The Cell the basic unit of life came from the Latin word cella meaning storeroom or chamber term first used by Robert Hooke in 1665 while observing cork cells
The Cell Composed of:1. Protoplast – the site of cellular metabolism2. Cell wall-outermost part of a plant cell
THE PROTOPLAST Made up of: 1. Nucleus 2. Cytoplasm consists of a liquid, colloidal phase of the protoplast (cytosol/hyaloplasm/cytoplasmic ground substance) with membrane-bound organelles
THE PROTOPLAST 2. Cytoplasm with membrane-bound organelles Bounded by double membranes Bounded by single membrane ribosomes endomembrane systems cytoskeleton
PLASMA MEMBRANE(ectoplast/plasmalemma) Controls passage of various substances into and out of the protoplast In transfer cells, are highly invaginated, which facilitates transfer of materials It coordinates the synthesis and assembly of cell wall microfibrils (cellulose)
BIOLOGICAL MEMBRANESMembrane Protein2 types: Integral proteins- integrated into the bilayer • May have access to only one side of the membrane • Span the entire bilayer and have access to both sides of the membrane (transmembrane protein) Peripheral proteins- bound to the hydrophilic surface of transmembrane protein
NUCLEUS • nformation I center of the cell • ontains the C bulk of the cell’s DNA • ucleolus- site N of rRNA synthesis
Cytoplasm Cytosol Non-particulate portion; the liquid portion Contains proteins and other solutes Often assumes the physical properties of a gel Endomembrane system These membranes are either in direct contact or connected via transfer of vesicles, sacs of membrane.
Cytoplasm system Endomembrane System includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, vacuoles, and the plasma membrane. Cellular organelles Membrane-limited compartments Serve to compartmentalize the cells Cytoskeleton
Nuclear envelope with 2 membranes; with pores through which molecules of RNA may leave the nucleus and enter the cytoplasm
• ndoplasmic reticulum- continuous with nuclear Eenvelope• types of ER 2-smooth- tubular; site of lipid synthesis-rough - lamellar; site of synthesis of membrane proteins and proteins to be secreted outside the cell and into the vacuole
• olgi bodies (also called dyctyosomes, golgi stacks, Ggolgi apparatus or simply golgi)-Consist of stacks of cisternae-polarized structure-receiving end from ER is cis face-shipping side is the trans face -finishes, sorts and ships cell products
VACUOLE• nveloped by tonoplast/vacuolar membrane E• ontains a variety of inorganic ions,organic acids, sugars, Cenzymes and secondary metabolic products includingpigments• lays a role in maintaining water balance of cells; active p cytosolabsorption of ions result in increase in turgorpressure in the cell and its expansionand growth• omparable to lysosomes C of animal cells Cell wall chloroplast
MITOCHONDRIA• ites of respiration and S• nveloped by 2 E• nner membrane is I invaginated (cr• nzymes for ATP production E itochondrial matrix,a mfluid- filled space with DNA,
PLASTIDS• riginate from proplastid pigments OTypes:Chloroplastids• ontain photosynthetic C pigments• ite of photosynthesis SChromoplastids• ontain carotenoid pigments C• ften so concentrated that they form crystalline deposits O
PLASTIDSLeucoplastids • olorless plastids C • ypes: T 1. Amyloplastids store starch 2. Elaioplastids store fats 3. roteinoplasts- store p proteins
-etioplast is a plastid that develops in the absence of light; nochloroplast, no chlorophyll; characterized by prolamellar bodiescomposed of tubular membranes which comprise aparacrystalline lattice
MICROBODIES• ounded by a single membrane B• eroxisomes- P -major site of O2 consumption; uses O2 in oxidation reactions that convert harmful metabolic by-products into nontoxic substances such as water -break down fats -participate in photorespiration; enzymes in peroxisomes help minimize the lossorganic products due to photorespiration.
Glyoxysomes- contain enzymes for the conversion offats to carbohydrates during seed germinationCytoskeleton s a network of fibers i extending throughout the cy t provides mechanical I support and maintains t provides anchorage for I many organellesand cytosolic enzymes.
CYTOSKELETON lays a major role in cell motility. p -This involves limited movements of parts of the cell (streaming cytoplasm, vesicle and organelle movement). -The cytoskeleton interacts with motor proteins. -Three main types of fibers in the cytoskeleton: • icrotubules m • icrofilaments m • intermediate filaments.
MICROTUBULES pprox 25 nm diameter A omposed of 13 spherical protein subunits (dimers of α Cand ß tubulin) omprise the spindle fibers in dividing cells that move Cchromosomes during cell division.
MICROTUBULES unction as tracks that guide motor proteins carrying f organelles to their destination. esists compression to the cell. r
MICROTUBULES phragmoplast, a complex of microtubules that guides the orderly alignment of the vesicles in the midzone
MICROTUBULES xert some control over orientation of microfibrils ebecause in regions of cell wall growth and cellulosemicrofibril synthesis , microtubules below theplasmalemma are routinely observed in an orientationparallel to that of the newly synthesized microfibrils
ACTIN MICROFILAMENTS bout 7 nm in diameter a omposed of globular actin. C n actin microfilament consists of a twisted double A chain of actin subunits. elp maintain cell shape. h
ACTIN MICROFILAMENTS Involved in cleavage furrow formation On the cytoplasmic side of the cleavage furrow a contractile ring of actin microfilaments and the motor protein myosin form. Contraction of the ring pinches the cell in two
ACTIN MICROFILAMENTS nvolved in cytoplasmic streaming i -This speeds the distribution of materialswithin the cell.
Intermediate filamentsintermediate in size at 8 - 12 nanometers are specialized for bearing tension. re more permanent fixtures of the cytoskeleton than are athe other two classes. hey reinforce cell shape t uclear side of the envelope is lined by the nuclear nlamina, a network of intermediate filaments that maintainthe shape of the nucleus.
ERGASTIC SUBSTRANCES- products of cellmetabolism torage products S tarch in the form of starch grains s roteins which form aleurone grains p ils in elaioplasts or spherosomes (enveloped by o single membrane or may be lacking) axes- long-chain lipid compounds, that occur as w part of the protective coating (cuticle) on the epidermis
LIPID BODIES OR OLEOSOMES• unction: storage and transport of lipids f
ERGASTIC SUBSTRANCES- products of cellmetabolismWaste productsCrystals-calcium oxalate crystals May be a form of stored calcium-calcium carbonate crystalsSilica –common constituent of epidermal cell wall of grasses -silica bodies – masses of silica which fill some epidermal cells -provides protection from herbivory and mechanical strength
ERGASTIC SUBSTRANCES Tannins and tanniniferous substances are phenolic by-products primary function – protective,their astringency serving as a repellent to predators an impediment to the invasion of parasitic organisms