Presentation on theme: "CELL STRUCTURE Common Features of Cells"— Presentation transcript:
1 CELL STRUCTURE Common Features of Cells All have plasma membrane (cell membrane)All have nuclear regionAll have cytoplasmcytoplasmnuclear regioncell membrane
2 STRUCTURE OF CELL MEMBRANE The cell membrane has a two-layered structure mainly made of protein, lipid and carbohydrate moleculesProtein molecules are embedded in the lipid bilayerCarbohydrate molecules may branch out from the external surface of the membraneCarbohydrate chains bonded to lipids form glycolipidsCarbohydrate chains bonded to proteins form glycoproteins
4 STRUCTURE OF CELL MEMBRANE Fluid – Mosaic Model of Cell Membrane: (by Singer and Nicholson)CARBOHYDRATESPROTEINSGLYCOIPDGLYCOPRTEINPHOSPHOLIPIDS
5 Proteins in the cell membrane do several different functions.
6 PROTEINS OF CELL MEMBRANE Transport Proteins:Control the movement of substances through the cell membraneReceptor proteins:They bind with messenger molecules to begin or stop metabolic activitiesEnzymes:Catalyze reactionsStructural proteins:Help bind the membrane to neighboring cells or structural elements in the cytoplasmIdentity proteins:Distinguish the cell from other cells
8 PERMEABILITY OF CELL MEMBRANE Selective permeability enables the cell to protect the inner balance (homeostasis).
9 PERMEABILITY OF CELL MEMBRANE The molecules that can pass EASILY through the cell membraneThe molecules that CANNOT pass through the membraneSmall molecules such asWaterOxygenCarbon dioxideGlucoseAmino acidsUreaMolecules that can dissolve lipids such asAlcoholEtherPolymers
10 PERMEABILITY OF CELL MEMBRANE Electrically neutral molecules enter and leave cells more easily than electrically charged ions.In animal cells (+) ions can pass easier than (-) ions.Lipid molecules (fatty acids, glycerol) pass through cell membranes easily.Fat soluable vitamins (A, D, E,K) can pass easier than water soluable vitamins.
11 Prevents the cell contents from interacting with the surrounding medium Gives shape and mechanical strength to the cellControls the material transport
12 CYTOPLASM AND ORGANELLES Fluid-filling part of the cellOccupies the space between the membrane and the nucleusIncludes the cytoskeleton, organelles and cytosol.65-95% waterContains many substances (granular proteins mostly)Also contains carbohydrates, lipids, enzymes, minerals, vitamins and pigments
14 CYTOPLASM AND ORGANELLES Organelles: In eukaryotic cells there are secondary compartments covered with cell membrane. These are called organelles.An organelle is the part of the cell which is responsible for a specific function.
15 CYTOPLASM AND ORGANELLES Cytoskeleton:is the skeleton of the cellan interconnected system of protein fibers and thin strandsgives cells their shape and internal organizationcomposed of microtubules and microfilaments
16 CYTOPLASM AND ORGANELLES Cytoskeleton:Microtubules are linked in parallel rows.In animal cells microfilaments are found. They play role in muscle contraction.
17 CYTOPLASM AND ORGANELLES The cytoplasm of a eukaryotic cell includes the following organelles:ribosomeendoplasmic reticulummitochondrionGolgi bodieslysosomeperoxisomevacuoleplastidscentrosome
18 RIBOSOME Tiny, granular structures Found in all cells without any exceptionMade of RNA and proteinSome are found freely in cytoplasm and some are attached to the ERRibosomes are produced in nucleolus
19 RIBOSOME Function: Proteins synthesis Ribosomes are made of two subunitsBacterial cells have smaller ribosomes.When there is no protein synthesis in the cell these subunits are separate from each other. They come together in order to be functional.
22 ENDOPLASMIC RETICULUM Made of cell membraneFound in all cells except red blood cells and bacterial cellsTwo types:Smooth ER (no ribosomes on it)Rough ER (ribosomes on the outer surface)
23 ENDOPLASMIC RETICULUM Functions:carries proteins to Golgi bodyprovides a pathway for the transport of molecules throughout the cellsmooth ER synthesizes lipidsprovides support to the celldivides the cytoplasm into compartments (different type of chemical reactions can take place at the same time)plays role in the contraction of skeletal muscles
25 MITOCHONDRIAis the place where aerobic cellular respiration takes place in eukaryotic cellssurrounded by double-layered membraneinner membrane has foldings called cristae, which provides a large surface area for the chemical reactionsthe fluid that fills the interior space is called matrixmatrix includes ribosomes, DNA, RNA and proteinscan duplicate itself
27 Golgi BodyConsist of a stack of flat, membrane –enclosed sacs and small vesiclesPresent in all cells except blood and sperm cellsPlant cells have more golgi than animal cellsThey have connections with the membranes of E.R.
28 Golgi Body Functions of golgi: Secretion Modifiying the molecules like glycoproteins and glycolipids coming from the E.R, and releasing them to cytoplasm.The vesicles originating from the golgi moves towards the cell membrane and the cell mebrane expands.It forms lysosomes.Some vacuoles are formed by golgi.Helps formation of cell wall in plants.
29 Golgi bodies are highly developed in gland cells. For ex, their number is very high in salivary glands. Gastric glands and cells which produce nectar in plants.
30 LysosomeThey are spherical structures surrounded by a single membrane.They are formed by golgi.They contain hydrolytic (digestive) enzymes.When lysosomes burst and release these enzymes, the cell starts to digest itself. It is called autolysis.Mostly found in animal cells that make phagocytosis. For ex; humans white blood cells.
31 LysosomeFunctions:They digest intracellular and extracellular molecules.They digest worn –out cell organelles.They function in defence of the cell.They are found at the head part of the sperm cells and let sperms hydrolizye the outer wall of the egg.
32 LysosomeFunctions:They function in defense of the cell. For ex; white blood cells contain high no. of lysosomesThey are found at the head part of the sperm cells and let sperms hydrolyze the outer wall of the egg.
33 Peroxisome They bud from the membranes of E.R. As a result of breaking down amino acids and fatty acids, a highly toxic molecule, H2O2 (hydrogen peroxide) is produced.Peroxisomes contain catalase enzyme that breaks down H2O2.They are especially found in liver, heart and muscle cells in humans.
34 VacuolesThey are fluid filled organelles surrounded with single membrane.Minerals, waste products, nutrients and some pigments are stored in vacuoles.They are found both in animal and plant cells, but animal cells have smaller vacuoles than plant cells.The immature plant cells have small vacuoles. As the plant cell matures merge to form one big vacuole.
35 Vacuoles There are three types of vacuoles: 1. Digestive vacuole: Found in unicellular organisms and white blood cells.They are formed when a food molecule is taken into the cell and it’s surrounded by the cell membrane.
36 Vacuoles 2. Contractile vacuole: Found in unicellular organisms that live in fresh water. For ex:ParameciumThey pump out the excess water that goes inside the organism.@
37 Vacuoles 3. Storage vacuole: In plants, toxic waste materials are stored in storage vacuoles.They also store some pigments that give colorto plant parts.
38 PLASTIDS They are found only in plant cells!!! They are surrounded by double membrane.There are three types of plastids:ChloroplastsLeucoplastsChromoplasts
39 Chloroplast They contain the green pigment chlorophyll. Outer membraneInner membraneGranaStromaThey contain the green pigment chlorophyll.Chlorophyll converts the light energy into chemical energy (photosynthesis).
41 Chloroplast Grana: Stroma: Outer membraneInner membraneGrana:Stroma:Formed with the foldings of thylakoid membranesInclude the chlorophyll pigmentFluid-filling partInclude enzymes, DNA, RNA, ribosomes and other organic molecules
42 ChloroplastThe main function of chloroplasts is photosynthesis. They convert light energy into chemical energy and store it in ATP.But the ATP produced in the chloroplasts never get out of this organelle. They are used in photosynthesis only.
43 ChromoplastThey contain different color pigments that give red, yellow, orange color to different parts of plants.These pigments do not play role in photosynthesis.They are sensitive to light.When chloroplasts are exposed to sunlight they can turn into chromoplasts. (Ex. Green tomato Red tomato)
44 Leukoplasts Leucoplasts: They are usually located at tissues that are not exposed to sunlight (ex: roots)They store starch, oil and other plant products.Ex:Potato starchCorn lipidBean proteinThey can turn into chloroplast when they are exposed to light.Potato
45 Centrosome made up of two perpendicular cylinders called centrioles contains microtubuleslocated near the nucleusfunction in cell divisionthey produce spindle fibers which moves the chromosomes during cell divisionplant cells don’t have centrosomes
46 Cell Wall plants, fungi, algae and bacteria have cell wall is not alivemain function: protects the cell, gives its shape, gives mechanical support
48 Nucleus DNA is located in nucleus in a eukaryotic cell. usually cells have one nucleus.Bacteria, and mature red blood cells do not have nucleus.control center for cell metabolism and reproductionif it is removed the cell dies
49 Experiments on nucleus ABCDThe cell is divided into two as shownThe cell is divided into two as shownThe nucleus of the cell is removedAn ameba cellIIIIIIAmeba (lives)I dies II livesBoth cells die because nucleus is destroyedThe cell dies
54 2. Nucleoplasm: fluid – filling part of the nucleus includes water, protein, DNA, RNA, minerals and nucleotides
55 3. Nucleolus (pl.Nucleoli): dense mass of irregular size and shapeproduces ribosomes and involved in protein synthesisthe cells which have a high metabolic rate have more nucleoli than the othersnucleolus
56 It is visible under light microscope only during cell division HistonesCoiling startsChromatinChromosomeChromatin strandsIt is visible under light microscope only during cell divisionIt is not visible under light microscope (cannot be seen before and after cell division)