Transcript Macromolecules and Cell Structure

Macromolecules and Cells
Molecular biology of the cell and
cell theories
Atoms
e
P
e
e
e
Hydrogen atom (H)
6P
6N
e
e
Carbon atom (C)
e
Bonds form Molecules
molecule: two or more atoms chemically bonded together
• Ionic bonds are formed between atoms that
become oppositely charged. The charged atoms
are ions, which are formed after donating or
accepting electrons. Example: NaCl
• Covalent bonds are formed when electrons are
shared between atoms. H-H indicates single
covalent bond whereas O=C indicates double bond
• Hydrogen bonds result from attraction between
partial charges of different molecules.
Carbohydrates
Example: Glucose, C6H12O6 (chemical formula)
H-C=O
H-C-OH
OH-C-OH
H-C-OH
H-C-OH
H-C-OH
H
Glucose molecule folds into a
6-sided shape (hexagon)
Because it has 6 carbons it is
called a hexose sugar
Carbohydrates
Pentose sugars
• Ribose: C5H10O5
– Found in RNA
• Deoxyribose: C5H10O4
– Found in DNA
Carbohydrates
Monosaccharides
• Glucose
• Fructose
• Galactose
• Ribose
Disaccharrides
• Lactose
• Maltose
• Sucrose
+
synthesis reaction
Polysaccharides
Lipids
• Mostly insoluble in water
• Large sections of hydrocarbon (with few oxygens) are
hydrophobic
• Fatty acid: COOHCH2CH2CH2CH2…
• Can bind to other macromolecules such as glycerol
(below)
H
H-C-OH
COOHCH2CH2CH2CH2…
H-C-OH
COOHCH2CH2CH2CH2…
H-C-OH
COOHCH2CH2CH2CH2…
H
triglyceride
Phospholipids
• Consists of two fatty and a phosphate (PO4) acids
attached to a glycerol molecule
Phosphate head is hydrophilic
Fatty acid tails are
hydrophobic
Amino Acids
• The building blocks of proteins
Amino group
H
O
H
N
C
H
R
C
OH
Variable group
Carboxylic
acid group
Proteins
• Primary structure is a chain of amino acids
• Can fold into secondary and tertiary structures
• Protein subunits can combine to form quaternary
structure
AA
AA
AA
AA
AA
Protein synthesis: formation of primary structure of
protein. Complex process that involves
ribosomes, tRNA, mRNA, and DNA
Secondary and tertiary structures
Helical
shapes
What do proteins/polypeptides do?
•
•
•
•
•
Some are Enzymes, catalysts for reactions
Some are important in regulation/communication
Some help maintain structure
Some are infectious agents called Prions
Proteins are expressions of genes and help make up
phenotypic characteristics of organisms
Gene
RNA
Protein
Nucleotides
•
•
•
•
•
•
Consist of nitrogenous base +pentose sugar+ phosphate
Nucleotide monophosphate (NMP): 1 phosphate
Nucleotide diphosphate (NDP): 2 phosphates
Nucleotide triphosphate (NTP): 3 phosphates
Exist for all nitrogenous bases: A, G, T, C,U
Nucleotides are high energy compounds and building
blocks for nucleic acids (DNA and RNA)
• Pentose sugar in RNA is ribose and in DNA is
deoxyribose
• Nucleotides with deoxyribose are dNTP
Nucleotides
• Nitrogenous bases : Adenine, Guanine, Cytosine,
Thymine, and Uracil (RNA only)
Nitrogenous base
(adenine)
P
Pentose sugar
P
P
Phosphates and high energy bonds
Nucleic acids
• RNA: ribonucleic acid
• DNA: deoxyribonucleic acid
• Primary structure consists of chain (strand) of
nucleotides linked from sugar to phosphate
• Can be single stranded or double stranded
• Can fold into many secondary and tertiary structures
including helices
• Both DNA and RNA can be hereditary material of
microorganisms
Single stranded nucleic acid
NTP
Double stranded nucleic acid
Nitrogenous bases protrude from the
sugar phosphate backbone like
rungs of a ladder
Short piece of DNA is called an
oligonucleotide
Nucleic Acids
Nitrogenous bases that protrude from the sugar
phosphate backbone form hydrogen bonds between
two strands of nucleic acid
Base pairing occurs as follows:
DNA
5’…ACTGCT…3’
3’…TGACGA…5’
RNA
5’…ACUGCU…3’
3’…UGACGA…5’
2 hydrogen bonds
between A and T
3 hydrogen bonds
between C and G
Complex Biomolecules
•
•
•
•
•
•
•
•
•
Usually assembled inside cells by enzymes
Glycolipids
Lipoproteins
Glycoproteins
Nucleoproteins (ribosomes)
Peptidoglycan (bacterial cell wall)
Lipopolysaccharide (outer membrane of bacteria)
Many other types
Note: as we will see later, many of these can be
antigens stimulate an immune response
Ribosomes
21 different proteins
16SrRNA
30S subunit
31 different proteins
70S ribosome
(prokaryotes)
50S subunit
23S rRNA and
5S rRNA
Membranes
• Made of phospholipid bilayers, proteins, and other
complex biomolecules
• When formed into a spherical shape, can become a
vessel for hereditary material
• Vary in complexity and composition depending on the
type of organism
• May play a vital role in the survival of organisms
Phospholipid bilayer
Intracellular
Extracellular
Theories about cells
• Cell theory: cells are the basic units of all living things
• ‘Primordial Soup’ Theory
– A separate, but complementary theory to evolution
– Occurred over millions or billions of years
– Organic molecules formed from the highly reducing atmosphere
of early earth in an aqueous environment
– The earliest cells coalesced from organic molecules by the
inclusion of autocatalytic molecules within simple lipid micelles or
droplets
• Endosymbiont theory: organelles such as mitochondria
evolved from living organisms
Variation in Bacterial Cell Structure
• Cell morphology (size and shape)
• Cell membranes (inner and sometimes an outer)
• Cell wall (most of the time)
• Accessory structures (e.g. flagella, fimbriae)
Diversity of Structure in Microorganisms
Nucleic acid
Viruses
Protein coat (capsid)
Membrane and
spikes
Circular
DNA
Prokaryotes
membrane
peptidoglycan
membrane
Eukaryotes
organelles
DNA contained within
nucleus
Variation in bacterial cell wall structure
Gram-positive bacteria have thick layer of peptidoglycan
which often contains teichoic acid
Gram-negative bacteria have thinner cell wall but have
lipopolysaccharide in an outer membrane
Acid-fast bacteria have cell wall similar to G+, but lots of
lipid and less peptidoglycan
Mycoplasmas lack cell wall
Variation in Bacterial Cell Walls
Cell wall
bilayer
LPS
Prokaryotes
Eukaryotes
DNA not contained
within a membranous
nucleus
DNA in form of linear
chromosomes
Chromosome is circular
piece of DNA
May contain plasmids
(small circular DNA)
Contain ribosomes but
generally lack
membranous organelles
DNA inside of nucleus
DNA contains introns and
exons
Contain variety of
membranous and nonmembranous organelles
May be single-celled or
multicellular