Lec 4 Bio PDF

Field of Basic Science Biology Ⅰ (BIO131) Lecture 4 : Cell organelles Dr : Emad H. El-Bilawy Date : 30/10 /2024 Prokaryotic cell Inclusions & Granules(Storage Bodies) :- - Inclusion bodies are several kind of storage food deposits within the cytoplasm of prokaryotic cells. - Many inclu...

Field of Basic Science Biology Ⅰ (BIO131) Lecture 4 : Cell organelles Dr : Emad H. El-Bilawy Date : 30/10 /2024 Prokaryotic cell Inclusions & Granules(Storage Bodies) :- - Inclusion bodies are several kind of storage food deposits within the cytoplasm of prokaryotic cells. - Many inclusion bodies store nutrients when nutrients are abundant and utilized it when nutrients are rare. - It is vary in size, number & content. Prokaryotic cell Inclusions & Granules(Storage Bodies) :- 1-Polysaccharide granules: this inclusion granules for storing Polysaccharides. 2-Carboxysomes granules : this inclusion granules contain enzymes required for carbon dioxide fixation during photosynthesis. 3-Metachromatic granules : this inclusion granules composed of the reserve of inorganic phosphate that can be used in synthesis of ATP. 4-Gas vacuoles : Hollow, cylindrical cavity covered by protein. The size of the gas vacuole in the cell determined the level of the cell in the water to receive sufficient amounts of oxygen, light and nutrients. Prokaryotic cell Endospores (spores):- -The endospore is a specialized highly resistant differentiated bacterial cell produced by certain gram positive Bacteria. It is differ significantly from the vegetative. Where, it is metabolically inactive and can survive a long time under very harsh conditions. - Spores can also survive very high or low temperatures and high UV radiation for extended periods. This makes them difficult to kill during sterilization -Germination results in leaving the dormant stage and once again becoming a typical, Prokaryotic cell Endospores (spores):- -The genus Bacillus and Clostridium Bacteria are two common disease causing bacteria that produce endospores as needed – Bacillus B. anthracis, causative agent for anthrax – Clostridium C. tetani, causative agent for tetanus **- It formed under the unfavorable environmental condition and it can remain dormant indefinitely but germinate quickly when the appropriate trigger is applied. Prokaryotic cell - Endospores structure: It is consists of :- 1- Coat 2-Cortex 2 Core : Nuclear structure (DNA). -Endospores Position: it may present in the a. Median b. Terminal c. Sub-terminal Prokaryotic cell Mesosomes A large invaginations of the plasma membrane, irregular in shape. - Types of Mesosomes:- a. Latteral mesosomes :- it responsible on increase in membrane surface, which may be useful as a site for enzyme activity in respiration, transport and attachment of bacterial chromosome. a. Septal mesosomes : it may participate in cell replication by formation of cross walls during cell division.  Eukaryotic cell organelles Nucleus = The control center -Present only in Eukaryotic cell. -Repository of the genetic information by holding the nucleic acid. - Parts of nucleus:- 1 Chromosome: strands that contain genetic material 2 Nucleolus: dark spot in the middle of the nucleus that responsible to make ribosome. 3 Nuclear envelope: the membrane surrounding the nucleus. -Most eukaryotic cells possess a single nucleus, and if more it known as muti-nucleii. - Nuclear pores – control movement in and out. -In eukaryotes, the DNA is divided into multiple linear chromosomes  Eukaryotic cell organelles Cytoplasm = Cytosol -It is a clear thick jelly-like material. -Function: Support and protect cell organells. -Composition: Dense gelatinous solution of sugars, amino acids, & salts 70-80% water.  Eukaryotic cell organelles Ribosomes - Cell’s protein synthesis machinery. - Found in all cell types in all three domains. - Ribosomes may be free in cytoplasm or associated with internal membranes. Eukaryotic cell organelles Endoplasmic reticulum a-Rough endoplasmic reticulum (RER) Attachment of ribosomes to the membrane gives a rough appearance. Synthesis of proteins to be secreted, sent to lysosomes or plasma membrane. b-Smooth endoplasmic reticulum (SER). Variety of functions – synthesis of lipids , store Ca2+, detoxification. Ratio of RER to SER depends on cell’s function Golgi apparatus Functions in packaging and distribution of molecules synthesized at one location and used at another within the cell or even outside of it.  Eukaryotic cell organelles Lysosomes -Membrane-bounded digestive vesicles - Arise from Golgi apparatus - Contain enzymes that catalyze breakdown of macromolecules Fuse with target to initiate breakdown -Recycle old organelles, or digest cells and foreign matter that the cell has engulfed by phagocytosis  Eukaryotic cell organelles Vacuoles -Membrane-bound structures typically found in plants -Various functions depending on the cell type -Different types of vacuoles: a-Central vacuole in plant cells. b-Storage vacuoles in plants. Eukaryotic cell organelles Mitochondria -Found in all types of eukaryotic cells - Bound by membranes a. Outer membrane. b. Inner membrane (shaped into folds called cristae). -On the surface of the inner membrane, and also embedded within it, are proteins that carry out oxidative metabolism. -Mitochondria has its own DNA Eukaryotic cell organelles Chloroplasts - Organelles present in cells of plants and some other eukaryotes. - Surrounded by two membranes. - Contain chlorophyll and other (accessory pigments) for photosynthesis - Thylakoids are membranous sacs within the inner membrane. - Chloroplast has its own DNA  Cell envelope -The cell’s organelles and its intracellular solutes are contained within the cell by its membrane. External covering outside the cytoplasm. Maintains cell integrity Composed of two basic layers:- a. Cell wall b. Cytoplasmic membrane (Cell membrane) a- Cell wall Almost all prokaryotes have a cell wall and some eukaryotes (plants). It Constitute ~ 10-20% of the dry weight of the cell. Cell wall is the outer covering layer of the cell. It is rigid to protect the weak cytoplasmic membrane with some elasticity to maintain the shape of the cell. Cell envelope If present, it surrounds the cytoplasmic membrane - But, it is not a regulatory structure like cytoplasmic membrane - It is not selectively permeable (anything that can fit ,can pass through the cell wall). - Animal cells do not have cell walls.  Cell envelope Cell Wall Functions:- 1- Mechanical protection. 2-Maintains characteristic shape (gives the cell its shape): Where it is rigid wall compensates for flexibility of membrane and keeps cell from assuming a spherical shape. 3- Provides a rigid platform for surface appendages. Flagella, pili and cilia emanate from the wall and extend beyond it. The chemical composition of the cell wall is an important factor in analysis and differentiation of organisms. But, it cannot control the entry or exit of substances, nutrients and ions, or even fluid to or from the cell. Reference Physics in Biology and Medicine, 4th edition by Paul Davidovits. Essentials of Biophysics by P. Narayanan. Losos, Jonathan B., Kenneth A. Mason, Susan R. Singer, Peter H. Raven, and George B. Johnson. Biology. 2008.12th edition. McGraw Hill. http://connect.mheducation.com/connect