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Keystone Test
Prokaryotic vs. Eukaryotic Cells
Prokaryotic cells
Existed before eukaryotes
Small- very simple organisms
Have no membrane-bound organelles
Have no nucleus; their genetic material (DNA)floats
in nucleoid
 Have a cell wall outside of the plasma membrane
o Examples: Bacteria, blue-green algae
Eukaryotic cells
Larger than prokaryotes- complex
Many membrane bound organelles
Genetic material (DNA) found inside the nucleus
o Examples: Plants, Animals, amoeba
Prokaryotic and Eukaryotic
• Have the following
o Plasma (cell) membrane
o cytoplasm
o Ribosomes
o Contain DNA
Levels of Organization
• Organelle→ cell→ tissue → organ → organ system
→ multicellular organism
• Organelle- each performs a specific function (job)
within the cell
Organelles “little organs”
• Ribosomes- synthesize (make) proteins
• Mitochondria- provide energy (ATP) for cells
• Lysosomes- contain digestive enzymes that
break down worn out or damaged cell parts
• Nucleus – contains DNA (chromosomes) which
directs and regulates all cell activities
Organelles “little organs” (ctd)
• Endoplasmic reticulum (ER)
o Rough ER- transports materials throughout the cell (intracellular
o Smooth ER- produces lipids; important in detoxification
• Golgi bodies (apparatus)- modifies, packages, and
secretes organic molecules
• Plasma membrane- helps maintain homeostasis
because it is selectively permeable (regulates what
enters/leaves the cell)
o Made of phospholipid bilayer
o “fluid mosaic model”
Biological Organic Macromolecules
• Organic- contains carbon, living (or came from
something once living)
• Carbon can make 4 bonds; important for these
molecules because allows formation of large,
complex, and diverse molecules
• Carbon often bonds with itself forming chains
(carbon backbone)
• Macromolecule- Giant molecule
• 4 biological organic macromolecules
Nucleic acids
Functional Groups
• Clusters of atoms that influence the characteristics
of the molecules they make up
• Can use these to identify type of organic
Macromolecule Building Blocks
• Monomers- (micro-molecules) – small, simple
molecules which are the “building blocks” that
bond together to create larger molecules
called polymers (macro-molecules)
o Mono=1
o Poly=many
• Macromolecule- giant molecule made up of
many polymers
Making Large Molecules
• Dehydration Synthesis/Condensation Reactionbuilding larger molecules from smaller molecules by
removing water
• Monomers combine by removing H+ and OHwhich combine to form water in the process of
making a bond
• Reaction which breaks polymers into smaller
molecules (monomers
• Water added to break a bond
• Opposite of condensation
• Carbohydrates – organic compounds composed of
carbon, hydrogen, and oxygen
• Used as energy or structural materials
o Recognized by twice as many hydrogen as carbon and oxygen (ratio 1:2:1)
• Monomers= monosaccharide (1 sugar)
o Ex. Glucose
• Disaccharide= 2 sugars
o Ex. lactose
• Polysaccharide= many sugars
o Ex. starch
Elements – C, O, H
Large non-polar organic molecules
Do not dissolve in water
Store more energy because of higher number of
carbon-hydrogen bonds
• Examples: triglycerides, phospholipids, steroids,
waxes, and pigments
• Composed of 3 fatty acids joined to 1 glycerol
• Composed of 2 fatty acids and 1 phosphate group attached
to a glycerol
• Cell membranes made of 2 layers of phospholipids
– Forms a barrier between inside and outside of cell
• Composed of 4 carbon rings with various functional
groups attached to them
o Ex: cholesterol
• Needed for cells to function properly
Function of Lipids
• Protection
• Insulation
• Storage of Energy
Composed of: C, H, O, N
Monomers – amino acids
Dipeptide – 2 amino acids bonded together
Polypeptides – long chains of amino acids
o Proteins are composed of 1 or more polypeptides
o Held together by peptide bonds
Amino acids
• 20 different amino acids
• Each contain
Hydrogen atom
Carboxyl group
Amino group
R group (side chains
that give proteins
different shapes and
Functions of Proteins
• Build and maintain tissues (structural proteins)
o 1/3 of human proteins are this type
• Regulates cell activities (functional proteins)
o 2/3 of human proteins are this type
• RNA or protein molecule that acts as a biological
• Important for cell function
• Very specific! enzymes work on a specific substrate
because that substrate fits into it’s active site
• Enzyme is NOT changed in the reaction
What are Enzymes
• Most enzymes are proteins
• Act as a catalyst - substance that speeds up a
reaction without being changed in the process
• Enzymes lower the activation energy required for a
specific reaction to occur.
• An organism contains thousands of different
• Each one is specific to a different chemical
• Example: An enzyme with the job of cutting a
protein will not cut a fatty acid or a starch
Lock and Key Model
• “Induced fit model”
• The substrate changes the
shape of the enzyme once it
attaches at the active site.
• The shape change weakens
chemical bonds in the
substrate making it easier to
undergo chemical reactions
Lock and Key Model
• After the reaction takes place, the enzyme releases
the new products formed from the reaction
• Enzyme returns to original shape – ready to accept
new substrates
Factors Affecting Enzyme
• Temperature
• Increasing temperature initially increases the rate of
reaction- more product is formed
• Increasing temperature too much denatures the
enzyme, which changes the shape of the active
site- the substrate can no longer bind and the
reaction will not occur
• All enzymes have an optimum temperature, at
which the maximum rate of reaction occurs; in the
human body most function temperature at 37.0ºC
Factors Affecting Enzyme
• pH
• All enzymes have an optimum pH
• Any change in pH above or below the optimum will
decrease the rate of reaction
• extreme changes in pH can cause enzymes to
• optimum pH in the human body varies with location
(ex. in the stomach, enzymes function in an acidic
Nucleic Acids
• Elements – C, H, O, P, N
• Monomers – nucleotides
o Nucleotides consist of
• Phosphate group
• 5-Carbon Sugar
• Ring shaped nitrogen base
• Large complex organic molecules
• Store and transport important
information in the cell
DNA (double helix)
• Deoxyribonucleic acid
• Contains sugar deoxyribose
• Hereditary information in
DNA is stored as a code
made up of four chemical
bases: adenine (A), guanine
(G), cytosine (C), and
thymine (T)
• Directs cells activity
• Determines characteristics
of organism
• Ribonucleic acid
• Contains sugar ribose
• Helps make correct proteins to keep the cell
growing and functioning correctly
• Single stranded
• Bases found in RNA are adenine (A), guanine (G),
cytosine (C), and uracil (U)
• Uracil replaces thymine (thymine only found in DNA,
uracil only found in RNA)
Plasma (Cell) Membrane
Composed of:
Phospholipids (main
Phosphate head
fatty acid tail
Cholesterol: makes
membrane firm and
impermeable to
water soluble
Membrane proteins
“Phospholipid Bilayer”
*makes cell membrane
selectively permeable
Plasma (Cell) Membrane
• Selectively permeable: allows selected molecules
to enter/leave the cell
• Helps maintain homeostasis
• Homeostasis- the ability of all life to maintain a
stable internal environment
• Separates internal and external environment
• Allows cell to excrete wastes and interact with
Fluid Mosaic Model
Types of Membrane Transport
1. Passive Transport
Requires no energy input from the cell
2. Active Transport
Requires energy input from the cell
Passive Transport
• 4 Types
1. Diffusion
2. Osmosis
3. Facilitated Diffusion
4. Diffusion through Ion Channels
• Movement of molecules from an area of higher
concentration to an area of lower concentration
• Caused by concentration gradient- difference
in concentration of molecules across a distance
• Requires no energy input
• Driven by kinetic energy until
equilibrium is reached
equilibrium- state in which the
concentration of a substance is the
same throughout a space
Molecules still move when they are
in equilibrium-they move in
opposite directions at the same
Diffusion Across a Cell Membrane
Depends on:
size of molecule
chemical nature of membrane (polar or non-polar)
Substances that pass easily through cell membrane:
Small, non-polar molecules (no ions!!!)
o Ex. carbon dioxide and oxygen
What is Osmosis?
• Movement of water molecules across
membrane from an area of higher
concentration to an area of lower
• Diffusion of H2O
• Net direction depends on solute/solvent
concentration inside and outside the cell
The terms hypotonic, hypertonic, and isotonic
describe solutions based on their solute
concentration relative to the cell; compare solute
outside of cell to solute inside cell
Isotonic Environment
• Solution is isotonic to cell:
– Concentration of solute molecules are the same
inside and outside of the cell
– Water moves into and out of the cell at the same
– No net movement of water
Hypertonic Environment
• Solution is hypertonic to cell:
– The concentration of solute molecules outside
of the cell is higher than the concentration of
solute molecules inside the cell
– Net movement of water out of the cell
causing the cell to shrink.
H2 O
← → HO
Hypotonic Environment
• Solution is hypotonic to cell:
– Concentration of the solute molecules
outside the cell is lower than the
concentration of solute molecules inside
the cell
– Net movement of water into the cell, causing
swelling or breakage
H2 O
→ ←HO
Effects of Osmosis on Plant and Animal Cells
Animal cells
solution is isotonic to the cell
* The cell stays the same
Solution is hypertonic to the cell
 In plants, the cell shrinks away from the cell
wall, and turgor pressure decreases creating a
condition called plasmolysis
 In animals, the cell will shrink and become
shriveled; called crenation
Solution is hypotonic to the cell
 In plants, the central vacuoles will fill
causing cell to swell. The pressure exerted by
water on cell wall is turgor pressure
 In animals , the cells will swell and
eventually undergo cytolysis, which is cell
Plant cells
What is Facilitated
• Diffusion of molecules from an area of higher
concentration to an area of lesser concentration
that requires the help of carrier proteins
• No energy required because molecules are
transported down a concentration gradient with
assistance of carrier proteins
• Transports molecules unable to move across the cell
membrane even when a concentration gradient
Molecules may not be soluble in lipids or too large to pass through
pores in membrane
• Carrier proteins are specific; bind to 1 type of
Facilitated Diffusion of
• Important example of facilitated diffusion is
transport of glucose (ose=sugar)
• Glucose = too large to diffuse easily across cell
problem- cells depend on glucose for energy
• When glucose concentration inside cell < than
glucose concentration outside of cell, carrier
proteins transport glucose into cell
Ion Channels
• Transportation of ions through ion channels from an
area of higher concentration to an area of lower
• Small passageways through the cell membrane
used for transportation of ions
• Transports ions important to cell function, but
insoluble in lipids
o Example: Cl-, Ca+ , Na+ , K+
• Each ion channel specific for one ion
Active Transport
• Transport of substances across membrane from an
area of lower concentration to an area of higher
• Materials move against, or up, their concentration
• Requires cell to expend energy (ATP)
• Types of Active Transport
1. Cell Membrane Pumps
2. Endocytosis
3. Exocytosis
Cell Membrane Pumps
• Carrier proteins that use energy(ATP) to move
substances up their concentration gradient
• Similar to carrier proteins involved in facilitated
• Specific
• Protein shape altered to shield molecule
• Protein returns to original shape after molecule released
Sodium Potassium Pump
Uses 1 ATP to transport 3 Na+ ions out
of the cell and 2 K+ ions into the cell
• Important for maintaining Na+ and K+ concentration
some animal cells need higher concentration of Na+ ions
outside cell and higher concentration 0f K+ ions inside cell
to function properly
Creates electrochemical gradient
Endocytosis and
• Used to transport large substances across the cell
• Example: macromolecules and nutrients
• Used to transports large quantities of small
 Both use vesicles for transport and require cell to
use energy (ATP)
• Process by which cells ingest external fluid,
macromolecules, and other large particles,
including other cells
2 Types of Endocytosis
• Based on type of substance taken into the cell
1. Pinocytosis “cell-drinking”
Transport of solute or fluid
2. Phagocytosis “cell-eating”
Transport of large particles or whole cells
• Process by which cells release large particles
contained in vesicles out of the cell
• Reverse of endocytosis
• Secretion and excretion are types of exocytosis
Where do Living Things
get Energy?
• Directly or indirectly, almost all energy in living
systems comes from the sun
• Organisms that use photosynthesis obtain energy
directly from the sun and store it in the bonds within
organic compounds (glucose)
What is Photosynthesis?
• Process carried out by autotrophs that uses light
energy from the sun, water, and carbon dioxide
to produce carbohydrates and oxygen
• Light energy is converted to chemical energy
• Occurs ONLY in green plants, algae and some
bacteria because they contain specialized
structures called chloroplasts
2 Stages of Photosynthesis
• Light Reactions
o Light is reguired!
o Light energy (sunlight)
converted to chemical
energy (ATP and NADPH)
• Calvin Cycle (Dark
o Light not directly required
but products of light
reaction are necessary (ATP
and NADPH); energy stored
in ATP and NADPH needed
to produce glucose
o Organelles found in plant cells that have a double membrane
(inner and outer)
o contain the pigment chlorophyll that absorbs sunlight
o Photosynthesis occurs in this organelle; light energy converted
into chemical energy
Biochemical Pathways
o Biochemical pathway =
series of chemical
reactions where the
product of a reaction is
the reactant in the next
• Organic
and oxygen produced
in photosynthesis are
reactants for cellular
Harvesting Chemical Energy
• Autotrophs and
heterotrophs undergo
cellular respiration to
convert chemical energy
in organic compounds
(from photosynthesis) to
metabolically useable
energy (ATP)
• Chemical components
important to life are
recycled by
photosynthesis and
cellular respiration;
energy is not recycled
• ATP is a nucleotide
• Phosphate bonds break easily by hydrolysis to release
o ATP + H2O → ADP + Pi
• Major energy currency of the cell; supplies the energy
that drives all cellular processes
• One of the monomers used in the synthesis of RNA
• Regulates many biochemical pathways.
Cellular respiration
• Process cells use to break down organic
compounds to produce adenosine triphosphate
• Glucose broken down - energy temporarily stored in
• Generates 38 molecules of ATP
• Provides energy necessary for all life activities
o Cellular maintenance
o Production of macromolecules that make up cells
Cellular Respiration
• C6H12O6 + 6O2 → 6 CO2 + 6 H2O + ATP
• Chemical equation
opposite of overall chemical equation for
• Primary fuel for cellular respiration = glucose
Photosynthesis and
Cellular Respiration
Steps in Cellular
Aerobic Respiration
• Occurs in mitochondria
• 2 stages
1. Krebs Cycle
o Produces 2 ATP
2. Electron Transport Chain
o Electron transfer produces 34 ATP
• Net gain of 36 ATP from aerobic respiration
Anaerobic Respiration
• Lactic Acid Fermentation
o 2 pyruvic acid molecules from glycolysis → lactic acid
o Net gain of 2 ATP produced in glycolysis
• Alcohol Fermentation
o 2 pyruvic acid molecules from glycolysis → CO2 and ethyl
o Net gain of 2 ATP produced in glycolysis
• No ATP produced in fermentation pathways – only
electron carriers
The Cell Cycle
• Process by which a eukaryotic cell separates the
chromosomes in its nucleus into 2 identical sets
• Results in cell growth and division into two daughter
• Interphase
• the cell prepares itself for cell division
• cell grows by increasing its supply of proteins and
the number of many organelles in all 3 phases
• G1 Phase- cell grows
• S Phase- chromosomes are replicated
• G2- cell prepares to divide
The Mitotic Phase
• Also called the M phase
• Includes both mitosis and cytokinesis
• In mitosis, the nucleus and duplicated
chromosomes divide and are evenly distributed
forming 2 daughter nuclei (nucleus plural)
• In cytokinesis, the cytoplasm is divided into 2;
begins when mitosis ends
The Cell Cycle
What is Meiosis
• Meiosis is a process of cell division that produces
gametes (eggs and sperm)
• Produces 4 cells, each with ½ the number of
chromosomes as the parent cell
• The purpose of meiosis
a) is to reduce the normal diploid cells (2 copies of
each chromosome / cell) to haploid cells, called
gametes (1 copy of each chromosome per cell)
• Diploid number in humans: 2n=46
2 Stages of Meiosis
• Cells duplicate their DNA and undergo 2 rounds of
• Meiosis I separates the duplicated homologues
from each other which reduces the number of
chromosomes in each cell
• Meiosis II separates the sister chromatids from one
• Offspring from meiosis have half the number of
chromosomes as their parent cell, because they
receive just one copy of each chromosome, rather
than two
• The study of heredity
• Gregor Mendel was the 1st to apply an
experimental approach to the question of
• Parents pass genes to their offspring that are
responsible for inherited traits
• Trait- variation of a particular character (ex. Red
flower, yellow flower)
• Gene- unit of inheritance in DNA
Principle of Segregation
• Mendel's principle of
segregation states that
during gamete formation
the alleles in each gene
segregate and pass
randomly into gametes
• Hybrids- the offspring of 2
different true-breeding
• Monohybrid Cross- parent
generation differs in only 1
character (ex. Flower color)
• In a monohybrid cross, the
F2 generation displays two
phenotypes in a 3:1 ratio
Mendel’s Hypotheses
• There are alternative forms of genes- alleles (ex. Gene for
flower color exists in one form for red and another for white)
• For each inherited character, an organism has 2 alleles for the
gene controlling that characteristic, on from each parent
o Homozygous- alleles are the same
o Heterozygous- alleles are different
• When only 1 of 2 different alleles in a heterozygous individual
shows up as a trait, that allele is the dominant allele
(represented by a capital letter). The allele for the trait not
shown is recessive (represented by a lower case letter)
• The 2 alleles for a characteristic segregate (separate) during
the formation of gametes so that each gamete carries only 1
allele for each character- principle of segregation
Punnett Square
• Diagram that
shows all possible
outcomes of a
genetic cross
• Can be used to
probabilities of a
particular outcome
if you know the
genetic makeup of
both parents
Genotype and Phenotype
• Phenotype- observable trait
• Genotype- genetic makeup or combination of
• Breeds an individual with an unknown genotype,
but dominant phenotype, with a homozygous
recessive individual
Dihybrid Cross
• A cross with organisms differing in 2 characteristics
Relationship Between DNA, Genes, Alleles,
and Chromosomes
• The sequence of
nucleotides in a section of
DNA (the gene) determine
the sequence of amino
acids in a polypeptide, the
type of protein being
• A gene is just the specific
portion of the DNA
molecule that contain the
information required to
synthesize a particular
• A single DNA molecule
contains many GENES
• Genes have more than 1
allele for a characteristic
Multiple Alleles and
• for many genes, more than 2 alleles exist; for
example, multiple alleles control the characteristic
of blood type
• Codominance- Heterozygote expresses both traits;
shows the separate traits of both alleles (ex. Blood
Blood Type
Codominance Example
Polygeneic inheritance
• 2 or more genes affect a single character
DNA Replication
• Process by which DNA is copied
• Protein synthesis requires two steps: transcription
and translation.
• Transcription is the synthesis of RNA from a DNA
• Only one strand of DNA is copied.
• A single gene may be transcribed thousands of
• After transcription, the DNA strands rejoin.
• Some of the RNA produced by transcription is not
used for protein synthesis. These RNA molecules
have other functions in the cell.
• Translation is the
process where
ribosomes synthesize
proteins using the
mature mRNA
transcript produced
during transcription.
• The diagram shows a
ribosome attach to
mRNA, and then
move along the
mRNA adding amino
acids to the growing
polypeptide chain.
• fundamental physical and functional unit of
• carries information from one generation to the
• a segment of DNA, composed of a transcribed
region(region for transcription) and a regulatory
sequence that makes possible transcription
(sequence to start and stop transcription)
DNA as a Genetic Material
• 1. The complementary base pairing enable
replication and coping of DNA in a semiconservative manner.
• 2. DNA molecule is metabolically stable—allows the
information to be transferred from generation to
another with only little variation.
• 3. The H-bond can be easily broken and reformed,
allowing DNA replication and transcription
One Gene, One Polypeptide
• States that each gene is responsible for directing
the building of one, specific polypeptide (may be
an enzyme, structural protein, etc.)
• Used to be one gene, one enzyme
• Explains the relationship between genotype
and phenotype
o Genotype (genetic makeup)the sequence of nucleotide
bases in an organisms DNA
o Phenotype- organisms specific
traits (ex. Brown hair)
Beneficial Results of One
Gene, One Polypeptide
• Many inherited diseases , including hemophilia and
cystic fibrosis, result when a single defective gene
causes the production of a non-functional protein
• Gene therapy attempts to replace the defective
genes with normal ones, allowing the body to
produce the necessary protein and function