Human Biology
• Science is the study of the natural world
• Biology is the study of living things
• Living things have a different molecular composition than nonliving things
• Everything is composed from the same set of around 100 different
elements
• Living organisms combine elements in unique ways, to make molecules
• Living things require energy and raw materials (molecules)
• Metabolism consists of the physical and chemical processes
involved in transforming energy & molecules so that life can
be maintained
• Living things are
made of cells
• Cell is the
smallest unit that
exhibits all the
characteristics of
life
• Cells arise from
existing cells
• Some organisms
exist as only one
cell
• Living things maintain
a relatively constant
internal environment
known as
‘homeostasis’
• Living things respond
to their external
environment to keep
homeostasis relatively
constant
• Living things grow &
reproduce
• Populations of lining
things evolve to better
survive environmental
changes
• Biologists grouped
living things into 5
kingdoms:
• Monera – bacteria –
have no nuclei
• Animalia
• Plantae have green
pigment called
chlorophyll to
capture energy of
sunlight to use in
photosynthesis
• Fungi are
decomposers
• Protista are
unicellular or simple
multicellular
eukaryotes
• Animals are
divided into
subgroups
• ‘Vertebrate’ is the
subgroup that
humans belong to
• ‘Species’ are the
smallest units of
the classification
system populations of
organisms with
similar physical &
functional
characteristics that
interbreed and
produce fertile
offspring
• Things that
differentiate
humans:
• Bipedal – we are
mammals that
prefer to stand
upright and walk
on two legs
• Opposable thumbs
• Large brain mass
relative to body
size
• Capacity for
complex language
• Evolution is what caused the diversity of life
• It is an unpredictable and natural process of descent
over time due to genetic modifications
• Populations of organisms undergo slow changes that
make them different from their ancestors, caused by
mutations to their genes
• Evolution is affected by natural selection, historical
events, changing environments, and chance
• Microevolution is a result of
genetic changes that create a
new species from an existing one
• Macroevolution is change that
happens to many species as a
result of an environmental event
• Charles Darwin hypothesis that
life arose and descended from
one early life form – descent with
modification from the original life
• Evidence from fossils – remnants
of organisms covered with layers
of sediment (stratification), which
aids in dating over time
• On organisms,
homologous structures
have a common origin,
analogous structures
have a common
function, and vestigial
structures are ones that
evolved to have no
current important
function
• Similarities are seen in
comparisons of
embryos and
development of organs
• Similarities in proteins
and genes show
relationships
• Continental drift, natural
selection, and extinctions
from environmental
events affect gene flow
• Humans are primate
mammals
• Primates have 5 fingers,
flat nails, forward-facing
eyes and include
lemurs, monkeys, apes,
and humans (hominids
with bigger brains)
• All have opposable
thumbs
• Apes are a sub-group –
gibbons, orangutans,
gorillas, chimps
• Ardipithecus ramidus –
primates diverged from
apes 4.4 million years
ago in Africa – ‘Ardi’
• Australopithecus
afarensis an African
hominid is a direct
ancestor of humans, 3.2
million years ago – Lucy
was found in Ethiopia
They walked upright,
had thick teeth enamel,
males were much larger
than females, and they
had long arms to travel
in trees
• Homo habilis –
toolmakers, 2.4 million
years ago, with larger
brains, used stone tools
• Homo erectus, from 1.8 million
years ago, migrated to Java and
China, used specialized tools,
and engaged in more
socialization
• Homo heidelbergensis gave rise
to the Neanderthals, discovered
in Germany
• Homo sapiens (today’s human)
evolved from Homo erectus in
Africa, crossed to Yemen, then
migrated to all parts of the
world
• Homo floresiensis – another
extinct species, discovered in
Indonesia in 2004
• Science is defined as
knowledge of the
natural world
• The process used to
get that knowledge is
the called the
scientific method
• Get an idea & test it
• Observe & generalize
– inductive reasoning
• Formulate an
hypothesis
• Make a testable
prediction – deductive
reasoning ‘if…, then…’
• Experiment or observe
• Draw conclusions
• Experimental
method:
• Controlled
experiments –
everything is
similar (controlled)
except for one
thing - the
controlled variable
• Modify the
hypothesis and
repeat
• Make the findings
known
• Well tested
hypothesis
becomes a theory
• Critical
thinking
requires
skepticism
• Matter is anything that has mass and occupies space
• An element is the fundamental unit of matter that can’t be
further broken down into different structures
• An atom is the smallest unit of any element that still retains
its physical and chemical properties
• The nucleus of an atom is
made up of positive
charged protons and
neutral particles called
neutrons
• Atomic number = number
of protons
• Atomic weight = average
number of protons plus
neutrons for that element
• Electrons – small
negatively charged
particles that orbit the
nucleus
• Electrons orbit in shells:
• 2–8–8
• In a neutral atom #
protons = # electrons
• Isotopes of an atom
have different
numbers of neutrons
• Some are unstable
because they give off
energy until they
become more stable
• Radioisotopes give off
radiation but are also
useful
• They decay into other
elements at a set rate,
are used to see the
age of fossils
• Ions of an atom have a
different number of
electrons, so they have
a positive charge if
there are less
electrons, or negative
charge if there are
more electrons
•
•
•
•
Molecules are atoms attached to each other
Energy is the capacity to do work
Stored energy is called potential energy
Energy in motion is called kinetic energy
• Atoms are most
stable when
their outer
electron shell is
completely
filled
• Covalent bonds
involve sharing
electrons to fill
the outer shell
• This is one way
to connect
atoms to make
a molecule
• Ionic bonds
occur between
oppositely
charged ions,
that are weaker
than covalent
bond and break
down in
aqueous
solutions to
form
electrolytes
• Hydrogen
bonds are weak
ionic bonds
when there is
attraction
between
positive and
negative ends
of the
molecules
• Important
example is
water
• Living organisms
contain primarily 6
elements: oxygen,
carbon, hydrogen,
nitrogen, calcium,
phosphorus
• All life depends on
water
• Water molecules are polar
with (+) & (-) sides (poles)
• It is a liquid at body
temperature
• Water can absorb and hold
heat energy which
prevents dramatic changes
in body temperature – 98.6
or 37 centigrade
• Water is the universal
biological solvent –
organism chemicals are
dissolved in water
• Polar molecules are
attracted to water so they
are called hydrophilic
• Nonpolar molecules are
repelled by water, called
hydrophobic
• A molecule of water can
break down into a
hydrogen and hydroxide
ion
• pH measures hydrogen
ion concentration, as the
negative log of its
concentration
• Water is pH of 7.0, which
is neutral
• Acids are solutions that
break down to form
hydrogen ions
• Bases break down to form
hydroxide ions or to get
the ability to combine
with a hydrogen ion
• Acids have pH
less than 7
• Bases have pH
greater than 7
• Blood pH is
7.35 – 7.45
• Buffers minimize changes in pH by either taking up
or adding hydrogen ions
• Organic molecules
contain carbon and
are held together by
covalent bonds
• Carbon (C) makes
up 0.03% of the
earth and 18% of
the body’s weight
• C has 6 electrons, 2
in inner orbit, 4 in
outer orbit
• Forms covalent
bonds
• Cells build
macromolecules
using dehydration
synthesis and break
them down using
hydrolysis
• Carbohydrates are
used by living
organisms for
energy and
structural support
• Monosaccharides
are the simplest
form and link to
create
oligosaccharides
• Important
carbohydrates are
glucose, fructose,
sucrose, ribose,
deoxyribose
• Polysaccharides are joined in straight or branched chains by
dehydration synthesis
• Glycogen is storage polysaccharide of glucose in animals
• Starch is equivalent in plant
• Cellulose is a glucose polysaccharide used for structure by
plants that we do not have the enzymes to break down
• Lipids are hydrophobic
– insoluble in water
• Triglycerides are made
from glycerol and 3
fatty acids
• Saturated fats have 2
hydrogens for each
carbon
• Unsaturated fats (oils)
have double bonds
between carbons
• Lipid is stored in
adipose tissue
• phospholipids have a
phosphate group
substituting for one
fatty acid
• Steroids are also
hydrophobic
• Have backbone
of three 6
carbon rings
and one 5
carbon ring
• Cholesterol is
most common
form & is an
important
component of
cell membranes
and steroid
hormones
• Proteins are strings of amino acids – there are 20 different
amino acids
• Each has an animo group, carboxyl acid group, and an R group
• R groups can be neutral, polar, negative, positive, nonpolar
• Our cells can make 11 amino acids and an important cell
function is to form polypeptides & proteins
• Proteins are linked amino acids
• Primary structure is the simple
sequence of amino acids
• Secondary structure is how the
chain of amino acids interacts
with each other
• Tertiary structure is the outward
appearance of the protein from
hydrogen bonding, disulfide
covalent bonds between
cysteines, affected by
environment – hydrophobic,
hydrophilic parts
• Quarternary structure – how
different polypeptides associate
with each other
• Enzymes are proteins that help with biochemical
reactions – are catalysts (speed up the reaction)
• Take reactants (substrates) and turn them into
products by using their shapes and charges (+ or -)
• Cells are enclosed by a plasma membrane
• Raw materials, energy, waste enter & leave only by crossing
the membrane
• Eukaryote cells have an internal nucleus enclosed by nuclear
membrane
• The cell membrane is a phospholipid bilayer with
cholesterol & proteins, called a fluid mosiac –
because it is not rigid
• The cell membrane is selectively permeable
• Things cross the membrane by diffusion, osmosis,
facilitated transport (all follow a concentration
gradient and don’t take energy), or active transport
– movement against a concentration gradient which
requires energy
• Phagocytosis, pinocytosis, use of receptor proteins
are other methods
• If the cell is hypotonic, (like when the body is
dehydrated) it loses fluids to surrounding solution &
shrinks, if hypertonic (like when the body is bloated)
the opposite happens
• isotonic means the same concentration as the
surrounding solution
• Organelles are working units in the cell, and include
the nucleus, ribosomes, rough and smooth
endoplasmic reticulum, golgi apparatus, lysosomes,
perixosomes, vesicles, and mitochondria
• Flagella, cilia, microvilli, centrioles are structures
associated with the cell
• The nucleus is the part of the cell that contains the chromosomes
• Chromosomes are made up of DNA, humans have 23 pairs altogether, 22 of
autosomes, and one pair of sex chromosomes
• There are pairs because of one is inherited from the father and one from
the mother
• Areas of the chromosomes called genes hold the instructions for making
specific proteins – the genetic code
• Genes of the paired chromosomes are called alleles, can be alike
(homozygous) or different (heterozygous), one from the mother, one from
the father; can be dominant or recessive; can affect appearance or function
• Nucleic acids store
genetic information
• DNA is the
abbreviation for
DeoxyriboNucleic
Acid – and it makes
up genes that
contain instructions
for producing
RiboNucleic Acid
• RNA contains
instructions for
making proteins
• Both are made of
nucleotides that
have a 5 carbon
sugar, a nitrogenous
base, and
phosphate groups
• DNA bases are
adenine, thymine,
cytosine, guanine
• A-T C-G
• Genetic code is on one
of the DNA strands,
the other side holds it
together
• Every 3 bases codes
for a specific amino
acid
• These are instructions
for formation of a
strand of messenger
RNA that is specific for
the amino acid
sequence of proteins
• RNA bases are
adenine, uracil,
cytosine, guanine
• Messenger RNA
brings the genetic
information to
either ribosomes
or rough
endoplasmic
reticulum for
protein synthesis
• At the ribosome,
transfer RNA
matches the
messenger RNA
code and brings
amino acids, which
become linked by
dehydration
synthesis to form
proteins
• Proteins that get secreted go from the rough endoplasmic reticulum to the
golgi apparatus, where they are altered into the final product
• Lysosomes are membrane bound proteins that function in waste
management
• Smooth endoplasmic reticulum functions in different ways - as storage
containers for ions, sites of detoxification, sites of lipid synthesis or breakdown, depending on the cell’s needs
• Metabolism –
chemical reactions
in the organism,
either anabolism
where molecules
get assembled into
larger molecules
that contain more
energy – a process
that requires
energy; or
catabolism – larger
molecules are
broken down, which
releases energy
• Energy is stored in
ATP
• ATP – Adenosine
TriPhosphate – has
adenine, ribose, and
three phosphate groups
• phosphate group bonds
store huge amounts of
potential energy that is
released when the bond
is broken
• Then ATP becomes
adenosine diphosphate
(ADP) and inorganic
phosphate
• Both proteins in the
cytoplasm & the
mitochondria make ATP
from glucose breakdown
• Mitochondria
produce huge
amounts ATP, and
there are more in
cells that require
more energy
• They are thought
to originate from
bacteria that
became
incorporated into
cells many
millions of years
ago
• Glucose chemical
formula is C6H12O6
• Glycolysis is a process
that happens with
enzymes in the
cytoplasm
• Glucose is split into 2,
three carbon
molecules called
glyceraldehyde-3phosphate, producing
2 ATP –
• It gets converted to
pyruvate, then lactic
acid if no oxygen is
available
• High energy hydrogen
ions and electrons are
taken by nicotinamide
adenine dinucleotide
(NAD)
• Pyruvate enters the mitochondria & is converted to
acetyl CoA to enter the citric acid (Krebs) cycle, that
gives off CO2 & makes ATP and more NADH & a
similar FADH2
• NADH & FADH2 bring hydrogens & electrons to the electron transport chain
• Concentration of hydrogen is higher in the outer compartment than in the
matrix
• Molecules pass hydrogens through the electron transport chain into the
outer compartment
• Oxidative phosphorylation – hydrogens diffuse back into the matrix thru a
protein that uses the energy from diffusion to make ATP as they go into the
inner compartment - makes 34 ATP and water
• Fats & proteins can
also be used for
energy
• Fats carry more than
twice the energy of
carbohydrates
• Triglycerides are
broken down to
glycerol and fatty
acids
• Glycerol can be
converted to glucose
or pyruvic acid
• Fatty acids become
acetyl groups for
citric acid cycle
• Proteins can enter
after amine group is
broken off
• Vitamins are important
chemicals essential for
normal function
• The body makes vitamin
D in our skin
• Bacteria in the colon
make vitamin K, B6, and
biotin
• Fat soluble vitamins are
absorbed if there is fat in
the diet – vitamins A & E
& D & K are fat soluble
• Water-soluble vitamins
are easy to absorb but
are excreted rapidly in
the urine, and all the B
vitamins are coenzymes
in carbohydrate, nucleic
acid, or amino acid
metabolism