Transcript Keystone Test Preparationx

Keystone Test
Preparation
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
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o Examples: Bacteria, blue-green algae
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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
Cells
• Have the following
organelles:
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
highway)
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
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Carbohydrates
Lipids
Proteins
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
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
Example:
Hydrolysis
• Reaction which breaks polymers into smaller
molecules (monomers
• Water added to break a bond
• Opposite of condensation
reaction/dehydration
synthesis
Carbohydrates
• 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
Lipids
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
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Triglyceride
• Composed of 3 fatty acids joined to 1 glycerol
Phospholipids
• 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
Steroids
• 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
Proteins
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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
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Hydrogen atom
Carboxyl group
Amino group
R group (side chains
that give proteins
different shapes and
functions)
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
Enzymes
• RNA or protein molecule that acts as a biological
catalyst
• 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
enzymes
• Each one is specific to a different chemical
reaction
• 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
Activity
• 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
Activity
• 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
denature
• optimum pH in the human body varies with location
(ex. in the stomach, enzymes function in an acidic
environment)
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
o DNA
o RNA
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
RNA
• 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)
DNA vs. RNA
Plasma (Cell) Membrane
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Composed of:
Phospholipids (main
component)
Phosphate head
fatty acid tail
Cholesterol: makes
membrane firm and
impermeable to
water soluble
substances
Membrane proteins
“Phospholipid Bilayer”
*makes cell membrane
selectively permeable
Plasma (Cell) Membrane
Functions
• 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
environment
Fluid Mosaic Model
Types of Membrane Transport
1. Passive Transport
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Requires no energy input from the cell
2. Active Transport
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Requires energy input from the cell
Passive Transport
• 4 Types
1. Diffusion
2. Osmosis
3. Facilitated Diffusion
4. Diffusion through Ion Channels
Diffusion
• 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
rate!!
Diffusion Across a Cell Membrane
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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
concentration
• Diffusion of H2O
• Net direction depends on solute/solvent
concentration inside and outside the cell
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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
rate
– No net movement of water
H2O
←
→HO
2
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
2
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
2
Effects of Osmosis on Plant and Animal Cells
Animal cells
Condition
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
bursting
Plant cells
What is Facilitated
Diffusion?
• 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
exists
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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
molecule
Facilitated Diffusion of
Glucose
• Important example of facilitated diffusion is
transport of glucose (ose=sugar)
• Glucose = too large to diffuse easily across cell
membrane
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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
concentration
• 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
concentration
• Materials move against, or up, their concentration
gradient.
• 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
diffusion
• Specific
• Protein shape altered to shield molecule
• Protein returns to original shape after molecule released
Sodium Potassium Pump
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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
difference
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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
Exocytosis
• Used to transport large substances across the cell
membrane
• Example: macromolecules and nutrients
• Used to transports large quantities of small
molecules
 Both use vesicles for transport and require cell to
use energy (ATP)
Endocytosis
• 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”
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Transport of solute or fluid
2. Phagocytosis “cell-eating”
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Transport of large particles or whole cells
Exocytosis
• 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
Reaction)
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
Chloroplast
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
reaction
• Organic
compounds(glucose)
and oxygen produced
in photosynthesis are
reactants for cellular
respiration
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
• ATP is a nucleotide
• Phosphate bonds break easily by hydrolysis to release
energy
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
(ATP)
• Glucose broken down - energy temporarily stored in
ATP
• 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
Overview
• C6H12O6 + 6O2 → 6 CO2 + 6 H2O + ATP
• Chemical equation
opposite of overall chemical equation for
photosynthesis
• Primary fuel for cellular respiration = glucose
Photosynthesis and
Cellular Respiration
Steps in Cellular
Respiration
Aerobic Respiration
Summary
• 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
Summary
• 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
alcohol
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
cells
• 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
division
• 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
another
• 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
Meiosis
Genetics
• The study of heredity
• Gregor Mendel was the 1st to apply an
experimental approach to the question of
inheritance
• 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
varieties
• 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
predict
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
alleles
Testcross
• 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
synthesized.
• A gene is just the specific
portion of the DNA
molecule that contain the
information required to
synthesize a particular
protein
• A single DNA molecule
contains many GENES
• Genes have more than 1
allele for a characteristic
Multiple Alleles and
Codominance
• 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
type)
Blood Type
Codominance Example
Polygeneic inheritance
• 2 or more genes affect a single character
DNA Replication
• Process by which DNA is copied
Transcription
• Protein synthesis requires two steps: transcription
and translation.
• Transcription is the synthesis of RNA from a DNA
template.
• Only one strand of DNA is copied.
• A single gene may be transcribed thousands of
times.
• 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.
Transcription
Translation
• 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.
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Gene
• fundamental physical and functional unit of
heredity
• carries information from one generation to the
next
• 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
normally