1

Cell Biology

Biological Molecules

A few notes: Mono = one Monomer = “one piece”

- a basic building block - able to bond into long chains

Poly = many Polymer = “many pieces”

- many molymers

2

Polymerization •  any process is which relatively small molecules

(monomers) combine chemically to produce a very large chain-like network molecule called a polymer

Condensation Synthesis Reaction •  Aka “synthesis” or “condensation” or “dehydration

synthesis” •  Forms a polymer •  Is an ANABOLIC (building-up) reaction •  Water = by-product formed

Monomers Polymer Water

3

Hydrolysis Reaction •  Literally means “reaction with water” •  A chemical process in which a molecule is

cleaved into two parts by the addition of WATER •  Is a CATABOLIC (breaking down) reaction •  Water is needed

Monomers Polymer Water

4

CARBOHYDRATES

CARBOHYDRATES “CHO” •  “sugars” •  Primarily consist of C, H, O

•  Approximate Ratio of 1:2:1 •  Empirical or “simplest formula for a carbohydrate is CH2O

•  Energy Source •  Suffix - “ose”

•  GLUCOSE, FRUCTOSE

5

Monosaccharides •  Simple sugars that comprise ALL CHO’s •  All have the same chemical formula (C6H12O6)

•  Therefore called ISOMERS (“equal parts”)

Isomers - having the same chemical composition but with different structural arrangement

Monosaccharides

E.g. GLUCOSE (C6H12O6) •  blood sugar

•  A hexose sugar

E.g. FRUCTOSE (C6H12O6)

•  Found in fruits, honey, some vegetables

•  A hexose sugar

Note: the molecular formula is the same but the shape of the ring and arrangement of the hydrogen and hydroxyl groups are different.

6

Disaccharides (di = two; saccharide = sugar)

•  When 2 monosaccharides (monomers) combine chemically they form a disaccharide (dimer)

3 most common forms: 1. SUCROSE (table sugar) - glucose + fructose

2. MALTOSE (malt sugar; grain sugar) - glucose + glucose

3. LACTOSE (milk sugar) - glucose + galactose

•  Like monosaccharides, they are soluble in water •  They cannot be stored in the body

•  Glycosidic bond needs to be broken by hydrolysis to form simple

sugars for energy release in cell respiration.

7

Polysaccharides (poly = many; saccharide = sugar)

•  Long chains of many monosaccharides (monomers) joined together by glycosidic bonds to form a polysaccharide (polymer)

•  3 important polysaccharides (all are polymers of GLUCOSE)

1.  STARCH - plant storage polysaccharide - a mixture of Amylose and Amylopectin

2.  GLYCOGEN - animal storage polysaccharide - found in muscle and liver primarily - broken down very quickly to glucose for energy

3.  CELLULOSE - in plants only - cannot be broken down by AMYLASE enzyme and thus cannot be digested in humans

-  Straight chain -  Few side branches -  Plant source

-  Highly branched -  Many side branches -  Animal Source

-  Unbranched -  Plant source

8

Main Functions of Carbohydrates •  Provide a quick, short term ENERGY source for all

living organisms •  Structural role in plants (Cell Wall contains cellulose) •  Cell-Cell recognition by CHO on surface of cell

membrane •  Storage compounds (starch and glycogen)

9

Test your Knowledge

1. This molecule shown on the left is an example of: a) disaccharide b) starch c) monosaccharide d) polysaccharide

2. The elements C, H, O are generally found in what ratio? __________

3. What is the empirical or simplest formula of any carbohydrate ? ___________

4. What is the reaction in which the addition of water causes the subunits of a

macromolecule to separate and degradation takes place?

5. Plants store glucose as _______________ whereas animals

store glucose as _____________.

6. The process of ___________________ joins two monosaccharides to form

A disaccharide.

LIPIDS

10

LIPIDS •  Mixed group of HYDROPHOBIC compounds

•  “Insoluble” in water

•  Contains fats, oils, waxes, rubbers, sterols: •  Composed of C, H, and O (same as Carbs) •  Energy Storage (vs Carbs. - “Energy Source”)

•  C-H bond represents usuable energy

•  Lipids have double the C-H bonds of a Carbohydrate

1. Triglycerides (FATS and OILS) •  Commonly called FATS and OILS

•  FATS - Solids at room temperature

•  OILS - Liquid at room temperature

•  Made up of glycerol and fatty acids

Ra, Rb, Rc represent groups of carbon and hydrogen atoms in which the carbon atoms are attached to each other in an un-branched chain.

11

Glycerol •  Central component in fats and oils

•  A three-carbon alcohol

•  Contains three - OH hydroxyl groups

•  Soluble in water (hydrophilic)

Fatty Acids

•  A carboxylic acid •  Carboxyl group (COOH) plus a

chain of atoms (mostly C and H)

•  Water insoluble (hydrophobic)

•  Contain an even number of C-atoms (4-36)

Saturated Fatty Acids •  All bonds are single •  Number of atoms attached to each carbon is the

maximum of 4 (thus is “saturated”)

Unsaturated Fatty Acids •  Some double bonds •  “kinky” chain

12

Fatty Acids

Saturated

Unsaturated

energy More - b/c more C-H

Less - b/c fewer C-H

naming If it has 1 C=C Then “monounsaturate”

If it has many C=C then

“polyunsaturate” (omega 3&6 Essental FA’s)

2. Phospholipids •  Major constituent of cell membranes (“lipid bilayer”) •  Precursor of prostaglandins

•  Short-lived “hormones” that operate close to home •  ie. Uterine smooth muscle contraction associated with birthing

•  ie. Found in seminal fluid; decreases female immune response to sperm

13

Structure •  Similar to triglycerides HOWEVER one of the three fatty

acid is replaced by a phosphate functional group •  Hydrophobic “Tails” •  Hydrophillic “Head”

Phosphate Group - ORANGE Fatty Acid Groups - BLUE Glycerol - RED

14

3. Steroids •  Cholesterol

•  component on cell membranes in animals and functions to moderate membrane fluidity

•  Bile Salts •  Help to emulsify dietary fats

•  Hormones (estrogen and testosterone) •  Vitamine D

•  Aids in calcium uptake by bones

Structure •  Based on a molecules with

four fused carbon rings •  Each steroid differs by

arrangements in the rings and by functional group attached to it

15

Low Density Lipoproteins (LDL) •  “bad cholesterols” •  LDL carries cholesterol from liver to cells •  Used as a structural component of cell

membranes or converted to steroid hormones •  Too much LDL is associated with artiosclerosis

High Density Lipoproteins (HDL) •  “good cholesterols” •  Acts like a cholesterol scavenger so excess

cholesterol can be removed and converted to bile acids and excreted through digestive tract

Function of Cholesterol •  Structural component of cell membranes •  Essential component of myelin sheath that

insulates neurons •  Precursor for lipid soluble vitamins (ADEK) •  Precursor for steroid hormones

16

Test your Knowledge 1. ________________ is the precursor of ________________:

a) testosterone, cholesterol b) cholesterol, lipids c) cholesterol, testosterone and estrogen d) testosterone and estrogen, cholesterol

2. ________________ are made of one glycerol and three fatty acid molecules that can be recognized by their -COOH ending

a) steroids b) phospholipids c) triglycerides d) all of the above

3. __________ are liquid at room temperature and have _____________ between any two carbon atoms. 4. Name two different types of steroids. 5. Why are fats referred to as TRIGLYCERIDES?

PROTEINS

17

PROTEINS •  Polymers of AMINO ACID monomers

e.g. antibodies, enzymes, most hormones, hemoglobin. structural support in much of our tissues

•  Composed of C, H, O, N (sometimes Sulfur) •  Tend to be BIG compounds

Amino Acid (monomer)

R- Group (Radical Group) - chain of atoms “Rest of…”

Polypeptide (Polymer) •  Two or more amino acids bonded by a covalent (peptide)

bond •  Formed by dehydration synthesis

Synthesis of a Dipeptide

18

Protein Structure: •  The shape of a protein is critical to its function

•  Protein Structure can be described in four levels: •  Primary •  Secondary •  Tertiary •  Quaternary

Primary Structure •  Shape: linear sequence of amino acids

•  “Like strings of pearls”

•  Linked by peptide bonds (C-N)

19

Secondary Structure •  Shape: helical or pleated sheet

•  Looks like primary proteins coiled into a slinky

•  Held in place by hydrogen bonds

Secondary Structure •  Pleated Sheet

20

Tertiary Structure •  Shape: globular

•  Secondary protein folded back upon itself and creating a 3-D structure

•  Globular shape determines its function

•  Folding caused by covalent bonding between R-groups in structure

Part of this protein is hydrophilic

•  Twists and turns to maximize surface

area in contact with water

Part of this protein is hydrophobic •  Twists and turns to minimize surface

area in contact with water

Quaternary Structure •  Shape: Multimeric

•  Composed of two or more polymers joined together e.g Hemoglobin (made of two alpha and two beta chains)

21

Protein Denaturation: •  Recall: A protein’s shape is critical to function

•  A small change is structure can reduce or destroy function

•  Occurs when proteins are exposed to: •  Extremes of temperatures (e.g heat breaks H-bond) •  Extremes of pH (distrupts H-bond)

•  May unfold or DENATURE proteins = loss of shape

Function of Proteins:

1. Enzymes •  Catalysts that speed up chemical reactions •  Function determined by teritary structure •  End in -ase (e.g. amylase, lipase)

2. Structural Proteins •  Keratin - builds hair and nails •  Collagen - give strength to skin, cartilage, tendons, ligaments •  Actin and Myosin - bone and muscle fibres

3. Membrane Proteins •  Proteins that act as channels or pores, carriers, and pumps

22

Function of Proteins:

4. Hormones •  Chemical messengers that influence cellular functions

(metabolism, growth, development and homeostasis)

5. Plasma Proteins

•  Plasma = liquid portion of blood consists of 7-8% protein •  Contribute to blood osmotic pressure by pulling water from

tissues •  E.g. Albumin, globulins, fibrinogen

Test your Knowledge

1.  What is the basic unit of protein?

2.  How many different types of amino acids are there?

3.  Name three different types/levels of protein structure and describe the bonding associated with each.

4.  What are three major functions of proteins and briefly describe each.

5.  Draw a structural diagram to represent a typical amino acid.

23

NUCLEIC ACIDS

•  Two Types: •  DNA - Deoxyribonucleic Acid •  RNA - Ribonucleic Acid

•  C, O, H, N, P

NUCLEIC ACIDS

DNA RNA

Function Genetic information DNA synthesis

Protein synthesis

Sugar (pentose)

Deoxyribose sugar Ribose sugar

Shape Double Helix Single Strand

24

•  Decribed by Watson and Crick (1950’s) as a double helix •  Composed of many NUCLEOTIDES (monomers) •  Nucleotides have three main parts:

1.  A phosphate group 2.  A pentose (5-C) sugar (see previous chart) 3.  A nitrogen containing base

Structure of DNA

DNA is a polymer of nucleotides: •  Sugars and phosphates form a linear sugar

backbone •  Bases project from the sides of the backbone

DNA has 4 different bases: 1.  Adenine (A) 2.  Thymine (T) *replaced with uracil in RNA*

3.  Guanine (G) 4.  Cytosine (C)

25

Purine Pyrimidine

Adenine Thymine

Guanine Cytosine

“Complementary pairs”

DNA

A T

C G

Purine Pyrimidine

Adenine * Uracil *

Guanine Cytosine

“Complementary pairs”

RNA

A U

C G

26

Complementary Base Pairing

Types of RNA (a brief intro…) •  mRNA (messenger RNA) •  tRNA (transfer RNA) •  rRNA (ribosomal RNA)

27

mRNA •  Single stranded •  Transcribed from DNA template •  mRNA carries the a.a. sequence (“blueprint”) from

the nucleus to the site of protein synthesis (ribsomes)

tRNA •  Single stranded; “cloverleaf” tertiary structure •  Transports a specific a.a. to the ribosome for

assembly into an elongating polypeptide (translation)

28

rRNA •  Central component of ribosomes

•  where proteins are manufactured

•  Catalyzes the assembly of amino acids into a polypeptide chain

•  Single stranded

ATP - Adenosine Triphosphate •  High ENERGY molecule (“Energy Currency”)

•  Releases energy for all metabolic work in the cell

•  Structure: 1.  Adenine 2.  Ribose sugar (5-C Sugar) 3.  Three (3) phosphate groups

29

•  Last two phosphate bonds can be easily broken and will releas energy :

Test your Knowledge 1.  What do the letters DNA and RNA stand for?

2.  DNA has four different types of bases. What are they called?

3.  Nucleic Acids are composed of many nucleotides. They are composed of three main parts. Name these parts.

4.  T/F: DNA has a sugar-nitrogen backbone.

5.  T/F: The base Guanine will always bond with Cytosine.

6.  Who were the first scientists to describe DNA as a double helix structure?

7.  What do the letters ATP stand for?

8.  Describe the three subunits that make up an ATP molecule.