2History of the CellRobert Hooke is a scientist from England.He experimented with clocks, telescopes and microscopes.He became famous for the observation of thin slices of bark through the microscope in 1667.It was this observation that led him to….THE DISCOVERY OF THE CELL !
3How did he discover the Cell? He sharpened his knife as keen as a razor blade.He cut off a very thin piece of cork with his knife.He placed the thin piece of cork on a black object plate.Through the microscope, he observed that the cork cells were perforated and porous, much like a honeycomb.
5Microscopes Light microscope can magnify objects up to 1000 x Thus, many organelles cannot be seen clearlyElectron microscopecan magnify objects upto > xThus, many organelles can be seen more clearly
6Micrographs What is it? A camera can be fitted to a microscope to take pictures. This picture is called themicrograph.
7Micrographs Photomicrograph Taken using a light microscope Pictures are in colourElectronmicrographTaken using an electron microscopePictures are in black- and-white but images can be artificially colourised.
9What does a cell consist of? cell wallcytoplasmnucleus
10What does a cell consist of ? ProtoplasmNucleus + Cell surface membrane + CytoplasmOrganelles- Specialised structures within the cell
11Parts of a Cell The protoplasm of a cell is made up of three parts: CytoplasmProtoplasm between the cell surface membrane and nucleusWhere most cell activities occurContains enzymes and specialised structures (organelles)Cell surface membraneSurrounds the cytoplasmPartially permeableHence controls substances entering or leaving the cellnucleoplasm nucleolus chromatinnuclear envelopeNucleusConsists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatinFunctions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans.
14Cell wallNon-living cell wall made of cellulose that encloses the entire plant cell, surrounding the cell membrane.The cell wall is fully permeable and is absent in animal cells.Function:It protects the cell from injury and gives the plant cell a fixed shape.
15What does a cell consist of? Cell wallOnly exist in plant cellsAbsent in animal cells
16What does a cell consist of? PhotomicrographCell wall
17Parts of a Cell The protoplasm of a cell is made up of three parts: CytoplasmProtoplasm between the cell surface membrane and nucleusWhere most cell activities occurContains enzymes and specialised structures (organelles)Cell surface membraneSurrounds the cytoplasmPartially permeableHence controls substances entering or leaving the cellnucleoplasm nucleolus chromatinnuclear envelopeNucleusConsists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatinFunctions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans.
19CytoplasmCytoplasmDrawing of Onion epithelial cellCheek cell
20Parts of a Cell The protoplasm of a cell is made up of three parts: CytoplasmProtoplasm between the cell surface membrane and nucleusWhere most cell activities occurContains enzymes and specialised structures (organelles)Cell surface membraneSurrounds the cytoplasmPartially permeableHence controls substances entering or leaving the cellnucleoplasm nucleolus chromatinnuclear envelopeNucleusConsists of nucleoplasm, nuclear envelope, one or more nucleoli and chromatinFunctions: controls cell activities (e.g. cell growth and repair of worn out parts) ; ;essential for cell division. Cells without nucleus cannot divide and have short lifespans.
22Nucleus- what is inside? Chromatin -A network of thread-like structures in the nucleus-It controls the activities of the cell, such as cell division-Each chromatin is made up of proteins and deoxyribonucleic acid (DNA)DNA contains:-Hereditary information-Instructions that a cell needs for carrying out all chemical reactions within itself.
23Nucleus- what is inside? Chromosome - When the cell is dividing, chromatin condenses and becomes highly coiled structures called chromosomes (which appear as thick, rod-shaped structures under light microscope)chromosome
26Vacuole -Fluid-filled space enclosed by a membrane Function: -Contained in the cytoplasmFunction:-Storage of substances within the cell
27Water; food substances VacuoleAnimalPlantSize and numberSmall and manyLarge and only oneContentsWater; food substancesCell sap (contains dissolved substances such as sugars, mineral salts and amino acids, enclosed by a membrane called tonoplast)How long do they exist?TemporarilyMore permanent
34Mitochondria (sin: Mitochondrion) -Small, sausage-shaped-Can be seen clearly under electron microscopeFunction:- Aerobic respiration occurs in the mitochondria-Aerobic respiration is the process whereby food substances are oxidised to give energy the cell needs to carry out activities like growth and reproduction
41In summary- Most cells share certain features: ProtoplasmCytoplasmNucleusGel-like substanceforming major part of cellSite where mostorganelles are found:Mitochondria (sausageshaped)-for cell respirationCentrioles -involved in cell divisionChloroplasts -Contains chlorophyll,green pigment needed forphotosynthesisVacuoles -fluid-filled storage sacsRibosomes-Synthesise proteinsCell surface membraneNucleoli- Building proteinsNucleoplasm- small roundmass of protoplasm calledthe nucleoplasmNuclear envelope-Separates nuclear contentfrom the surroundingCytoplasmChromatin threads- Found innucleoplasm, containhereditary materials whichcondense to form chromosomesPartially permeablemembrane coveringof cellControls substancesentering and leaving cell
44Rough endoplasmic reticulum Rough endoplasmic reticulum (RER) has a surface that appears rough because of small particles called ribosomes that are attached to its outer surface. The outer surface of the RER is continuous with the nuclear envelope.Ribosomes are small round structures that are either attached to the membrane of the RER or lie freely in the cytoplasm. They are needed to synthesise proteins.The ribosomes attached to the RER make proteins that are usually transported out of the cellThe ribosomes lying freely in the cytoplasm make proteins that are used within the cytoplasm of that cell.The RER transports proteins made to the Golgi apparatus for secretion out of the cell.
45Smooth endoplasmic reticulum The smooth ER (SER) does not have ribosomes attached to its membrane. SER is more tubular that than the RER. It is connected to the RER.The SER synthesises fats and steroids and converts harmful substances into harmless materials.
46Golgi apparatus Golgi apparatus or Golgi body is shaped like a disc. It consists of a stack of flattened spaces surrounded by membranes. Vesicles or tiny spherical spaces enclosed by a membrane can be seen fusing with one side of the Golgi apparatus and pinching off from the opposite side.The Golgi apparatus stores and modifies substances made by the ER and packages these substances in vesicles for secretion out of the cell.
47Plant and animal cells: Similarities Both have nucleiBoth have cell membranesBoth have cytoplasmBoth have mitochondria, ribosomes, ER, Golgi apparatus, vesicles
48Plant and animal cells: Differences Plant cellMany small vacuolesA large central vacuoleChloroplasts presentNo chloroplastsNo cell wallCellulose cell wallcentrioles presentNo centriolesNo regular shapeRegular shape
49Differentiation Growth in an organism involves cell division. New cells produced may change and develop into new tissues.This process by which a cell becomes specialised for a specific function is called differentiation. Cells may develop special structures or lose certain structures for them to carry out specific functions.e.g. Human cells become differentiated to form various types of cells:liver cells, muscle cells, sperm cells, epithelial cells, blood cells, etce.g. Plant cells differentiate to form xylem cells, phloem cells, etc
50Root Hair Cell Functions Adaptations Long and narrow to increase thesurface area: volume ratio,thus water and mineral salts can be efficiently absorbed from the soil.Absorption of water & mineral salts from soil
51Surface Area to Volume Ratio CubeSurface area/cm2Volume/cm3Surface area: volumeSide 1 cmSide 2 cmSide 3 cm6:16 cm21 cm38 cm324 cm23:127 cm354 cm22:1
52Xylem Vessels Functions Adaptations Long & thin tubes, To conduct water & salts from roots to leavesLong & thin tubes,no cross walls or protoplasm which enables water to move easily through the lumen (central space)To provide support forstem & leavesLignin deposited on wall
53Red Blood Cells Functions Adaptations -Circular biconcave, increases the SA to Vol. ratio.-no nucleus, enabling it tocontain more haemoglobinTo carry oxygen around the body
54Tissues A group of cells work together to form a tissue. muscle cell muscle tissue made up of muscle cellsepithelial cellepithelial cellgland cellneuronesepithelium in the trachea (tissue) made up of epithelial cells and gland cellsepithelium in the lungs (tissue) made up of epithelial cellsnervous tissue made up of neurones (nerve cells)connective tissue cellintestinal epithelial cellconnective tissue cellcartilage in the trachea (tissue) made up of connective tissue cellsconnective tissue in the lungs made up of connective tissue cellsintestinal epithelium (tissue) made up of intestinal epithelial cellsA group of cells work together to form a tissue.
55TissueA group of similar cells which work together to perform a specific function-Cells of the same type form simple tissueE.g. epidermis tissue (plants) and epithelial tissues (animals)-Cells of different types form complex tissueE.g. connective tissue (animals), blood, vascular tissue (plants)
56intestinal epithelium (tissue) Organsmuscle tissueepithelium (tissue)stomach (organ)trachea (organ)nervous tissuecartilage (tissue)intestinal epithelium (tissue)epithelium (tissue)lungs (organs)intestine (organ)muscle tissueconnective tissueDifferent tissues combine to form an organ.
57Systems Several organs work together to make up an organ system. stomach (organ)trachea (organ)respiratory system (organ system)digestive system (organ system)lungs (organs)intestine (organ)Several organs work together to make up an organ system.
58Specialised Cells, Tissues, Organs & Systems digestive system (organ system)respiratory system (organ system)human (organism)Various organ systems work together to make up an organism.
59CELL Protoplasm Cellulose cell wall (found only in plants) Tissues OrgansOrgan systemsmade up ofOrganismProtoplasmCellulose cell wall(found only in plants)consists ofNucleusCytoplasmCell surface membranewhichwhichwhichcontrols cell activitiessurrounds the nucleus and is where most cell activities occuris the partially permeable, outer covering enclosing the cytoplasmand containscontains organellesChromatin (made up of DNA)Ribosomes (involved in protein synthesis)Mitochondria (sites of energy release)Chloroplasts (in plant cells)Vacuoles (contain water and food substances)
60You should be able to:Know the functions and identify from diagram and photomicrographs, the nucleus, chloroplast, ribosome, mitochondrion, endoplasmic reticulum.Examine under the microscope an animal cell(from fresh liver& human check cell) anda plant cell (from Hydrilla & onion )Compare and contrast the structures of plant and animal cellRelate the adaptations of a cell structure to its functions for the following: Absorption-root hair cells/ Conduction and support- xylem vessels /Transport of oxygen-red blood cellsDifferentiate between the terms cell, tissues, organ and organ system.