Cell Structure and Function PDF

The Human Cell - Dr.Sonam Yoezer Outcomes 1. What is cell ? 2. Contents of cell ? 3. Organelles 4. Cellular respiration 5. Function of organelles? What is cell? 1. The smallest structural and functional unit of life. 2. Building block of life. Contains : Cell membrane, nucleus Cytoplasms a...

The Human Cell - Dr.Sonam Yoezer Outcomes 1. What is cell ? 2. Contents of cell ? 3. Organelles 4. Cellular respiration 5. Function of organelles? What is cell? 1. The smallest structural and functional unit of life. 2. Building block of life. Contains : Cell membrane, nucleus Cytoplasms and organelles. Eukaryotic vs Prokaryotic Nucleus : Eukaryotic has nuclear membrane. Prokaryotic has DNA in nucleoid region. Size : Eukaryotic cells are larger than prokaryotic : 10-100 micro meter vs 0.1 to 5.0 micro meter Complexity : prokaryotes lack membrane bound organelles (ER, Golgliapparatus and lysosomes.  Cell Division : mitosis for both and meiosis in eukaryotes Cytoskeleton : less complex and rudimentary cytoskeleton in prokaryotes. Ribosomes : larger ribosomes (80S) smaller ribosome (70S) Main contents of the cell ? Water Proteins Lipids Carbohydrates Nucleic acid Electrolytes Vitamins Trace minerals, peptides, steroids, glycoproteins…  Which atom makes the most part of you? Oxygen : 65% of body mass Carbon : 18 percent Hydrogen : 10 % of body mass Nitrogen : 3% of body mass  By number of atoms : Hydrogen : 63% (4.4 X 10 27 atoms) Oxygen : 25 % Carbon : 10 % Important electrolytes Sodium (0.1% i.e 100gm in 70kg ; 2.6 X 10 24 ) Potassium (0.2% i.e 140 gm in 70 kg, 2.2 X 10 24 ) Calcium Magnesium Chloride Phosphate Zinc, Iron, copper, manganese, molybdenum, iodine Gold? (0.2 mg (200 mcg) in a 70 kg How big/small is a cell ? Animal cell : 10 -30 micrometers Smallest? Longest ? Biggest? In human Neurons can reach over a meter in human Muscle cells can be 30 cm long Smallest : 6-8 micometer Largest : Oocyte about 100 micro meter Plasma Membrane is a thin, pliable, elastic structure. Consists of two layers of phospholipids (bilayer) with some protein molecules embedded in them. One end (phosphate end) of each phospholipid molecule is hydrophilic and soluble in water. The other end (fatty acid portion) is hydrophobic and soluble in fats.  The hydrophilic phosphate portions: in contact with intracellular water on the inside extracellular water on the outside surface. The hydrophobic portions: are repelled by water but are mutually attracted. Cell membrane Proteins (globular) Integral proteins: Embedded partially or throughout the bilayer. Functions: Transport : Aquaporins, Glucose Transorter (GLUT), Sodium-potassium pump. Receptors : G-Protein coupled receptors, Insulin receptors.  Enzymatic proteins : cytochrome P450; Adenylyl cyclase Cell Adhesion Molecules : cadherins and integrins. Glycoproteins and glycocalyx : cell recognition, immune response, cell adhesion, structural support. Eg. ABO blood group antigen Anchoring proteins for cell size and structure maintenance. Eg. spectrins, dystrophin.  Ion channels : ions such as : calcium, sodium, chloride. Toll-like receptors : recognize Pathogen associated molecular patterns and activate innate immune response. This will stimulate and lead to two key transcription factors. Cytokines : TNF – alpha, IL-6 and IL-1beta. Signal transduction proteins. Convert extracellular signal into intracellular responses : Receptor Tyorsine Kinases : Epidermal Growth Factor Receptor (EPGFR) in cell growth and differentiation and Insulin. G Protein Coupled Receptors : ligands activate G-protein and modulate adenylate cyclase and phospholipase C. eg. Adrenaline and 2. Peripheral proteins: Attach to exterior or interior surface. Bound to integral proteins or phospholipids. Functions : structural support, cell signaling and aiding in cell’s response to external stimuli. 3. Cholesterol : Modulating membrane fluidity and stability Organelles Organum : latin for tools -elle : French for a mini version Specializes structures within the cell that performs specific functions essentials for the cell’s survival and operations. Functions of Cell membrane Selective permeability Protection from outside Anchoring and attachment points for cytoskeleteon giving support and shape. Receptors molecules allow the cell to receive signals and communicate. Molecules on surface for recognition and adhesions, immune response and tissue formation. Organelles  Nucleus  Mitochondria  Ribosomes  Endoplasmic reticulum  Golgi apparatus  Lysosomes  cytoskeleton Cell transportation Passive transport : No energy required 1. Simple Diffusion : small non polar. High to low concentration. 2. Facilitated Diffusion : Glucose and ions. Across cell membrane through channels and proteins. 3. Osmosis : across semi permeable membrane along concentration gradient. Active Transport 1. Primary active transport : sodium/potassium pump. 2. Secondary active transport (AKA Co-transport). Two types : Symport: eg. sodium glucose transporter Antiport: eg. sodium calcium exchanger, sodium hydrogen exchanger. Cytoskeleton pic here Cytoplasm - is a cell component present inside the cell membrane except nucleus. - The jelly-like fluid portion of the cytoplasm is called cytosol - Cytoplasm = cytosol + organelles Endoplasmic reticulum Network of tubular structures called as cisternae and flat vesicular structures. Cisternal space is connected to the space between the two membrane surfaces of nuclear membrane. Rough ER (Granular) - covered in ribosomes. - synthesize proteins that are then transported to be used inside or outside the cell. - Also send to golgi bodies Smooth ER (Agranular) - more tubular sacs, not covered by ribosomes. - It contains enzymes important for synthesizing fats and lipid substances Golgi Apparatus Is composed of four or more stacked layers of thin, flat, enclosed vesicles lying near one side of the nucleus. is prominent in secretory cells. Examples : Pancreatic acinar cells, salivary glands, plasma cells – antibodies, enodcine glands : thyroid, goblet cells – mucus.  functions in association with the endoplasmic reticulum. - endoplasmic reticulum vesicles (transport vesicles) continually pinch off from the endoplasmic reticulum and then fuses with the Golgi apparatus. Used to store, pack and distribute proteins and lipids made in the ER to form lysosomes, secretory vesicles, and other cytoplasmic components Ribosomes Tiny granules composed of rRNA and proteins. synthesize new protein molecules in the cell. 80 S in eukaryotes 70S in prokaryotes S = Svedberg unit : sedimentation rate : size and density. Lysosomes are vesicular organelles that form by breaking off from the Golgi apparatus. Contains hydrolase (digestive) enzymes. Function: provides an intracellular digestive system that allows the cell to digest the following :  damaged cellular structures food particles that have been ingested by the cell (protein is hydrolyzed to form amino acids, glycogen is hydrolyzed to form glucose, and lipids are hydrolyzed to form fatty acids and glycerol ) Peroxisomes - are physically similar to lysosomes, but they are different in two important ways. 1st: formed by self-replication (or perhaps by budding off from the SER) rather than from the Golgi apparatus. 2nd: contain oxidases rather than hydrolases Secretory Vesicles (secretory granules ) - Are storage vesicle. - formed by the endoplasmic reticulum– Golgi apparatus system which are then released from the Golgi apparatus into the cytoplasm. - store protein proenzymes. (enzymes that are not yet activated). Mitochondria - The “powerhouse“ - of the cell. - sausage-shaped structures in the cytoplasm Function: - involves in cellular respiration through which chemical energy is made - adenosine triphosphate (ATP). - Example: Cardiac muscle has more than adipocytes Cellular respiration Multistep process that cells use to convert glucose and oxygen to ATP, carbondioxide and water. Glycolysis : Happens in cytoplasm. Glucose to pyruvate. Anaerobic process. End product: 2 molecules of ATP and 2 molecules of NADH. Citric Acid Cycle Citric acid cycte (Kreb’s cycle) : Takes place in Mitochondrial matrix , pyruvate is further broken down releasing electrons transferred to NADH and FADH2. These are High energy electron carriers.  Electron Transport Chain : inner mitochondrial membrane , series protein complexes transfer electrons from NADH and FADH2 to oxygen. (ETC is embedded in the cell membrane for prokaryotes) Chemiosmosis and ATP synthesis : proton enters into the mitochondrial matrix through ATP synthase. ADP and Inorganic phosphate  Mitochondria are self-replicative  Mitochondrial DNA is inherited exclusively from the mother  Mitochondrial deficiency, Mitochondrial disease Cytoskeleton Micro filaments (actin) : cell shape and cell movement Intermediate Filaments (keratins, vimentin) : maintain structure Microtublues (tubulin) : intracellular transport and mitotic spindle in cell division. synthesized by ribosomes. originate as precursor proteins  then polymerize in the cytoplasm. Network of protein fibers : Structural support Maintain cell shape Various cellular movement. Dynamic structure and participates in : Cell division, intracellular transport and cell signaling Nucleus is the “control center” of the cell and sends messages to the cell to grow and mature, replicate, or die. Every cell in body has a nucleus ( except mature erythrocytes).  contains chromosomes: body’s genetic material in the form of large double chains of molecules of deoxyribonucleic acid (DNA) Chromosomes = clusters of DNA molecules Functional subunits of chromosomes are called genes. The genes reproduce to create two identical sets of genes mitosis forms two daughter cells. Functions Genetic material storage : contains DNA Regulate gene expression and cellular response to stress, signaling pathway and external stimuli Cell division and DNA replication Nuclear transport of mRNA, ribosomal Nuclear Membrane (Nuclear envelope) is a two separate bilayer membranes. The outer membrane is continuous with the endoplasmic reticulum The nuclear membrane is penetrated by several thousand nuclear pores. Nucleolus Nucleolus: Synthesize and assemble rRNA in to ribosomal sub-units. enlarges when the cell is actively synthesizing proteins. Formation of the nucleoli begins in the nucleus.  First, specific DNA genes in the chromosomes cause RNA to be synthesized. Synthesized RNA is stored in the nucleoli, but most of it is transported outward through the nuclear pores into the cytoplasm. Then plays role in forming cytoplasmic Coming up next….