Cell Scale PDF

Cell scale S6bio4 Mr Maes  Cell structure  Tasks:  Read syllabus about cell structure and do the following tasks:  Draw and label the following eukaryotic cells (plant and animal)  Write down in a table the different parts of...

Cell scale S6bio4 Mr Maes  Cell structure  Tasks:  Read syllabus about cell structure and do the following tasks:  Draw and label the following eukaryotic cells (plant and animal)  Write down in a table the different parts of the eukaryotic cells and their functions  Draw and label the following drawings of a chloroplast and mitochondrion  Write down in a table the different parts of a chloroplast and a mitochondrion and their functions  Mark the parts you need to know for compo, for long test you need to know all of them  · L - - -- Numbe Organelle name Function(s) r 1 Nuclear membrane Keeps genetic material (RNA and DNA) separate from the rest of the cell 2 Nuclear pore Exchange substances nucleus -> rest of the cell 3 Nucleolus Creating rRNA (= part of ribosomes) Nucleus Regulates all metabolic processes in the cell + storage of genetic material 4 en 5 Chromatine and Contain genetic material (DNA) Chromosomes (condensed) 6 Cytosol (all fluid in the cell Transporting nutrients/waste products to without organelles) and from organelles/protecting organelles Cytoplasm (all fluid Same as cytosol + all functions of all containing the organelles) organelles 7 Plasma membrane/cell Exchange substances cell -> environment membrane cell 8 Mitochondrion/Mitochond Energy supplier of the cell (respiration rium takes place), make ATP + make DNA, RNA, ribosomes Num Organelle name Function(s) ber 9 Rough ER Transport substances cell nucleus -> rest of the cell, transport proteins (made in ribosomes) to Golgi complex, make ER membranes 10 Smooth ER Role in metabolic processes, e.g. production of lipids (fats) or rendering toxic substances harmless (e.g. alcohol). In short: production, degradation and transport of substances. 11 Golgi complex/apparatus Final processing lipids and proteins from ER + storage + transport substances outside the cell 12 Lysosome Transport enzymes, which break down substances inside and outside the cell (speeding up chemical processes) 13 Free ribosome Building/making proteins 15 Microfilaments (protein Firmness and movement of some animal threads) cells, keep organelles in place 16 Microtubules (protein tubes) Same as microfilaments + pull chromosomes/chromatids apart Num Organelle name Function(s) ber 17 Fat drop Building material, fuel, reserve dust 18 Centrioles Role in cell division + making cilia and whiptails Plastids (Chloroplasts, Photosynthesis, starch supply, colour (plant amyloplasts, chromoplasts, cell) leukoplasts) 19 Chloroplast Photosynthesis (plant cell only) 20 Cell wall Plant cell sturdiness 22 Plasmodesma Transport of substances between cells, because it is channel / pore in cell wall. 23 Vacuole (central) Storage of moisture, waste products (also breakdown), nutrients. With plant cell also storage dyes and for firmness. 24 Tonoplast (vacuole Protects vacuole, moisture + 'keep clean' of membrane) internal environment  Chloroplast Number Name Function(s) 1 Outer membrane Allow molecules smaller or equal to 5000 Daltons (a unit of molecular weight) to pass through. 2 Inner membrane Do not let ions through, but O2, CO2 and H2O do. There is chlorophyll for 1st step of photosynthesis 3 intermembraneal space contains enzymes that use ATP to (between inner and phosphorylate other nucleotides. outer membrane) Part of photosynthesis takes place there. 4 Stroma (liquid in Protect DNA, ribosomes, enzymes. chloroplast) Part of photosynthesis takes place there.  Chloroplast Num Name Function(s) ber 5 Stromathylakoid Connects the grana 6 Granumthylakoid Photosynthesis 7 Granum (stack of thylakoids) Photosynthesis 8 Fat droplet Building material, fuel, reserve dust 9 Ribosomes Building/making proteins (enzymes) for photosynthesis 10 Starch grain fuel 11 circular DNA Code for protein synthesis (not all proteins)  Mitochondrium Numb Name Function er a type mitochondrium with transverse cristae b type with cristae parallel to the longitudinal axis c type with tubular cristae 1 outer membrane Transport molecules. 2 inner membrane Do not let ions through, but O2, CO2 and H2O (so small particles). Creates ATP. Part of respiration 3 intermembrane space contains enzymes that use ATP to phosphorylate other nucleotides. Part of respiration process takes place there. 4 Matrix (the space within Make DNA, RNA, ribosomes. Part of the inner membrane) respiration process takes place there.  Mitochondrium Num Name Function(s) ber 5 Cristae (folds) The purpose of these folds is to create a much larger surface area, allowing more work to be done in a small space. Holding ATPases. 6 ATPase complexes ('stemmed Hydrolysis and condensation of balls') on cristae ATP. Part of respiration process. 7 Ribosomes Build/make proteins for respiration process. 8 circular DNA Code for protein synthesis (not all proteins) in mitochondrion Introduction to Microscopy Microscopy is the use of any technique which produces a visible image of a structure which is too small to be seen in detail by the human eye. The invention and use of the microscope has resulted in the development of many scientific theories. Microscopes are a USD fundamental tool used in A biological sciences. This image was captured using low temperature scanning electron microscopy (SEM). The structure would not be visible without the use of microscopy.  Compound Microscopes The compound microscope (right) is a fundamental tool used in biology. High powered light microscopes are used to magnify objects up to 1500 times. They are called compound microscopes because there are two or more separate lenses involved. Thin and mostly transparent samples are required so that the light from the microscope can pass through the sample easily to reveal the detail. Compound Eye piece lens Microscope Objective lens Arm Mechanical stage Coarse focus Condenser knob In-built light source Fine focus knob  Dissecting Microscopes Dissecting microscopes (such as the one shown right), are a type of binocular microscope. They are used at a low magnification (X4 to X50). A dissecting microscope has two separate lens systems, one for each eye. A 3-D view of the specimen is produced. Because of this they are sometimes called stereo microscopes.  Dissecting Eyepiece lens Microscopes Height adjustment knob Eyepiece focus Focus knob Objective lens Light source Stage  Magnification A blow fly: actual size - no magnification Magnification refers to how much larger a sample appears to be compared to its actual size. As magnification level increases so does the blurriness of the sample. x5 magnification x20 magnification x50 magnification  Resolution An important factor determining the usefulness of a microscope is its resolving power or resolution. High resolution Resolving power is a measure of the clarity of the image. It is the minimum distance two points can be separated and still be distinguished as two separate points. For example, what appears to the unaided eye as one star in the sky may be resolved as two stars with the use of telescope. Medium resolution Electron microscopes have a greater resolution than optical microscopes because electron beams have wavelengths much shorter than those of visible light. Examples of high, medium and low resolution for separating two objects viewed under the same magnification are shown right. Low resolution  Bright Field Microscopy With a conventional bright field microscope, we see objects in the light path because natural pigmentation or stains absorb light differentially, or because they are thick enough to absorb a significant amount of light despite being colorless. Onion cells X50 Onion cells X50 Bright field Dark field Bright field lighting reveals Dark field illumination is very little detail, unless a excellent for viewing cell is stained or naturally near-transparent pigmented. Cell walls and specimens. The nucleus nuclei may be visible. Staining enhances contrast of each cell is visible. and reveals more detail under bright field illumination.  Electron Microscopes Electron microscopes (EM) use a beam of electrons instead of light to produce an image. · Scanning electron An EM can magnify up to levels of 2 X 106 times the original sample size. microscope Specimens must be properly prepared for viewing and are dead. · Transmission electron Microscope The higher resolution of EMs is due to the shorter wavelengths of electrons relative to light particles. Dept of Ph ysics: Ch inese University of Ho ng Kong Dept of Ph ysics: Ch inese University of Ho ng Kong Scanning electron microscope Transmission electron microscope  Electron Microscopes Electron microscopes are of two basic types: Scanning electron microscopes. Electrons are bounced off the surface of an object to produce a detailed image of the external appearance. The image right shows a lymphocyte taken using SEM. Transmission electron microscopes. TEM is used to view extremely thin sections of SEM lymphocyte material to reveal detailed images within a structure or organelle. The TEM of the ultrastructure of a lymphocyte (bottom right) reveals its internal details. Photographs taken using electron microscopy are called electron micrographs. They are black and white unless false color is applied. TEM lymphocyte (false color)  Microscopes Compared Key differences between TEM, SEM, and light microscopy are outlined below: Light microscope TEM SEM Radiation source light electrons electrons Wavelength 400-700 nm 0.005 nm 0.005 nm Lenses glass electromagnetic electromagnetic living or non-living non-living supported non-living supported Specimen supported on glass on a small copper on a metal disc within slide grid in a vacuum a vacuum Maximum resolution 200 nm 1 nm 10 nm Maximum magnification 1500 x 250 000 x 100 000 x colored dyes impregnated with coated with carbon Stains heavy metals or gold Type of image may be colored monochrome monochrome  Animal & Plant Cells Animal and plant cells have many organelles in common, as well as several features specific to each. Specialized features of each are labelled on the diagrams of a animal cell and a plant cell below. Lysosome Chloroplast Centrioles Cell wall Starch granule Animal Cell Plant Cell Features Shared by Plant and Animal Cells Some cellular organelles are commonly found in both plant and animal cells, while others are found exclusively in just one or the other cell type. Organelles and structures common to both plant and animal cells include: nucleus plasma membrane ribosomes mitochondria Golgi apparatus endoplasmic reticulum (rough and smooth) cytoskeleton vacuoles and vesicles, although these differ in size and function in plants and animal cells. end of cell a of beginning a new one Plasma Membrane Located: Surrounds the cell forming a boundary between the cell contents and the extracellular environment. Structure: Semi-fluid phospholipid bilayer in Phospholipid which proteins are embedded. bilayer Protein Some of the proteins fully span the membrane. Function: Forms the boundary between the cell and the extracellular environment. Regulates movement of substances in and out of the cell. Size: 3–10 nm thick. The plasma membranes of two adjacent cells joined with desmosomes Ribosomes Small subunit Located: Free in the cytoplasm or bound to rough endoplasmic Large reticulum. subunit Structure: Made up of ribosomal RNA and protein and composed of two subunits, a larger and a Polypeptide smaller one. chain Function: Synthesis of polypeptides (proteins). Size: 20 nm. Ribosome s Polypeptides being produced on a polyribosome system micrometer nanometer Mitochondria Folded inner membrane forms cristae Located: Cytoplasm Structure: Rod shaped or cylindrical organelles occurring in large numbers, especially in metabolically Smooth outer membrane very active cells. Bounded by a Matrix double membrane; the inner layer is extensively folded to form partitions called cristae. Mitochondria contain some DNA. Function: The site of cellular respiration (the production of ATP). Size: Variable but 0.5–1.5 µm wide and 3.0–10 µm long. A single mitochondrion in cross section  Rough Endoplasmic Rough ER Reticulum Membranous tubules Ribosome Located: Continuous with the nuclear membrane and extending to the cytoplasm as part of the endomembrane system. Structure: A complex system of membranous tubules studded Transport with ribosomes. Connected to the smooth ER but vesicle budding off structurally and functionally distinct from it. Function: Synthesis, folding, and modification of proteins. Transport of proteins through the cell. Membrane production. Size: Variable according to cell size. Smooth Endoplasmic Reticulum Membranous tubules lacking ribosomes Located: In the cytoplasm as part of the endomembrane system. Structure: A system of membranous tubules similar in appearance to the rough ER but lacking ribosomes. Transport vesicle budding Function: off Synthesis of lipids, including oils, phospholipids, and steroids. Carbohydrate metabolism. Transport of these materials through the cell. Detoxification of drugs and poisons. Size: Variable according to cell size.  Golgi Apparatus Transfer vesicle from the ER Located: Cisternae Cytoplasm, associated with the ER. Structure: Stack of flattened, membranous sacs called cisternae. Function: Modification of proteins and lipids Vesicle from the ‘shipping’ received from the ER. side of the Golgi Sorting, packaging, and storage of proteins and lipids. Transport of these materials in vesicles through the cell. Manufacture of some certain macromolecules, e.g. hyaluronic acid. Size: 1-3 µm diameter Also called: Golgi, Golgi body  Nucleus Nuclear pores Located: Variable location; not necessarily near the center of the cell. Structure: Surrounded by a nuclear envelope and encloses the genetic material (chromatin). Nuclear envelope comprises a double membrane perforated by pores ~100 nm in diameter. The two membranes are separated by a space of ~20-40 nm. Function: Contains most of the cell’s genetic material, which regulates all the Nucleolus Nuclear activities of the cell. membrane Chromatin Size: 5 µm diameter.  Nucleolus Located: Within the nucleus. Depending on the organism, there may be more than one. Structure: A prominent structure which appears under EM as a mass of darkly stained granules and fibers adjoining part of the chromatin. Function: Synthesis of ribosomal RNA Assembly of ribosomal subunits. Nucleolus Size: 1-2 µm diameter.  Centrioles Microtubules Located: In the cytoplasm, as part of the cell cytoskeleton. Usually next to or close to the nucleus. Structure: Found as a pair, each one composed of nine sets of triplet microtubules arranged in a ring. Function: Involved in organizing microtubule assembly (spindle formation) but not essential as they are absent from the cells of higher plants. Size: 0.25 µm diameter. Centriole in cross section  Vacuoles and Vesicles Located: In the cytoplasm; often numerous. Structure: Vacuoles and vesicles are both membrane-bound sacs, but vacuoles are larger. Function: food vacuoles in animal cells are formed by phagocytosis of food particles. contractile vacuoles of freshwater protists pump excess water from the cell. central vacuole of plants provides cell volume and stores inorganic ions and metabolic wastes. Size: varies according to cell type and size. Food vacuole in a human lymphocyte  The Cell Cytoskeleton Located: A network throughout the cytoplasm. Structure: A dynamic system of microtubules, microfilaments, and intermediate filaments. An actin stain reveals the iStock cytoskeleton of a fibroblast Function: shape and mechanical support for the cell regulation of cellular activities, e.g. guiding secretory vesicles. especially important in animal cells. involved in cell movement (motility). Size: microtubules: 25 nm microfilaments (actin filaments): 7 nm intermediate filaments: 8-12 nm Specialist Plant Cell Features A small number of cellular organelles are typically found in plant cells but not in animal cells. Organelles and structures found in plant cells are: cellulose cell wall plastids iStock chloroplasts amyloplasts chromoplasts Cross section through a buttercup stem showing the individual cells  Chloroplasts Located: Grana Within the cytoplasm of plant leaf Stroma (and sometimes stem) cells. Structure: Specialized plastids containing the green pigment chlorophyll. Two outer membranes are separated by a narrow inter-membrane space. Inside the chloroplasts are stacks of flattened sacs or thylakoids which are stacked together as grana. Chloroplasts contain some DNA Function: The site of photosynthesis Size: 2 X 5 µm.  Cellulose Cell Wall Located: Middle lamella Surrounds the plant cell and lies outside the plasma membrane. Structure: Cellulose fibers, with associated hemicelluloses (branched polysaccharides) and pectins. Between the walls of adjacent cells, is a sticky substance called the middle lamella. Function: protects the cell maintains cell shape Pectin Hemicelluloses s Cellulose fibers prevents excessive water uptake Diagrammatic representation Size: 0.1 µm to several µm thick. of plant cell wall structure  Plastids Located: Colorless In the cytoplasm. amyloplasts in potato Structure: tubers Double membrane-bound structures. The inner membranes typically possess the enzymes that determine what plastids do. Function: Different plastids have particular roles: Chloroplasts; site of photosynthesis Chromoplasts: contain red, orange, and/or yellow pigments and give color to plant organs such as flowers and fruits. They serve as attractants and identifiers. Amyloplasts: storage of starch and fats. Size: variable depending on type Chromoplasts provide the bright color of flowers and fruit Specialist Animal Cell Features A small number of cellular organelles are typically found in animal cells but not in plant cells. Organelles and structures found in animal cells are: lysosomes cilia flagella TEM of a human lymphocyte Lysosomes Membrane proteins Located: Free in the cytoplasm. Structure: Single-membrane-bound sac of hydrolytic enzymes. Lysosomes bud off the Golgi apparatus. Hydrolytic Function: enzymes break down compounds intracellular digestion of by adding water macromolecules (fats, protein, polysaccharides, and nucleic acids) Lysosomes in a recycling of cellular components lymphocyte. (autophagy) Note how they are budding low internal pH maintained by H + from the Golgi pump in the lysosomal membrane Size: varies according to cell size Cilia and Flagella 2 central single microtubules Located: 9 doublets of microtubules Anchored to the cell membrane of some animal cells and unicellular eukaryotes. Plasma membrane Structure: extension Core of microtubules sheathed in an Basal body anchors the extension of the plasma membrane. cilium Microtubules are arranged in a 9+2 pattern with nine doublets of microtubules arranged in a ring around two single microtubules. Function: Cell motility or, in cells held in place, they move fluid across the cell surface. Size: Cilia: 0.25 µm X 2-20 µm Flagella: 0.25 µm X 10-200 µm TEM of cilia in cross section  Viruses VIRUS Viruses were first identified in the late 1800s with the discovery that tobacco mosaic disease was caused by a virus. Viruses are pathogens which cause disease in plants, animals, and bacteria. Viruses that kill bacteria are called Tobacco mosaic virus bacteriophages or phages. Viruses are non-cellular. There is debate about whether they can be classed as living organisms because they do conform to the existing criteria on which a five or six kingdom classification system is based. Viruses are obligate intracellular parasites, they are incapable of metabolism or CDC reproduction without utilizing a host cell. Small pox, caused by the Variola virus  Viral Structure Tobacco Mosaic Virus Retrovirus (HIV) Glycoprotein RNA spikes of viral envelope RNA Capsomere Capsid Reverse transcriptase 50 nm Protein capsid; there is no plasma membrane Viruses take on many forms, but the key structural components are evident in all morphologies. The tobacco mosaic virus (above left) and HIV retrovirus (above right) demonstrate the main features of viruses: a protein coat or capsid surrounding the viral genetic material and enzyme (if present).  Viral Morphology Viruses can be distinguished and classified in two main ways. Their format of their genetic material (e.g. DNA or RNA) Their morphology (shape) which generally takes on one of three forms: Polyhedral Rod Tail fibers Helical (they may be rod Polyhedral: capsid appears Complex (a mix of shaped), e.g. Ebola or spherical, e.g. adenovirus, first polyhedral and helical), tobacco mosiac virus isolated from human adenoids. e.g. T4 bacteriophage.  A New View on Viruses The identification in 2004 of a new family of viruses, called mimiviruses, Core prompted a rethink of the previously ds DNA 90% coding capacity conservative view of viruses. 10% ‘junk’ 1.2 million base pairs Mimivirus is a very large virus ~911 genes for (400 - 800 nm) found in certain protein species of amoebas. additional genes Mimivirus contains over 1000 genes; Capsid their existence suggests a fourth domain of life. 400 nm The lineage for mimiviruses is Fibrils thought to be very old. It has opened debate about whether they existed prior to cellular organisms. Acanthamoeba polyphaga mimivirus  Bacterial Cells Bacterial cells are prokaryotic cells. They lack many eukaryotic features (e.g. a distinct nucleus and membrane-bound cellular organelles). The bacterial cell wall is a prominent feature of bacterial cells. It is a complex, multi-layered structure A CDC and often has a role in conferring virulence on a bacterial strain. Rocky Mountain Laboratories, NIAID, A. Bacillus cereus grown on a blood agar plate. B. cereus produces a toxin which causes vomiting or diarrhea when toxin levels are sufficiently high. B. SEM of Salmonella typhimurium bacteria invading cultured human cells. Salmonella is a common B NIH cause of gastroenteritis amongst humans.  Bacterial Cells Photo: NY State Department of Health Gram positive cocci Escherischia coli Campylobacter Bacteria are very diverse in morphology and metabolism. The generalized diagram of a bacterial cell above is useful for demonstrating the key components of bacterial cells. Cell Wall A complex, semi-rigid structure that gives the cell shape, prevents rupture, and serves as an anchorage point for flagella. The cell wall is composed of a macromolecule called peptidoglycan; repeating disaccharides attached by polypeptides to form a lattice. The wall also contains varying amounts of lipopolysaccharides and lipoproteins. The amount of peptidoglycan present in the wall forms the basis of the diagnostic gram stain. In many species, the cell wall contributes to virulence (disease-causing ability). Cell Membrane The plasma membrane is similar in composition to eukaryotic membranes, although less rigid. Bacteria lack membrane-bound organelles, so in some bacteria the plasma membrane becomes invaginated to form a specialized membranous structure (e.g. for cellular respiration). Bacillus megaterium, clearly showing the plasma membrane (dark blue). Note the thick cell wall (brown) surrounding the entire cell. Glycocalyx outside of cell · slimy wall part on · used to move around The glycocalyx is a viscous, gelatinous layer outside the cell wall composed of polysaccharide and/or polypeptide. If firmly attached to the wall, it is a capsule. If loosely attached, it is a slime layer. Capsules contribute to virulence in pathogenic species, e.g. Bacillus anthracis, by protecting the bacteria from the host’s immune system. In some species, the glycocalyx enables attachment to substrates. Far left: The capsule of Bacillus anthracis (the cause of anthrax) is revealed with an Indian ink stain. Left: Heavily encapsulated strains form slimy colonies on agar. Photos CDC Flagella Some bacteria have long, filamentous appendages, called flagella, that are used for locomotion. Flagella may be variously arranged: A single polar flagellum = monotrichous One or more flagella at cell ends = polar Distributed over the entire cell = peritrichous Vibrio vulnificus is a flagellated bacterium found in warm ocean environments. (SEM X 26,000). CDC Fimbriae Fimbriae are hair-like structures that form a fringe around some bacteria. Fimbriae are shorter, straighter, and thinner than flagella. Fimbriae are used for attachment to other cells. They are not used for movement. Pili are similar to fimbriae, but are longer and less numerous. They are involved in bacterial conjugation and as phage receptors. Escherichia coli bacterium (right) with a fringe of fimbriae (false color SEM). In this case, the fimbriae aid attachment to the intestinal wall. Chromosomes DNA is loose in the cell > can - easily exchange genetic info Bacterial DNA is organized in a single circular strand. This makes them haploid for most genes. Bacteria cells lack a nuclear membrane so their DNA is located within the cytoplasm in an area called the nucleoid. Some genes are found on both plasmids and on the chromosome. It is possible for free ribosomes to attach to mRNA while the mRNA is still in the process of being transcribed from the DNA. In this TEM of bacterial cells, the nuclear region appears as a lighter central zone called the nucleoid. Plasmids Bacterial plasmids are small, circular DNA molecules (accessory chromosomes) which can reproduce independently of the main chromosome. There may be more than one per cell; a group of plasmids may contain several copies of a gene. Plasmids can move between cells, and even between species, by conjugation. This property accounts for the transmission of antibiotic resistance between bacteria. Plasmids are also used as vectors to carrying specific DNA sequences in recombinant DNA technology.  Bacterial Cell Shapes Most bacterial cells range between 0.20-2.0 µm in diameter and 2-10 µm length. In terms of gross morphology (appearance), there are several basic shapes: Bacilli: rod shaped Cocci: spherical Spirilla: spiral or corkscrew shaped Vibrio: comma shaped curved rods live in tics-lime disease gives you a cold USD A Escherichia coli Staphyloccus aureus Borrelia burgdorferi  Protists The protists are a diverse group and not a natural (monophyletic) group. Essentially, they include the organisms that cannot be classified into any other kingdom. A The protists vary in size and appearance; from plant-like algae, to animal-like protozoans, and fungus-like slime molds. They exhibit features typical of generalized eukaryotic cells, but also have specialized features. B Protists are found almost anywhere there is water. Some protists are found within larger organisms (as parasites or symbionts). Protozoans are the animal-like protists. They include: A. Radiolarians, ocean holoplankton. B. Paramecium, a freshwater ciliate. C C. Stentor roeseli, a freshwater ciliate. are green,lasts can - photosynthesize Euglenoid Flagellates Euglenoid flagellates, such as Euglena, are Flagellum Eye spot: involved in found in freshwater environments. beats for light movement detection Euglena is autotrophic and are capable of Nucleus photosynthesis, but are also capable of heterotrophy when deprived of light. Chloroplast Gullet All lack a cell wall. The body is covered by a tough, proteinaceous pellicle. One, or sometimes two, long, conspicuous flagella, Second, very small, which are used in locomotion. flagellum Size: 130 x 50 µm. Pellicle: A tough, flexible protein layer supporting the plasma membrane that allows the cell to change its shape. Paramylon Contractile vacuole: granules Euglena (130 X 50 µm) regulates water balance. store starch-like energy reserves  Chlamydomonas Chlamydomonas is a photosynthetic green alga. Its habitat is fresh water. Movement is achieved by the action of two flagella. Size: 20 x 10 µm. Chloroplast Pyrenoid: the Nucleus region of starch formation. Contractile vacuole: Cell wall: regulates water composed balance. of cellulose. Cytoplasm Flagella for movement. Eye spot: involved in light detection.  Amoeba Amoeba is a genus of protozoa characterized by pseudopods used for movement. The naked amoebas and the foraminferans belong to a group of animal-like protistans called rhizopods. Amoeboids are heterotrophic, ingesting food and accumulating it inside a vacuole. Amoeba are found in freshwater environments, and many moist habitats including soil. Some are pathogenic. Contractile vacuole: involved in water regulation. Size: 800 x 400 µm. Nucleus Food vacuole: contains ingested food Pseudopod: flowing projections of cytoplasm Food is ingested allow movement and enable food by phagocytosis to be engulfed by phagocytosis.  Paramecium Paramecium is a genus of ciliated protozoans. They are characterized by their external covering of hair-like cilia. Cilia are structures for motility, and they continuously beat to enable movement. Paramecium are heterotrophic, and ingest food via an oral groove. Paramecium are found in freshwater and marine environments. Food vacuoles: Size: 240 x 80 µm. contain ingested food. Contractile Oral groove: vacuole lined with cilia to help move the food into the Cilia: hair-like base of the oral structures for groove. movement Food Nuclei: two types which carry out Anal pore: undigested different functions. contents of food vacuoles are released when they fuse with the cell membrane  Fungi The fungi is a large kingdom of eukaryotic organisms which includes the yeasts, molds, and fleshy fungi. Fungi can be unicellular or multicellular. Fungi have valuable economic roles in industry and are important as decomposers in food chains. All fungi are heterotrophic. For survival, they need: a source of nitrogen an organic carbon source such as cellulose growth factors such as vitamins some ions, e.g. magnesium and phosphorus temperature between 5°C and 25°C Water Oxygen (few are anaerobic) neutral to slightly acid pH  Single Celled Fungi Yeasts are an example of a single celled fungi. They are nonfilamentous, and typically oval or spherical in shape. Storage Budding cell Reproduction is by fission or budding. granule Yeasts are facultative Rough anaerobes, and used in endoplasmi c reticulum the brewing, wine making and baking industries. Nucleus Nucleolus Nuclear Golgi pore apparatus Vacuole Parent cell Mitochondria underground Filamentous Fungi Molds are multicellular, filamentous fungi. They are often divided by septa into uni-nucleate, cell-like units. When conditions are favorable, hyphae grow to form a filamentousSome mass called a mycelium. species have Rough hyphae divided by Nucleus endoplasmic crosswalls (septa) reticulum Vesicles Vacuole Rigid, chitinous cell Mitochondrion wall Golgi apparatus Fungal mycelium  Cell Sizes Most cells are between 1 and 100µm and visible only using a microscope. Cell size is very diverse, a range of cells is shown below to illustrate this. A virus (a non-cellular particle) is included for comparison. Eukaryotic cells e.g. plant, animal, and Human Parenchyma cell fungal cells white blood of flowering plant Size: 10-100 µm diameter. Cell cells organelles may be up to 10 µm.. Prokaryotic cells Size: typically 2-10 µm Length: 0.2-2 µm diameter Viruses Upper limit: 30 µm long Size: 0.02-0.25 µm(20- 250 nm)  Relative Sizes The following scale shows the size range of some representative cellular organelles, cells, and multicellular structures. The scale is logarithmic to accommodate the range of sizes shown. From left to right, each reference measurement marks a tenfold increase in diameter or length. Leaf tissue Plasma DNA Animal membrane cell Plant cell Golgi Ribosome Nucleus Leaf Biochemistry Version: 1.0 Introduction to Molecules Organism Tiger Living things can be organized into several different levels or tiers of structure. The most basic of these is the molecular level. Cellular level Heart muscle cells Organelle level Mitochondrion Molecular level Amino acid -lysine  Biological Molecules All objects are made up of millions of Water (H2O) molecules too small to see with the naked eye. molecules For example, a glass of water contains millions of water molecules. Esserals  Biological Molecules Water is not always pure, and may contain other molecules. When one or more substances are added together, a mixture is formed. zinwaterChlorineser sodium - I Na+ L Cl– Na+ Cl– Na+ Cl– Cl– Na+ This mixture contains salt (NaCl) and water (H2O).  j Types of Biological Molecules O T The molecules that make up living things can be grouped into five classes: not only meat ↑ Water Proteins Lipids Datama Nucleic acids Carbohydrates The Importance of Biological Molecules An understanding of the structure and function of biological molecules is necessary in many branches of biology, especially biochemistry, physiology, and molecular genetics.  Biological Formulae Biological molecules can be portrayed by: molecular formula structural formula Molecular Formula Structural Formula The molecular formula The structure of a molecule expresses the number of can be conveyed by a atoms in a molecule, but does molecular model. not convey its structure. C 3H 7O 2S This space filling model shows Molecular formula for the amino the structural formula for the acid cysteine amino acid cysteine Illustrating the Structure of Molecules Sticks Lines Spheres Surface Mesh Dots Ribbon Cartoon  Biological Formulae There are several ways of expressing a molecule’s structural formula. For example, glucose has the molecular formula C6H12O6. The structural formulae are: to draw don't have just recognize Space filling model β-D-glucose Structural formula α glucose (ring form) Structural formula (straight form) Ball and stick model Important Biological Molecules Carbon Biological molecules that contain carbon are said to be organic compounds. Most cellular material is organic. Hydrogen In addition to carbon, organic molecules commonly include atoms of oxygen and hydrogen. Nitrogen and sulfur are components of Oxygen organic molecules such as amino acids and nucleotides. Compounds that do not contain carbon Nitrogen are said to be inorganic molecules. Sulfur  Chemical Bonds Atom Chemical elements are able to form chemical bonds. These are linkages made between the atoms in molecules. Bonds act as a chemical glue to hold atoms together. Chemical bonds are formed when atoms share or transfer electrons. Bond The Structure of an Atom An understanding of an atom’s structure is required to understand how chemical bonds form. An atom comprises a nucleus orbited by negatively charged electrons. lections move e have The nucleus is made up of: can S Nucleus positively charged protons. neutrons, which have no charge. Neutron The diagram on the right depicts a sodium atom. Its nucleus contains: 11 positively charged protons Proton 12 neutrons (no charge). Eleven negatively charged electrons orbit the nucleus in three electron shells. Electron  Electron Shells Electron All atoms have electron shells. valency shell Each shell contains electrons, which orbit around the nucleus. The number of shells and number of electrons vary with the type of atom. The number of electrons in each shell can be calculated by: Nucleus 2n2 where n = the shell number In general, atoms are most stable when they have eight electrons in their outermost shell. sFable A sodium (Na) atom has 11 electrons The outer shell is called the within three electron shells: valency shell. 2 in the first shell 8 in the second shell 1 in the third shell  Chemical Bonds Atoms tend to lose or gain electrons until they have a stable configuration. Na Cl This can be illustrated by the formation of sodium chloride. Sodium and chloride atoms When sodium reacts with chloride, it releases the single electron in its valency shell to chloride. The sodium atom now has 10 electrons and the chloride atom Na+ Cl– now has 18 electrons. Both have eight electrons in their valency shells. Ionic bond The atoms now exists as ions, The sodium and chloride atoms have because they have each lost or taken on ionic forms, and have formed gained an electron. a chemical bond based on electrostatic attraction. The compound they form together is sodium chloride (NaCl). Covalent Bonds H H Covalent bonds form when electron pairs between two atoms are shared. H-H The number of electrons required to Two hydrogen atoms (above) each have complete an atom’s valency shell will one electron in their valency shell. They determine how many bonds an atom share an electron so the valency shell will form. has its full complement of two electrons. Only one covalent bond is possible The bonds are directional and determine the strength of the bond. Non-metals tend to form covalent bonds readily. A line is used to depict the covalent O O bond (e.g. H-H). Two oxygen atoms (right) form an oxygen molecule by sharing O=O two pairs of electrons. A double covalent bond (=) is formed. Ionic Bonds Ionic bonds result from the electrostatic attraction between two atoms of opposite charge. Na Cl When electrons are transferred between atoms, the atoms become charged ions. These take two forms: Cation: an ion with a positive charge (has lost an electron). Na+ Cl- Anion: an ion with a negative charge (has gained an electron). Ionic bond A transfer of electrons leaves the sodium with a net charge of +1 and the chloride with a net charge of -1. The ions are attracted together because of their opposite charge, and a sodium chloride (NaCl) crystal is formed (left).  Hydrogen Bonds used to start or stop reaction Hydrogen bonds involve at least one hydrogen atom. - A hydrogen atom covalently linked to an electronegative atom, is attracted O to another electronegative atom (often oxygen or nitrogen atoms). H H Hydrogen bond The formation of a water dimer* is an + + example of hydrogen bonding. A water molecule (H2O) has a slight positive charge on the hydrogens and a slight negative charge on the oxygen. Electrical attraction between the negative charge of one molecule and the positive charge of another results in formation of a hydrogen bond. Hydrogen bonding is also important in the A water dimer forms by hydrogen bonding between the formation of proteins and nucleic acids (e.g. DNA). positive and negative charges of two water molecules. *Dimer: a molecule composed of two identical subunits linked together Disulfide Bonds Stronger Protein chain A disulfide bond (or sulfur bridge) H H is a single covalent bond between two sulfur containing atoms. C SH HS C Disulfide bonds are important in H H the folding and stability of proteins. Cysteine Disulfide bonds occur between residues cysteine, a sulphur containing amino acid. H H C S S C H H Disulfide bond  Functional Groups Organic compounds usually comprise a carbon skeleton with reactive or functional groups attached. Functional groups are often involved in chemical reactions, and play an important role in the structure and function of the molecule. Cartoon courtesy of Nick Kim  Functional Groups Functional groups have definite Structural chemical properties that they retain Group Found in Formula not matter where they occur. Carbohydrates, Hydroxyl OH alcohols These functional groups determine the characteristics and chemical C Carbonyl Formaldehyde reactivity of molecules. For example: barelyused O Amino groups make a molecule · O more basic. Amino acids, Carboxyl C vinegar Carboxyl groups make a OH molecule more acidic. H Most chemical reactions that occur Amino N Ammonia in organisms involve the transfer of H a functional group as an intact unit Sulfhydryl Proteins, S H rubber from one molecule to another. O– Common biological functional Phospholipids, Phosphate O P O– nucleic acids, groups are shown in the table right: ATP O  Hydroxyl Group -OH H H Hydroxyl The hydroxyl group consists of an group oxygen atom joined by a single covalent bond to a hydrogen atom. H C C OH Organic molecules containing hydroxyl groups are alcohols. H H A metal hydroxide is formed when a hydroxyl group is joined to a metal (e.g. sodium hydroxide). Structural formula of ethanol, shown as a straight chain (top) and a space filling model (bottom). Carboxyl Group -COOH H O The carboxyl functional group consists of a carbon atom joined by covalent bonds to two oxygen atoms, H C C one of which in turn is covalently bonded to a hydrogen atom. H OH Organic molecules containing carboxyl groups are called carboxylic acids (organic acids). One valence electron on the carbon is available for bonding to another atom so that the carboxyl group can form part of a larger molecule. In this acetic acid molecule, the carboxyl group is highlighted.  Carbonyl Group -CO H H The carbonyl group is a O functional group composed of a Propanal is an carbon atom joined to an oxygen H C C C example of an atom by a double bond. aldehyde. If the carbonyl group occurs at H H H the end of a carbon molecule it is called an aldehyde. H O H H C C C H H H If the carbonyl group occurs within the carbon compound it is called a ketone. Acetone is an example of a ketone.  Amino Group -NH2 H O H A amino group consists of one nitrogen atom attached by covalent Amino bonds to two atoms of hydrogen. A C C N group lone valence electron on the nitrogen is available for bonding to HO H H another atom. Glycine (above, and space Organic molecules containing filling model below) is the amino groups are called amines. simplest amino acid Amines are weak bases. The amino group is common to all amino acids, which in turn are the building blocks of proteins.  Phosphate Group -PO3 A phosphate group composed of H O one phosphorous atom bound to OH OH four oxygen atoms. Organic molecules containing H C C C O P O– phosphate groups are called organic phosphates. The phosphate group is one of the H H H O– three components of nucleotides and often attached to proteins and other biological molecules. The phosphate group of this glycerol phosphate molecule A free phosphate ion in solution is shown in red. and is called inorganic phosphate (denoted Pi) to distinguish it from phosphates bound in molecules.  Macromolecules Carbohydrates Lipids Proteins Nucleic Acids Every time you need to know: how they are formed/broken down, their general structure (need to recognise them) and their functions. At the end you need to know the differences and simularities  Carbohydrates ex : glucose CH , 206 Carbohydrates are a family of organic molecules made up of carbon, hydrogen, and oxygen atoms. Some are small, simple molecules, while others form long polymers. Carbohydrates have the general formula (CH2O)x. Simple carbohydrates are generally called sugars.The most common Deoxyribose arrangements found in sugars are: Pentose, a five sided sugar, e.g. ribose and deoxyribose. 6 Hexose, a six sided sugar, e.g. glucose and fructose. A structural formula and Glucose 1 4 symbolic form are shown. In solution, these naturally form rings rather than straight chain structures.  Carbohydrates Carbohydrates are important as both energy storage molecules and as the structural elements in cells and tissues. The structure of carbohydrates is closely related to their functional properties. Sugars (mono-, di-, and trisaccharides) play a central role in energy storage. Carbohydrates are the major component of most plants (60-90% of dry weight). Weaving cloth Carbohydrates are used by humans as a cheap food source... Collecting thatch for roofing Carrying wood...housing and clothing. Cotton, linen, and coir are all made up of...and as a source of fuel,... cellulose, a carbohydrate polymer.  Monosaccharides gives energy to your body Monosaccharides are used as a primary energy source for fueling cellular metabolism. Monosaccharides are single-sugar molecules. They include: S glucose (grape sugar and blood sugar). C fructose (honey and fruit juices). Monosaccharides generally contain between three and seven carbon atoms in their carbon chains. The 6C hexose sugars occur most frequently. Glucose is a monosaccharide sugar. It occurs in two forms, the L- and D- forms. All monosaccharides are reducing The D-glucose molecule (above) can be sugars, meaning they can utilized by cells while the L-form cannot. participate in reduction reactions. our body can only use the D-form  Disaccharides Disaccharides are double-sugar molecules joined with a glycosidic bond. S They are used as energy sources and as building blocks for larger molecules. Disaccharides provide a convenient way to transport glucose. The type of disaccharide formed depends on the monomers (single units)involved and whether they are in their α- or β- form. Only a few disaccharides (e.g. lactose) are classified as reducing sugars. Disaccharides Sucrose alpha formconfiguration beta formation ↑ Components: α-glucose + β-fructose Source: A simple sugar found in plant sap. Maltose Components: α-glucose + α-glucose Source: Maltose is a product Juniper of starch hydrolysis and is sap found in germinating grains. Lactose Components: β-glucose + β-galactose A sucrose molecule (above) Source: Milk depicted as a stick molecule. Cellobiose Components: β-glucose + β-glucose Milk (right) contains the Source: Partial hydrolysis of cellulose. disaccharide, lactose. Polysaccharides - Cellulose Symbolic form of cellulose Cellulose is a glucose polymer. It is an Glucose monomer important structural material found in plants. It is made up of many unbranched β-glucose molecules chains of - held together by 1, 4 glycosidic links. 1,4 glycosidic bonds create Parallel chains are cross-linked by hydrogen unbranched chains bonds to form bundles called microfibrils. Cellulose microfibrils are very strong. They form a major structural component of plant cells, e.g. in the cell wall. made of cellulose The cellulose structure is shown (right) as a ball and stick model. Cellulose is repeating chains of β-glucose molecules.  broken down the mouth structured in by more Polysaccharides - Starch? T enzymes creates an energy reserve Symbolic form of amylopectin Starch is a polymer of glucose, made up α-glucose molecules. of long chains of↳ 1,6 glycosidic 1 1 bonds create Starch contains a mixture of:energy 4 6 branched chains 1 25-30% amylose: long unbranched 4 chains of many hundreds of glucose 6 linked by 1-4 glycosidic bonds. Oses Sugars =... 4 70-75% amylopectin: branched... ases = enzymes/proteins Starch granules chains with 1-6 glycosidic bonds every 23-30 glucose units. Starch is an energy storage molecule in plants. It is found concentrated in insoluble starch granules within plant cells. Photo: Brian Finerran Starch can be easily hydrolyzed to glucose when required. brokendown by - works on amyos are Polysaccharides - Glycogen Glycogen is chemically similar to amylopectin, but is more extensively branched. 1,6 bonds It is composed of α-glucose molecules, but there are more Symbolic form of glycogen 1,6 glycosidic links mixed with the 1,4 glycosidic links. Glycogen is the energy storage compound in animal tissues and in many fungi. It is more water soluble than starch and is found mainly in liver and muscle cells, which are both centers of high metabolic activity. Glycogen is readily hydrolyzed Glycogen is abundant in metabolically active tissues such as liver by enzymes to release glucose. (left) and skeletal muscle (right). The glycogen stains dark magenta.  Modified Polysaccharides Nitrogen containing NHCOCH3 NHCOCH3 6 group on each glucose 6 O O O O 5 3 2 5 3 2 4 1 4 1 4 1 4 1 3 2 5 O 3 2 5 O O NHCOCH3 6 NHCOCH3 6 Chitin is a tough modified polysaccharide made up of chains of β-glucose molecules. Structurally, it is almost the same as cellulose except that the -OH group at carbon atom 2 is replaced by a nitrogen-containing group (NH.CO.CH3). Chitin forms bundles of long parallel chains. The exoskeleton of an It is found in the cell walls of fungi and it is an insect is made of chitin essential component of the arthropod exoskeleton. Condensation & Hydrolysis p! Carbohydrate breakin, Carbohydrate condensation molecules hydrolysis ↓ Monosaccharides are joined H20 does it Compound sugars can be together to form broken down into their disaccharides and constituent polysaccharides. monosaccharides. Water is released in the A water molecule provides process. the hydrogen and hydroxyl groups required. Energy is supplied by a nucleotide sugar such as The reaction is catalyzed by ADP-glucose. enzymes. g hydrolysis O condensation Condensation & Hydrolysis 2 monosaccharides Condensation Hydrolysis reaction reaction t H2O enzymes t Disaccharide + H2O O enzymes (ex amylase) · Glycosidic bond condensation : H2o is released comes from monosaccharides H20 is gained during hydrolosis -> creates energy  Condensation & Hydrolysis 2 α-glucose molecules Condensation Hydrolysis H2 O Maltose molecule Glycosidic bond  Lipids Lipids are a group of organic compounds with an oily, greasy, or waxy consistency. Like carbohydrates, lipids contain carbon, hydrogen, and oxygen, but in lipids, the proportion of oxygen is much smaller. They are relatively insoluble in water and tend to be hydrophobic (water repellent). Lipids are soluble in organic solvents such as ethanol and ether. Typical lipids, e.g. neutral fats, consist of fatty acids and glycerol (below). H O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 H Glycerol Three fatty acids  Lipids Lipids can be classified as: 1) simple lipids: fats, oils, and waxes. 2) phospholipids and related molecules. Plasma membrane 3) steroids Lipids have many roles, including as: Phospholipids are the primary structural 1) biological fuels component of all cellular membranes, such as the plasma membrane (false color TEM above). 3) hormones Dept. Biological Sciences, University of Delaware 2) structural components of membranes keeps Fats provide twice as much energy as carbohydrates. Fat cell heat in your body Capillary Fats and oils are not macromolecules but, because of their hydrophobic properties, they aggregate into globules. Proteins and carbohydrates can be converted Lipids are often stored in special adipose into fats stored in adipose tissue. tissue, within large fat cells (above). Biological Roles of Lipids Mitochondrion (false color TEM) Lipids are concentrated sources of energy and can be broken down (through fatty acid oxidation in the Waxes and oils, when mitochondria) to provide fuel secreted on to surfaces for aerobic respiration provide waterproofing in plants and animals. Phospholipids form the structural framework of cellular membranes, e.g. the plasma membrane (above).  Biological Roles of Lipids The white fat tissue (arrows) is visible in this ox kidney Fat absorbs shocks. Organs that are prone to bumps and shocks (e.g. kidneys) are cushioned with a relatively thick layer of fat. Lipids are a source of metabolic water. During respiration, stored lipids are metabolized for energy, producing water and carbon dioxide. Stored lipids provide insulation in extreme environments. Increased body fat levels in winter reduce heat losses to the environment.  Fats and Oils The most common lipids in living things are the neutral fats. They make up the fats and oils found in plants and animals. Fats and oils are formed by condensation reactions between fatty acids and glycerol to form ester links (–COO–). One fatty acid = monoglyceride Two fatty acids = diglyceride Globules of fat or oil are Three fatty acids = triglyceride or triacylglycerol. compact and relatively inert Triacylglycerols are the most common of these. Water is lost to form an ester bond H O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 O H C OH OH C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 H Glycerol Three fatty acids  Fats and Oils The difference between fats and oils Oils are liquid at room temperature, while fats is their physical state at 20°C. are solid Fats are solid at 20°C. Oils are liquid at 20°C These differences in the physical properties of fats and oils are a result of the type of fatty acid attached to the glycerol molecule. The fatty acids making up triacylglycerols are long unbranched hydrocarbon chains Palmitic acid: a saturated fatty acid (CH3(CH2)n –), ending with a carboxylic acid (–COOH). Some are saturated fatty acids, with a maximum number of hydrogen atoms. Some are unsaturated, with double Linoleic acid: a saturated fatty acid bonds and fewer hydrogen atoms.  Saturated Fatty Acids Saturated fatty acids contain the maximum number of hydrogen atoms. They do not contain any double bonds or other functional groups along the chain. Saturated fatty acids form straight chains. Lipids containing a high proportion of saturated fatty acids tend to be solids at room temperature, i.e. fats, such as butter and lard. O H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H Palmitic acid is a saturated fatty acid. All of the spaces on the carbon bonds are filled by hydrogens, which results in a straight chain molecule, as shown in the space filling model (right).  Unsaturated Fatty Acids easier to break down Unsaturated fatty acids contain some carbon atoms that are double-bonded with each other (all of the spaces are not taken by hydrogen atoms). Lipids with a high proportion of unsaturated fatty acids are oils and tend to be liquid at room temperature. The unsaturated nature causes kinks in the straight chains. When aligned in a lipid molecule, the kinked fatty acids do not pack in closely together; hence the more fluid structure of oils. O H H H H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H Linoleic acid is an unsaturated fatty acid. The double bonds between the carbon atoms prevent bonds to hydrogen. The double bonds produce a kink in the chain as shown on the space filling model (right). Kink  Phospholipids If one of the fatty acid groups of a triacylglyerol is replaced by a phosphate group, the the molecule is known as a phospholipid. A phospholipid consists of: a glycerol molecule two fatty acid chains # a phosphate (PO43-) group (ionised under the conditions in cells) H2C Nonpolar, COO hydrocarbon tails of two fatty acids condensed with HC COO glycerol O– H2C O P O– O Fatty acid Glycerol Fatty acid Phosphate group from phosphoric acid (HPO4) condenses with the Symbolic representation third -OH of glycerol PO43- of a phospholipid  Phospholipids - The phosphate end of the molecule is polar and attracted to water (hydrophilic) while the fatty acid end is non-polar and is repelled (hydrophobic). => As a result, phospholipids naturally form a bilayer with the hydrophobic ends orientated inwards. The phospholipid bilayer forms the main component of cellular membranes. Glycerol and phosphate ‘head’: the hydrophilic Theerd part of the molecule -tail Hydrocarbon tail: hydrophobic part of ↑ the molecule. doesn't like water can't dissolve in water Steroids The basic structure of a steroid(shown symbolically above) ↑ is three six carbon atom rings, and Steroids are classified as lipids, but their one five carbon atom ring. structure is quite different from that of other lipids. The basic structure of a steroids is: three 6 carbon atom rings one 5 carbon atom ring. Examples of steroids include: sex hormones (testosterone and estrogen) hormones such as cortisol and aldosterone cholesterol is a sterol lipid and is a precursor to several steroid hormones. Steroid sex hormones are responsible for both primary and secondary sexual characteristics in males and females.  Lipid Condensation and hydrolysis Water is lost to form an ester bond Triacylglycerols (also called H O triglycerides) form when glycerol H C O H OH C CH2 CH2 CH2.............CH3 bonds with three fatty acids. O Glycerol is an alcohol H C O H + OH C CH2 CH2 CH2.............CH3 containing three carbons. O H C O H OH C CH2 CH2 CH2.............CH3 Each carbon is bonded to a hydroxyl (–OH) group. H Glycerol Three fatty acids When glycerol bonds with the fatty acid, an ester bond is H O formed and water is released. ↑ H C O C CH2 CH2 CH2.............CH3 + H2 O Three separate condensation O reactions are involved in H C O C CH2 CH2 CH2.............CH3 + H2 O producing a triglyceride. O H C O C CH2 CH2 CH2.............CH3 + H2 O ⑧ H Triacylglycerol (triglyceride) Water  Introduction to Nucleic Acids Nucleic acids are biochemical macromolecules involved with the transmission of inherited information. There are two main types of nucleic acids involved with inheritance: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Nucleic acids are polymers made up of many units ↓ called nucleotides. consists of nucleotides DNA (space filling model right) is the most commonly occurring nucleic acid.  Nucleotides A nucl