Cell Structure and Functions PDF

MC_101_: ANATOMY AND PHYSIOLOGY LECTURE LECTURE #4: CELL STRUCTURE AND ITS FUNCTION PROFESSOR: Prof. Daisy Sucaldito 1ST SEMESTER | A.Y 2022-2023...

MC_101_: ANATOMY AND PHYSIOLOGY LECTURE LECTURE #4: CELL STRUCTURE AND ITS FUNCTION PROFESSOR: Prof. Daisy Sucaldito 1ST SEMESTER | A.Y 2022-2023 ○ For energy OBJECTIVES ○ Cell metabolism - cells have connections I. Identify the structure of the cell and its various with each other for their cellular activities functions II. Explain the important processes that happen Synthesis of molecules inside the cell III. Discuss the relationship between cell function ○ Ribosome synthesize protein molecules and aging which is necessary for our body ○ Smooth ER synthesizes lipids; used for the synthesis of molecules ORGANELLES Specialized structures in cells that perform specific Communication functions ○ Our cells undergo positive and negative Like the organs existing in the human body (ex: feedback heart, liver, lungs, etc) ○ Example: you are in an environment Example: nucleus, mitochondria, ribosomes wherein you tried to touch a hot surface; CYTOPLASM your sensory receptors detected that A jelly-like substance that holds organelles information and sent it to the brain – then it Basic structure of a cell becomes integrated and evaluated, and Where the organelles are being suspended in the information will be sent to your nerves for your hand to move away from that CELL MEMBRANE surface. Also termed the plasma membrane A structure that encloses the cytoplasm Reproduction and inheritance Protects the cell acts as a guard ○ Produce Germ cells and sex cells GENERALIZED CELL ○ Reproduction of humans, plants, animals ○ Reproduction of living organisms ○ Inheritance Cells contain our nucleus that contains genetic information (DNA) Your DNA can be inherited from your family members (DNA is passed down) CELL MEMBRANE Encloses cell cytoplasm The cell membrane is the outermost component of a cell (like the skin protecting our body) It forms a boundary between material in inside the cell and the outside Whenever we say cell, it has 3 basic structures. inside (Organelles, Cell membrane, Cytoplasm) Materials inside the cell are intracellular and those outside the cell are extracellular FUNCTIONS OF THE CELL outside Smallest units of life It acts as a selective barrier. ○ Can retain characteristics of an organism ○ Not all substances can pass through that is being produced (either inside or outside) ○ Human reproduction of germ cells, sex ○ Selective permeability cells, somatic cells, or even an organism Cell metabolism and energy use ○ Mitochondria - the powerhouse of the cell MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A., TABANAO, K. | 1NU02 1  CELL MEMBRANE STRUCTURE Some substances require a vesicular transport The fluid-mosaic model is the model used to across the membrane. describe the cell membrane structure ○ Vesicular transport – literally a vesicle endocytoi carrying substances coming from the a The membrane contains phospholipids, outside going inside (and vice versa) cholesterol, proteins, and carbohydrates Like Tupperware where food can ○ Not smooth because of the presence of be stored. these macromolecules The vesicle must fuse with the cell membrane for Phospholipids form a bilayer transport Phospholipids contain 2 regions: polar and ↳ hydrophilic nonpolar ↳hydrophobic ACTIVE TRANSPORT AND PASSIVE TRANSPORT PHOSPOLIPID STRUCTURE Polar head region that is HYDROPHILIC. ACTIVE TRANSPORT ○ exposed to water around the Active membrane transport does require the cell membrane. to expend energy, usually in the form of ATP. Active membrane transport mechanisms include Nonpolar tail region that is HYDROPHOPIC. ○ facing the interior of the membrane active transport, secondary active transport, endocytosis, and exocytosis. PASSIVE TRANSPORT Passive membrane transport does not require the cell to expend energy. Passive membrane transport mechanisms include diffusion, osmosis, and facilitated diffusion. NOTE: It is known to be a fluid mosaic model because of the presence of different macromolecules. MOVEMENT THROUGH THE CELL MEMBRANE The cell membrane has selective permeability. ○ which allows only certain substances to pass in and out of the cell Substances found INSIDE THE CELL with higher concentration ○ enzymes, glycogen, and potassium DIFFUSION Diffusion generally involves the movement of Substance found OUTSIDE THE CELL with higher substance in a solution down a concentration concentration gradient. (Higher to Lower) ○ sodium, calcium, and chloride A solution is generally composed of two major CELL MEMBRANE PASSAGE Some substances, like O2 and CO2 can pass parts, SOLUTES AND SOLVENT. directly through the cell membrane’s phospholipid bilayer Solutes – are substances dissolved in a ○ Because they are very small molecules predominant liquid or gas, which is called the solvent. Some substances must pass through ○ Such as ions or molecules, tend to move transmembrane protein channels, such as Na+ from an area of high concentration of a through its channels ○ When we say cell membrane passage or solute to an area of low concentration things that can pass through the cell (in of that same solute in solution and out), it could be depending on the: CONCENTRATION GRADIENT ROUTE TRANSPORT THROUGH THE MEMBRANE A concentration gradient is the difference in the depends on the size, shape, and charge of the concentration of a solute in a solvent between substance two points divided by the distance between the ○ Size: small or big two points. ○ Shape: kasya ba ○ Those two points are not the same (solute and solvent have unbalanced Some substances require carrier molecules to concentrations) transport them across the cell membrane, such as glucose. MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 2  The concentration gradient is said to be steeper when the concentration difference is large LEAK AND GATED CHANNELS and/or the distance is small. Two classes of cell membrane channels include leak channels and gated channels DIFFUSION LEAK CHANNELS Constantly allow ions to pass through Can have a constant flow of a substance May leak GATED CHANNELS Limit the movement of ions across the membrane by opening and closing NOTE: Parang gate ng bahay (opens and closes) 1. When a salt crystal is placed into a beaker of water, a concentration gradient exists between the salt from the salt crystal and the water that surrounds it 2. Salt ions move down their concentration gradient into the water (because it is being dissolved). LEAK AND GATED MEMBRANE CHANNELS 3. Salt ions and water molecules are distributed evenly throughout the solution. Even though the salt ions and ↑ water molecules continue to move randomly, an equilibrium exists, and no net movement occurs because no concentration gradient exists. LEAK AND GATED SUBSTANCES Lipid soluble substances can diffuse directly through the phospholipid bilayer ○ Like dissolves like Water soluble substances, such as ions, can diffuse across the cell membrane only by passing through cell membrane channels DIFFUSION THROUGH THE CELL MEMBRANE In this example, the K+ leak channels (purple) is always open, allowing K+ to diffuse across the cell membrane. The gated Na+ channel (pink) regulates the movement of Na+ across the membrane by opening and closing l. PASSIVE MEMBRANE TRANSPORT OSMOSIS Movement/Diffusion of water (a solvent) across a selectively permeable membrane Higher to Lower water concentration OSMOTIC PRESSURE Force required to prevent movement of water Non-lipid-soluble molecules (small red) diffuse across cell membrane through membrane channels Depends on the difference of the solution ○ They are just repelled concentrations inside a cell to outside the cell. ○ In order for them to pass through, they ○ Hypotonic, Isotonic, Hypertonic must use a transmembrane channel Specific non-lipid-soluble HYPOTONIC molecules – have to go through a Hypo means “under” membrane channel that’s LOWER SOLUTE CONCENTRATION than Water integrated to the cell membrane concentration relative to the cytoplasm of the cell itself. Less solute, Higher Water Water moves by osmosis into the cell, causing it Lipid soluble molecules (orange) diffuse directly to swell through the phospholipid bilayer/cell ○ Lysis - if the cell swells enough, it can membrane. cause a rupture non lipid soluble-passes through a transmembrane channel Cell looks bloated since maraming lipid soluble-passes directly through phospholipid bilayer water tapos Konting solute MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 3 NOTE: Tip to help remember hypotonic; Like cooking, if you don't add enough flavor to the food that you are cooking, for example, not enough salt or sugar, the food will taste bland or not flavorful. Therefore, it is hypotonic. If you try to make coffee with 1 liter of water and 1 pack of coffee powder, it will taste really bland. This is because of the fewer solute concentration of coffee powder. Adding 5 grams of chocolate powder to the container and 1 liter of water, it is bland. CARRIER-MEDIATED TRANSPORT Some water-soluble, electrically charged or large sized particles cannot enter or leave through the cell membrane by diffusion. Substance include; ○ Amino Acids ISOTONIC ○ Glucose Same solute concentration inside and outside ○ Some polar molecules produces by cell the cell. Carrier-mediated transport mechanisms include The cell will neither shrink or swell. FACILITATED DIFFUSION and ACTIVE TRANSPORT. Example: 5 solute concentration and Red blood cells which CARRIER MOLECULES have the same solute concentration. Nothing will Proteins within cell membrane involved in happen. carrier-mediated transport. FACILITATED DIFFUSION Does NOT require ATP for energy. ACTIVE TRANSPORT Does require ATP for energy. FACILITATED DIFFUSION Moves substances across the cell membrane from an area of HIGHER CONCENTRATION to an area of LOWER CONCENTRATION of that substance. HYPERTONIC HIGHER SOLUTE CONCENTRATION than Water Concentration Water moves by osmosis from the cell into the hypotonic solution, resulting in cell shrinkage or crenation (wrinkle) Example: When a red blood cell is placed in a hypertonic solution (higher solute concentration), the cell will try its best to neutralize the environment and equalize the concentration but it is not possible. It will try to move the water inside the cell to the outside of the cell, resulting in shrinkage. Too much solute less water causes cronation or shrinkage MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 4  ACTIVE TRANSPORT RECEPTOR-MEDIATED ENDOCYTOSIS Moves substances across the cell membrane from A specific substance that binds to the receptor an area of HIGHER CONCENTRATION to an area molecule and is transported into the cell. of LOWER CONCENTRATION of that substance. PHAGOCYTOSIS It goes against the concentration gradient Often used for endocytosis when solid particles are ingested. Example: Phagocytosis-solid Sodium-potassium pump present in cell PINOCYTOSIS membranes. Smaller vesicles formed and they contain liquid rather than solid particles. SODIUM POTASSIUM PUMP Moves Na+ out of cells and K+ into cells. Pinocytosis - Liquid EXOCYTOSIS Result is a higher concentration of Na+ outside Involves the use of membrane-bound sacs called the cells and Higher concentration of K+ inside secretory vesicles that accumulate for release cells. from the cell. (GOING OUT) Vesicles move to the cell membrane and fuse, ultimately releasing the material by exocytosis. EXAMPLE: Digestive Enzymes GENERAL CELL STRUCTURE INTERIOR OF A CELL ○ Cytoplasm - jelly-like fluid that surrounds the organelles. ORGANELLES - Specialized structures that performs certain functions ○ Nucleus SECONDARY ACTIVE TRANSPORT ○ Ribosomes Uses the energy provided by a concentration ○ Endoplasmic Reticulum gradient established by the active transport of ○ Golgi Apparatus one substance such as Na+ to transport to other ○ Lysosomes substances. ○ Peroxisomes ○ Mitochondria No additional energy is required. ○ Cytoskeleton ○ Centrioles COTRANSPORT ○ Cilia Diffusing substance move in the same direction ○ Flagella ○ Microvilli COUNTERTRANSPORT Diffusing substance move in a direction opposite CELL NUCLEUS to the initial active transported substance. Located near at the center of the cell Bounded by a nuclear envelope ○ Nuclear membrane - contains nuclear pores ○ Nucleoli - diffuse bodies with no surrounding membrane ○ Nuclei - contains 23 pairs of chromosomes which consists of DNA and Proteins ○ Chromatin - when a chromosomes are loosely coiled RIBOSOMES Dense particles consisting of two subunits, each composed of ribosomal RNA and Protein. The sites for protein synthesis. Found at two locations: ○ Free in the cytoplasm. ENDOCYTOSIS ○ Attached to rough endoplasmic reticulum. Process that brings materials into cells using vesicles. (GOING IN) MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 5  Peroxisome-contains enzyme for breakdown of H202 (Hydrogen Peroxide - digestive system of L deadly for cells ENDOPLASMIC RETICULUM PEROXISOMES celle It is a series of membranes forming sacs and They are small, membrane-bound vesicles tubules that extends from the outer nuclear containing enzymes that break down fatty acids, membrane into the cytoplasm. amino acids, and hydrogen peroxide (H2O2). ○ Hydrogen peroxide is a by-product of fatty ROUGH ENDOPLASMIC RETICULUM acid and amino acid breakdown and can Involved in protein synthesis and is rough due to be toxic to a cell. attached ribosomes. ○ Enzymes in peroxisomes break down Membranous network of flattened sacs or tubes. hydrogen. Externally studded with ribosomes. Vesicle formed from the Golgi complex. Site where building materials of cellular membrane Sites of intracellular digestion. are found. The stomach of the cell. Site of protein synthesis. Responsible for autolysis of injured cells. SMOOTH ENDOPLASMIC RETICULUM MITOCHONDRIA Has no attached ribosomes and is a site for lipid synthesis, cellular detoxification, and it stores Responsible for producing a considerable amount calcium ions in skeletal muscle. of ATP by aerobic (with O2) metabolism. Have inner and outer membranes. ROUGH ER-protein synthesis Inner membranes fold into projections called CRISTAE. SMOOTH ER-lipid Synthesis The POWERHOUSE of the cell. GOLGI APPARATUS Site for ATP synthesis. “Golgi Complex” Mitochondrial ONA Consists of closely packed stacks of curve, Mitochondrial Matrix-contains (M+ONA) membrane-bound sacs Collects, modifies, packages, and distributes MITOCHONDRION proteins and lipids Forms vesicles Mitochondrion are the major sites for the production of ATP, which cells use as an energy source. Mitochondria carry out aerobic respiration (requires LYSOSOMES O2) Membrane-bound vesicles formed from Golgi Apparatus CYTOSKELETON Contains variety of enzymes that function as intracellular digestive systems The cytoskeleton gives internal framework to the Example: WBC phagocytizing bacteria cell. It consists of protein structures that support the cell, LYSOSOME ACTION hold organelles in place, and enable the cell to 1. Vesicle forms around material outside of the cell change shape. 2. Vesicle pinched off from cell membrane and These protein structures are microtubules, becomes a separate vesicle microfilaments, and intermediate filaments. 3. Lysosome pinched off from Golgi Apparatus 4. Lysosome fuses with vesicle 5. Enzymes from lysosomes mix with the material in vesicle and enzymes digest with material Supports the cell Microtubules - cell structure for Microfilaments-provides Lysosomes-contains enzymes Intermediate Filaments-mechanical support digestion for intracellar activities MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 6  DNA DEOXYRIBONUCLEIC ACID Contains the information that directs protein synthesis; a process called gene expression. DNA molecule are composed of nucleotides joined together to form two (2) nucleotide strands. Two (2) strands are connected and resemble a ladder that is twisted along its axis. Each consists of a 5 - CARBON SUGAR, a PHOSPHATE GROUP, and a NITROGENOUS BASE. Each nucleotide on one DNA strand has a specific bonding pattern to another nucleotide on the opposite strand. - Microtubules are the largest among the three. - GENE is a sequence of nucleotides that Example: 25 nm provides a chemical set of instructions for - Intermediate filaments is the 10 nm making a specific protein. - Microfilaments is the smallest 8 nm GENE EXPRESSION CENTRIOLES Which is protein synthesis, involves The centrosome is a specialized area of cytoplasm TRANSCRIPTION and TRANSLATION. close to the nucleus where microtubule formation TRANSCRIPTION involves copying DNA into occurs. messenger RNA. It contains two centrioles, which are normally TRANSLATION involves messenger RNA being oriented perpendicular to each other. used to produce a protein. Each centriole is a small, cylindrical organelle composed of microtubules. TRANSCRIPTION The centriole is involved in the process of mitosis. Takes place in the nucleus of the cell. Involves of copying of DNA inorder to be a messenger CILIA DNA (template) determines the structure of mRNA CELL NUCLEUS through transcription Project from the surface of certain cells. During transcriptions,the double strands of a DNA Responsible for the movement of materials over the segment separate, top of the cells, such as MUCUS. DNA nucleotides of the gene pair with a RNA Are cylindrical structures that extend from the cell nucleotides that form the mRNA and are composed of microtubules. made up of MICROTUBULES FLAGELLA Have a structure like that of cilia but are much longer, and they usually occur only one (1) per cell. Sperm cells each have one flagellum, which propels the sperm cell. Tail-like MICROVILLI Specialized extensions of the cell membrane that are supported by microfilaments. Do not actively move as cilia and flagella do. Are numerous on cells that have them, they increase the surface area of those cells. Abundant on the surface of cells that line the intestine, kidney, and other areas in which TRANSCRIPTION absorption is an important function. DNA contains one of the following Supported by MICROFILAMENTS nucleobases:thymine,adenine,cytosine,or WHOLE CELL ACTIVITY guanine Messenger RNA (MRNA) contains A cell’s characteristics are determined by the type uracil,adenine,cytosine or guanine of proteins produced. The proteins produced are in turn determined by the genetic information in the nucleus. Information in DNA provides the cell with a code for its cellular processes. MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 7  TRANSCRIPTION TWO STRANDS of DNA SEPARATE from each other, and each strand serves as a template to DNA nucleotides pair only with a specific RNA produce a new strand of DNA. nucleotides. DNA’s thymine pairs with RNA’s adenine Nucleotides in the DNA of each template strand DNA’s adenine pairs with RNA’s uracil pair with the new nucleotides that are DNA’s cytosine pairs with RNA’s guanine subsequently joined by enzymes to form a new DNA’s guanine pairs with RNA’s cytosine strand of DNA. The sequence of nucleotides in the DNA template determines the sequence of nucleotides in the strand of DNA. Replication of DNA gives two identical chromatids joined at a centromere; both form one chromosome. TRANSLATION Occurs in the cell cytoplasm after mRNA has exited the nucleus through the nucleus pores The mRNa attaches to a ribosome Codons (3 nucleotide bases which code for specific amino acids) on the mRNA are read by anticodons (3 nucleotide bases) on transfer RNA (tRNA) A series of 3 nucleotides of each tRNA molecule (the anticodon) pairs with the codon of the mRNA. DNA REPLICATION Transfer RNA transports specific amino acids from cytoplasm to ribosome-mRNA and initiates formation of the polypeptide chain ○ Repeated until the entire polypeptide is complete. NOTE: Some codons do not code for amino acids but STOP CODONS perform other functions such as STOP CODON. VAG ○ Stop Codon - codes for no AA VAA START CODON Also acts as a signal for stopping addition of AA to a protein UGA AUG THE CELL CYCLE During growth and development, cell division occurs to increase the number of cells or replace damaged or dying ones. The cell division involves a new cycle. It has 2 major phases; ○ Interphase = nondividing phase ○ Mitosis = cell dividing phase Cell spends most of its life in interphase performing its normal functions. INTERPHASE CELL GENETIC CONTENT During INTERPHASE, the DNA is REPLICATED. Each human cell (except for gamete/sex cells) ○ DNA is located in the chromosomes in the contains 23 pairs of chormosomes, a total of 46 cell’s nucleus. (diploid). ○ Both sperm and egg cells contain 23 chromosomes (haploid) TOTAL. MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 8  One pair of chromosomes are the sex produced, chromosomes ○ XX chromosome - FEMALE ○ XY chromosome - MALE MITOSIS Formation of 2 DAUGHTER CELLS from a single parent cell. Divided into 4 phases; ○ Prophase ○ Metaphase ○ Anaphase ○ Telophase PROPHASE During prophase, chromatin condenses to form visible chromosomes. Microtubules, termed spindle fibers, form to assist in breaking the centromere between the chromatids DIFFERENTIATION and move the chromosomes to opposite sides of A sperm cell and an oocyte unite to form a single the cell. cell, then a great number of mitotic divisions occult to give the trillions of cells of the body. The nuclear membrane dissolves. DIFFERENTIATION - process by which cells METAPHASE develop with specialized structures and During metaphase, the chromosomes align near the functions. center of the cell. During differentiation of a cell, some portions of The movement of the chromosomes is regulated by DNA are active, but others are inactive. the attached spindle fibers. ANAPHASE At the beginning of anaphase, the chromatids separate and each chromatid is called chromosome. Each of the two sets of 46 chromosomes is moved by the spindle fibers toward the cell centriole at one of the poles of the cell. At the end of anaphase, each set of chromosomes has reached an opposite pole of the cell, and the cytoplasm begins to divide. TELOPHASE During telophase, chromosomes in each of the daughter cells become organized to form two APOPTOSIS separate nuclei, one in each newly formed Termed cell death - a normal process by which daughter cell. cell numbers within various tissues are adjusted and controlled. Chromosomes begin to unravel and resemble the genetic material during interphase. In developing fetus, apoptosis removes extra tissue, such as cells between the developing Following telophase, cytoplasm division is fingers and toes. completed, and two separate daughter cells are In some adults, it eliminates excess cells to maintain a constant number of cells within the tissue. MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 9  CELLULAR ASPECTS OF AGING Various causes for cellular aging; ○ Existence of a cellular lock ○ Presence of death genes ○ DNA Damage ○ Formation of free radicals ○ Mitochondrial Damage TUMORS Abnormal proliferation of cells Due to problems occurring in the cell cycle Some tumors are benign, some are malignant ○ Malignant - Cancerous Malignant tumors can spread by a process termed METASTASIS. SOURCES: ANAPHY Cells structure and functions recorded lecture Seeley’s Essentials Anatomy and Physiology 11th ed. MENESES, M., PAREDES, J., PAREDES, S., PINO, R., PLURAD, N, QUIÑONES, M., RAMOS, A., REPE, A. TABANAO, K. | 1NU02 10