Cell Structure and Function PDF

CELL STRUCTURE AND FUNCTION Dr. Nehemiah B. Mula  CELL The basic unit of all living cells, including humans  FUNCTIONS OF CELL Cell Metabolism and Energy Use ○ Involves all chemical reactions within a cell ○ Metabolic reactions that involve...

CELL STRUCTURE AND FUNCTION Dr. Nehemiah B. Mula  CELL The basic unit of all living cells, including humans  FUNCTIONS OF CELL Cell Metabolism and Energy Use ○ Involves all chemical reactions within a cell ○ Metabolic reactions that involve energy transfers Synthesis of Molecules ○ Produce various types of molecules including proteins, nucleic acids, and lipids Communication ○ Cells communicate with each other by using chemical and electrical signals Reproduction and Inheritance ○ Cells contain a complete copy of all genetic information of the individual ○ As person grows, cell divide to produce new cells, each containing same genetic information  01 CELL PARTS AND THEIR FUNCTION  PLASMA MEMBRANE Outermost component of a cell and serves several functions: ○ As boundary separating the cytoplasmic (intracellular) substances from the extracellular space ○ Encloses and supports the cell contents ○ Attaches cells to the extracellular environment or to other cells ○ Recognition and Communication ○ Determines which substances move in and out of the cell Electrical charge difference across the plasma membrane is called membrane potential ○ More positive ions outside the cell ○ More negative ions inside the plasma membrane Consists mainly of lipids and proteins with very little carbohydrates ○ Protein: 45-50% ○ Lipids: 50% ○ Carbohydrates: 4-8%  PLASMA MEMBRANE 2 predominant lipids present: ○ Phospholipids Forms the lipid bilayer which has a polar head (hydrophilic) and nonpolar tail (hydrophobic) ○ Cholesterol Present in smaller amount compared to the phospholipids and are interspersed among phospholipids Amount of cholesterol is a major factor in determining the fluid nature of the membrane Limits the movement of phospholipids, providing stability to the membrane Plasma membrane is described as a Fluid-Mosaic model ○ Plasma membrane is highly flexible and can change its shape and composition through time ○ The lipid bilayer functions as a dense liquid in which other molecules such as proteins are suspended  PLASMA MEMBRANE Types of membrane proteins present ○ Integral protein Penetrate deeply into the lipid bilayer, extending from one surface to another ○ Peripheral protein Attached on either the inner or outer surfaces of the lipid bilayer PLASMA MEMBRANE PLASMA MEMBRANE PLASMA MEMBRANE PLASMA MEMBRANE  PLASMA MEMBRANE Plasma membrane separates extracellular material from the cytoplasm and is a selectively permeable Molecules and ions can move across the plasma membrane in different ways, depending on the chemical characteristics of the molecules and ions and the structure and function of the cell  PLASMA MEMBRANE DIFFUSION ○ Movement of solutes from an area of higher solute concentration to lower solute concentration ○ Particles will continue to move randomly until an equilibrium is achieved ○ A concentration difference occurs when solutes are not evenly distributed in a solvent - concentration gradient ○ Rate of diffusion is influenced by several factors Magnitude of concentration difference Temperature of the solution Size of the diffusing particle Viscosity of the solvent  PLASMA MEMBRANE OSMOSIS ○ Diffusion of water across a semipermeable membrane ○ Water will diffuse from a solution with proportionately more water and into a solution with proportionately less water ○ Osmotic pressure is the forced required to prevent water from moving by osmosis across a semipermeable membrane ○ Three terms to describe osmotic pressure of a solution Isosmotic Solutions with the same osmotic pressure Hyperosmotic One solution has a greater concentration of solute particles, therefore a greater osmotic pressure Hyposmotic More dilute solution (less solute)  PLASMA MEMBRANE OSMOSIS When applying osmosis in cells, three additional terms describe the tendency of cells to swell or shrink when placed to a solution  PLASMA MEMBRANE FACILITATED DIFFUSION ○ Mediated transport process that moves substances into or out of the cells from a higher to a lower concentration ○ Carrier proteins and channel proteins carry out facilitated diffusion ○ Rate at which molecules or ions are transported is directly proportional to their concentration gradient up to the point of saturation PLASMA MEMBRANE  PLASMA MEMBRANE PRIMARY ACTIVE TRANSPORT ○ Mediated transport process that requires energy provided by ATP ○ Movement of substance against the concentration gradient (from lower to higher concentration) ○ Example Na-K ATPase pump  PLASMA MEMBRANE SECONDARY ACTIVE TRANSPORT ○ Involves the active transport of an ion (Na), establishing a concentration gradient ○ The tendency for the ions to move back into the cell provides energy necessary to move a different ion ○ Example Sodium-Glucose Transporter (SGLT) Movement of sodium down its concentration gradient provides energy to move glucose molecules into the cell against their concentration gradient PLASMA MEMBRANE  CYTOPLASM CYTOPLASM ○ Cellular material outside of the nucleus but inside the plasma membrane ○ Consist of the cytosol and organelles CYTOSOL ○ Fluid portion of the cytoplasm ○ Colloidal, viscous solution dissolved in ions and molecules as well as suspended proteins, many of which are enzymes for metabolism of molecules  CYTOPLASM CYTOSKELETON ○ Proteins from the cytoplasm make up the cytoskeleton ○ Supports the cell and holds nucleus and other organelles in place ○ Responsible for change in shape and movement of cell organelles ○ Consist of 3 groups of proteins Microtubules Hollow tubes composed mainly of tubulin 25 nm in diameter with 5 nm thick wall Involved in cell division and transport of intracellular materials Form essential components of certain cell organelles such as centriole, spindle fibers, cilia, and flagella  CYTOPLASM CYTOSKELETON ○ Consist of 3 groups of proteins (continuation) Actin Filaments (Microfilaments) Small fibrils about 8 nm in diameter Provide structure to the cytoplasm and mechanical support for microvilli Changes in shape involve the breakdown and reconstruction of actin filaments Muscles contain high number of highly organized actin filaments Intermediate Filaments Protein fibers about 10 nm in diameter that provide mechanical strength to cells Support the extensions of nerve cells  CYTOPLASM CYTOPLASMIC INCLUSIONS ○ Aggregates of chemicals either produced or taken in by the cell ○ Examples: Lipid droplets Glycogen granules Hemoglobin Melanin Lipochromes  NUCLEUS Large, membrane-bound structure located near the center of the cell Contains a nucleoplasm surrounded by a 2-membrane nuclear envelope The inner and outer membrane fuse to form pore-like structures called nuclear pores Where DNA and RNA synthesis occurs Nucleolus ○ Dense region within the nucleus and lacks a surrounding membrane ○ Where subunits for ribosomes are manufactured  RIBOSOME Site for protein synthesis ○ Each ribosome has a smaller and a larger subunit ○ Can be found free in the cytoplasm or attached to an intracellular membrane complex called endoplasmic reticulum ○ Free ribosomes primarily synthesize proteins used inside the cell ○ Ribosomes attached to the endoplasmic reticulum produce integral membrane proteins and proteins secreted from the cell  ENDOPLASMIC RETICULUM Series of membranes distributed throughout the cytoplasm and is continuous with the outer membrane of the nuclear envelope Consist of broad, flattened, interconnecting sacs and tubules (interior spaces called cisternae) Rough endoplasmic reticulum is called rough because of the ribosomes attached to it Smooth endoplasmic reticulum manufactures lipids and participates in detoxification Smooth endoplasmic reticulum of skeletal muscles stores Calcium for muscle contraction  GOLGI APPARATUS Flattened, membranous sacs, containing cisternae that are stacked to each other Packaging and distribution center where proteins and lipids are modified, packed, and distributed Materials enter from the endoplasmic reticulum at the cis face and exit through the trans face  SECRETORY VESICLE Structures that pinch off from the Golgi apparatus move to the surface of the cell then contents are released to the exterior by exocytosis Membrane of this vesicles are then incorporated into the plasma membrane Secretory vesicles tend to accumulate in some cells and will not release its contents into the exterior unless they receive a signal  LYSOSOME Membrane-bound vesicles that form at the Golgi apparatus Contain variety of hydrolytic enzymes that function as intracellular digestive systems Digest nucleic acids, proteins, polysaccharides, and lipids Certain white blood cells have large numbers of lysosomes that contain enzymes to digest phagocytized bacteria Lysosomes also digest the organelles of the cell that are no longer functional – autophagy  PEROXISOME Membrane-bound vesicles that are smaller than lysosomes. Peroxisomes contain enzymes that break down fatty acids. Breakdown of these molecules can produce Hydrogen peroxide (H2O2) as a toxic by-product Peroxisomes also contain the enzyme catalase which breaks down hydrogen peroxide to water and oxygen PROTEOSOMES Large protein complexes containing enzymes that break down and recycle other proteins within the cell  MITOCHONDRIA Organelles that provide the majority of the energy for the cell Major sites for ATP production Each mitochondrion has an inner and an outer membrane separated by an intermembrane space ○ Inner membrane has numerous infoldings called cristae; material located inside the inner membrane is called matrix 2 major enzyme systems take place in the mitochondria ○ Krebs cycle: matrix ○ Electron Transport Chain: inner membrane  CENTRIOLES AND SPINDLE FIBER Specialized zone of cytoplasm close to the nucleus which is the center of microtubule formation called Centrosome Within centrosome are 2 centrioles ○ Each centriole is a small,cylindrical organelle about 0.3-0.5 um in length ○ Oriented perpendicular to each other ○ The wall of the centriole is composed of 9 evenly spaced, longitudinal, parallel units with each unit consists of 3 parallel microtubules Microtubules called spindle fibers extend out in all directions from the centrosome during cell division  CILIA AND FLAGELLA CILIA ○ Structures that project from the surface of cells and are capable of movement ○ Cylindrical in shape measuring about 10 um in length and 0.2 um in diameter The shaft is enclosed by a plasma membrane ○ Cilia are numerous on surface cells that line the respiratory tract and female reproductive organs ○ Cilia move small particles across the cell surface FLAGELLA ○ Have a similar structure to that of the cilia but they are longer ○ Sperm cells are the only human cell that possess a flagella ○ Flagella help move the entire cell  MICROVILLI Cylindrically shaped extensions of the plasma membrane about 0.5 - 1.0 um in length and 90 nm in diameter The presence of microvilli increases the surface area Microvilli are found on the cells of intestines and even in kidney, and other areas where absorption is an important function  01 CELL CYCLE  CELL CYCLE Includes all changes a cell undergoes from the time it is formed until it divides to produce new cells Has 2 stages: ○ Interphase ○ Cell Division Mitosis: division of nucleus Cytokinesis: division of cytoplasm  INTERPHASE Phase between cell division; nearly all of the life cycle of a typical cell is spent in this phase Cell carries out the metabolic activities necessary for life and performs its specialized functions Divided into 3 subphases: ○ G1 (Gap phase) Cell carries out routine metabolic activities ○ S (Synthesis phase) DNA is replicated ○ G2 (2nd gap phase) Cell prepares for cell division Many cells do not divide for long periods of time and do not follow the normal cell cycle pattern and instead enters the G0 phase  CELL DIVISION MITOSIS Division of the cell’s nucleus into 2 new nuclei During mitosis, chromatin becomes very densely coiled to form compact chromosomes call mitotic chromosomes ○ Each copy of the chromosome is called chromatid ○ Each chromatid is attached to a centromere ○ The kinetochore is a protein structure that binds the centromere and provides a point of attachment for microtubules Divided into 5 phases: ○ Prophase ○ Prometaphase ○ Metaphase ○ Anaphase ○ Telophase CYTOKINESIS Division of the cell’s cytoplasm to produce 2 new cells Begins in the anaphase and continues through telophase ○ First sign is the formation of cleavage furrow ○ A contractile ring composed of actin pulls the plasma membrane inward CELL DIVISION CELL DIVISION  APOPTOSIS Also known as programmed cell death Normal process by which cell number within various tissues is adjusted and controlled Apoptosis is regulated by specific genes that code for proteins ○ Once these proteins enter the cytosol, they activate other proteins that carry out many events of apoptosis Chromatin condenses ad fragments → fragmentation of the nucleus → death and fragmentation of the cell Macrophages phagocytize the cell fragments Thank you CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon, and infographics & images by Freepik Please keep this slide for attribution