Cell Biology - Cell Structure and Function PDF

Cell Biology CELL STRUCTURE AND FUNCTION Slides prepared by Prof. Dr. Mekky Abouzied Professor of Biochemistry and Molecular biology  Outline By the end of this session, the students 1. Introduction will be able to:...

Cell Biology CELL STRUCTURE AND FUNCTION Slides prepared by Prof. Dr. Mekky Abouzied Professor of Biochemistry and Molecular biology  Outline By the end of this session, the students 1. Introduction will be able to: 1. Define cell, cell theory, and organelle 2. History of cell 2. List differences between eukaryotic and prokaryotic cell 3. Cell theory 3. Demonstrate plant and animal cell 4. Describe plant cell wall and cell membrane 5. Describe the movement of substance across 4. Cell types the cell membrane 6. Identify and describe the major cell organelles 5. Cell organelles 7. Define cytoskeleton  1. Introduction ❖Cell biology: It is a branch of biological science which deals with the study of structure, function, molecular organization, growth, reproduction and genetics of the cells. ❖ Cell biology is mainly concerned with the study of the structure and function of specialized cells. Cell What is cell? CELL is the basic unit of life It performs all life functions like: Nutrition, Excretion, Metabolism, Respiration, etc. in latin “cella” means a "Small room“ It is The basic structural, functional, and biological unit of all known living organisms Often called the "building blocks of life"  2. History of cell ‫لإلطالع‬  Robert Hooke ̶ Observed sliver of cork ̶ Saw “row of empty boxes” ̶ Coined the term “Cell” ‫لإلطالع‬  Cell Size ‫لإلطالع‬  Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell Cell shape A cell’s shape reflects its function Bacteria cell Red blood cell Plant cell  3. Cell theory The theory states that: 1. All living organisms are made up of cell and their products. 2. Cell is the structural and functional unit of the organism. 3. New cells are formed by division of pre-existing cells. (this principle discarded the idea of spontaneous generation) ( Viruses are an exception to cell theory.)  Properties of a Cell Cells are Highly complex and organized Possess a genetic program and the means to use it Capable of producing more of themselves Acquire and utilize energy Carry out a variety of chemical reactions Able to respond to stimuli Capable of self-regulation  Organisms Organisms which are made The organisms which are made up of a single cell are called up of a number of cells are called Unicellular organisms. Multicellular Organisms. Examples are Amoeba, Examples are Fungi, plants, bacteria, etc animals.  Unicellular Organisms Multicellular Organisms Organism is represented by a single cell. A large number of cells are present. A single cell performs all the functions. Different tissues perform various functions of the in the body. They reproduce by asexual methods. Some specialized cells take part in reproduction. nutrients enter and leave the cell by Each cells perform special functions. diffusion. The life span of the individual is short. Life span is long.  4. Cell types Cell Prokaryotic cell e.g Bacteria Eukaryotic cell Plant cell Animal cell  Prokaryotic cell vs. Eukaryotic cell Prokaryote Cell Eukaryote Cell Size small Large Number of cells Unicellular Multicellular Membrane Has single membrane and cell Membrane bilayer wall Nucleus No nucleus. well defined nucleus Cell division by fission By mitosis. DNA Circular DNA Linear DNA. Histone proteins No Histones. Histones found Organelles No organelles Membrane bound Organelles. Ribosomes free in cytoplasm. on ER surface 50S +30S {70S} 60S+40S {80S} Cytoskeleton Absent, has flagella Present. Ex- fungi, Ex- bacteria, rickettsia plants, animals Animal cell v/s plant cell  Eukaryotic cell A) Animal cell ENDOPLASMIC RETICULUM (ER) Nuclear Rough Smooth envelope Flagellum ER ER Nucleolus NUCLEUS Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome Eukaryotic cells: B) Plant cell 5. Cell organelles A cell is composed of cytoplasm and various structures or cell organelles like cell wall, cell membrane (plasma lemma), endoplasmic reticulum, ribosomes, golgi bodies, lysosomes, spherosomes, chloroplasts, mitochondria, centriole and nucleus. Cell Organelles: are sub-cellular, microscopic structures which have characteristic form and function where certain life processes take place. They are bounded by a membrane to keep their contents separate from the external environment. Based On their membranes, there are three types, I. double membraned (Nucleus) II. single membraned (Peroxisomes), III. and no membrane (Ribosomes).  Cell wall A nonliving and rigid coat which forms a Protective layer that surrounds the plasma membrane in plant cells Functions : ❖Provide plants with a definite shape, mechanical support and strength. ❖Plant cell wall consist primarily of cellulose plasma membrane ❖Boundary of the cell. ❖Made of a phospholipid bilayer, with protein molecules scattered all over. ❖Functions : 1. it is a selectively permeable membrane, allowing the entry and exit of selected materials into the cell. 2. It protects the cells from injury  MOVEMENT ACROSS CELL MEMBRANES Few molecules move freely across plasma membrane whereas others find it difficult. Molecules like those below move freely Water (H20) Carbon dioxide (CO2) Ammonia (NH3) Oxygen (O2) There are two major ways in which substances can enter or leave a cell: 1.passive transport 2.active transport 1. Passive Transport ❖ Simple Diffusion ❖ Facilitated Diffusion ❖ Osmosis (water only) 2. Active Transport ❖ Molecules ❖ Particles 3. Endocytosis ( Phagocytosis & Pinocytosis) 4. Exocytosis  Passive Transport No energy required Movement From High concentration to low concentration Simple Diffusion: Facilitated Diffusion: no carrier via specific carrier protein It continues until the concentration of Selection depends on size, shape, charge substances is uniform throughout Channels (are specific) help molecule or EXAMPLES OF MAJOR DIFFUSION ions enter or leave the cell IN BIOLOGY Channels usually are transport proteins Gas exchange at the alveoli (Aquaporin facilitate the movement of Gas exchange for photosynthesis water) Gas exchange for respiration  Osmosis: It’s the movement of water molecule from lower solute concentration to higher solute concentration through a selective permeable membrane Special form of diffusion Fluid flows from lower solute concentration to higher Requires selective permeable membrane ‫الصورة لإلطالع‬  Active Transport Molecular movement requires energy (against concentration gradient) Eg: Sodium-potassium pump A uniporter carries one molecule or ion. A symporter carries two different molecules or ions, both in the same direction. An antiporter also carries two different molecules or ions, but in different directions An electrochemical gradient (Na+ concentration - green), is generated by primary active transport. The energy stored in the Na+ gradient provides the energy to move other substances against their concentration gradients (Glucose - blue), a process called co-transport or secondary active transport ‫لإلطالع‬  Endocytosis &Exocytosis Endocytosis Movement of large Exocytosis material Particles, Reverse of endocytosis organisms ,large Cell discharges material molecules From outside into inside the cell.  Forms of Endocytosis Phagocytosis – “cell eating” Pinocytosis – “cell drinking” Receptor- mediated endocytosis ‫الصورة لإلطالع‬  Cytoplasm ❖Everything in a cell except the nucleus is cytoplasm. ❖ Clear, gelly-like, watery substance surrounding the organelles. ❖ Composition: Water (90%), Organic and inorganic compounds (10%) ❖Function ✓Maintains the shape and consistency of the cell. ✓ Allows for chemical reactions necessary in metabolism. ✓Site for many metabolic pathways. Ex: Glycolysis, Protein synthesis , fatty acid synthesis, purine synthesis. ✓Functional components within cytoplasm ❖ Mitochondria (animal cells) /Chloroplast (plant cells) ❖ Nucleus ❖ Ribosomes ❖ Endoplasmic reticulum ❖ Golgi Apparatus ❖ Lysosomes ❖ Vacuole ❖ Microbodies  Mitochondria Chloroplast Release & store energy Types: Mitochondria (release energy) Chloroplasts (store energy)  Mitochondria 1. Mitochondria are found in most aerobic eukaryotic cells and produce ATP. 2. Mitochondria are semi-autonomous, containing their own ribosomes and DNA for protein synthesis. Function of Mitochondria ✓ Sites where aerobic part of respiration called Kreb's Cycle is performed. ✓ Provide energy for vital activities of living cells. ✓ Provide intermediates for synthesis of various chemicals like fatty acids, steroids, amino acids, etc.  Nucleus: Control center of cell Large & Spherical in shape Most prominent cell organelle (Double membrane). Home for chromosome Function ❖ DNA replication and RNA transcription of DNA occur in the nucleus. ❖ It contains a nucleolus inside, which is responsible for RNA processing  Ribosomes: Protein Factories The ribosome is a large complex of RNA and protein molecules. Ribosomes can be found either floating freely or bound to rough endoplasmatic reticulum in eukaryotes, Have two subunits (large & small) 70s: 50s + 30s, 80s: 60s + 40s ‫الصورة لإلطالع‬  Endoplasmic reticulum ❖E.R (endo means inside + cytoplasmic) reticulum means network network of membranes inside the cytoplasm) ❖Interconnected network of tubules and vesicles extended throughout cytoplasm. Two types of ER Rough ER - studded with ribosomes ❖Site of proteins synthesis Smooth ER – ❖site for synthesis of steroids and other lipids, Ca++ storage in muscles ❖Detoxification of drugs, toxins, alcohol (especially in liver) ❖Site of Glycogen metabolism.  Golgi complex/Apparatus POST OFFICE OF CELL Cluster of membrane vesicles Appears like : Stacks of flattened sacs Function: Receive and modify the proteins made by rough ER protein packaging, modification & secretion glycosylation and sulfation of protein moving proteins within the cell Vesicle fuses with plasma membrane protein is released by exocytosis E.g. pancreatic enzymes & insulin “ sorting sites” ‫الصورة لإلطالع‬  Lysosomes (Suicidal bags) Spherical vesicles with a single membrane. filled with digestive enzymes - used for intracellular digestion. It contains Hydrolytic enzymes ( glucosidase, cathepsin, lipase, ribonuclease It has an Acidic pH 4.6-5 Function They are responsible for decomposing cellular waste products. Digest food [used to make energy] Clean up & recycle [digest broken organelles] Garbage disposal. Breakdown bacteria entering cell, worn out organelles, intracellular digestion. ‫الصورة لإلطالع‬  Peroxisomes Spherical or oval in shape Contain TWO enzymes catalase peroxidase Function Protects the cell from free radicals and antioxidant. Vacuole ❖Membrane bound sac ❖ Contains liquids or solids ❖ Larger than vesicles Function Storage container for water, food, enzymes, wastes, pigments, etc.  Cytoskeleton ❖ A network of protein filaments that extends throughout the cytoplasm. ❖There are Three types of filamentous proteins - 1. Microtubules 2. Intermediate filaments 3. Microfilaments ❖Functions: Role in cell morphology, intracellular transport, cell motility, cell division  ‫‪Structure‬‬ ‫‪.‬‬ ‫الصورة لإلطالع‬  FACTS RELATED TO CELL ✓ The Smallest organelle: RIBOSOME ✓ The Largest organelle: PLASTID(plant) MITOCHONDRIA (animal) ✓ The Largest cell structure: NUCLEUS ✓ VIRUSES are neither prokaryotic nor eukaryotic. ✓ MITOCHONDRIA and PLASTIDS can replicate themselves. Organelles – “factory components with function” Support: Cell wall , cell membrane, cytoskeleton, microtubules Controls material entering and leaving: Cell membrane, pores Internal transport system: Endoplasmic reticulum Powerhouse: mitochondria Control center: nucleus, organelle DNA for mitochondria and chloroplast Production of key products: ribosomes, endoplastic reticulum, chloroplasts Packaging center for shipment of products: Golgi Apparatus, ER Shipment of materials out of cell: Golgi Apparatus, vesicles Storage of liquids and solids: Vacuole, vesicles, plastids, Recycling center: Lysosomes and perixosomes Convert light energy to chemical energy: chloroplasts Allows new cell factories to be produced: nuclear DNA, centrioles, cell wall Thank you