IMMUNE SYSTEM AND DEFENSE MECHANISMS
1. Understand how bacteria utilizes physical barriers and other mechanisms to protect itself
● Capsule: made of
● Cell wall: made of
● Plasma membrane
● Toxic molecules
● Enzymes that detoxify antibiotics
● Mutation or
modification of target
● Restriction and
2. How do fungi defends itself against bacteria and also infect plants?
● Cell wall: made of
● Toxic molecules to
● Mutagenic chemicals
● Enzyme cellulase
infects and destroys
● Rapid growth rate
● Deep hyphae (roots)
3. List various ways plants defend against bacteria, fungi and animals utilizing various barriers, toxins and chemical signals
● Cell wall (primary and secondary): made of
● Bark, thorns, leaf hairs, waxy coating/cuticle
● Toxic, hallucinogenic, carcinogenic,
● Secondary metabolites
● Enzymes that defend against fungal
● Detoxify herbicides
Don't forget about the age old question of What is the purpose of logic?
4. What are some examples of innate immunity and acquired immunity in animals and humans?
● Skin, mucus, hair, secretions
● Histamines, toxic peptides
● White blood cells: macrophages
● Killer T cells
● B cells recognize antigens (using
membrane surface proteins) and store the information
● When the real infection occurs, B cells produce specific antibodies to
recognize virus or bacteria and degrade them
○ How vaccines work
5. Consider the common themes that run across the domains and kingdoms
All living organisms go through some type of respiration process to produce energy. ● Eukaryotes Don't forget about the age old question of What are the sources of international law?
○ Animals use nutrients consumed to fuel cellular respiration to produce ATP (energy) ○ Plants also do cellular respiration, but they also conduct photosynthesis ■ Using light energy, carbon dioxide, and water to produce glucose and If you want to learn more check out How does language influence our thinking?
oxygen, and water
○ All prokaryotes use anaerobic respiration/fermentation in order to make ATP
INTRODUCTION TO METABOLISM
Course guide chapter 8
1. Define metabolism, anabolism and catabolism and give examples for each
All living cells have the life property of metabolism.
● Metabolism: the sum of all biochemical reactions that take place in an organism ○ What makes and sustains cells
○ Metabolic processes break down (catabolism) and produce (anabolism) organic molecules
■ These processes provide energy for cells to move, transport, and more
○ Anabolic processes synthesize or build up molecules
■ Example: photosynthesis (making glucose, oxygen, and water)
○ Catabolic processes break down or degrade molecules
■ Example: respiration (breaking down nutrients)
2. Describe how the two laws of thermodynamics apply to biological systems
Thermodynamics: study of heat and its transformation to mechanical energy ● First law of thermodynamics: energy can be transferred or transformed, but it can’t be created or destroyed We also discuss several other topics like What are the differences in crops between high islands and low lying atolls?
○ The total energy of the universe is constant
○ Example: in photosynthesis, light energy is transformed into chemical energy; there is not a decrease in light energy and subsequent increase in chemical energy ● Second law of thermodynamics: every energy transfer or transformation leads to increased entropy (randomness) in the universe
3. Define entropy, enthalpy and free energy and give examples. Understand how they are related to each other in the free energy equation AND
4. Know examples of exergonic, endergonic, exothermic and endothermic reactions and combinations of the same. No need to memorize the bond energies
Free energy equation: ΔG = ΔH - T (ΔS)
[Δ stands for “delta”, which represents net change (final - initial)]
● ΔG: Free energy (the energy available to do work)
○ -ΔG: exergonic reaction
■ Net loss of energy; release of free energy
■ Spontaneous and favorable
■ Example: melting ice; respiration
○ +ΔG: endergonic reaction
■ Net gain of energy; consumption of free energy
■ Nonspontaneous and unfavorable
■ Example: climbing uphill; photosynthesis
● ΔH: enthalpy (total potential energy/heat content)
○ -ΔH: exothermic reaction
■ Net loss/release of heat/potential energy
■ Example: burning gas
○ +ΔH: endothermic reaction
■ Net gain/consumption of heat/potential energy
■ Example: melting ice
● ΔS: entropy (measure of randomness)
○ -ΔS: decreased entropy
○ +ΔS: increased entropy
● T: absolute temperature in Kelvin
All of these concepts relate together in the free energy equation.
Example: the photosynthesis reaction/equation is:
● Endergonic: gain in energy (glucose is produced); consumes energy
● Endothermic: consumes heat
● -ΔS: it is an anabolic process
5. Understand how Keq is calculated with given concentrations of reactants and products Equilibrium occurs when ΔG = 0.
The equilibrium constant (Keq) is the ratio of the concentration of products to the concentration of reactants at equilibrium.
● [product] / [reactant]
● A higher equilibrium constant = a faster reaction
● Example: ΔG = -0.4 ; ΔG = -7.0
○ The second reaction has a higher constant, and therefore the reaction will occur faster than the first one
6. What is ATP and how it is used to drive endergonic processes through energy coupling?
ATP (adenosine triphosphate) is an energy molecule used to fuel work in the cell. And ATP hydrolysis (ATP + H2O → ADP + Pi) is a thermodynamically favorable exergonic reaction, so it can be coupled with endergonic reactions that aren’t spontaneous.
● ATP can be broken down (exergonic, spontaneous/favorable) and this reaction is used to help fuel endergonic (nonspontaneous/unfavorable) reactions
● Example: glucose + fructose → sucrose + H2O
○ This reaction is endergonic and nonspontaneous (+ΔG)
○ But ATP is used to drive the reaction forward
■ To make the reaction occur spontaneously, ATP is broken down into ADP and Pi (this itself is an exergonic and spontaneous reactions)
7. Describe enzymes and how do they help in a catalytic reaction. Know the relationship between the enzyme active site, catalysis, free energy and activation energy changes
Enzymes are biological catalysts; they are proteins that accelerate reactions by lowering the activation energy of the reaction.
● The activation energy (or energy of activation) of a reaction is the amount of energy that must be consumed to break the bonds
○ Enzymes don’t change the activation energy, but they lower it, therefore allowing the reaction to occur more quickly than it would without the enzyme
● Enzymes are specific to a particular substrate: the reactant used by an enzyme ○ The substrate binds at the active site on the enzyme
○ Enzymes recognize substrates by their molecular shape and function groups ○ Enzymes physically conform to fit their substrate when the substrate binds; this is called induced fit
● Course guide pg 63
8. Know the different factors affecting enzyme activity and examples
There are 4 major factors that affect enzyme activity
● Temperature: enzymes function at an optimal temperature (different for different enzymes) ● pH: same as temperature, there is an optimal pH for enzymes
● Salt concentration: enzymes require the presence of certain salts at certain concentrations
● Substrate: enzymes are specific to their substrate, so an enzyme needs the right substrate to perform properly
Vmax is the highest velocity of the enzyme, or the maximum rate of reaction. ● Vmax is achieved when all active sites are filled with the substrate
● The rate of the reaction is measured by Km
○ Km: substrate concentration at which the rate of the reaction is half its maximum ■ Substrate concentration at which half the enzyme active sites are filled with substrates
● There are different Vmax and Km values for each substrate
Cofactors are molecules that help activate enzymes.
● Inorganic cofactors: Zn, Fe, Cu
● Organic cofactors: coenzyme A, NAD+, FAD, NADP+
9. Understand the substrate concentration, competitive inhibitors, non-competitive inhibitors affect enzyme activity. Know how these inhibitors affect the Vmax and Km
Activators are molecules that bind to the enzyme and change the enzyme’s conformation with a positive effect on the enzyme’s activity.
Inhibitors are molecules that bind to the enzyme, change its conformation, and cause reduced enzyme activity
● Competitive inhibitors: inhibitors that compete with the substrate for the active site ○ Reversible
○ Vmax is unchanged, but Km increases
● Non-competitive inhibitors: bind to the enzyme at some place other than the active site and change the enzyme’s conformation, making it less active or inactive
○ Cannot be undone by adding the correct substrate
○ Vmax decreases, Km remains the same
● Irreversible inhibitors: bind to active site, make the enzyme permanently inactive
10. Understand how allosteric, feedback and chemical modification regulate enzyme activity.
Allosteric regulation: “allo” means alternate; “steric” means conformation/shape ● Allosteric enzymes have active and inactive forms
○ They are complex enzymes with separate catalytic and regulatory subunits ○ An activator or inhibitor binds to the enzyme, changes its conformation to active or inactive form, respectively
○ Course guide pg 66
● The end product of a biosynthetic pathway, or an intermediate of another pathway inhibits an earlier enzyme and stops the whole pathway
● Course guide pg 66
Course Guide Chap. 9
1. State an overview of cellular respiration in terms of the overall redox changes and energy-coupled reactions that occur.
Glucose + oxygen → carbon dioxide + water + energy
C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP
● This is a basic general equation for aerobic respiration
● There are 4 major processes that make up respiration:
○ Glycolysis (occurs in cytoplasm)
○ Acetyl coA formation (occurs in mitochondria)
○ Krebs cycle (occurs in matrix in mitochondria)
○ Oxidative phosphorylation (occurs in inner membrane of mitochondria)
● Respiration utilizes energy compounds (carbs, fats, proteins that we get from food) to generate energy in the form of ATP
Respiration consists of redox reactions (reduction and oxidation)
● Reduction reactions: gain of electrons, loss of oxygen
● Oxidation reactions: loss of electrons, gain of oxygen
● “OIL RIG”
○ Oxidation is loss; reduction is gain (of electrons)
ATP hydrolysis allows for energy coupling during many respiration reactions
● ATP hydrolysis is a favorable, exergonic reaction, so it can be coupled with unfavorable, endergonic reactions to help them occur
2. Summarize the major net inputs, outputs and key steps of cellular respiration processes (glycolysis, acetyl CoA formation, citric acid cycle and oxidative phosphorylation). 3. Be able to connect how the outputs of one process become inputs of another process of aerobic respiration (glycolysis, acetyl CoA formation, citric acid cycle and oxidative phosphorylation).
Glycolysis is the first step in respiration. It is the breaking down of glucose.
● Step 1: the enzyme hexokinase phosphorylates glucose - first committed step for glycolysis ○ Glucose + ATP → (hexokinase) → glucose 6-phosphate
● Step 3: the enzyme phosphofructokinase phosphorylates fructose 6-phosphate ○ Fructose 6-phosphate + ATP → (phosphofructokinase) → fructose 1,6 biphosphate + ADP
● Glucose →
● 2 ADP, Pi →
● 2 pyruvates
● 2 ATP
● 2 NAD+ →
● 2 NADH
Acetyl CoA formation is the second step in respiration and is a one-step process ● Pyruvate formed during glycolysis is transported into the mitochondrion, where a pyruvate dehydrogenase complex oxidizes it and converts it to acetyl CoA
○ CO2 is released
○ NAD+ is reduced and becomes NADH
● Pyruvate (input) → acetyl CoA (output)
○ Other outputs are CO2 and NADH
The Krebs cycle/citric acid cycle is the third step.
● Step 1: acetyl CoA (2C) + Oxaloacetate (4 C) → (water is added) → citrate (6 C) + CoA + H ● Step 3: isocitrate dehydrogenase converts isocitrate to ketoglutarate
○ NAD+ is reduced to NADH
● 2 A CoA →
● 6 NAD+ →
● 2 FAD →
● 2 ADP, 2 Pi →
● 4 CO2, 2 CoA
● 6 NADH
● 2 FADH2
● 2 ATP
Oxidative phosphorylation is the final step.
● NADH and FADH2 lose their electrons to the electron transport chains (a series of membrane proteins). The ETC transfer the electrons to oxygen, which is the final electron acceptor ○ This is why aerobic respiration requires oxygen
○ Water is generated as a byproduct
● While the electrons go through the ETC, protons (H+) are pumped out of the matrix into the intermembrane space, creating a greater concentration of protons in the intermembrane space ○ The protons then move from high to low concentration and cross the inner membrane by passing through ATP synthase
○ This fuels ATP synthesis, allowing multiple ATP molecules to be made
● NADH →
● FADH2 →
● ADP, Pi →
● O2 →
4. Explain how energy stored in different types of food molecules can be released in a series of redox processes to produce ATP by oxidative phosphorylation and substrate-level phosphorylation.
ATP is made by either substrate level phosphorylation (SLP) or oxidative phosphorylation, during respiration.
● SLP: ATP is made by transferring a phosphate from a high energy phosphate, to ADP ○ ADP + Pi → ATP
○ The enzyme kinase is responsible for this
○ This is how ATP is made during glycolysis and the Krebs cycle
● Oxidative phosphorylation is the major aerobic process that generates the most ATP during respiration
○ Protons are pumped from the matrix out to the intermembrane space of the mitochondrion; the protons then come back to the matrix, crossing through ATP synthase on the inner membrane
○ The protons going through ATP synthase fuels this protein, allowing for ATP synthesis ○ This is how ATP is made during oxidative phosphorylation during respiration
5. Tell where the steps of cellular respiration occur in prokaryotic and eukaryotic cells, and explain the role of mitochondrial structure in the latter
Occurs in cytoplasm
Acetyl CoA Formation
Cytoplasm → mitochondria
Mitochondria matrix and inner membrane
Mitochondria matrix and inner membrane
Mitochondria structure: explained above in summary/steps of respiration
6. Describe how cellular respiration is regulated in cells. Be able to predict responses to changing conditions such as lack of oxygen, lack of carbohydrate fuels, relative abundance of ATP/ADP, or the presence of specific toxins.
Without oxygen, respiration cannot occur, and the only option is fermentation. ● This is how prokaryotes always make ATP, but it can occur in eukaryotes if there is little or no oxygen
● Without oxygen, there is no final electron acceptor at the end of the ETC in oxidative phosphorylation, so there is only ATP made during glycolysis
○ NAD+ needs to be regenerated in order to keep glycolysis going; this can occur in two different types of fermentation:
● Alcohol fermentation
○ 2 pyruvates made during glycolysis are converted to acetaldehyde
○ CO2 is released
○ Acetaldehyde is hydrogenated to form ethanol, using NADH as the reducing agent (by alcohol dehydrogenase) - so NAD+ is regenerated
○ Ethanol is a byproduct, makes alcohol
○ 2 ATP are produced
● Lactic acid fermentation
○ Performed by animals in muscle cells
○ NAD+ is regenerated by converting pyruvate into lactate
■ Lactate goes to the liver to be reconverted into glucose for later use
○ Causes muscle fatigue
Respiratory poisons can affect respiration
● Uncouplers of proton gradient make the membrane leaky; no proton gradient is created, so no ATP synthesis can occur
● ATP synthase inhibitors bind to ATP synthase and stop the production of ATP ● Electron transport inhibitors block electron transport at various stages - results in reduced or lack of proton gradient and ATP synthesis
○ Block O2 from accepting electrons
Course Guide Chap. 10
1. Summarize why photosynthesis is important to life on earth and write a summary equation for photosynthesis, identifying the inputs and outputs.
Photosynthesis allows photoautotrophic plants to utilize solar energy from the sun to fix atmospheric CO2 into carbohydrates. Photosynthesis creates carbs and other organism compounds, which make up all other organic molecules.
● Heterotrophic organisms depend on photoautotrophs for food and oxygen, which are made from photosynthesis
Photosynthesis summary reaction:
6CO2 + 12H2O → (light energy) → C6H12O6 + 6O2 + 6H2O
● Carbon dioxide and water along with light energy (inputs) → produce glucose, oxygen, and water (outputs)
● This is a reduction reaction, it is endergonic, endothermic, and anabolic
2. Describe the major events that take place during light reactions and Calvin cycle of photosynthesis.
3. Discuss cyclic vs noncyclic electron flow, and the net inputs and outputs of each. 4. Describe the Calvin cycle, including the role of ATP and NADH, net inputs and the ultimate product(s) of the reaction.
5. Know the rate limiting step 1 and enzyme, RuBisCO of Calvin cycle and how it is regulated.
Photosynthesis consists of two major sets of reactions: the light reactions, and the Calvin cycle (occur in this order).
The light reactions require the presence of light, and occur on the thylakoid membrane of the chloroplast.
● There are two photosystems (membrane proteins) on the thylakoid membrane, which harvest light energy from the sun to generate ATP and NADPH in the stroma
○ These photosystems contain chlorophyll and other pigments that absorb light ○ Each has its own reaction center, where specialized chlorophyll a molecules emit excited electrons
○ The excited electrons in the PS are transferred in either cyclic or non-cyclic
● Reaction center absorbs light with 700 nm peak (color is
● Reduce NADP+ to NADPH in
non-cyclic photophosphorylation ● ATP synthesis
● Present in cyclic and non-cyclic photophosphorylation
● Primitive in evolution
● Reaction center absorbs light with 680 nm peak (orange-red)
● Splits water into two H+, 2
electrons, and ½ of O2
● ATP synthesis
● Only in non-cyclic
● Most recent in evolution
● In cyclic photophosphorylation, excited electrons in PS I reaction center are received by the primary electron acceptor
○ They then go through an ETC (series of membrane proteins) before returning to the PS I reaction center
■ This creates a proton gradient that will drive ATP synthesis
○ This process occurs in primitive plants, and when no NADPH is needed
● In non-cyclic photophosphorylation, the electrons start in PS II reaction center, go through the ETC, to arrive at the PS I reaction center
○ ATP is generated from this electron transfer
○ The electrons from PS I are transferred to a membrane protein, where they are used to reduce NADP+ to NADPH
○ H2O is split to replace the electrons lost by the PS II reaction center
■ H is kept, O2 is released into the air as the oxygen we breathe
○ ATP and NADPH is made (these will be used in the Calvin cycle)
The Calvin cycle occurs after the light reactions, and are light-independent. This cycle requires the ATP and NADPH generated during the light reactions. It occurs in the stroma.
● 1: carbon fixation (key step)
○ CO2 combined with 3 RuBP → generates 2 3-phosphoglycerate by the enzyme rubisco ■ Key regulatory step to control the synthesis of sugars by CO2 fixation
● 2: reduction reactions
○ The phosphoglycerate is phosphorylated into 1,3 bisphosphoglycerate kinase ■ Uses ATP from the light reactions
○ 1,3 bisphosphoglycerate is dephosphorylated and reduced to glyceraldehyde 3-phosphate
■ NADPH → NADP+ + Pi
○ glyceraldehyde 3-phosphate goes through a series of reactions to produce glucose and other sugars
● 3: regeneration of RuBP
○ glyceraldehyde 3-phosphate molecules are used in a series of steps to regenerate 3 molecules of RuBP
○ Allows the cycle to start over and continue
○ Uses 3 ATP
● Rubisco is regulated by concentration of CO2 and O2 in the cell, Mg2+ concentration, pH, and NADPH levels
6. Describe how light energy is harvested and how its absorption is related to wavelength.
Sunlight is a form of electromagnetic wave energy with particular photons (individual particles of light). ● Photon energy is inversely proportional to its wavelength
● R O Y G B I V
750 nm (longest wavelength, lowest energy) - 380 nm (shortest wavelength, highest energy) ● Photosystems I and II are what harvest light energy from the sun
○ They contain chlorophyll pigments that absorb photons
● Plants are green because they reflect green light
7. Identify parts of the leaf and chloroplast where light reactions and Calvin cycle takes place
The light reactions occur on the thylakoid membrane of the thylakoid in the chloroplast. The Calvin cycle occurs in the stroma of the chloroplast.
Course guide pg 85
8. Trace the path of an excited electron from its absorption of solar energy to the production of ATP and NADPH.
● Step 1: excited electrons start in the reaction center of photosystem II
● Step 2: the electrons go through the ETC on the membrane, and arrive at the PS I reaction center ○ This electron transport creates a proton gradient in the thylakoid space
○ NADPH is created when NADP+ is reduced at the end of the ETC
● Step 3: ATP synthesis occurs when the protons in the thylakoid space cross the membrane through ATP synthase, fueling the protein and making ATP
9. Compare and contrast chemiosmosis and ATP production in mitochondria and chloroplasts.
● Both use chemiosmosis to generate ATP through these steps:
○ Electrons pass through the ETC, which creates a proton gradient on the other side of the membrane, as protons are pumped through the membrane
○ This proton gradient becomes a proton motive force, crossing the membrane again by going through ATP synthase, this drives the phosphorylation of ADP, therefore allowing ATP synthesis
● In mitochondria, these steps take place in the matrix, inner membrane, and intermembrane space
○ Inputs: NADH, FADH2, ADP, Pi, O2
○ Outputs: NAD+, FAD, ATP, H2O
● In chloroplast, they take place on the thylakoid membrane and in the stroma ○ Inputs: NADP+, ADP, Pi, light energy, H2O
○ Outputs: ATP, NADPH, O2
● In mitochondria, NADH is oxidized to NAD+
● In chloroplast, NADP+ is the electron acceptor, it is reduced to NADPH
10. Understand how photorespiration affects C3 photosynthesis with PEP carboxylase.
C3 plants only use the Calvin cycle to fix CO2. The majority of plants are C3 plants. ● Rubisco will utilize the process of photorespiration when water is in limited supply (hot, sunny days) and stoma are closed to conserve moisture
● Rubisco fixes O2 into RuBP without making sugar or ATP
● This will occur until CO2 levels are back to normal within the cell
11. Compare and contrast C4 and CAM photosynthesis and the ways to minimize photorespiration.
C4 plants have alternate strategies to overcome photorespiration and maximize CO2 fixation. ● The enzyme phosphoenolpyruvate carboxylase (PEP carboxylase) fixes CO2 into 4-C sugars ○ Has no affinity for O2
○ Even during hot weather, CO2 fixation continues and photorespiration is minimized ● These plants use C3 and C4 pathways
CAM plants don’t have separate cells for C3 and C4 pathways.
● They carry out C3 reactions during the day, and use C4 reactions at night ● This is common in succulent desert plants to fix CO2
MITOSIS AND MEIOSIS Course Guide Chap. 11 and 12
1. Know the three different types of cell division and the types of cells and organelles that would undergo such divisions.
Types of cell division: binary fission, mitosis, meiosis
● Binary fission is how prokaryotes, mitochondria, and chloroplasts undergo cell division ○ No nucleus is involved
○ They have circular DNA, and a relatively smaller genome
● Mitosis: all eukaryotes undergo cell division through mitosis
○ Only for somatic cells
○ Involves nucleus division
○ Generates identical cells (which can then differentiate to form different tissues) ● Meiosis: eukaryotes use meiosis for sex cell division
○ Reduction division
○ Chromosome numbers are reduced by half
○ Generates variations to form gametes (egg and sperm)
2. Describe the major steps in the process of binary fission, mitosis and meiosis and the key event that is unique to each stage.
Prokaryotes have one single large circular chromosomes, which is replicated, and multiple small circular extrachromosomal DNA called plasmids.
● R plasmids produce antibiotic resistance
● F plasmids are responsible for fertility conjugation
● C-factors are toxins
The DNA and plasmids replicate and the cell grows in size and volume.
● A new cell wall is formed in the middle of the cell, called a septum
○ It allows a new cell wall and membrane to form and separate the cells
● Plasmids are distributed randomly (so new cells are not exactly identical)
Mitosis consists of 6 stages.
● Before mitosis occurs, the cell goes through interphase
○ G1 phase: growth and division within the cell
○ S phase: DNA replication
○ G2 phase: more internal growth
● Prophase (first stage of mitosis)
○ Nuclear envelope is still intact
○ Chromatin condenses into chromosomes
■ Two sister chromatids join together at the centromere to form one chromosome ○ Centrioles in the cell migrate to opposite poles
○ Nuclear envelope disassembles
○ Centrioles attach to chromosomes with spindle fibers
■ Attach at the kinetochore
○ Chromosomes line up in the middle of the cell at the metaphase plate
○ Chromosomes migrate to opposite ends of the cell
■ With the help of motor proteins and enzymes
● Telophase and cytokinesis
○ Cell divides into two new ones
■ Plants form a cell plate in the middle
■ Animal cells form a cleavage furrow in the middle
○ Nucleus divides
○ 2 identical cells are made
Meiosis consists of meiosis I and meiosis II
● Meiosis I
○ Prophase 1: nuclear envelope intact; chromatin → chromosomes; crossing over occurs; spindle fibers attach to one side of the centromere
○ Metaphase 1: homologs (homologous chromosomes) line up at the metaphase plate and migrate to opposite poles; independent assortment occurs
○ Anaphase 1: sister chromatids are still attached; kinetochore microtubules depolymerize to become shorter and shorter
○ Telophase and cytokinesis 1: plant cells form cell plate, animal cells form cleavage furrow
■ There is now one long and one short chromosome in each new cell
■ 2 cells are formed with just one set of chromosomes each - sister chromatids are still attached
● Meiosis II
○ Prophase 2: no crossing over; chromatin condenses to chromosomes; spindle fibers attach to both sides of centromere; nuclear envelope disappears
○ Metaphase 2: chromosomes line up in middle, more independent assortment occurs ○ Anaphase 2: sister chromatids separate and move to opposite poles; nondisjunction may occur
○ Telophase and cytokinesis 2: chromosomes disperse into chromatin; nuclear envelope forms in each new cell
■ 4 cells are formed with genetic variation
■ Each has half the number of chromosomes and amount of DNA than that of their parent cells
3. Differentiate between mitosis and meiosis and the sources of variation in sexual reproduction.
Mitosis is cell division of somatic cells.
● Generates 2 identical cells.
Meiosis is cell division of sex cells.
● Generates 4 genetically different cells, each with a reduced number of chromosomes
Sexual variation sources:
● Crossing over: homologs overlap each other and swap pieces of genetic information, resulting in genetic recombination
● Independent assortment: homologs randomly distribute themselves
● Random fertilization (not a part of meiosis): any sperm can mate with any egg 4. Understand how cell division is controlled with examples of proteins involved.
Regulation of cell division is very important, without it, cancer may occur. Cell division is a tightly controlled sequence.
● There are checkpoints throughout the cell cycle
● G1 checkpoint before S phase: decides if cell is ready to replicate DNA or not ● G2 checkpoint before mitosis: decides if cell is ready to divide or not
○ Needs to take into consideration, proteins, DNA, hormones, nutrients, and the environment
● CDK (cell division kinase) + cyclin protein = MPF (maturation promoting factor) ○ Major protein that regulates cell division
○ S-MPF regulates S phase
○ M-MPF regulates mitosis
○ Phosphorylate proteases can be made to degrade cyclin