Cell Structures and Functions PDF

MTHAPP100 LECTURE OUTLINE Topic: Cell Structures and its Functions Lecturer: Wilson John DG Sarao, RMT, MD ORGANELLES Specialized structures in cells with specific functions CYTOPLASM Jelly-like substance that holds o...

MTHAPP100 LECTURE OUTLINE Topic: Cell Structures and its Functions Lecturer: Wilson John DG Sarao, RMT, MD ORGANELLES Specialized structures in cells with specific functions CYTOPLASM Jelly-like substance that holds organelles CELL MEMBRANE STRUCTURE CELL aka Plasma Membrane MEMBRANE The fluid-mosaic model - Phospholipids Structure that encloses the - Cholesterol cytoplasm - Proteins - Carbohydrates - Phospholipids form a bilayer. - Phospholipids contain 2 regions: polar and nonpolar. - is the model used to describe the cell membrane structure FUNCTIONS OF THE CELL A phospholipid molecule has a polar head Smallest units of life region that is hydrophilic (water-loving) Cell metabolism and energy use and a nonpolar tail region that is Synthesis of molecules hydrophobic (water-hating). The polar region is exposed to water Communication around the membrane. Reproduction and inheritance The nonpolar region is facing the interior of the membrane. CELL MEMBRANE MOVEMENT THROUGH THE CELL MEMBRANE aka Plasma Membrane Boundary and outermost component of a cell Selectively Permeable - Intracellular: Inside - The cell membrane has selective - Extracellular: Outside permeability, which allows only certain Acts as a selective barrier. substances to pass in and out of the cell. Intracellular - Enzymes, Glycogen, And Potassium Extracellular - Sodium, Calcium, And Chloride  MTHAPP100 LECTURE OUTLINE QUICK NOTES 🙂 Major INTRACELLULAR Cation - POTASSIUM Major EXTRACELLULAR Cation - SODIUM Remember! PI-SO Potassium In, Sodium Out Major EXTRACELLULAR Anion - CHLORIDE ACTIVE TRANSPORT vs PASSIVE TRANSPORT CELL MEMBRANE PASSAGES Passive membrane transport DOES NOT require the cell to expend energy. Pass freely: O2 and CO2 - Example: (Simple) Diffusion, Osmosis, Transmembrane protein channels: Na+ Facilitated Diffusion Depends on the following: Active membrane transport REQUIRES the cell to expend energy, usually in the - Size form of ATP. - Example: Active Transport, Secondary Active - Shape Transport, Endocytosis, Exocytosis - Charge (SIMPLE) DIFFUSION Movement of substances in a solution Carrier Molecules to Transport: Glucose based on concentration gradient Solute Movement: Vesicular transport across the membrane. - HIGH concentration to a LOW concentration Vesicle fusion with the cell membrane for transport  MTHAPP100 LECTURE OUTLINE CLASSES OF CELL MEMBRANE CHANNELS OSMOSIS Leak channels Diffusion of water across a selectively permeable membrane - constantly allow ions to pass through. Solvent Movement Gated channels - Higher water concentration to Lower water concentration - limit the movement of ions across the Osmotic Pressure membrane by opening and closing. - force required to prevent movement of water across cell Lipid Soluble Substances membrane - Diffuse directly through the phospholipid - depends on the difference of bilayer solution concentrations inside a cell relative to outside the cell. Water-soluble Substances - Ions, can diffuse across the cell membrane only by passing through cell membrane channels OSMOTIC PRESSURE AND THE CELL A cell may be placed in solutions that are either hypotonic, isotonic, or hypertonic compared to the cell cytoplasm. A. HYPOTONIC - Lower concentration of solutes - Higher concentration of water relative to the cytoplasm of the cell - Solution has lower osmotic pressure than the cell. B. ISOTONIC  MTHAPP100 LECTURE OUTLINE - Same solute concentrations inside and FACILITATED DIFFUSION outside the cell - The cell will neither shrink nor swell. Carrier-mediated transport process that moves substances across the cell C. HYPERTONIC membrane from an area of Higher concentration to an area of lower - Higher solute concentration concentration - Lower water concentration solution - Energy in the form of ATP is not - Water moves by osmosis from the cell into required. the hypertonic solution, resulting in cell shrinkage, or crenation. CARRIER-MEDIATED TRANSPORT Carrier Molecules Proteins within the cell membrane involved in carrier-mediated transport ACTIVE TRANSPORT - Amino Acids Carrier-mediated process moves substances - Glucose Lower concentration to higher - Some polar molecules produced by concentration against a concentration the cell gradient Facilitated Diffusion and Active Transport - Requiring ATP - Sodium-Potassium Pump SODIUM-POTASSIUM PUMP Na+ out of cells K+ into cells - The result is a higher concentration of Na+ outside cells and a higher concentration of K+ inside cells.  MTHAPP100 LECTURE OUTLINE ENDOCYTOSIS Process that brings materials into cell using vesicles Receptor-mediated endocytosis - specific substance binds to the receptor molecule and is transported into the cell Phagocytosis (Cell-eating) - endocytosis when solid particles are ingested Pinocytosis (Cell-drinking) - smaller vesicles formed, and they contain liquid MNEMONIC: PI-SO (Potassium In, Sodium Out) SECONDARY ACTIVE TRANSPORT uses the energy provided by a concentration gradient established by the active transport of one substance, such as Na+ to transport other substances. No additional energy is required above the energy provided by the initial active transport pump. In cotransport, the diffusing substance moves in the same direction as the initial active transported substance. In countertransport, the diffusing substance EXOCYTOSIS moves in a direction opposite to that of the Use of secretory vesicles to release out of initial active transported substance. the cell - membrane-bound sacs that accumulate materials for release from the cell - secretion of digestive enzymes.  MTHAPP100 LECTURE OUTLINE 23 pairs of chromosomes which consist of DNA and proteins Chromosomes - Loosely coiled and collectively called chromatin. - When a cell prepares to divide, the chromosomes become tightly coiled and are visible when viewed with a microscope. Nucleoli - Diffuse bodies with no surrounding membrane that are found within the nucleus GENERAL CELL STRUCTURE - One to several nucleoli within the nucleus Cytoplasm Subunits of ribosomes - AKA Cytosol - cytoplasmic organelle, are formed - Interior of a cell within a nucleolus - jelly-like fluid that surrounds the organelles - Exit the nucleus through nuclear pores Organelles MUST KNOW! - Specialized structures that perform certain functions There are a total of 46 chromosomes in the human - Nucleus, ribosomes, endoplasmic reticulum, body, but the total pair of chromosomes is 23. 22 of 23 chromosomes are autosomes, while the Golgi apparatus, lysosomes, peroxisomes, 23rd will determine the gender/sex of the offspring mitochondria, cytoskeleton, centrioles, cilia, (sex chromosome). Chromosomes are made up flagella, and microvilli. of long strands of DNA, which contain all the body's The Nucleus genes. Large organelle usually located near the XX- Females center of the cell XY- Males Bounded by a nuclear envelope - Outer and inner membranes with a narrow space between them Nuclear Membrane - Nuclear pores, through which materials can pass into or out of the nucleus.  MTHAPP100 LECTURE OUTLINE CHROMOSOME STRUCTURE GOLGI APPARATUS aka Golgi Complex, consists of closely packed stacks of curved, membrane-bound sacs. Forms vesicles, some of which are secretory vesicles, lysosomes, and other vesicles Collects, modifies, packages, and distributes ENDOPLASMIC RETICULUM 🙂 proteins and lipids manufactured by the ER (just like Shopee/Lazada ) series of membranes forming sacs and tubules that extends from the outer nuclear membrane into the cytoplasm Rough ER Protein synthesis and is rough due to attached ribosomes Smooth ER No attached ribosomes Site for lipid synthesis, cellular detoxification Stores calcium ions in skeletal muscle cells (Sarcoplasmic reticulum) LYSOSOMES Membrane-bound vesicles formed from the Golgi apparatus Contain a variety of enzymes that function as intracellular digestive systems (Ex:  MTHAPP100 LECTURE OUTLINE Lysozymes, Proteases, Phosphatases and cause severe bioenergetic dysfunction and cellular many others) damage if allowed to accumulate. Continued Vesicles formed by endocytosis may fuse exposure can lead to the collapse of redox with lysosomes in order to breakdown homeostasis, organ failure, microvascular materials in the endocytotic vesicles. dysfunction and fatal septic shock One example is white blood cells phagocytizing bacteria. MITOCHONDRIA Small organelles produce ATP by aerobic (with O2) metabolism Inner and outer membranes separated by a space Outer Membranes - Smooth contour Inner Membranes have Cristae - Numerous folds project into the interior of the mitochondria The material within the inner membrane is the mitochondrial matrix and contains enzymes and mitochondrial DNA (mtDNA). Cells with a large energy requirement have more mitochondria than cells that require less energy. PEROXISOMES Small, membrane-bound vesicles Contains enzymes that break down fatty acids, amino acids, and hydrogen peroxide (H2O2) - The enzymes in peroxisomes break down hydrogen - Hydrogen peroxide is a by-product of fatty acid and amino acid breakdown and can be toxic to a cell NICE TO KNOW! Hydrogen peroxide is a highly toxic membrane-permeable metabolic poison that can  MTHAPP100 LECTURE OUTLINE CYTOSKELETON Internal framework to the cell Protein structures - supports the cell - hold organelles in place - enables the cell to change shape Microtubules, Microfilaments, Intermediate Filaments MICROTUBULES Hollow structures formed from protein subunits Helping to support the cytoplasm of cells Assisting in cell division Forming essential components of certain organelles, such as cilia and flagella NICE TO KNOW! Respiratory cilia are tiny hair-like projections, which line parts of the lungs and the respiratory tract. Respiratory cilia work in conjunction with mucus-secreting goblet cells. Any particulates, such as dust or germs, which the lungs breath in, are trapped by mucus. Cilia project from the surface of certain cells. They are responsible for the movement of materials over the top of cells, such as mucus. Cilia are cylindrical structures that extend from the cell and are composed of microtubules. Respiratory Cilia Flagella are microscopic hair-like structures involved in the locomotion of a cell. The word “flagellum” means “whip”. The flagella have a whip-like appearance that helps to propel a cell through the liquid. Flagella is usually seen in the motile tail of sperm cells of males. Flagellum of Sperm MICROFILAMENTS Small fibrils formed from protein subunits that: - structurally support the cytoplasm - For cell movement  MTHAPP100 LECTURE OUTLINE - Microfilaments in muscle cells enable the cells to shorten, or contract. INTERMEDIATE FILAMENTS Fibrils formed from protein subunits Provide mechanical support to the cell Smaller in diameter than microtubules Larger in diameter than microfilaments A specific type of intermediate filament is keratin, a protein associated with skin cells. MICROVILLI Specialized extensions of the cell membrane that are supported by microfilaments. DO NOT actively move as cilia and flagella do Increase the surface area of those cells - They are abundant on the surface of cells that line the intestine, kidney, and other areas in which absorption is an important function. CENTRIOLES Centrosome - Specialized area of cytoplasm close to the nucleus where microtubule formation occurs - It contains two centrioles, which are normally oriented perpendicular to each other. - Each centriole is a small, cylindrical organelle composed of microtubules. - The centriole is involved in the WHOLE CELL ACTIVITY process of mitosis. Depends on type of proteins produced - Determined by the genetic information in the nucleus.  MTHAPP100 LECTURE OUTLINE - Information in DNA provides the cell GENE EXPRESSION with a code for its cellular processes. Gene expression, which is protein synthesis, involves transcription and translation. DEOXYRIBONUCLEIC ACID (DNA) - Transcription involves copying DNA into messenger RNA. Directs protein synthesis (Gene expression) - Translation involves messenger Nucleotides joined together to form two RNA being used to produce a nucleotide strands protein. - Two strands are connected - Resemble a ladder that is twisted around its long axis. - 5-carbon sugar (Deoxyribose), a phosphate group, and a nitrogenous base. RECALL! NUCLEOSIDE: sugar + nitrogenous base NUCLEOTIDE: sugar + nitrogenous base + phosphaTe group Each nucleotide on one DNA strand has a TRANSCRIPTION specific bonding pattern to another nucleotide on the opposite strand. Transcription takes place in the nucleus of Gene the cell. - sequence of nucleotides that DNA determines the structure of mRNA provides a chemical set of through transcription. instructions for making a specific During transcription, the double strands of a protein DNA segment separate, and DNA nucleotides of the gene pair with RNA nucleotides that form the mRNA. DNA contains one of the following organic bases: thymine, adenine, cytosine, or guanine. DNA nucleotides pair only with specific RNA nucleotides. - DNA’s thymine pairs with RNA’s adenine.  MTHAPP100 LECTURE OUTLINE - DNA’s adenine pairs with RECALL! RNA’s uracil. - DNA’s cytosine pairs with TRANSCRIPTION happens in the Nucleus RNA’s guanine TRANSLATION happens in the Cytoplasm - DNA’s guanine pairs with RNA’s cytosine. TRANSLATION Translation occurs in the cell cytoplasm after mRNA has exited the nucleus through the nuclear pores. The mRNA attaches to a ribosome. Codons (3 nucleotide bases) on the mRNA are read by anticodons (3 nucleotide bases) on transfer RNA (tRNA). Transfer RNA transports specific amino acids from the cytoplasm to the ribosome-mRNA complex and initiates formation of the polypeptide chain. The process continues until the entire polypeptide is completely formed. MTHAPP100 LECTURE OUTLINE