Presentation on theme: "Cells. Cell Theory Cells are the fundamental (smallest) units of life. All organisms are composed of cells. All cells come from preexisting cells. (Proved."— Presentation transcript:
Cell Theory Cells are the fundamental (smallest) units of life. All organisms are composed of cells. All cells come from preexisting cells. (Proved by Pasteur who disproved spontaneous generation in 1859.) Spontaneous Generation Formulated in 1838 by Schwann and Schleiden.
Surface area to volume ratio Cells have a large surface area to volume ratio. The cell’s volume determines the rate of chemical activities over time. The cell’s surface area determines the amount of substances a cell can take in an expel. Because cells need to transport substances frequently, small size is essential. How do you increase cell SA without increasing size?
SA Increase the folding to increase SA. The respiratory tract has the SA of a tennis court due to folding… The intestines has the SA of a football field…. The excretory system has large SA for N removal: Ammonia in fish Urea in humans and animals Uric acid in birds and reptiles
Since cells are small we need ocular assistance… Most cells are < 200 μm in size. Minimum resolution of human eye is 200 μm. Resolution is the distance apart that two objects must be in order for the eye to view them as distinct not a blur. Microscopes improve resolution.
Types of Microscopes Light microscopes- glass lens and visible light to form a magnified image of an object. Magnifies about 1000x. Electron microscopes-uses electromagnets to focus an electron beam. The beam is then directed to a fluorescent screen/photographic film to create a visible image. Magnifies about 1,000,000x. Can see subcellular.
Cell Similarities 1. All cells have a cell membrane. (Phospholipid bilayer.) 2. All cells contain DNA.
Cell Membrane Structure 1. Phospholipids- are amphipathic. They line up to form a barrier from the water that is inside/outside the cell. Remember Phosphate heads are (-) Phosphates prevent hydration shells around each phospholipid. 2. Proteins- are amphipathic. A. Integral run through c.m. Function: structure and transport B. Peripheral- on one side of c.m. Function: attachment of cytoskeleton and ECM
C.M. Proteins Cont. The proteins of the cell membrane can have several functions. Molecule transport (Helps move food, water, or something across the membrane.) Act as enzymes (To control metabolic processes.) Cell to cell communication and recognition (So that cells can work together in tissues.) Signal Receptors (To catch hormones or other molecules circulating in the blood.)
Membrane Protein Functions Enzymes Signal Receptor ATP Transport Enzymatic activity Signal transduction
Membrane Protein Functions Glyco- protein Cell-cell recognition Intercellular joining Attachment to the cytoskeleton and extra- cellular matrix (ECM)
C.M. Cont. 3. Cholesterol- keeps c.m. flexibility. Also prevents plant cell membranes from freezing
Synthesis Question (U1,D12) Question: All living cells have to have a cell membrane to remain living and intact. All cells are mostly water inside the cell. Cells live mainly in a watery environment. Water is a polar molecule. In four sentences or less, how does the presence of water on the inside and outside of a cell contribute to the structure of cell membranes? (5 Points) 1pt. Discussion of negative phosphorus atoms, of phospholipids being attracted to water and forming a barrier in the bi-layer. 1pt. Discussion of the bi-layer needed to prevent water from forming hydration shells around the phospholipids. 1pt. Discussion of the fatty acid tails being protected sandwiched in-between the Phosphorus barriers. 1pt. Correct use of scientific terms. 1pt. Answer has no more than three sentences. (Following Directions.)
Prokaryotic Cells “Kary” means kernel, in this case the nucleus. Prokaryotes compose the Domains: Archaea and Bacteria. Do not have membrane bound organelles. Thought to have been the “first cells”
Prokaryotes Can live in more diverse environments than eukaryotes. Can sustain life on more diverse energy sources than eukaryotes. Typically smaller than eukaryotes. Tend to aggregate in chains or clusters.
1. Plasma membrane regulating incoming/outgoing substances. 2. Nucleiod- contains DNA, not a defined region 3. Cytoplasm: (2 parts) Cytosol-consists mostly of water with ions and water soluble molecules such as proteins Insoluble particles including ribosomes. Ribosomes are RNA and proteins. Prokaryote Composition
Specialized Prokaryotic Features Some prokaryotes developed specialized features. Why? 1. Cell Walls- located exterior to the cell membrane. Dissimilar to plant cell walls Cell walls typically contain peptidoglycan an amino sugar Sometimes have an outer membrane. Sometimes a capsule:= Slime layer made of polysaccharides; prevents drying out and aids in attachment to other cells (sickness)
Cell Walls, Internal Membranes, & Flagella and Pili Plasma membrane will fold in to form specialized compartments for photosynthesis, cell division, or catabolic activities. Structures of Movement Flagella- made of protein flagellin, rotates like an axel for movement. Pili- aka cilia, hairlike projections for movement
Cytoskeleton- helical structures just inside the plasma membrane. Composed of proteins similar to actin. Actin makes up cytoskeleton in eukaryotes. Cytoskeleton commonly found in rod shaped bacteria.
Eukaryotic Cells Eukaryotic cells ~10x bigger than prokaryotes. Have membrane bound organelles. Organelle can be membrane bound or not. Organelles have a specific functions and shapes. The role/function of an organelle is defined by the chemical reactions that take place
Cell fractionation and microscopy Cell organelles first detected by light microscopes. Cell fractionation-break down plasma membrane, organelles separate based on size/density. Biochemical analysis can then be done to detect for certain macromolecules Many organelles identical in plants and animals.
Nucleus Typically the largest organelle in animal cells. Site of DNA (chromatin vs. chromosome). Nucleolus- site of RNA and ribosome synthesis.
Nuclear Structure Surrounded by a double membrane called the nuclear envelope. ~3500 nuclear pores exist in the envelope The pores consist of over 100 different proteins These proteins will aggregate in pore complexes of 8 proteins. Small molecules can get into the pores, larger molecules need a nuclear localization signal. (chain of amino acids)
Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 2)
Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 1)
Ribosomes- NOT ORGANELLES Function: protein synthesis per nucleic acid instructions Location: Attached to Endoplasmic reticulum-out of cell proteins, free-floating in cytoplasm-in cell proteins inside mitochondria and chloroplasts. Composed of two different subunits: rRNA- ribosomal RNA Protein molecules (>50 different ones)
Endomembrane System Made up of Endoplasmic Reticulum and Golgi Bodies/Apparatus Vesicles serve as transporters of substances between the endomembrane structure and within the cell.
Endoplasmic Reticulum Location: extends from the outer membrane of the nuclear envelope. Two Types: RER,SER Because of its many folds it has a surface area greater than the cell membrane The interior of the ER is called the lumen Tubes are called cisternae
Rough Endoplasmic Reticulum It is called rough because ribosomes are temporarily attached. Site of protein synthesis Proteins undergo folding within the RER Proteins can then be shipped to incorporated endomembranes (GB), other organelles, or extracellular locations.
Smooth Endoplasmic Reticulum No ribosomes attached Function: Modification of some proteins from RER Hydrolysis of glycogen Synthesis of lipids, phospholipids, and steroids Detoxifies blood Stores calcium
What does this mean? Cells that synthesize a lot of proteins have a lot of ER. e.g. Gland cells that secrete enzymes and WBC Cells that modify molecules that enter the body (food) have a lot of ER e.g. liver cells have lots of SER
Golgi Bodies/Apparatus Flattened membranous sacs called cisternae, think stacks of pancakes Functions: further modifies proteins by attaching sugars to them so they can leave through the c.m. (glycoproteins) Concentrates, packages, and sorts proteins to be shipped extracellular Makes cellulose/starch for plant cell walls
Lysosome Originate from the Golgi bodies Contain digestive enzymes to hydrolyze all 4 macromolecule types (enzymes=lysozymes) When molecules enter through phagocytosis: called the phagosome (vesicle/vacuole with macromolecule) Phagosome attaches to primary lysosome forming a secondary lysosome where digestion takes place
Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 1) Small particles diffuse through cytoplasm
Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 2)
Lysosomes and Autophagy Autophagy- organelles are ingested, hydrolyzed, and released into the cytoplasm for reuse. Plant cells do not have lysosomes, but their central vacuole contains digestive enzymes.
Mitochondria and Chloroplasts Prior to the mitochondria and chloroplasts, breakdown of fuel molecules begins in the cytosol. Both organelles transform energy from one form to another Chloroplasts take light energy and convert it into chemical energy. Mitochondria take molecules such as glucose and convert it into a usable form of energy
Mitochondria and Cellular Respiration Mitochondria make ATP (adenosine triphosphate) through cellular respiration. Cells that require the most energy have the most mitochondria per volume. (Liver cells have ~1000/cell.) Mitochondria can reproduce by binary fission Contains its own DNA, ribosomes, and enzymes Thought to have been purple bacteria.
Figure 4.13 A Mitochondrion Converts Energy from Fuel Molecules into ATP Outer Membrane- little resistance to flow of materials. Inner Membrane- folded (cristae): greater surface area than O.M. Controls flow of substances Embedded with proteins to synthesize ATP Matrix- contains enzymes, DNA, and ribosomes
Chloroplast Type of Plastid (plastid-pigment container) Located in plants and algae Have DNA, ribosomes, enzymes Reproduce by binary fission Thought to have been blue green algae
Peroxisomes Membrane bound organelles that contain toxic peroxides. Peroxides are unavoidable by-products of chemical reactions, that can be safely broken down within the peroxisome.
Vacuoles Membrane bound organelle filled with an aqueous solution and many solutes. Function: Central-Storage Food vacuoles- in simple eukaryotes, used in lieu of digestive system. Intake of food cause a vacuole which fuses with a lysosome, and chemical energy is released in to the cell. Contractile vacuoles- typically in protists; helps with movement as a result of filling with water because of osmotic pressure differences.
Figure 4.18 Vacuoles in Plant Cells Are Usually Large
Removes excess water in aquatic single celled organisms
Cytoskeleton Not a membrane-bound organelle. Function: Supports and maintains cell shape Provides for some cellular movement Positions organelles with in the cells Some fibers can act as tracks that motor proteins can move organelles intracellularly Interacts with extracellular structures to anchor the cell in place. Types: microfilaments, intermediate filaments, and microtubules
Microfilaments-smallest cytoskeleton Can exist alone, in bundles, or networks Made up of actin (protein). These PULL. Microfilaments responsible for: Cytoplasmic streaming- movement of cytoplasm Pinching/Mitotic Movement- formation of daughter cells Pseudopodia- “False feet” for movement
Intermediate filaments-medium cytoskeleton Fibrous proteins of the keratin family. Function: stabilize cell structure.
Microtubules-largest cytoskeleton Function: move organelles or cell. Composed of the protein microtubulin. Examples: Cilia and flagella Centrosomes/Centrioles Spindle Fibers
Synthesis Questions U1,D16 Question: The one part of evolution tries to show unity and diversity exists among all organisms on earth. All living organisms on Earth are either composed of Prokaryotic cells or Eukaryotic cells. In no more than four sentences, justify unity by stating one cellular structure all organisms have in common and for diversity state two structures that all eukaryotic cells possess that Prokaryotic cells do not possess. For each structure state the structures function within the cell. (5 Points)
1pt. (Half point for one of the following: DNA, ribosomes, cell membrane, cytoplasm) (Half point for structures purpose: information, making proteins, Holding cell together, space to work) 1pt. Structure 1 with correct function from following list RER – make proteins SER – lipids and carb metabolism, detoxification Mitochondria – Making energy Chloroplast – Sugar production Golgi Apparatus – protein modification Vesicles – Storage Lysosomes – Digestion Cytoskeleton – support Cell Wall or ECM - protection 1pt. Structure 2 with correct function 1pt. Correct use of scientific terms. 1pt. Answer has no more than three sentences. (Following Directions.)
Extracellular Matrix Area outside of animal cells Composed of fibrous proteins like collagen and proteoglycans/glycoproteins (proteins + sugar). The extracellular matrix is specific to the tissue type, and is made of proteins and fluids the cells secrete.
Function of Extracellular Matrix Holds cells together in tissues Contributes to physical properties of cartilage, skin, and other tissues. Helps filter materials passing between tissues. Helps orient cell movements during embryonic development and tissue repair. Role in chemical signaling.
Figure 3.20 Phospholipids (A) Repeat Fig 3.20A here
Cell Membrane All biological membranes consist of lipids, carbohydrates, and proteins. The cell membrane is sometimes referred to as the fluid mosaic model. This is because it prevents a lot of hydrophillic substances from rapidly entering, and embeds a lot of floating proteins.
Figure 5.2 A Phospholipid Bilayer Separates Two Aqueous Regions
Cell Membrane Content Phospholipids can vary with respect to fatty acid chain length, degree of unsaturation (presence of double bonds), and phosphate groups present. 25% of lipid content can be cholesterol. Most cholesterol in membranes is not detrimental to your health; maintains membrane integrity.
Cell Membrane Fluidity Fluidity is affected by: Lipid composition Temperature When temp. decreases, membrane fluidity decreases. Therefore cellular function decreases. Plants and animals that hibernate may change their lipid content (sat. to unsat. F.A. tails to achieve shorter tails) to survive. Fluidity=FunctionNo Fluidity=No Function
Membrane Proteins All membranes have proteins. Two Types of Membrane Proteins: Integral- hydrophobic and hydrophillic regions, located within the membrane. Include transmembrane proteins. Peripheral- only have hydrophillic regions, interact with other hydrophillic regions of other proteins or heads of phospholipids.
Transmembrane Proteins Transmembrane proteins are a type of integral protein. Extend out on both sides of the membrane. R groups from amino acids determine hydrophobic/hydrophillic location. Integral proteins are only on one surface of the cell membrane. (Inside or outside)
Carbohydrates in Cell Membranes Located on the outer surface of cell membranes. Serve as a recognition site for other cells and molecules. Sometimes carbohydrates fuse with lipids and proteins: Glycoproteins = carbohydrate covalent bond protein Glycolipid = carbohydrate covalent bond lipid
Cell Recognition Cell recognition- one cell specifically binds to another cell of a certain type. An example would be sperm and egg fusing. Homotypic binding- same glycoprotein sticks out of both cells, and the exposed similar carbohydrates bind cells together. eg. tissues Heterotypic binding- different glycoproteins stick out from cells, but they have an affinity for one another so they bind together. eg. fertilization
Cell Adhesion Cell Adhesion- the connection between two cells is strengthened. Cell Junction- result of cell adhesion; 3 types.
1. Tight Junctions Link epithelial cells which line organs and inside of mouth. Function of T.J. prevent substances from moving between cells, and dictate the function of each region of the cell. Like a quilted pattern (Controls membrane proteins)
2. Desmosomes Connect adjacent cell membranes like a spot weld. Allow substances to move everywhere but the connection. Desmosome attached to intermediate filaments inside each cell
3. Gap Junctions Function in communication between cells. (Desmosomes and tight junction have mechanical functions.) Connexons are the channel proteins that span between cells and allow for molecules and ions to pass through
Theory of Endosymbiosis 1.Prokaryotes first absorbed food through environment. 2.Then Photosynthesis evolved. 3.Larger cells engulfed smaller cells, but smaller cells were not digested. 4.The smaller cell divided along with the bigger cell. 5.The big cell provides protection, the little cell provides energy. 6.1980s, Margulis suggests endosymbiosis of chloroplast and mitochondria because they have their own circular DNA, ribosomes, and same size as prokaryotes.
Endosymbiosis Theory is strengthened by: Prokaryotes and eukaryotes share: Nucleic acids as genetic material Same 20 amino acids in protein structure D sugars and L amino acids
2011 Released Essay Prokaryote vs. Eukaryote Scoring Guide