The Cell and the Cytoplasm PDF

THE CELL AND THE CYTOPLASM Prepared by: Catherine Denise M. Palabyab, RMT, MD Medical Laboratory Science Department LEARNING OBJECTIVES Explain the different functions and the physiology of the cell Recognize microscopic features of the cell Be able to identify the differe...

THE CELL AND THE CYTOPLASM Prepared by: Catherine Denise M. Palabyab, RMT, MD Medical Laboratory Science Department LEARNING OBJECTIVES Explain the different functions and the physiology of the cell Recognize microscopic features of the cell Be able to identify the different cell stages Appreciate the structure of the human cell THE HUMAN CELL WHAT IS A CELL? The cell is the basic structural, functional and biological unit of life THE HUMAN CELL FUNCTIONS OF A CELL: 1. Structure and support 2. Growth and Division 3. Cellular metabolism 4. Cellular respiration 5. Cellular transport 6. Cell communication 7. Waste elimination 8. Homeostasis 9. Protein synthesis 10. Storage and expression of genetic information THE HUMAN CELL FUNCTIONS OF A CELL 1. Structure and Support Cells have a cytoskeleton (microtubules, microfilaments, and intermediate filaments) to maintain cell shape THE HUMAN CELL FUNCTIONS OF A CELL 2. Growth and Division Cells would also undergo a process called mitosis (in eukaryotes) or binary fission (in prokaryotes) to replicate and divide, contributing to growth, development, and tissue repair. THE HUMAN CELL FUNCTIONS OF A CELL 3. Cell Metabolism glycolysis, the Krebs cycle, and oxidative phosphorylation, to generate energy in the form of ATP. THE HUMAN CELL FUNCTIONS OF A CELL 4. Cellular Respiration Using oxygen to break down glucose to produce energy (Aerobic respiration) THE HUMAN CELL FUNCTIONS OF A CELL 5. Cellular Transport Regulate movement of subtances entering and leaving the cell Osmosis and Diffusion Active and Passive Transport THE HUMAN CELL FUNCTIONS OF A CELL 6. Cellular Communication Cells communicate with each other through chemical signals. Signaling molecules, such as hormones, allow cells to coordinate their activities and respond to changes in the environment. THE HUMAN CELL FUNCTIONS OF A CELL 7. Waste Elimination Cells eliminate waste products Exocytosis Lysosomes for degradation. THE HUMAN CELL FUNCTIONS OF A CELL 8. Storage and Expression of Genetic Information DNA and RNA- carries instructions for protein synthesis THE HUMAN CELL FUNCTIONS OF A CELL 9. Protein Synthesis Ribosomes - synthesizes proteins based on information from DNA (Translation) THE HUMAN CELL FUNCTIONS OF A CELL 10. Homeostasis maintaining stability of the internal enviromnemt of the body in response to external changes PROKARYOTES VS EUKARYOTES Eukaryotic cell Prokaryotic cell more complex structure, Simpler in structure Contains a true nucleus, Lacks a true nucleus (+) membrane-bound Smaller than eukaryotic cells organelles No membrane bound Larger ribosomes (80s) organelles reproduce through mitosis 70s ribosomes or meiosis unicellular multicellular PROKARYOTES VS EUKARYOTES THE HUMAN CELL 3 MAIN PARTS OF A CELL 1. CELL MEMBRANE 2. CYTOPLASM 3. NUCLEUS THE HUMAN CELL CELL MEMBRANE CELL MEMBRANE - Boundary or the border of the human cell THE HUMAN CELL CELL MEMBRANE CELL MEMBRANE AKA plasma membrane Outer surface of the cell Made up of a phospholipid bilayer embedded with proteins and carbohydrates ○ Phosphate head- (+) charged→ hydrophilic ○ Lipid tail → (-) charged→ hydrophobic Tail portions join one another hence→ Phospholipid bilayer THE HUMAN CELL CELL MEMBRANE Two layers of fats = lipid bilayer 4 Components: 1. Phospholipid 2. Cholesterol 3. Protein 4. Carbohydrate THE HUMAN CELL CELL MEMBRANE 1. Phospholipid Looks like balloons Most abundant component Has both hydrophilic and hydrophobic portions ______________: If a substance has both hydrophilic and hydrophobic portions THE HUMAN CELL CELL MEMBRANE 2. Cholesterol- Inserted among phospholipids Maintains structural integrity, fluidity and stability of the membrane by limiting membrane movement 3. Protein 4. Carbohydrate - always placed outside the membrane THE HUMAN CELL CELL MEMBRANE Selective Permeability The phospholipid bilayer allows certain substances to pass while blocking others, maintaining a constant intracellular environment. THE HUMAN CELL CELL MEMBRANE SELECTIVE PERMEABILITY Permeable Substances Impermeable Substances Oxygen, carbon dioxide, cannot cross the membrane water, steroids, and freely and require specific lipid-soluble chemicals transport mechanisms. can permeate the phospholipid bilayer. THE HUMAN CELL CELL MEMBRANE MEMBRANE PROTEINS Integral membrane proteins - facilitate the transport of impermeable substances via pump molecules or protein channels. - incorporated within the membrane. Peripheral Proteins -Do not protrude into the phospholipid bilayer - Not embedded in the cell membrane -assoc with the cell mm on both its extracellular an intracellular surfaces -loosely attached THE HUMAN CELL CELL MEMBRANE THE HUMAN CELL CELL MEMBRANE Endocytosis and Exocytosis: a. Endocytosis transfers molecules and solids into the cell interior, while exocytosis releases material from the cell cytoplasm across the membrane. THE HUMAN CELL CELL MEMBRANE Types of Endocytosis: a. Pinocytosis: Cells ingest small molecules of extracellular fluids or liquids. “Cell drinking” b. Phagocytosis: Cells ingest large particles like bacteria, worn-out cells, or cellular debris. c. Receptor-mediated endocytosis: A selective process where specific extracellular molecules bind to receptors on the cell membrane and are internalized.. THE HUMAN CELL CELL MEMBRANE Mechanism of Receptor-Mediated Endocytosis: Specific molecules bind to receptors The membrane indents, forming a pit coated with clathrin The pit pinches off to form a clathrin-coated vesicle that enters the cytoplasm. Examples of Receptor-Mediated Endocytosis: Uptake of low-density lipoproteins and insulin from the blood. THE HUMAN CELL CELL MEMBRANE ACTIVE TRANSPORT Transport of substances up or against their conc. gradient. Requires energy in the form of ATP to move molecules either through a pump or a protein carrier TYPES: PRIMARY ACTIVE TRANSPORT SECONDARY ACTIVE TRANSPORT ○ ANTIPORT ○ SYMPORT THE HUMAN CELL ACTIVE TRANSPORT PRIMARY ACTIVE TRANSPORT ○ the energy needed to pump molecules against their concentration gradient comes directly from the hydrolysis of ATP ○ pumps or transporters ○ Sodium-Potassium Pump (Na+/K+ Pump) SECONDARY ACTIVE TRANSPORT ○ the energy used for the transport of molecules is derived indirectly from the energy created by primary active transport. Symport/ Co transport Antiport THE HUMAN CELL SECONDARY ACTIVE TRANSPORT SYMPORT/ COTRANSPORT ○ Two molecules are transported across the membrane in the same direction.. ○ Sodium Glucose Co-trasnport in the small intestine ANTIPORT/ COUNTERTRANSPORT ○ transported molecule moves in the opposite direction to the ion that was initially pumped across the membrane. ○ sodium-calcium exchanger, where sodium ions move into the cell while calcium ions move out. ○ Na- Ca Exchanger PASSIVE TRANSPORT Substances cross a semipermeable membrane and move down its concentration gradient without using energy A.Diffusion ○ Movement from an area of higher concentration to a lower conc. ○ directly through a lipid bilayer ○ O2, CO2, steroids, lipid soluble molecules B. Facilitated Diffusion: ○ Movement of larger, polar or charged molecules ○ through protein channels or carriers ○ Glucose, amino acids Osmosis ○ Passive movement of water across a selectively permeable membrane from a region of lower concentration (hypotonic) to an area of higher concentration (hypertonic) THE HUMAN CELL ACTIVE TRANSPORT PASSIVE TRANSPORT Transport of substances up their conc. Gradient. Substances cross a semipermeable membrane and move Requires energy in the form of ATP to move molecules down its concentration gradient without using energy either through a pump or a protein carrier A.Diffusion TYPES: ○ Movement of molecules from an area of higher concentration to a lower conc., PRIMARY ACTIVE TRANSPORT directly through a lipid bilayer ○ O2, CO2, steroids, lipid soluble molecules SECONDARY ACTIVE TRANSPORT B. Facilitated Diffusion: ○ ANTI -PORT ○ Movement of larger, polar or charged ○ SYMPORT molecules through protein channels or carriers ○ Glucose, amino acids Osmosis ○ Passive movement of water across a selectively permeable membrane from a region of lower concentration to an area of higher concentration THE HUMAN CELL TRANSPORT OF SUBSTANCES ACCROSS THE CELL MEMBRANE THE HUMAN CELL NUCLEUS The largest organelle of the cell Most of the time, it is situated in the center Control center of the cell NUCLEOLUS Spherical structure inside the nucleus Synthesizes ribosomes THE HUMAN CELL CYTOPLASM CYTOPLASM The space inside a cell membrane Area between the cell membrane and the nucleus Composed of solid structures and liquid portions: o Organelle (solid structures) -functional structures of the cells that act like small organs in our body (smaller than the organs in our body) o Cytosol (fluid/liquid portions) - where the organelles are suspended THE HUMAN CELL CYTOPLASM = Organelles + cytosol + inclusion THE HUMAN CELL CYTOPLASM = Organelles + cytosol + inclusion 1— Nucleolus 2 — Nucleus 3 — Ribosome (the dots) 4 — Vesicle 5 — RER 6 — Golgi apparatus” 7 __Cytoskeleton 8 — SER 9 — Mitochondrion 10 — Vacuole 11 — Cytosol 12 — Lysosome 13 — Centriole 14 — Cell/Plasma Membran THE HUMAN CELL INCLUSION BODIES Not a functional organelle May or may not be present in the cell Most are stored nutrients or stored waste products Lipofuscin, lipid, glycogen, etc. MEMBRANOUS ORGANELLES MEMBRANOUS ORGANELLES NUCLEUS Control center of the cell; the “ boss” Contains DNA which is why it can control other organelles Mitochondria do not follow the nucleus. ○ Mitochondria have their own sets of DNA and RNA.to produce their own set of proteins ○ Some of their proteins are still included in DNA found in nucleus Chromatin: responsible for the dark appearance of the nucleus in a stained specimen MEMBRANOUS ORGANELLES MITOCHONDRIA Powerhouse of the cell Consists of an inner and outer membrane Inner membrane: with numerous folds called the cristae Primary function: Generates energy via cellular respiration in the form of ATP ○ Glycolysis ( cytoplasm) ○ Kreb’s cycle (mitochondrial matrix) ○ Oxidative Phosphorylation ( inner mitochondrial membrane) MEMBRANOUS ORGANELLES ENDOPLASMIC RETICULUM Transport system of a cell Extensive network of sacs, vesicles, and inter- connected flat tubules called cisternae Two types: ○ Rough endoplasmic reticulum ( with ribosomes) for protein synthesis, protein modification, and membrane synthesis. ○ Smooth endoplasmic reticulum ( without ribosomes) lipid synthesis, detoxification, and carbohydrate metabolism, MEMBRANOUS ORGANELLES ENDOPLASMIC RETICULUM FUNCTIONS: SMOOTH ER ROUGH ER Lipid Synthesis Protein Synthesis Detoxification Protein Modification Membrane Synthesis Carbohydrate Metabolism: Sac-like and stacks of flattened cisternae More tubular or sac-like with Continuous with the outer membrane of the interconnected channels nuclear envelope NOT BASOPHILIC BASOPHILIC STAINING- attracts basic Abundant in: Hepatocytes and dyes (blue/purple) adrenal gland cells Tissues with Abundant Rough ER: Cells that are actively engaged in protein synthesis and secretion, such as cells of the pancreas (for insulin production) and cells that secrete antibodies. MEMBRANOUS ORGANELLES GOLGI APPARATUS a system of membrane-bound, smooth, flattened, stacked, and slightly curved cisternae Receive proteins from the RER Package proteins to form secretory vesicles MEMBRANOUS ORGANELLES GOLGI APPARATUS Cis face ○ nearest the incoming budding vesicles ○ Convex shape Trans face ○ Opposite side ○ maturing inner concave side Vesicles from the endoplasmic reticulum move through the cytoplasm to the cis side of the Golgi apparatus and bud off from the trans side to transport proteins to different sites in the cell cytoplasm. MEMBRANOUS ORGANELLES LYSOSOMES Produced by Golgi Apparatus “Suicide bags of the cell” Contain digestive enzymes called acid hydrolases Main function: intracellular digestion or phagocytosis of microorganisms, cell debris or worn out organelles As the lysosome is breaking down lipids, proteins, carbohydrates, and damaged organelles, the accumulated waste products of the digestion will eventually become the LIPOFUSCIN MEMBRANOUS ORGANELLES LYSOSOMES Produced by Golgi Apparatus “Suicide bags of the cell” Contain digestive enzymes called acid hydrolases Main function: intracellular digestion or phagocytosis of microorganisms, cell debris or worn out organelles As the lysosome is breaking down lipids, proteins, carbohydrates, and damaged organelles, the accumulated waste products of the digestion will eventually become the LIPOFUSCIN MEMBRANOUS ORGANELLES PEROXISOMES similar to lysosomes, but are smaller. contain several types of oxidases → enzymes that oxidize various organic substances to form hydrogen peroxide (highly toxic) Peroxisomes also contain the enzyme catalase→ eliminates excess hydrogen peroxide by breaking it down into water and oxygen molecules The site for beta oxidation of VERY LONG chain fatty acids NON MEMBRANOUS ORGANELLES NON MEMBRANOUS ORGANELLES RIBOSOMES role in protein synthesis abundant in the cytoplasm of protein-secreting cells. unattached or free ribosomes: synthesize proteins for use within the cell cytoplasm. ribosomes that are attached to the membranes of the endoplasmic reticulum: synthesize proteins that are packaged and stored in the cell as lysosomes, or are released from the cell as secretory products. NON MEMBRANOUS ORGANELLES RIBOSOMES 40S Small Subunit: small subunit It contains ribosomal RNA (rRNA) and proteins. involved in binding to mRNA (messenger RNA) during the initiation of protein synthesis. 60S Large Subunit: The large subunit has a sedimentation coefficient of 60S. It also contains ribosomal RNA (rRNA) and proteins. The 60S subunit is responsible for the elongation and termination phases of protein synthesis. NON MEMBRANOUS ORGANELLES CYTOSKELETON OF THE CELL Microfilaments, Intermediate Filaments, Microtubules NON MEMBRANOUS ORGANELLES CYTOSKELETON MICROFILAMENTS( ACTIN) thinnest structures of the cytoskeleton. composed of the protein actin and are most prevalent on the peripheral regions of the cell membrane. involved in cell movement, cell division (cytokinesis), and the maintenance of cell shape. distributed throughout the cells and are used as anchors at cell junctions. NON MEMBRANOUS ORGANELLES CYTOSKELETON INTERMEDIATE FILAMENTS INTERMEDIATE FILAMENTS Thicker than microfilaments and more stable Vimentin - mesenchymal cells. Desmin filaments: smooth and striated provide structural support to the cell and help muscles. maintain cell shape. Neurofilament nerve cells Glial filaments :astrocytic glial cells of the Intermediate filaments are often involved in nervous system. Lamin intermediate filaments: the inner layer of anchoring organelles within the cell and providing the nuclear membrane. mechanical strength to tissues. NON MEMBRANOUS ORGANELLES CYTOSKELETON INTERMEDIATE FILAMENTS Vimentin - mesenchymal cells. Desmin: smooth and striated muscles. Neurofilament nerve cells Glial filaments :astrocytic glial cells of the nervous system. Lamin: the inner layer of the nuclear membrane. NON MEMBRANOUS ORGANELLES CYTOSKELETON MICROTUBULE largest elements of the cytoskeleton. Composed of two-protein alpha and beta subunit, and tubulin. originate from the microtubule-organizing center, the centrosome Plays a role in intracellular transport, serving as tracks for motor proteins to move cellular components. Microtubules are involved in the formation of structures such as cilia and flagella, → essential for chromosome segregation during cell division NON MEMBRANOUS ORGANELLES CENTROSOME AND CENTRIOLES area of the cytoplasm located near the nucleus Within the centrosome are two small cylindrical structures called centrioles Fxns: microtubule organization, cell division, cellular organization, and the formation of cilia and flagella Centrioles ○ perpendicular to each other. ○ consists of nine evenly spaced clusters of three microtubules arranged in a circle. NON MEMBRANOUS ORGANELLES CYTOSKELETON CELL SURFACE MODIFICATION MADE OUT OF MICROTUBULES: 1. CILIA 2. FLAGELLA 3. MICROVILLI NON MEMBRANOUS ORGANELLES CYTOSKELETON CELL SURFACE MODIFICATION MADE OUT OF MICROTUBULES: NON MEMBRANOUS ORGANELLES CYTOSKELETON CELL SURFACE MODIFICATION MADE OUT OF MICROTUBULES: NON MEMBRANOUS ORGANELLES CYTOSKELETON CELL SURFACE MODIFICATION MADE OUT OF MICROTUBULES: NON MEMBRANOUS ORGANELLES CYTOSKELETON CELL SURFACE MODIFICATION MADE OUT OF MICROTUBULES MICROVILLI Nonmotile apical surface modifications Well developed in the intestine Main function of is absorption CELL DIVISION CELL DIVISION Two major events: Mitosis and Cytokinesis. Mitosis: the chromatin in the nucleus condenses into chromosomes and is equally divided between the two forming cells. Cytokinesis: i separates the cytoplasm to produce the two daughter cells. The daughter cells have the same number of chromosomes as the parent cell. Human cells have 23 pairs of chromosomes CELL DIVISION INTERPHASE Most of the time, a cell is not dividing and is in interphase. during this phase the cell carries out various functions and prepares for the next cell division. the nucleus is visible with a darker nucleolus G0 phase of interphase, the cell performs its specialized functions and is not preparing to divide. G1 phase a time for protein synthesis, growth, and replication of organelles, including the centriole pair. The longest phase and the most variable part of interphase S phase: DNA replication occurs. After DNA replication, each chromosome is double stranded and consists of two chromatids; G2 phase another time for protein synthesis; at this time, replication of the centriole pair is completed. The cell double checks the duplicated chromosome for errors incase repairs are needed. CELL DIVISION INTERPHASE CELL DIVISION M PHASE (MITOSIS) The four stages of mitosis : 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Telophase and the latter part of anaphase are together referred to as cytokinesis CELL DIVISION PROPHASE Chromosomes become visible In early prophase, the chromosomes are long and disorganized Late prophase: the nuclear envelope breaks down, and the chromosomes shorten and move toward the middle of the cell. In the cytosol, the two centriole pairs begin moving to opposite sides of the cell. Between the centrioles, microtubules appear as spindle fibers and extend across the cell. CELL DIVISION METAPHASE chromosomes line up in the middle of the cell at the metaphase plate. Spindle fibers extend across the cell from one pole to the other and attach to the centromeres of the chromosomes. The cell is now prepared to partition the genetic material and give rise to two new cells. CELL DIVISION ANAPHASE Separation of the chromosomes Spindle fibers pull apart the chromatids of a chromosome and drag them toward opposite poles of the cell. individual chromatids are considered chromosomes. Cytokinesis marks the end of anaphase as a cleavage furrow develops along the metaphase plate and the plasma membrane pinches. Cytokinesis continues into the next stage of mitosis, telophase. CELL DIVISION TELOPHASE Cytokinesis divides the cytoplasm of the cell Each daughter cell has a set of organelles and a nucleus containing a complete set of genes. Ends as the cleavage deepens along the metaphase plate and separates the cell into 2 identical daughter cells These daughter cells are in interphase and, depending on their cell type, may divide again. End of Lecture