Introduction to Cells - 1st Lecture

Lecture: 1 Introduction to Cell  Features of the cell A cell is the smallest unit that can carry out the processes of life; examples: Obtaining energy DNA Replication Basic unit of all living things. All organisms are made up of one or more cells. A cell ha...

Lecture: 1 Introduction to Cell  Features of the cell A cell is the smallest unit that can carry out the processes of life; examples: Obtaining energy DNA Replication Basic unit of all living things. All organisms are made up of one or more cells. A cell has the same basic structure. 2  The word cell was first used by Robert Hooke, a British biologist and early microscopist. 3  The Cell Theory Biologists in the early part of the 19th century Schwann and Schleiden suggested that cells were the basic unit of all living things Virchow observed that cells divide to produce more cells, so all cells arise from pre-existing cells. All organisms are composed of one or more cells. 4 Simple light binuclear electron microscopes Developments of microscopes 5 Cell size 6 Cell functions Able to pass nutrients into and out of the cell s gasses into and Respiratory to get energy Growth Reproduction Responding and adapting to external effects 7  Cell shapes Different cells have different shapes. The shape of the cell depends on its function; red cells Humans have cells of various shapes; ✓ circular and biconcave (red blood) ✓long and stretched and branched cells (nerve nerve cell cells). ✓long and narrow cells (columnar epithelium muscle cell in muscle cells), etc. 8 cell types 9 10  Prokaryotic Cella Eukaryotic cell Size is 0.1- 5.0 um Size is 5-100 um Nucleus is absent Nucleus is present Membrane-bound nucleus absent. Membrane-bound Nucleus is present. One chromosome is present, but not true chromosome plastids More than one number of chromosomes is present. Unicellular Multicellular Lysosomes and Peroxisomes absent Lysosomes and Peroxisomes present Microtubules absent Microtubules present Endoplasmic reticulum absent Endoplasmic reticulum present Mitochondria absent Mitochondria present Cytoskeleton absent Cytoskeleton present Ribosomes smaller Ribosomes larger Vesicles present Vesicles present Golgi apparatus absent Golgi apparatus present Chloroplasts absent; chlorophyll scattered in the cytoplasm Chloroplasts present in plants Submicroscopic in size Flagella is present and made up of only one fiber Microscopic in size, membrane-bound Cell wall chemically complexed Cell wall is present in plants and fungi and chemically simpler Vacuoles absent Vacuoles present Transcription occurs in the cytoplasm Transcription occurs inside the nucleus. Examples: Bacteria and Archaea Examples: Protists, Fungi, Plants, and Animals 11  Cell organelles A single cell is able to keep itself functional; a small factory, by owning a series of compartments called organelles. An organelle is a biological structure that does a specific function inside a cell. Examples: ▪ Plasma membrane ▪ Cytoplasm ▪ Nucleus 12  Cell organelles 1. Cell membrane is the physical boundary between the inside of the cell (intracellular) and its outside (extracellular). components a) lipids b) Proteins c) Carbohydrates Function: 1. Membrane is semi-permeable Q1. Do bacteria have a cell membrane? 2. Protection 3. Cell communications Q2. Do viruses have a cell membrane? 13 https://www.sciencefacts.net/cell-membrane.html  Cell organelles 2. Cytoplasm Jellylike fluid that fills the space between the plasma membrane and the nuclear membrane. Components: I. Cytosol made up of water, salts, organic molecules, and proteins. II. cellular organelles except for the cell nucleus, why? Functions: 1. Helping in cell growth. Q1.What is the division of cytoplasm called? 2. Distributing nutrients 14  Cell organelles 3-Nucleus Separates the genetic material (DNA) from the rest of the cell. The nucleus is the largest organelle in the cell. Components: 1. Nuclear envelope is made of two lipid bilayers that separates nucleus from cytoplasm. 2. nuclear pores 3. Chromatin a complex of genetic material (DNA or RNA) and proteins 4. Nucleolus contains genes for ribosomal RNA. Q1. Do prokaryotes have a nucleus? 15  Cell organelles 4.Ribosomes A ribosome is an intercellular structure made of both rRNA and protein. Can be in the cytosol or attached to the endoplasmic reticulum. Component: two subunits: large and small. Function: Production of protein 16  Cell organelles 5-Endoplasmic Reticulum (ER) System of membranous channels and network. Internal production & delivery system of the cell. Type and Function 1. Rough ER is containing ribosomes, Site of protein synthesis. 2. Smooth ER without ribosomes. Site of phospholipids synthesis. Q.1. Do prokaryotes have endoplasmic reticulum? 17  Cell organelles 6-Golgi apparatus Consists of a stack of curved saccules. Receives molecules, changes them, and then sort them for transport to different cell parts; cell post office. Function: Receives protein and lipid-filled vesicles from the ER, packages, modification, and distributes them within the cell or for export out of the cell (secretion of proteins). Post-translational modification (glycosylation). Q.1. What substance do Golgi bodies prepare for secretion? 18  Cell organelles 7-Mitochondria Double membrane-bound cell organelle They produce a huge amount of energy in the form of ATP and thus called the ‘powerhouse of the cell’. Function 1) promoting the growth of new cells. 2) serving as the ‘energy currency’ of the cell by Q1. What simple sugar is broken down in the synthesizing ATP mitochondria? 19  Cell organelles 8-Vesicles Small compartments separated from the cytosol by at least one lipid bilayer. Function Store, transport, or digest cellular products and waste. 20  Cell organelles 9-Lysosomes Lysosomes are membrane-bound cell vesicles. Contain hydrolytic enzymes Function: Digestion: break down food into small particles, Destroy old cellular components. Phagocytosis to protect cells from pathogens. 21  Cell organelles 10-Chloroplast The chloroplast is a type of cell organelle called plastids found in plants and blue-green algae. The organelle of photosynthesis. chlorophyll: (a green pigment) that absorbs solar energy. Plastids contain their own DNA and some ribosomes. Function: A. synthesizing food using solar energy by the process of photosynthesis. 22  Difference between chloroplasts and mitochondria ❖ Chloroplasts absorb energy from sunlight and store it in sugars (photosynthesis). ❖ Mitochondria use chemical energy stored in sugars as fuels to generate ATP (cellular respiration). 23  Types of eukaryotic cells Plant cell Animal cell 24 Comparison between plant and animal cells 25  Starch and Glycogen Glycogen is a polysaccharide Starch is a polysaccharide that is the principal storage form that is the principal of glucose (Glc) in animal and storage form of glucose human cells. (Glc) in plant. 26 Reproduction and cell division 27 Reproduction and cell division Cell division is a biological process by which a parent cell duplicates its cell contents and divides to give rise to two or more daughter cells. It is an irreplaceable biological process in all living organisms; being the “means of growth, repair, and reproduction in multicellular organisms” and “the sole source of reproduction in unicellular organisms”. 28 Reproduction and cell division Cell division is a biological process by which a parent cell duplicates its cell contents and divides to give rise to two or more daughter cells. It is an irreplaceable biological process in all living organisms; being the “means of growth, repair, and reproduction in multicellular organisms” and “the sole source of reproduction in unicellular organisms”. 29 Reproduction of prokaryotic cells: “Binary Fission“ Populations of bacteria can grow very rapidly. Why ? Binary Fission is asexual way of reproduction. 30  Reproduction of eukaryotic cells diploid (2n) diploid (2n) Haploid (1n) 31  The cell cycle Cell cycle refers to the sequence of events that occur as a cell grows and divides. It is divided into 2 main stages: 1- Interphase: subdivided into 3 stages: i. GAP1(G1): the primary growth phase; cell grows larger in size. ii. Synthesis phase (S): cell synthesizes a copy of its chromosomes; DNA duplication. iii. GAP2 (G2) is the secondary growth phase, finishes growing, quick check of the replicated DNA, and preparations for cell division. 32  The cell cycle 2– Mitosis (M phase): is a cellular division that occurs in somatic cells in five continuous steps. Results of mitosis: I. Division of the duplicated chromosomes and cytoplasm (cytokinesis). II. Two genetically identical cells (2n). 33 34 Quiz Choose the best answer. 1. What is binary fission? A. An asexual mode of reproduction where a parent cell divides into two progeny cells B. A sexual mode of reproduction involving gametes C. An asexual mode of reproduction wherein the progeny buds off from the parent 2. How is binary fission different from mitosis? A. Binary fission occurs in prokaryotic cells. Mitosis occurs in eukaryotic cells. B. Binary fission involves the formation of a spindle apparatus; mitosis does not. C. Binary fission produces genetically identical daughter cells, similar to mitosis. 3. Cell divides for reproduction A. Binary fission B. Mitosis 5. Which process is similar to binary fission? C. Both binary fission and mitosis A. Mitosis B. Meiosis 4. Produces two cells with an identical genome C. Crossing over A. Binary fission B. Mitosis C. Both binary fission and mitosis 35 Fun to watch videos https://www.youtube.com/watch?v=0xe1s65IH0w 36