BSC 2010 UNIT TWO EXAM Chapter 5 Lipids Functions of Lipids 1 Structural cell membranes composed of lipids 2 Information signaling molecules hormones 3 Energy storage fat storage adipose tissue Lipids are a diverse group of hydrophobic molecules Fats acids carbon Lipids are the one class of large biological molecules that do not form polymers The unifying feature of lipids is having little or no affinity for water Lipids are hydrophobic because they consist mostly of hydrocarbons which form nonpolar covalent bonds The most biologically important lipids are fats phospholipids and steroids Fats are constructed from two types of smaller molecules glycerol and fatty Glycerol is a three carbon alcohol with a hydroxyl group attached to each A fatty acid consists of a carboxyl group attached to a long carbon skeleton Connected by ester linkages Micelle Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats Form micelles tails inside polar heads sticking out Fatty acids vary in length number of carbons and in the number and Saturated fatty acids have the maximum number of hydrogen atoms locations of double bonds possible and no double bonds Unsaturated fatty acids have one or more double bonds Saturated fats are solid at room temperature Most animal fats are saturated Fats made from unsaturated fatty acids are called unsaturated fats or oils and are liquid at room temperature Plant fats and fish fats are usually unsaturated Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen to prevent rancidity Hydrogenating vegetable oils also creates unsaturated fats with trans double These trans fats may contribute more than saturated fats to cardiovascular bonds disease The major function of fats is energy storage Humans and other mammals store their fat in adipose cells Adipose tissue also cushions vital organs and insulates the body Phospholipids In a phospholipid two fatty acids and a phosphate group are attached to glycerol The two fatty acid tails are hydrophobic but the phosphate group and its attachments form a hydrophilic head Phospholipids and Membranes When phospholipids are added to water they self assemble into a bilayer with the hydrophobic tails pointing toward the interior Phospholipids are the major component of all cell membranes Steroids Steroids are lipids characterized by a carbon skeleton consisting of four fused rings Cholesterol an important steroid is a component in animal cell membranes Although cholesterol is essential in animals high levels in the blood may contribute to cardiovascular disease Chapter Six Part One The Cell Theory Cells as the Fundamental Units of Life Theodor Schwann and Matthias Schleiden 1838 The cell is the unit of structure physiology and organization in living thins Cells have a dual identity as a distinct entity and a building block in the construction of organisms Cells form by free cell formation WRONG o We now know this last statement to be incorrect Modern Principles of Cell Theory All organisms are made of cells The cell is the simplest collection of matter that can live functional unit of all living things Cell structure is correlated to cellular function All cells come from preexisting cells by division and contain hereditary information Microscopy 1663 Robert Hooke discovered cells in a piece of cork with primitive microscope compound microscope 1670s Anton von Leeuwenhoek single lens microscope to observe bacteria and protozoa The quality of an image depends on Magnification the ratio of an object s image size to its real size Resolution the measure of the clarity of the image or the minimum distance of two distinguishable points Contrast visible differences in parts of the sample In a light microscope LM visible light passes through a specimen and then through glass lenses which magnify the image Electron Microscopes Scanning electron microscopes SEMs focus a beam of electrons onto the surface of a specimen providing images that look 3 D Transmission electron microscopes TEMs focus a beam of electrons through a specimen Cell Fractionation TEMs are used mainly to study the internal structure of cells Cell fractionation takes cells apart and separates the major organelles from one another Ultracentrifuges fractionate cells into their component parts Cell fractionation enables scientists to determine the functions of organelles Cell Structure The basic structural and functional unit of every organism is one of two types of cells prokaryotic or eukaryotic Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists fungi animals and plants all consist of eukaryotic cells Eukaryotic cells are compartmentalized Comparing Prokaryotic and Eukaryotic Basic features of all cells Plasma membrane Semifluid substance called cytosol Chromosomes carry genes Ribosomes make proteins Prokaryotic Cells No nucleus DNA in an unbound region called the nucleoid No membrane bound organelles Cytoplasm bound by the plasma membrane Eukaryotic Cells DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane bound organelles Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells The plasma membrane is a selective barrier that allows every cell phospholipids sufficient passage of oxygen nutrients and waste to service the volume of The general structure of a biological membrane is a double layer of The Cell A Living Unit Greater Than the Sum of Its Parts Cells rely on the integration of structures and organelles in order to function For example a macrophage s ability to destroy bacteria involves the whole cell coordinating components such as the cytoskeleton lysosomes and plasma membrane Cell Size is Limited The logistics of carrying out cellular metabolism sets limits on the size of The surface area to volume ratio of a cells cell is critical As the surface area increases by a factor of n2 the volume increases by a factor of n3 Small cells have a greater surface area relative to volume The Nucleus Information Central The nucleus contains most of the cell s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus separating it from the cytoplasm lipid bilayer The nuclear membrane is a double membrane each membrane consists of a Pores regulate the entry and exit of molecules from the nucleus The shape of the nucleus is
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