Download Basic Biochemistry

BASIC BIOCHEMISTRY
Chemical Bonding
1. Covalent Bond - strong bond,
formed by sharing of 2 or more
electrons

Example: C6H12O6 & any organic
molecules
2. Ionic Bond – formed by the
transfer of 1 or more electrons



Example: NaCl & MgCl2
Cation – positive
Anion - negative
…
3. Hydrogen Bonding – weak bond formed by
hydrogen w/i a molecule being attracted by
oxygen & nitrogen w/i a molecule

Important in DNA and proteins
Macromolecules of Life
Abundance in a cell:
 Proteins (55%)
 Nucleic acids (24%)
 Lipids (9%)
 Carbohydrates (5%)
 Lipopolysacharides (3%)
 Other (4%) = inorganics
Question: How Are
Macromolecules
Formed?
Answer: Dehydration Synthesis
 Also called “condensation reaction”
 Forms polymers by combining
monomers by “removing water”.
HO
H
HO
H
H2O
HO
H
Question: How are
Macromolecules
separated or
digested?
Answer:
Hydrolysis
 Separates monomers by “adding
water”
HO
H
H2O
HO
H
HO
H
Lipids
 Any biological molecule that has low solubility
in water & high solubility in nonpolar organic
solvents
 Hydrophobic; thus they are good barriers for
aqueous environments
 6 major groups:






Fatty acids
Tricylglycerols
Phopholipids
Glycolipids
Steroids
Terpenes
Lipids … Fatty Acids
 Building blocks for most complex lipids
 Long chains with a carboxylic acid at 1 end
 Can be saturated or unsaturated
 Saturated only single C-C bonds
 Unsaturated has one or more C=C (double bond)
 Oxidation gives huge amounts of chemical
energy for a cell
Lipids … Triacylglycerols
 A.K.A. triglycerides, fats, or oils
 Have a 3 Carbon backbone
(glycerol) that’s attached to 3
fatty acids
 Function is to store energy,
thermal insulation, and padding
to an organism
 Adipocytes (fat cells) contain
almost nothing but triglycerides
Lipids … Phospholipids
 Glycerol
backbone
with one of
the fatty acids
replaced by a
polar
phosphate
group
 Major
component of
membranes
 Amphipathic
Lipids … Glycolipids
 Phospholipid with one or
more carbohydrates
attached to glycerol
rather than phosphate
 Also amphipathic
 Found in the membranes
of myelinated cells of the
nervous system
Lipids … Steroids & Terpenes
Steroids
Terpenes
 4-ringed structure
 Includes vitamin A
 Includes hormones,
vitamin D, & cholesterol
(important for vision)
 Lipids are transported by lipoproteins in the
blood
 Classified by their density: (the greater the
ratio of lipid to protein, the lower the density)
 Very low density lipoproteins (VLDL)
 Low density proteins (LDL) – ‘bad cholesterol’
 High density lipoproteins (HDL) – ‘good
cholesterol’
Proteins
 Building block is amino acids linked together
by a peptide bond
 AKA polypeptides
 Nearly all protein in all species are built from
the same 20 amino acids
 10 are essential (ingested rather than
manufactured by body)
 Side chains differ from amino acid to amino
acid
Protein Structure
Primary Structure
 Number and sequence of
amino acids in a polypeptide
Secondary Structure
 Single chain can twist into an
α-helix or β-pleated sheets
 Both are reinforced with Hbonds between amino acids
Protein Structure…
Tertiary Structure
 3-D shape formed when
the peptide chain curls
and folds
 Created by 5 forces:
 Covalent disulfide bonds




b/w cysteine
Electrostatic ionic
interactions (acidic & basic)
Hydrogen bond
Van der Waals forces
Hydrophobic side chains
push away from water
toward center
Quaternary Structure
Protein Structure…
Quaternary Structure
 2 or more polypeptide
chains bond together
 Same 5 forces as tertiary
 A denatured protein has lost secondary,
tertiary, and quaternary structure
 Protein can sometimes form back when
denaturing agent is removed
 2 main functions of proteins:
 Structural (cell wall)
 Functional (enzymes)
 2 main types of proteins:
 Globular (functional)
 Enzymes
 Hormones
 Membrane pumps & channels
 Membrane receptors
 Intercellular and intracellular transport and storage
 Osmotic regulators
 Etc.
 Structural – maintain and add strength to cells
 Ex. Collagen
…
 Central Dogma
DNA → RNA → protein
↑
transcription
Genotype
↑
translation
Phenotype
Carbohydrates
 AKA sugars or saccharides
 Glucose accounts for 80% of carbs absorbed
by humans
 Liver converts most carbs to glucose
 Glucose turned to ATP during cellular respiration
 If cell has enough ATP, the glucose is turned to
glycogen (only animals) or fat
 Most cells absorb glucose via facilitated
diffusion – insulin increases absorption rate
 Plants form cellulose and starch from glucose
Carbohydrates …
 Building blocks are simple sugars
(monosaccharides)
 glucose, ribose, etc
 Cell wall constituents (peptidoglycan)
 Cell recognition factors in membranes
 lipopolysaccharides
 Serves as high energy storage compounds
(glycogen)
 Serve as bacterial ‘food’ (chemoheterotrophs)
2 monosaccharides make a disaccharide
Monomer to disaccharide to polysaccharide
Nucleic Acids
 Building blocks are nucleotides:
 5-C Sugar, phosphate group, & nitrogen base
 Nitogen bases: adenine, cytosine, guanine, thymine,
uracil (a=t) & (c=g) & (a=u)
 Nucleotides joined by phosphodiester bonds
 Examples of nucleic acids include DNA, RNA,
ATP, NADH, FADH2
 DNA is written 5’ to 3’
 Functions – information storage
 RNA has multiple functions:
 mRNA – RNA copy of DNA
 rRNA – part of ribosome, helps to make proteins
 tRNA – carries amino acids to ribosome
Pop Quiz
1. A molecule of DNA contains all of the following
except:
a)
b)
c)
d)
Deoxyribose sugars
Polypeptide bonds
Phophodiester bonds
Nitrogenous bases
2. Which of the following is a carbohydrate polymer
that is stored in plants and digestible by animals?
a)
b)
c)
d)
Starch
Glycogen
Cellulose
Glucose
…cont.
3. Excessive amounts of nitrogen are found in the urine
of an individual who has experienced a period of
extended fasting. This is most likely due to:
a)
b)
c)
d)
Glycogenolysis of the liver
The breakdown of body proteins
Lipolysis in adipose tissue
A tumor on the posterior pituitary causing excessive ADH
secretion
4. Metabolism of carbohydrate and fat spare protein
tissue. All of the following are true of fats except:
Fats may be used in cell structure
Fats may be used as hormones
Fats are more efficient form of energy storage than
proteins
d) Fats are less efficient form of energy storage than proteins
a)
b)
c)
… cont.
5. Which of the following is found in the RNA
but not the DNA of a living cell?
a) Thymine
b) Double helix
c) An additional hydroxyl group
d) Hydrogen bonds
Answers
1. B
2. A
3. B
4. C
5. C