Download BIOL241cell2JUN2012

25/06/12 (Bio)Chemistry and
Cytology
BIOL241
Introduction or Recap of Cell
Structure & chemistry
INTERCONNECTEDNESS •  Ma*er and Energy •  Atoms, molecules, and chemical bonds •  Importance of organic and inorganic nutrients and metabolites •  Structure and funcBon of carbohydrates, lipids, proteins, and nucleic acids •  Enzymes and ATP help run the metabolic reacBons of the body Energy
•  The capacity to do work (put matter into
motion)
•  Types of energy
– Kinetic – energy in action
– Potential – energy of position; stored
(inactive) energy: chemical energy
•  Energy is easily converted from one form
to another
•  During conversion, some energy is “lost”
as heat
1 25/06/12 Chemistry
•  Chemistry is the science that deals with
matter
•  Matter is anything that takes up space and
has mass
•  Smallest stable units of mass are atoms
But I thought this was biology?
• 
• 
• 
• 
MathemaBcs (the language of science) Physics (the structure of ma*er & energy) Chemistry (organic and inorganic structure) Biology: uses them all to understand Life. Atoms, Elements, Molecules
•  Elements are atoms of one particular
type (see the periodic table)
•  Molecules are groups of atoms that
(usually) contain more than one
element
è 2 25/06/12 Biologically significant elements
•  13 principal elements
–  Carbon (C)
–  Oxygen (O)
–  Hydrogen (H)
–  Nitrogen (N)
–  Calcium (Ca), phosphorus (P), potassium (K),
Sulphur (S), sodium (Na), chlorine (Cl),
magnesium (Mg), iodine (I), and iron (Fe)
•  13 trace elements
–  (e.g. zinc, manganese)
Atoms with unfilled electron
shells are reactive
•  Octet Rule
•  To become stable they form chemical bonds. •  Three main types of chemical bonds –  Intramolecular: •  Ionic bonds (charged atoms resulBng from the gain or loss of electrons) •  Covalent bonds (electrons are shared) –  Intermolecular •  Hydrogen bonds Covalent & Ionic Bonds
•  Molecules: atoms held together by
covalent bonds
•  Salts: molecules held together by ionic
bonds
Q: What are the strongest type of bonds?
3 25/06/12 H 2O
The body is mostly water (~2/3rd of total
body weight) so all chemical reactions in
the body occur in water
Covalent bonds are much stronger than
ionic bonds in water
H2O – “Special” Properties •  Water can dissolve organic and
inorganic molecules making a solution
•  Water is needed for chemical reactions
•  Water absorbs and retains heat
•  Water is an effective lubricant
H2O •  What is it about water that makes it so
special?
•  Water has all these amazing properBes due to its molecule’s ability to form hydrogen bonds 4 25/06/12 H-bonds b/t + & - charges
Mixtures and Solutions
•  Mixtures – two or more components physically
intermixed (not chemically bonded)
–  Solutions – homogeneous mixtures of components
–  Colloids (emulsions) – heterogeneous mixtures
whose solutes do not settle out
–  Suspensions – heterogeneous mixtures with visible
solutes that tend to settle out
Essen5al Molecules •  Nutrients:
–  essential molecules obtained from food (you
have to eat them to get them)
•  Metabolites:
–  molecules made or broken down in the body
5 25/06/12 Organic vs. inorganic
Organic molecules: •  Always contain carbon with hydrogen, and someBmes oxygen •  OUen soluble in water Inorganic: Electrolytes, minerals, and compounds that do not contain carbon with hydrogen. •  Important examples: oxygen, carbon dioxide, water, inorganic acids and bases, salts Vitamins and Minerals
•  Vitamins and minerals are essenBal nutrients that are required in very small amounts for healthy growth and development. Examples? •  They cannot be synthesized by the body and are essenBal components of the diet. Vitamins
•  Organic substances necessary for metabolism •  There are 13 known vitamins (e.g. A, B1, D, K) •  Some are fat soluble while others are water soluble •  Are Coenzymes that help carry out the reacBons of metabolism 6 25/06/12 Minerals
•  Inorganic compound (oUen salts or elements) necessary for proper body funcBon •  Can be bulk or trace minerals •  Are Cofactors in metabolic reacBons Electrolytes
•  Inorganic ions (usually minerals) that conduct electricity in soluBon •  Electrolyte balance is maintained in all body fluids; imbalance seriously disturbs vital body funcBons Electrolytes
Table 2–3
7 25/06/12 Biological Macromolecules •  Life depends on four types of organic macromolecules: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic acids Can you think of an example of each? 1. Carbohydrates
•  Contain carbon, hydrogen and oxygen in a raBo of 1:2:1 •  Account for less that 1% of body weight •  Used as energy source •  Called saccharides (sugars, starches) Glucose is a monosaccharide 8 25/06/12 Disaccharides Sucrose Lactose Polysaccharides •  Starch •  Glycogen •  Cellulose All are long strings of glucose molecules Difference lies in how they are bonded together Polysaccharides •  Polysaccharides or polymers of simple sugars PLAY Polysaccharides
Figure 2.14c 9 25/06/12 Polymers •  A polymer is any molecule made up of several repeaBng units. Starch is a polymer of glucose. 2. Lipids
•  Contain carbon, hydrogen, and oxygen but the raBo of C:H is 1:2 (much less O) •  May also contain other elements, phosphorous, nitrogen, and sulfur •  Form essenBal structures in cells •  Are important energy stores Lipids: Triglycerides (Fats and Oils) •  Consist of 3 fa*y acids and glycerol –  InsulaBon –  Energy –  protecBon Q: What’s the difference between saturated and unsaturated? 10 25/06/12 Lipids: Steroids and Cholesterol •  All consist of a complex ring structure Lipids: Phospholipids Amphipathic 3. Proteins
•  Consist of chains of amino acids liked together by pepBde bonds •  Enzymes are proteins 11 25/06/12 Protein Structure
•  Proteins are the most abundant and important organic molecules •  Basic elements: –  carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) •  Basic building blocks: –  20 amino acids Protein Structure – 4 levels
Primary: amino acid sequence Secondary: Hydrogen bonds form spirals or pleats (α-helix, β-sheet) TerBary: Secondary structure folds into a unique shape Quaternary: several terBary structures together: again: Shape!! Figure 2–20a
Protein structure 12 25/06/12 Shape and Function
•  Protein funcBon is based on shape •  Shape is based on sequence of amino acids •  Denatura5on: –  loss of shape and funcBon (due to heat, pH change or other factors) Protein FuncBons –  support: •  structural proteins –  movement: •  contracBle proteins –  transport: •  transport proteins –  buffering: regulaBon of pH –  metabolic regulaBon: •  enzymes –  coordinaBon and control: •  hormones –  defense: •  anBbodies AcBvaBon Energy •  Chemical reacBons in cells cannot start without help •  AcBvaBon energy gets a reacBon started Figure 2–7
13 25/06/12 CharacterisBcs of Enzymes Figure 2.20 Energy In, Energy Out •  Exergonic reacBons: –  produce more energy than they use •  Endergonic reacBons: –  use more energy than they produce KEY CONCEPT •  Most chemical reacBons that sustain life cannot occur unless the right enzymes are present 14 25/06/12 How Enzymes Work •  Substrates: –  reactants in enzymaBc reacBons •  AcBve site: –  a locaBon on an enzyme that fits a parBcular substrate Ac5ve site Amino acids + How Enzymes Work Enzyme (E) Substrates (S) Enzyme-­‐substrate complex (E-­‐S) H2O Free enzyme (E) Pep5de bond Internal rearrangements leading to catalysis DipepAde product (P) Figure 2–21
4. Nucleic acids
•  Contain C, H, O, N,
and P
•  DNA and RNA are
nucleic acids
•  Nucleotide consists
of
–  Sugar
–  Phosphate group
–  Nitrogenous base
15 25/06/12 Structure of DNA Figure 2.22b A nucleoBde: ATP
•  Energy storage for
cells
•  Many enzymes use
ATP
•  Provides a way to
run reactions that
are otherwise
endergonic
(require energy)
Membrane protein Pi P ATP is the
energy currency
of the cell
Solute Solute transported (a) Transport work ADP + Pi ATP Relaxed smooth muscle cell Contracted smooth muscle cell (b) Mechanical work Pi X P X Y + Y Reactants Product made (c) Chemical work Figure 2.24 16 25/06/12 Compounds Important
to Physiology
Table 2–8
Summary
•  Energy and matter
•  Atoms, molecules, and chemical bonds
•  Importance of organic and inorganic
nutrients and metabolites
•  Structure and function of
carbohydrates, lipids, proteins, and
nucleic acids
•  Enzymes and ATP help run the
metabolic reactions of the body 17