Diameter of about 10 nm (31 Cytoplasmic and nuclear intermediate filament in a rat kangaroo kidney epithelial cell. By Dr. Lynne Chang, Harvard Medical School slide 48 of 60

49 Microtubules are tubular protein microfilaments with nm Ø on the one hand for the mechanical stabilization of the cell on the other hand together with other proteins for movement and transport as well as for active movements of the whole cell The cytoskeleton (32 slide 49 of 60

50 The Extracellular Matrix (33 (34 Slide 50 of 60

51 The extracellular matrix The extracellular matrix (ECM) is the portion of animal tissue (especially connective tissue) that lies between the cells in the so-called intercellular space.The ECM is made up of a number of components that are divided into two large groups: basic substance and fibers (35 1. Plasma cell 2. Elastic fiber 3. Mast cell 4. Macrophage 5. Nerve fiber 6. Basic substance 7. Collagen fibrils 8. Neutrophil granulocyte 9. Reticulin fibers 10. Fibroblast 11. Capillary with endothelial cells 12. Fat cell

52 The extracellular matrix The ratio of the basic substance to the fiber content fluctuates depending on the location. The total amount of the extracellular matrix in the tissue also fluctuates, depending on its respective function.Historically, the ECM was only understood to have a function as glue (from it collagen) or as a tissue-internal water reservoir (36 Slide 52 of 60

53 The extracellular matrix Functions of the ECM in various tissues and organs: - Shaping of tissues and organs - Water content of tissues - Elasticity of tissues - Tensile strength and stability of bones, tendons and ligaments - Cytokine reservoir - Signal transduction in tissues - Anchoring and polarity specification for cells - Influence on wound healing processes Slide 53 of 60

54 Cell division Cell division or cytokinesis is the biological process of division of a cell The components of the mother cell including the plasma are divided among the daughter cells For this purpose, cell membranes are drawn in or formed between them, which usually results in two daughter cells (37 Slide 54 of 60

Cell division In eukaryotic cells, nucleus division (mitosis) usually takes place before cell division, but cell and nucleus divisions can also take place independently.As the daughter cells are usually supposed to receive copies of all essential cell components, cell division is strongly regulated.The cell division can start while the nucleus is still dividing in progress nuclear division + cell division = cell cycle (38 slide 55 of 60

56 Cell division Cells that are part of the cell cycle, in which cell growth and cell division alternate continuously, are described as proliferating (38 slide 56 from 60

57 Cell division (17 slide 57 of 60

58 Cell division The number of cell divisions per unit of time is the division rate> this is cell type-specific. In single-cell organisms, the time between two divisions corresponds to the generation time.Cells of eukaryotes that no longer divide after differentiation are referred to as post-mitotic Nuclei are formed, syncytia arise Syncytia can also arise, as with muscle fibers, through the fusion of mononuclear cells while preserving all nuclei Slide 58 of 60

59 Exercise questions 1. Name the three central statements cell theory. 2. What is the normal size (order) of a cell and why is the cell size limited? 3. What limits a cell to the outside and how is this structure built up? 4. What are the main differences between eukaryotic and prokaryotic cells? 5. What are eukaryotes? 6. Why is compartmentalization important for eukaryotic cell functions? 7. Which cell organelles are there in eukaryotes and what are their functions? 8. Which cells contain a particularly large number of mitochondria? 9. What is the function of the cytoskeleton? 10. Name the cytoskeletal filaments. 11. Briefly sketch the cell division. 12. What is the extracellular matrix, where can it be found and what is its function? Slide 59 of 67

60 Thank you very much

61 Image sources 1) 2) 3) 3b) 4) 5) 6) 7) private 8) private 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) Slide 61 of 60

62 Image Sources Slide 62 of 60

63 Image sources 1) 2) 3) 4) 5) 6) 7) private 8) private 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19) 20) 21) Slide 63 of 60