Biochemistry and Cell Biology 101

Biomolecular Quartet

• There are four primary types of biologically important molecules, known as the biomolecular quartet:– Carbohydrates (“carbs”)– Fatty Acids– Amino Acids– Nucleic Acids

Biomolecular Quartet

• Carbohydrates– Sugars

• Groups called saccharides or polysaccharides

– Often 6 carbon rings• Sometimes 6-C ladders

– Short term energy supply– Molecular recognition

Biomolecular Quartet

• Fatty Acids– Fats

• Polymers are called lipids

– Lumpy head with multiple straight carbon chains ending with -COOH

– Long term energy storage

Biomolecular Quartet

• Amino Acids– Consist of a central carbon surrounded by:

• A hydrogen atom

• An amine (NH3+) group

• A carboxylic acid (COO+) group

• A variable group

– 20 amino acids (8 or 9 are essential)

– Basic protein building block– Amino Acid (AA), peptide, polypeptide, protein

Biomolecular Quartet

Tryptophan

Methionine

Valine

Threonine

Phenylalanine

Leucine

Isoleucine

Lysine

Histidine

Grains

Legumes

Essential Amino Acids (cannot be made by body)

Biomolecular Quartet• Nucleic Acids

– Consists of:• A pentose (5 carbon

sugar)• A phosphate group• A purine or pyrimadine

(6C ring) base

– Forms the basis of the genetic code• DNA: Adenosine, Cytosine, Guanine, Thymine• RNA: Adenosine, Cytosine, Guanine, Uracil

Biomolecular QuartetAlanine GCU, GCC, GCA, GCG

Cysteine UGU, UGC

Aspartate GAU, GAC

Glutamate GAA, GAG

Phenylalanine UUU, UUC

Glycine GGU, GGC, GGA, GGG

Histidine CAU, CAC

Isoleucine AUU, AUC, AUA

Lysine AAA, AAG

Leucine UUA, UUG, CUU, CUC, CUA, CUG

Methionine AUG

Asparagine AAU, AAC

Proline CCU, CCC, CCA, CCG

Glutamine CAA, CAG

Arginine CGU, CGC, CGA, CGG, AGA, AGG

Serine UCU, UCC, UCA, UCG, AGU, AGC

Threonine ACU, ACC, ACA, ACG

Valine GUU, GUC, GUA, GUG

Tryptophan UGG

Tyrosine UAU, UAC

• Amino Acids– Coded by nucleic acid

triplets in DNA/RNA• 3 “letters” = codon• 3 “letters” of 4 types

gives 64 combinations to encode 20 amino acids.

• A = adenosine• C = cytosine• G = guanine• U = uracil

DNA

• Two interwoven strings of nucleic acids form the “double helix” of DNA.

•2 strands are complementary:–Adenosine pairs with Thymine–Cytosine pairs with Guanine

DNA• The helix is wound on

spools called histones. • Strings of histones form

chromatin fibers.• The chromatin fibers

loop and coil into chromatids.

• Two chromatids joined by a centromere form a chromosome.

DNA

• Each chromosome:– 2 short arms (p)– 2 long arms (q)

• Nomenclature:– TPH1 11p15.3-p14

• Chromosome 11

• p = Short arm

• Region 14-15.3

DNA Structure

• Each chromatid carries several to several thousand genes (about 20-30K total in humans).

• Genes control some characteristic of the organism. TPH1 on 11p14-15 is 21K BP (1335 BP), 444 AAs

DNA

• Humans normally have 23 pairs of chromosomes (46 total):– 22 pairs of autosomal

chromosomes– 2 sex chromosomes:

XX (female) or XY (male)

Genetics

• Monogenetic traits– A single gene controls the presence or absence of the trait.

– Dominant traits: One copy required to express the trait.• Ex. Brown hair, Widow’s peak, polydactyly, unattached earlobes, freckles,

curly hair, Huntington’s Disease

– Recessive traits: Two copies required to express the trait.• Ex: Blond hair, blue eyes, colorblindness, albinism, PKU, sickle cell

anemia, cystic fibrosis

– Homozygous: both parental genes the same.

– Heterozygous: both parental genes different.

Genetics

• Polygenetic traits– Several to many genes involved.– Most human behavioral and personality traits, and

mental health problems are polygenetic and can be influenced by environmental factors.

• Sex-linked traits– reside on either the X or Y chromosomes, but X is

usually implied since Y is so small.

• Sex-limited traits – present in both sexes but have an effect in one sex only,

or at least it has a much stronger effect in one sex than in the other. (ex: breast size, chest hair)

Genetics/Heritability

• Genetic does not necessarily imply heritable!

• Genes can be inherited, but

• Healthy genes can be changed by:– Random mutations– Ionizing radiation– Toxins– Etc.

Heritability

• An important question to ask is whether the observed differences among individuals depend more on differences in heredity or differences in environment.

• Researchers use the concept of heritability, an estimate of how much of the variance in some characteristic within some population is due to heredity. Range is 0 – 1.

Heritability• Twins

– Twins offer a unique opportunity to separate nurture (environment) from nature (genetics).

– Identical/Monozygotic/MZ: both twins have exactly the same DNA, since they came from a single fertilized egg. If separated twins show the same trait, it is most likely genetic (nature).

– Fraternal/Dizygotic/DZ: the twins have the same genetic similarity ( ¼ ) as any other siblings.

Heritability

• How do researchers determine the heritability of a human trait?

• 1st , to compare genetics, researchers compare the resemblance between monozygotic (identical) and dizygotic (fraternal) twins.– A stronger resemblance between monozygotic

twins indicates higher heritability.

Heritability

• 2nd, to examine the contribution of the environment, researchers examine the differences between adopted children and their biological and adoptive parents.– Resemblance to the biological parents indicates

high heritability; resemblance to the adoptive parents indicates low heritability and greater influence of environmental factors.

Heritability

• Personality traits – 0.5– MMPI Scales – 0.26 – 0.62, M = 0.44– MPQ - 0.39 – 0.58

• Schizophrenia, Depression – 0.5 – 0.6

• IQ – about 0.7

• Bipolar Disorder – 0.8

• Huntington’s – 1.0

Heritability

• Social/Antisocial

• Religiosity

• Conservatism

• Risk Taking/Harm Avoidance

• Anxiety

• Pessimism/Optimism

• Impulsive Aggression

• Persistence

The Cell

The Cell

• A cell is the basic structural and functional unit of all living organisms.

• Cells carry on all of the same life functions as the entire organism.

• About 50 trillion cells in the human body.

The Cell

• Bilipid membrane– Two lipid membrane layers tightly bound

• Hydrophobic inside, Hydrophilic outside

– The membrane is fluid– Embedded with channel, structural and

recognition proteins– Maintains internal cellular environment

Cell Membrane

The Cell

• Nucleus– Stores the genetic material– Surrounded by porous

nuclear envelope– Important genes are

copied and mRNA is exported thru the nuclear pores to the rough ER for protein synthesis

The Cell• Ribosomes

– Created in the nucleolus.– Synthesize proteins from Aas.

• Endoplasmic Reticulum– Rough ER

• Contiguous with nuclear membrane• Embedded with ribosomes• Protein synthesis

– Smooth ER• No ribosomes• Steroid and lipid synthesis

The Cell

• Golgi Apparatus– Packages proteins produced by ER into packets

called vesicles.

The Cell• Mitochondria

– Energy production: glucose->ATP– Some cells have only a few mitochrondria.– Nerves and muscle have hundreds or more.

The Cell

• Microtubules/ Microfilaments– Provide cellular structure– Protein/organelle transport

• Centrioles– Specialized groups of

microtubules.– Helps divide cell during

mitosis.

The Cell

• Vacuoles– Storage vesicles

• Peroxisomes– Contain powerful enzymes for detoxification

• Lysosomes– Contain digestive enzymes– Destruction of old cell parts

The Cell

• Cilia– Move in unison to propel

fluid over cell

• Flagella– Propels the cell

• Both have a 9+2 structure– 9 pairs of microtubules– Plus a center pair

The Cell

• Microvilli– Hair-like

projections that increase surface area

– Used for absorption in intestines, nose, lungs

The Cell

Cell Reproduction

• At conception there is only one cell.– 23 chromsomes from ovum, 23 from sperm.

• All cells of the first several generations are exactly identical.

• Specialization starts about the 5th or 6th generation.

• Each generation only gets more specialized.• Stem cells are unspecialized and can

develop into any type of cell.

Cell Reproduction• Mitosis – cell division

– The 46 chromosomes are duplicated, temporarily making 92.

– The copies are separated to opposite ends of the cell. – The cell divides down the middle.– This leaves two cells, each with 46 again.

Cell Reproduction

• Mitosis gone bad– The 46 chromosomes are duplicated,

temporarily making 92. – 45 copies move to one end, 47 to the other. – The cell divides down the middle.– The person is now a mosaic – some cells differ

genetically!

Cellular Groups

• Types of attachments between cells– Tight junctions

• Impenetrable junctions• Found in the blood-brain barrier

– Gap junctions• Loose junctions that allow substances to pass• Important embryonically, before circulation• Often have connexions, intercellular tubes

– Desmosomes (adhesion junction)• Structural connection proteins, gap junctions

Tissues

• A group of connected cells performing a similar function is called a tissue.

• Only 4 types of tissue:– Epithelial (“surface”) tissue– Connective tissue– Muscle– Nerves

• A group of related tissues which perform a given function is called an organ.

The Nerve Cell

• Several specializations from a normal cell:– No centrioles: nerves cannot replicate!– Long life (must last a lifetime)– Long and narrow vs. round-ish– Nissl bodies, specialized rough ER

• To handle neurotransmitter synthesis

– Extremely high metabolic rate• Many more mitochondria than normal cells

– Create action potentials, electrical pulses

The Nerve Cell• Cell body

– Biosynthetic center

• Dendrites– Receptive regions

• Axon– Arises from the axon hillock

– Impulse generation and transmission

– Ends in telodendria and terminal buttons

The Nerve Cell

• Classifications– Multipolar = many processes (dendrites + axon)

• Most abundant type in body & CNS

– Bipolar = 2 processes• Rare, mostly sensory

– (Pseudo)unipolar = one process• Form as bipolar and then the proximal processes

merge into one• Mostly found in the PNS

Types of Neurons

The Nerve Cell

• Helpers (glial cells)– Help during migration– Schwann cells & oligodendrocytes

• Speed transmission

– Astrocytes (CNS)• Hold nerves in place, anchor to blood supplies

– Microglia• Monitor nerve health, phagocytosis