Surface-to-volume ratio The bigger a cell is, the less surface area there is per unit volume Above a certain size, material cannot be moved in or out of cell fast enough Surface-to-Volume Ratio 4.2 How we see cells EARLY DISCOVERIES Mid 1600s - Robert Hookecork cells Late 1600s - Antony van Leeuwenhoekprotists, bacteria, sperm cells 1820s - Robert Brownplant cell nucleus Developing Cell Theory (mid 1800s) Matthias Schleidenplant tissue is composed of cells Theodor Schwannanimal tissue is composed of cells Rudolf Virchowall cells come from other cells Cell Theory 1) All life is composed of cells 2) Cell is smallest unit having properties of life 3) New cells come from previously existing cells Microscopes Light microscopes Simple Compound Electron microscopes Transmission EM Scanning EM Light Microscopes Living samples Natural color - Can resolve objects down to about 200 nm Electron Microscopy Uses streams of accelerated electrons rather than light Electrons are focused by magnets rather than glass lenses Can resolve structures down to 0.5 nm - Samples are dead Black-and-white images Transmission vs.
Microfilaments Microtubules found in cilia and flagella Microfilaments are found in pseudopods Cilia and Flagella Ciliashort, usually numerous hair-like projections that undulate Ex: Paramecium, human respiratory tract Flagellalonger, usually fewer whip-like projections Ex: Euglena, sperm cells All eukaryotic cilia and flagella have the same 9 2 structure of microtubulesevidence for evolution Pseudopods Temporary, irregular lobes that project from the cell and function in locomotion and prey capture Have microfilaments Ex: Amoeba How Cells Work Chapter 5 5.1 What Is Energy?
Scientists gather information about the things they plan to study Quaking aspen (Populus tremuloides) Herbivoresanimals that eat plants -forest tent caterpillar -large aspen tortrix -gypsy moth caterpillar Chemicals in aspen leaves Phenolic glycosides A caterpillars taste test Scientists predict what will happen in their experiments Different aspen trees have different amounts of chemicals that taste bad to caterpillars.
Aspen trees that dont get eaten by caterpillars grow more than aspen that do get eaten.
Made from amino acids Amino Acids Amino group Carboxyl group R group20 R groups, one for each different amino acid Protein Synthesis Protein is a chain of amino acids l 3.4 Proteins Very diverse Important for structure, nutrition, enzymatic reactions, cell communication.
Made from amino acids Amino Acids Amino group Carboxyl group R group20 R groups, one for each different amino acid Protein Synthesis Protein is a chain of amino acids linked by peptide bonds Peptide bond Type of covalent bond Forms through condensation reaction Primary Structure Sequence of amino acids Unique for each protein Two linked amino acids = dipeptide Three or more = polypeptide Primary Structure & Protein Shape Primary structure influences protein shape: H bonding between different amino acids R group interaction Secondary Structure Hydrogen bonds form between different parts of polypeptide chain These bonds give rise to coils (helices) or pleated sheets Examples of Secondary Structure Tertiary Structure Folding and coiling as a result of interactions between R groups Quaternary Structure Some proteins are made up of more than one polypeptide chain Polypeptides With Attached Organic Compounds Lipoproteins Proteins combined with fats Glycoproteins Proteins combined with sugars 3.5 Importance of Protein Structure The substitution of one amino acid (valine for glutamate) changes the shape of red blood cells and results in sickle-cell anemia.
2.2 Radioisotopes Isotopetwo or more forms of an element that differ in neutron number. Radioisotopes Used as tracers in experiments Used medicinally 2.3 Electrons and energy levels Electrons occupy orbitals.