section 5: molecules of life - macromolecules - biology...
TRANSCRIPT
Section 5: Molecules of Life - Macromolecules
Organic molecules – contain carbon and hydrogen atoms
A) Type of macromolecules
4 types:
Name subunit
Carbohydrates monosaccharides
Lipids Glycerol + 3 fatty acids
Proteins Amino acids
Nucleic acids nucleotides
B) Chemical reactions -forms macromolecules and takes them apart:
Dehydration synthesis
Subunits + subunit macromolecule + H2O
Hydrolysis
Dehydration synthesis -making macromolecules from subunits - Water is
given off
Hydrolysis – macromolecules break apart in presence of water to re-form
subunits
C) Carbohydrates
i. Why group these molecules?
Characterized by presence of this molecule grouping
H – C – OH (CHO)
Ratio of H to O is approximately 2 to 1 – same as with H2O (water) so
that’s why they are called hydrates of carbon – carbohydrates
ii. Function
used for quick and short term energy storage in cells.
iii. Types of carbohydrates
1. Simple carbohydrates
a. Monosaccharides – 3 to 7 carbons (1
ring) i.e.; glucose –6 carbon sugar
b. Disaccharides – 2 monosaccharides joined
together by dehydration
Synthesis ie. Maltose
2. Complex carbohydrates (aka polysaccharides)
More than 2 sugar molecules joined together
Macromolecules such as starch, glycogen, and cellulose contain many
1000’s of glucose units
Starch – from plant material, stored glucose units
Glycogen – from animal material, stored in liver by animals for short
term storage of glucose between meals
D) Lipids
i. Why group these molecules?
Do not dissolve in water - hydrophobic
ii. Function
Diverse functions
Some as hi energy storage molecules -more energy/gram than any other
macromolecule
Phospholipids –cell membranes
steroids –diverse function including hormones
iii. Types of Lipids
1. Fats and Oils
2. Phospholipids
3. Steroids
1. Fats and Oils
Composition:
Composed of glycerol + 3 fatty acids Lipid
Alcohol molecule long chain hydrocarbons with COOH
(organic acid)
+
=
also called triglyceride
Function:
Long term energy storage
Insulates against heat loss
Protective cushion around major organs
Fatty Acid types in Fats and Oils
Saturated
No double bonds between carbon atoms
Associated with cardiovascular disease because causes plaque buildup in
arteries
Unsaturated
double bonds between carbon atoms in carbon chain (wherever the # of H
is less than 2 per carbon)
Polyunsaturated fats
many double bonds between carbon atoms in carbon chain
Trans fats
chemically hydrogenated oils - semi solid - unhealthy
2. Phospholipids
Composition:
**important in forming cell membranes
Because polar hydrophilic (water loving) head and nonpolar
hydrophobic (water hating) tails: form spontaneous bilayer
in water
Bilayer (=2 layers)
Hydrophobic tails face inward and form hydrophobic interior
Hydrophilic heads face outwards towards H2O
3. Steroids
Specialized lipids with backbone of 4 fused carbon rings – the functional
group that is attached to this backbone is what makes each steroid
different from each other.
Several functions, mainly hormonal ie, testosterone and estrogen
Affect 2o sexual characteristics
E) Proteins -
essential in the structure and function of our cells.
i. Why group these molecules?
a name to describe a group of macromolecules with a certain structure (to
be described below) – with varied functions.
ii. Function
1. Support: structural proteins i.e., keratin, collagen, and elastin. Keratins
strengthen protective coverings such as hair, quills, feathers, horns, and
beaks. Collagens and elastin provide support for connective tissues such as
tendons and ligaments.
2. Enzymes: provides location for reactants to come together and speed up
chemical reactions in cells: often referred to as catalysts because they
speed up chemical reactions. i.e, lactase and pepsin. Lactase breaks down the
sugar lactose found in milk. Pepsin is a digestive enzyme that works in the
stomach to break down proteins in food.
3. Transport: channel and carrier proteins in plasma membrane allow transport
of ions and molecules into and out of cells. –i.e., carrier proteins move
Amino group
Acid group
R stands for the functional group – this is the part that is different for each amino acid – there are 20 different types of aa in humans
molecules from one place to another in the body. i.e hemoglobin – carries
oxygen in blood
4. Defence: antibodies formed by immune system combine with antigens: involved
in defending the body from antigens (foreign invaders). One way antibodies
destroy antigens is by immobilizing them so that they can be destroyed by
WBC.
5. Hormones: regulatory proteins: messenger proteins which help coordinate
certain bodily activities. i.e, insulin, oxytocin, and somatotropin. Insulin
regulates glucose metabolism by controlling the blood-sugar concentration.
Oxytocin stimulates contractions in females during childbirth. Somatotropin is
a growth hormone that stimulates protein production in muscle cells.
6. Movement: contractile proteins in muscle cause movement - responsible for
movement. i.e, actin and myosin. -involved in muscle contraction and
movement.
Video: protein function Youtube...uploaded by mikedolding?
iii. Structure of proteins
1. Subunits of proteins = Amino Acid
General structure– all proteins have this basic structure and an R group that makes
each amino acid unique.
carboxylic acid (type of organic acid)
2. Peptides:
2 amino acids join together in a dehydration synthesis rxn- the resulting
molecule is then called a peptide.
Polpeptide = many peptides= many joined amino acids
iv. Dehydration synthesis –formation of a peptide bond
dehydration
Hydrolysis
v. Shapes of proteins
Protein function depends on it attaining its final 3D shape this shape
determines how it binds to other molecules – fits like lock and key with
other molecules
If exposed to extreme heat or pH, proteins become denatured= becomes not
natural –loses natural 3D shape, so it no longer can fit into the lock and key
idea of other molecules – so it can no longer function like it should – they
lose both their secondary and tertiary structure
H
Bonding between R groups in aa is disturbed – in the tertiary structure –
which is its final shape – the bonding between the R groups breaks and
therefore the protein loses its shape
Causes irreversible change in shape of protein and therefore function: i.e.
Boiling eggs If proteins in a living cell are denatured, this results in
disruption of cell activity and possibly cell death.
vi. Levels of protein organization:
Level Shape Bonding
Primary 1o Linear chain of aa Peptide bonds between aa
Secondary 2o Helix (coiling)
Pleated sheet (folding)
Hydrogen bonds between
aa
Tertiary 3o globular Final 3D shape and
function: Ionic, covalent,
hydrogen bonds btwn R
groups
Quaternary (rare) 4o All shapes All bonding – 2 or more
associated polpeptides
1. Primary
= amino acids in a line (linear) – joined together by peptide bond
H O H H
H2N C C N C COOH
R OH H R
Peptide bond
Acid end of one amino acid bonds to the amine group of the next aa; Acid
end is negative, amine end is positive - Therefore polar
A Polypeptide = many peptides= many joined amino acids.
2. Secondary =helix coil (right handed spiral) or pleated sheet
linear chain takes on 3D shape
Hydrogen bonds hold 3D shape in place – bond between slightly + H end, and
other δ - atoms
In an alpha-helix, the protein chain is coiled like a loosely-coiled spring. The
"alpha" means that if you look down the length of the spring, the coiling is
happening in a clockwise direction as it goes away from you.
In a beta-pleated sheet, the chains are folded so that they lie alongside
each other
3. Tertiary Structure =globular structure = final 3D shape
held in place by covalent or ionic or hydrogen bonding between R groups.
held together by interactions between the side chains - the "R" groups
Hydrophilic parts are outside and hydropobic parts on the inside
*Important for structure
The 3o structure of a protein is the way the whole chain (including the 2o
structures) folds itself into its final 3-dimensional shape.
4. Quaternary structure
only for some proteins – when several polypeptides with their own 1o, 2o, 3o
structure bonds together
i.e, haemoglobin and enzymes
F) Nucleic Acids
essential in the structure and function of cells. Scientists who first discovered
them called them nucleic acids because they found them in the nucleus of the cell
i. Why group these molecules?
Nucleic acids are either DNA- deoxyribonucleic acid, or RNA – ribonucleic
acid
Both have subunit of a sugar+phosphate+base
ii. Function
DNA -deoxyribonucleic acid
stores genetic information –called genes – like a code
DNA replicates and transmits this genetic info during cell reproduction
Genes (the genetic info) specify the sequence of aa in the proteins (if this
is faulty will cause genetic faults –i.e. sickle cell anemia –where red blood
cells are misshapen and clog blood vessels leading to all sorts of problems)
RNA – ribonucleic acid
Is the intermediary that transmits the code regarding the aa sequence
in a protein – RNA is the nucleic acid directly involved in protein
synthesis
DNA is the keeper of the code, when needed it unravels and passes the code onto a
single strand of RNA – the RNA uses this code to make a protein. In a later
chapter, we describe how this happens.
iii. Structure of DNA and RNA
Both have nucleotide subunits
A Nucleotide is a molecular complex of 3 types of subunit molecules:
Phosphate, (Pentose) 5 C sugar, and nitrogen base
Linear chains of nucleotides form as phosphate and sugar backbone forms
between each nucleotide bonding together
RNA and DNA are polymers of nucleotides
DNA RNA
Double strand, double helix single strand
Sugar = deoxyribose sugar = ribose
4 nitrogen bases 4 nitrogen bases
Adenine (A) A
Thymine (t) Uracil (U)
Guanine (G) G
Cytosine (C) C
Nucleotides join to form a polynucleotide – called a strand
In DNA 2 strands twist around each other to form a double helix **Held
together by hydrogen bonds between bases
Complementary base pairs
A with T
G with C
have shapes that fit together
These complimentary base pairs allow DNA to replicate in a way that ensures the
sequence of bases will remain the same –it is like a code - this is important
because it is the sequence of bases that determine the sequence of aa in a protein.
it will not function if it isn’t correct.
iv. Specialized nucleotide – ATP Adenosine Triphosphate
ATP =adenosine triphosphate –special because normal structure of a
nucleotide is 1 phosphate, a sugar and a nitrogen base, ATP has 3
phosphates and the base is always adenine.
ATP = adenine + ribose (sugar) + 3 phosphate groups
ATP is an energy carrier in cells – hi energy molecule – the hi energy is
carried in the phosphate bonds
When ATP is broken down you get ADP (adenosine diphosphate) and when
the phosphate bond breaks between the ADP and the phosphate group that
breaks off, you get energy released.
Energy is used in cellular metabolism to synthesize macromolecules (such as
carbohydrates and proteins), in muscle cells the energy is used for muscle
contraction, and in nerve cells it is used for conduction of nervous impulses
After ATP breaks down it can be recycled by adding phosphate to ADP – an
input of energy is required to reform ATP
ATP is formed from the breakdown of glucose – glucose is used as energy
storage until required by the cell
A glucose molecule contains too much energy to be used as a direct source in
cell reactions. Instead the nrg of glucose is converted to ATP.ATP has an
amount of nrg that a cell can use to supply chemical reactions in cells.