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Cells Slide 5A.1 BIOM5010 Cellular Organization © A. Adler, 2011 – 2013 Cells Slide 5A.2 Cell Theory Cells are the smallest units that can live and reproduce on their own Discovery Microscope manufacturing (van Leeuwenhoek, 1632-1723) looked at tartar scrapings from his teeth Hooke (1635 – 1703) coined the term cell (like monk's cells: http://dexteroustongue.com/cell/) Cell Theory All organisms are composed of one or more cells The cell is the smallest unit of life Cells come from previously existing cells © A. Adler, 2011 – 2013 Cells Slide 5A.3 Cell Composition Cells composed of water and organic compounds Carbohydrates – store energy and structural Lipids – oils/fats which don't dissolve in water. Main store of energy in cells Proteins – Diverse class of biomolecules. Enzymes for reactions Structural elements (transport channels across cell wall) Signals “chemical weapons” against foreign bacteria Nucleic acids – Elements of genetic information © A. Adler, 2011 – 2013 Cells Slide 5A.4 Cell structure Eukaryote (plants, animal cells) – membranes around subcellular structures Prokaryote (bacterial cells) – only outer plasma membrane Sizes of cells 10–100 µm (smaller to 1µm for prokaryote) © A. Adler, 2011 – 2013 Cells Slide 5A.5 Cell structure: Membrane Membrane (cell / plasma membrane). to separate and protect a cell from environment made mostly from double layer of lipids and hydrophilic phosphorus molecules. within this membrane are protein molecules that act as channels and pumps that move different molecules into and out of the cell. 'semi-permeable', in that it can either let a substance (molecule or ion) contain receptor proteins that allow cells to detect external signaling molecules such as hormones. © A. Adler, 2011 – 2013 Cells Slide 5A.6 Cells in resting state Cells actively pump ions to maintain electrical charge. Sodium pump pumps 3Na+ out for 2K+ in. In resting state, membrane permeable to Cl– and K+. Impermeable to Na+. How many Na+ in cell of diameter d=100μm Estimate vol = d3 = 10–12m3 =1nL (actual = 0.52×) 10–9L×(12×10–3mol/L)×(6.023×1023 atoms/mol) = 7.2240×1018 Concentrations (mM = mmol/L) Na + K+ Cl – 120 5 125 3Na + / 2K+ © A. Adler, 2011 – 2013 12 120 5 Cells Slide 5A.7 Organelles Cell structure: Organelles As the body contains different organs, each organ performing a different function. Cells also have a set of "little organs," called organelles, specialized for different functions. There are several types of organelles in a cell. nucleus and golgi apparatus: are typically solitary, such as mitochondria, peroxisomes and lysosomes) can be numerous (hundreds to thousands). cytosol: gelatinous fluid that fills the cell © A. Adler, 2011 – 2013 Cells Slide 5A.8 Cell Nucleus Cell nucleus – cell's information center houses the cell's chromosomes, place where almost all DNA replication and RNA synthesis (transcription) occur. spherical and separated from the cytoplasm by a double membrane called the nuclear envelope, which isolates and protects a cell's DNA nucleolus (plural nucleoli) is a non-membrane bound structure composed of proteins and nucleic acids found within the nucleus. Ribosomal RNA (rRNA) is transcribed and assembled within the nucleolus. Genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence. deoxyribonucleic acid (DNA). Most organisms use DNA for their long-term information storage ribonucleic acid (RNA). used for information transport Foreign genetic material can also be artificially introduced into the cell by a process called transfection. This can be transient, if the DNA is not inserted into the cell's genome, or stable, if it is. © A. Adler, 2011 – 2013 Cells Slide 5A.9 Organelles: Mitochondria Mitochondria – the power generators generate the cell's energy by oxidative phosphorylation, using oxygen to release energy stored in cellular nutrients (typically pertaining to glucose) to generate ATP. Respiration occurs in the cell mitochondria. Energy + ADP → ATP ATP → ADP + Energy Mitochondria contain their own genome, which is separate and distinct from the nuclear genome of a cell, … much like prokaryotic cells © A. Adler, 2011 – 2013 Cells Slide 5A.10 Organelles: Ribosomes Ribosomes large complex of RNA and protein molecules. act as an assembly line where RNA from the nucleus is used to synthesise proteins from amino acids. © A. Adler, 2011 – 2013 Cells Slide 5A.11 Cell Division General view of cells in the growing root-tip of the onion, from a longitudinal section, enlarged 800x a. non-dividing cells, with chromatin-network and deeply stained nucleoli; b. nuclei preparing for division (spiremestage); c. dividing cells showing mitotic figures; e. pair of daughtercells shortly after division. Source: en.wikipedia.org/wiki/Cell_(biology) © A. Adler, 2011 – 2013 Cells Slide 5A.12 Questions What is the Cell Theory? Why wasn't it obvious before the microscope? What is the function of the cell membrane? What is the function of the cell nucleus? What is the function of mitochondria? © A. Adler, 2011 – 2013 Cells Slide 5A.13 Osmotic Pressure Osmosis: movement of solvent (water) molecules through a selectively permeable membrane to region of higher solute (ion) concentration, aiming to equalize the solute (ion) concentration. Net movement of water is from the less-concentrated (hypotonic) to the more-concentrated (hypertonic). This effect can be countered by increasing the pressure of the hypertonic solution © A. Adler, 2011 – 2013 From: en.wikipedia.org/wiki/Osmosis Cells Slide 5A.14 Hyper- / hypotonic Suppose a cell is placed in a solution of sugar or salt in water. If solution is hypotonic — higher water concentration than the cell — the cell will gain water through osmosis. isotonic — exactly the same water concentration as the cell — there will be no net movement of water hypertonic — lower water concentration than the cell — the cell will lose water by osmosis. Osmolarity = molar concentration of all solutes. Osmolarity is distinct from molarity because it measures moles of solute particles rather than moles of solute. The distinction arises because some compounds can dissociate in solution, whereas others cannot. © A. Adler, 2011 – 2013 Cells Slide 5A.15 Osmolarity Example Cell (volume 1nL) contains 0.2M/L protein. The cell is placed a large volume of 0.2M/L NaCl. No solute can cross the membrane. Is this hypo- / hyper- / isotonic? What happens? © A. Adler, 2011 – 2013 Cells Slide 5A.16 Cell (volume 1nL) contains 0.2M/L protein. The cell is placed a large volume of 0.2M/L NaCl. No solute can cross the membrane. Is this hypo- / hyper- / isotonic? What happens? Osmolarity inside is 0.2Osm. Outside the NaCl dissociates to we have (0.2 Osm Na+ + 0.2Osm Cl– ) = 0.4 Osm Solution is hypertonic relative to cell. Water will leave cell, until isotonic = 0.4 Osm Osmolarity Example Particles, P= 0.2mol/L × 1nL = 0.2 nmol (initial volume) Final volume, V: 0.4Osm = P/V V = P/(0.4Osm) = 0.2 nmol = 0.5nL In reality, cells need to match both Osm and electrical charge © A. Adler, 2011 – 2013 Cells Slide 5A.17 Saline Solution It is important for IV fluid for patients to be isotonic. Saline (saline solution): sterile solution of NaCl in water Normal saline (NS) — is the commonly-used term for a solution of 0.90% w/v of NaCl, about 300 mOsm/L or 9.0 g per liter. Also referred to as physiological saline or isotonic saline, neither of which is technically accurate. Source: en.wikipedia.org/wiki/Saline_(medicine) © A. Adler, 2011 – 2013 Cells Slide 5A.18 Questions Why are some sports drinks “isotonic”? As we sweat we loose salt, how does that change the ionic balance in the body? What happens to cells when we drink pure water? Battlefield medicine often involves dealing with patients that loose a lot of blood. One new idea in battlefield medicine is to take small amounts of very hypertonic saline. How does this help? © A. Adler, 2011 – 2013