AP BIOLOGY NOTES
Standard Deviation (SD)
A measure of how spread out the data is from the mean
Lower SD:
Data is closer to the mean
Greater likelihood that the independent variable (IV) is causing the changing in the dependent variable (DV)
Higher SD:
Data is more spread out from the mean
Factors, other than IV, are influencing DV
Calculating SD:
Calculate the mean
Determine the difference between each data point and the mean
Square the differences
Sum of the squares
Divide sample size (n) minus 1
Take the square root
Standard Error (SE):
How well the mean of a sample estimates the true mean of population
Measure of accuracy, if true mean is known
Measure of precision, if true mean isn’t known
Accuracy: How close a measured value is to the actual (true) value
Precision: How close the measured values are to each other
Look for overlap of error lines
If they overlap, the difference isn’t significant
If they don’t overlap, the difference may be significant
Chi-Squared (X²) Analysis:
A test that measures how a model compares to actual observed data
In genetics, you can predict genotypes based on probability (expected results)
Chi-Squared is a form of statistical analysis used to compare the actual results (observed) with the expected
Never take square root of X²
If the expected and observed values are the same - X² = 0
By calculating the X² value, you determine if there is a statistically significant difference between the expected and actual values
Null Hypothesis:
Your null hypothesis states that there is no difference between the observed and expected values
You will either accept or reject the null based on the chi-squared value that you determine
Calculating
Determine what your expected and observed values are
Actual values should be something you get from the data - no calculations
Expected is based on probability
Make a table
Degrees of Freedom:
# of categories minus 1
If X² > critical value, there is a significant difference
Animal Behavior:
Based on physiological systems and processes
A behavior is the nervous system’s response to a stimulus
Helps an animal
Obtain food
Find sexual reproduction partner
Maintain homeostasis
Ethology - Study of animal behavior
Behavioral Ecology - Study of ecological and evolutionary basis for animal behavior
Integrates proximate/ultimate explanations for animal behavior
Proximate causation, or “how” explanations
Environmental stimuli
Genetic, physiological, and anatomical
Ultimate causation or “why”
Evolutionary significance
Fixed Action Pattern:
A FAP is a sequence of unlearned, innate behaviors that is unchangeable
Once initiated, carried to completion
Triggered by an external cue - sign stimulus
Taxis:
Environmental cues trigger movement in particular direction
Taxis automatic, oriented movement toward/away from a stimulus
Kinesis:
Simple change in activity or turning rate in response to a stimulus
CER:
Claim: A statement that answers your question
Evidence: Scientific data to support the claim
Data needs to be appropriate (pictures, graph, table)
Observation
Reasoning: based on scientific principles
Each piece of evidence may have a different justification for why it supports the claim
Descent With Modification:
Evolution change is based on the interactions between populations and their environments which results in adaptations (inherited characteristics) to increase fitness
Evolution:
Descent with modifications (Darwin)
Change overtime in the genetic composition of a population from generation to generation
Aristotle:
Species are fixed (unchanged)
Scala naturae - Life forms arrange on ladder of increasing complexity
Old Testament (Creationism):
Earth - 6000 years old
Perfect species individually designed by God for a particular purpose
Carolus Linnaeus - Founder of Taxonomy:
Binomial nomenclature
Domain - Kingdom - Phylum - Class - Order - Family - Genus - Species
Dear - King - Philip - Came - Over - For - Good - Spaghetti
Humans:
D - Eukarya
K - Animalia
P - Chordata
C - Mammalia
O - Primata
F - Hominidae
G - Homo
S - Homo Sapien
Cuvier:
Paleontologist - Studies fossils
Deep strata (rock layers) - Very different fossils from current life
Opposed idea of evolution
Boundaries between strata = Many living species destroyed by catastrophic event, then repopulated by immigrant species
Hutton - Geologic change results from slow and gradual, continuous processes
Lyell - Earth’s processes same rate in past and present
Earth is very old
Slow and subtle changes in organisms - Big Change
Lamarck:
Published theory of evolution (1809)
Use and disuse - Parts of body used bigger, stronger
Inheritance of acquired characteristics - modifications that can be passed on
Importance - Recognized that species evolve, although explanation was flawed
Malthus:
More babies born than deaths
Consequences of overproducing within environment = war, famine
Struggle for existence
Darwin:
English naturalist
1831 - Joined the HMS Beagle for a 5-year research voyage around the world
Collected and studied plant and animal specimens, bones, fossils
Notable Stop - Galapagos Islands
Waited 30 years before publishing his ideas on evolution
Alfred Russell Wallace - Published paper on natural selection first (1859)
Mechanism for evolution is natural selection
Didn’t use ‘evolution’ but rather ‘descent with modification’
Natural Selection:
Adaptations enhance an organism’s ability to survive and reproduce in specific environments
Desert Fox - Large Ears, Arctic Fox - Small Ear
If humans can create substantial change over short time, nature can stay over long time
Homology:
Characteristics in related species that can have underlying similarity even though functions may differ
Homologous Structures - Similar anatomy from common ancestors
Embryotic Homologies - Similar early development
Vestigial Organs - Structures with little or no use
Molecular Homologies - Similar DNA and amino acid sequences
Convergent Evolution:
Distantly related species can resemble one another
Similar problems similar solutions
Analogous Structures: Similar structures, function in similar environments
Eg: Torpedo shape of shark, penguin, dolphin
Fossil Record:
Fossils - Remains or traces of organisms from past
Found in sedimentary rock
Paleontology - Study of fossils
Show evolutionary changes that occur over time and origin of major new groups of organisms
Pinky - Shrink
Ring - Nonrandom mating
Middle - Mutation
Index - Movement
Thumb - Adaptations
Hardy-Weinberg Equilibrium:
Large Population
Random Mating
No Mutations
No Movement
No Adaptations
R - Dominant Allele
r - Recessive Allele
RR - Homozygous Dominant
Rr - Heterozygous
rr - Homozygous Recessive
P + Q = 1 P = R P² = RR Q = r Q² = rr
P² + 2PQ + Q² = 1 2PQ = Rr
In nature it is not likely all conditions for H-W Equilibrium will be met - Populations are evolving
Allele/genotype frequency changes due to mutations and nonrandom mating are minor
Three major mechanisms of evolution
Natural Selection
Genetic Drift
Gene Flow
Mechanisms of Microevolution:
Natural Selection - Differential reproductive success
Genetic Drift - Unpredictable fluctuation of alleles from one generation to next
Significant genetic drift in small populations
Allele frequencies change at random
Can lose genetic variation in populations
Can cause harmful alleles to become fixes
Types
A. Founder Effect - Certain alleles over/underrepresented
B. Bottleneck Effect - Severe drop in population size
Types of Selection:
Directional - 1 of the extremes is favored
Stabilizing - Extremes are selected against - Middle is favored
Disruptive - Extremes are favored - Middle is selected against
Balancing Selection:
Diploidy:
Inherit 2 alleles
Recessive alleles hidden in heterozygotes
Heterozygote Advantage:
Heterozygotes have better survival
Eg: Heterozygotes for Sickle Cell Anemia protected against Malaria
Sexual Selection:
Certain individuals are more likely to obtain mates
Sexual Dimorphism - Difference between 2 sexes
Intrasexual Selection - Competition within the same sex
Intersexual Selection - Mate choice
Type of Evolution:
Gradualism:
Natural selection gradually changes the average features of a species
This process continues for long enough time for a species to change into a new species and the original species becomes extinct
Punctuated Equilibrium:
Periods of rapid speciation followed by long periods of stasis (no change)
Divergent:
One species evolved into 2 different species
Results in homologous structures
Convergent:
2 separate species in different areas evolve to look or behave in similar manner
Results in analogous structures
Coevolution:
2 species that have a partnership or symbiotic relationship
Evolve together to maintain the relationship
Natural Selection cannot make perfect organisms
1) Selection can only edit existing variations
2) Evolution is limited by historical constraints
3) Adaptions are often compromises
4) Chance, natural selection, and the environment interact
Phylogeny/Tree of Life:
Phylogeny - Evolutionary history of a species or group of related species usually organized into a phylogenic tree
Biological Species Concept:
Species - Population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
Reproductively compatible
Reproductive Isolation - Barriers that prevent members of 2 species from producing viable, fertile hybrid
Prezygotic: Prevent mating or hinder fertilization
Habitat Isolation
Temporal Isolation
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
Postzygotic: Prevent hybrid zygote from developing into fertile adults
Reduced hybrid viability - Miscarriage
Reduced hybrid fertility - No more mules
Hybrid breakdown - Smaller/weaker
Species:
Morphological - By body shape, size, and other structural features
Ecological - Niche/role in community
Phylogenic - Share a common ancestor, form one branch on tree of life
Allopatric - Geographically Isolated
Caused by geological events
Evolves by natural selection
Ex: Squirrels on N/S rims
Sympatric - Overlapping populations within same geographic area
Gene flow between subpopulations blocked by:
Polyploidy
Habitat differentiation
Sexual selection
Ex: Polyploidy in 80% of plants
Cells:
Prokaryote - Domain bacteria and archaea
Before
No nucleus
NDA in a nucleoid
Cytosol
No organelles other that ribosomes
Small size
Primitive
Ex: Bacteria
Eukaryote - Protists, Fungi, Plants, Animals
True
Has nucleus and nuclear envelope
Cytosol
Membrane-bound organelles with specialized structure and function
Much larger in size
More complex
Ex: Plant and animal cell
Cells must be small to maintain a large surface area to volume ration
Large surface area allows higher rate of chemical exchange between cell and environment
Membrane Structure and Function:
Cell membrane - Selectively permeable
Somethings in and out
Fluid mosaic model
Things can move
Made up of multiple components
Phospholipid
Proteins
Carbohydrates
Cholesterol
Diffusion - Movement from a high concentration to a low concentration
Simple Diffusion: Type of passive transport
No energy required
Equilibrium: State of balance (homeostasis)
Facilitated Diffusion: Channel/carrier protein
Active Transport:
Uses energy (ATP)
Low to high
Creates concentration gradient
Early Membrane Model:
(1935) Davison/Danielli - Sandwich model
Phospholipid bilayer between 2 protein layers
Problems - Varying chemical composition of membrane, hydrophobic protein parts
Membrane:
Low temps - Phospholipids with unsaturated tails (Kinks prevent close packing)
Cholesterol resists changes by:
Limit fluidity at high temps
Hinder close packing at low temps
Adaptations - Bacteria in hot springs (unusual lipids); winter wheat (high unsaturated phospholipids)
Membrane Proteins:
Integral Proteins:
Embedded in membrane
Determined by freeze fracture
Transmembrane with hydrophilic heads/tails and hydrophobic middles
Peripheral Proteins:
Extracellular or cytoplasmic sides of membrane
Not embedded
Held in place by the cytoskeleton or ECM
Provides stronger framework
Carbohydrates:
Function - Cell to cell recognition; developing organisms
Glycolipids, glycoproteins
Ex: Blood transfusions
Selective Permeability:
Small nonpolar molecules cross easily: hydrocarbons, hydrophobic molecules, CO2, O2, N2
Polar uncharged molecules. including H2O
Pass in small amounts
Hydrophobic core prevents passage of ions, large polar molecules - movement through embedded channel and transport proteins
Passive Transport:
No energy (ATP) needed
Diffusion down concentration gradient (high to low)
Ex: Hydrocarbons; CO2, O2, H2O
Water Potential:
H2O moves from high potential to low potential
Water potential - Free energy water
Solute potential - concentration (osmotic potential)
Pressure potential - Physical pressure on solution; turgor pressure
Pure water - MPa
Plant cells - 1MPa
Calculate Solute Potential:
-iCRT
i - Ionization constant (# of particles made in water)
C - Molar concentration
R - Pressure constant (0.0831 liter bars/mole-k)
T - Temperature in K (273 + C)
The addition of solute to water lowers the solute potential (more negative) and therefore decreases the water potential
Water Movement:
From and area of:
Higher potential to lower potential
Low solute concentration to high solute concentration
High pressure to low pressure
Facilitated Diffusion:
Transport Proteins - (Cannel or carrier proteins) help hydrophilic substances cross
Two ways:
Provide hydrophilic channel
Loosely bind/carry molecule across
Ex - Ions, polar molecules (H2O Glucose)
Aquaporin - Channel protein that allows passage of H2O
Active Transport:
Requires energy (ATP)
Proteins transport substances against concentration gradient (low to high)
Ex - Na+/K+ pump, proton pump
Electrogenic Pump - Generate voltage across membrane
Cotransport - Membrane protein enables “downhill” diffusion of one solute to drive “uphill” transport of other
Ex - Sucrose - H+ cotransporter (sugar loading in plants)
Passive:
Little or no energy
High to low
Down the gradient
Ex - Diffusion, Osmosis, Facilitated Diffusion
Active:
Requires energy
Low to high
Against the gradient
Ex - Pumps, exo/endocytosis
Osmoregulation:
Control solute and water balance
Contractile vacuole - “Bilge Pump” forces out fresh water as it enters by osmosis
Ex - Paramecium Caudatum - Freshwater protist
Bulk Transport:
Transport of proteins, polysaccharides, large molecules
Endocytosis - Take in macromolecules and particulate matter, form new vesicles from plasma membrane
Exocytosis - Vesicles fuse with plasma membrane, secrete contents out of cell
:
The highly complex organization of living systems requires constant input of energy and the exchange of macromolecules
Organisms use energy to maintain organization, reproduce, and grow
Metabolism:
The totality of an organism’s chemical reactions
Manage the materials and energy resources of a cell
Metabolic Rate - Total amount of energy an animal uses in a unit of time
In general, the smaller the organism, the higher the metabolic rate
Catabolic Pathways - Release energy by breaking down complex molecules into simpler compounds
Ex - Digestive enzymes break down food and release ATP
Anabolic Pathways - Consume energy to build complex molecules from simpler ones
Ex - Amino acids link to form muscle protein
Kinetic Energy - Associated with motion
Heat is KE associated with random movement of atoms or molecules
Potential Energy - Stored energy as a result of its position or structure
Chemical Energy is PE available for release
Energy can be converted from one form to another
Ex - Chemical to mechanical to electrical
Thermodynamics:
Study of energy transformations that occur in matter
Closed system - Isolated from its surrounding
Open system - Energy and matter can be transferred between the system and its surroundings
Organisms - Open systems
A net gain in energy results in energy storage or the growth of an organism
A new loss of energy results in loss of mass and/or death of an organism
A living cell isn’t at equilibrium
Constant flow of materials
Three kinds of work
Mechanical
Transport
Chemical
Cells manage energy resources to do work by energy coupling - using an exergonic process to drive an endergonic one
ATP (Adenosine Triphosphate) is the cell’s main energy source in energy coupling
ATP - Adenine Ribose 3 phosphates
Hydrolysis - Energy released
ATP Performance:
Exergonic release of Pi is used to do the endergonic work of cell
When ATP is hydrolyzed it becomes ADP
Catalyst - Substance that can change the rate of reaction without being altered in the process
Enzyme - Biological catalyst
Speeds up metabolic reactions by lowering the activation energy
Substrate Specificity:
The reactant that an enzyme acts on is called the enzyme’s substrate
The enzyme binds to its substrate forming an enzyme-substrate complex
The active site is the region on the enzyme where the substrate binds
Induced Fit - Enzyme fits snugly around substrate - “Clasping handshake”
An enzymes activity can be affected by temperature, pH, or chemicals
Structure/Function:
Change to the molecular structure of a component in an enzymatic system may result in a change of function or efficiency of the system
Denaturation - Disrupt protein structure
Reduce enzymatic activity
Environmental pH - Alter efficiency of enzyme activity - disrupts of H-Bonds
Cofactors: Non-protein enzyme helpers such as minerals (Zn, Fe, Cu)
Coenzymes: Organic cofactors (Vitamins)
Enzyme Inhibitors -
Competitive inhibitors - Binds to the active site of an enzyme, competes with substrate
Noncompetitive Inhibitors - Binds to another part of an enzyme → enzyme changes shape → active site is nonfunctional
Regulation:
To regulate metabolic pathways, the cell switches on/off the genes that encode specific enzymes
Allosteric Regulations - Proteins function at one site is affected by binding of a regulatory molecule to a separate site
Activator - Stabilizes active site
Inhibitor - Stabilizes inactive form
Cooperativity - One substrate triggers shape changes in another active site
Cellular Respiration:
Glycolysis
Krebs/Citric Acid Cycle
Electron Transport Chain
E flows into ecosystem as sunlight
Autotrophs transform it into chemical E (O2 replaced)
Cells use some of chemical E in organic molecules to make ATP
E leaves as heat
Energy Harvest:
Energy is released as electrons “fall” from organic molecules to O2
Broken down into steps -
Food (Glucose) NADH+ETC O2
Coenzyme NAD+ = Electron acceptor
NAD+ picks up 2e and 2H+ NADH (Stores E)
NADH carries electrons to the electron transport chain
ETC - Transfers e to O2 to make H2O - releases energy
Glycolysis:
“Sugar splitting”
Believed to be ancient (early prokaryotes - no O2)
Occurs in cytosol
Partially oxidizes glucose (6C) to 2 pyruvates (3C)
Net gain - 2ATP + 2NADH
2 H2O
No O2 required
Stage 1: Energy Investment
Cells use ATP to phosphorylate compounds of glucose
Stage 2: Energy Payoff
Two 3C compounds oxidized
For each glucose molecule
2 net ATP
2 molecules of NAH+ NADH
Substrate - Level Phosphorylation:
Generate small amount of ATP
Phosphorylation - Enzyme transfers a phosphate to other compounds
Pyruvate Oxidation:
Pyruvate Acetyl CoA
CO2 and NADH produced
Krebs Cycle:
Occurs in mitochondrial matrix
Acetyl CoA, Citrate, and CO2 released
Net gain - 2 ATP, 6NADH, 2FADH2 (electron carrier)
ATP produced by substrate - level phosphorylation
Electron Transport Chain (ETC):
Collection of molecules embedded in inner membrane of mitochondria
Tightly bound proteins + non-protein components
Alternate between reduced / oxidized states as accepts / donate e
Does not make ATP directly
Ease falls of e from food to O2
2H+ + ½ O2 → H2O
Photosynthesis:
Plants and other autotrophs are producers of biosphere
Photoautotrophs - Use light E to make organic molecules
Heterotrophs - Consume organic molecules from other organisms for E and carbon
Photosynthesis - Converts light energy to chemical energy of food
Chloroplasts - Sites of photosynthesis in plants
Stomata - Pores in leaf (CO2 enters / O2 exits)
Sites of Photosynthesis:
Mesophyll - Chloroplasts mainly found in these cells of leaf
Chlorophyll - Green pigment in thylakoid membranes of chloroplasts
6CO2 + 6H2O + Light Energy → C6H12O6
Redox Reaction - Water is split → E- transferred with H+ to CO2 → sugar
Oxidation → lose E-
Reduction → gain E-
Photosynthesis = Light reaction + Calvin Cycle
Nature of Sunlight:
Light = Energy = Electromagnetic radiation
Shorter Wavelength - Higher E
Visible Light - Detected by human eye
Light - Reflected, transmitted, or absorbed
Photosynthetic Pigments:
Pigments absorb different wavelengths of light
Chlorophyll - Absorbs violet blue / red light, reflect green
Chlorophyll A (Blue-Green) - Light reaction, converts solar to chemical E
Chlorophyll B (Yellow-Green) - Photoprotection, broaden color spectrum
Absorption Spectrum - Determines effectiveness of different wavelengths for photosynthesis
Calvin Cycle:
Uses ATP and NADPH to convert CO2 to sugar
Produces 3-C sugar G3P
Three phases
Carbon fixation
Reduction
Regeneration of RuBP (CO2 acceptor)
Photorespiration:
Metabolic pathway which -
Uses O2 and produces CO2
Uses ATP
No sugar production (Rubisco binds O2 → breakdown of RuBP)
Occurs in hot, dry bright days which stomata close (Conserve H2O)
Early atmosphere - Low O2, high CO2
Evolutionary Adaptations:
Problem with C3 plants
Co2 fixed to 3-C compound in Calvin Cycle
(Ex: Rice, Wheat)
Hot, dry days
Partially close stomata, lower Co2
Photorespiration
Lower photosynthetic output (No sugar made)
C4 plants
Co2 fixed to 4-C compound
(Ex: Corn, Sugarcane, grass)
Hot, dry days → Stomata close
2 cell types - Mesophyll / Bundle sheath cells
Mesophyll - PEP carboxylase fixes CO2
Bundle Sheath - CO2 used in Calvin Cycle
CAM Plants
Night - Stomata open → CO2 enters → converts to organic acid, stored in mesophyll cells
Day - Stomata closed → Light reactions supply ATP, NADPH; CO2 released from organic acids for Calvin Cycle
(Ex: Cacti, Succulent, Pineapple)
3 Phases of Signal Transduction:
Reception - The target cell’s detection of a signal molecule coming from the outside
Transduction - The conversion of a signal to a form that can bring a specific cellular response
Response - The specific cellular response to the signal molecule
Ligand:
Signaling molecule
Ex: Proteins, amino acid, steroids
Receptor:
Protein that detects specific ligands
Lock and key type fit
Types of Cell Signaling:
The type of signaling a cell uses is based on the distance between the cell it is trying to signal
4 main types:
Juxtracrine / Direct Communication
Cells are touching. One cell can recognize the molecules on the adjacent cell
Plant Ex: Plasmodesmata
Animal Ex: Gap Junctions
Orchestrates early embryo development
Paracrine
Ligands produced by cells can travel through extracellular fluid (diffusion) and can be read by other local cells
Short-lived molecules
Two outcomes:
Read by another cell
Degraded by enzymes
Endocrine
Ligand released by a cell and makes its way to the circulatory system
Can be spread to the enire body
Long-lived molecules known as hormones
Used extensively in plants and animals
Synaptic
Rapid communication with distant cells using nerve cells’ long fiber-like extensions
Ligands are called neurotransmitters
Chemical synapse - Association of the neuron and its target cells
Used by the nervous system
Ex: Touch
Autocrine signaling is another important signaling event
Occurs when a cell’s signals itself. Production and secretion of an extraellular mediator by a cell followed by binding of that mediator by receptor on the same cell to initiate signal transduction
Ex: Cancer cells making their own growth hormone rather than relying on its release from the pituitary gland
Cell Junctions:
Tight junctions - Belts around the epithelial cells that line organs and serve as a barrier to prevent leakage into or out of those organs
Plasmodesmata - Connect one plant cell to the next. They are analogous to gap junctions in animal cells
Feedback Regulation:
Negative Feedback Loop - Inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity
Positive Feedback Loop: Reinforces a stimulus to produce an even greater response
Desmosomes - ‘Spot Welds’ found in many tissues that are subjected to severe mechanical stress such as skin epithelium or the neck of the uterus, which must expand greatly during childbirth
Gap Junctions - Permit the passage of materials directly from the cytoplasm from one cell to the cytoplasm of an adjacent cell. In the muscle tissue of the heart, the flow of ions through the gap junctions coordinates the contractions of the cardiac cells.
Reception:
Occurs when a signal molecule (Ligand) binds to a receptor protein
Found in 2 places:
Plasma membrane
Binds to water-soluble ligands
Intracellular
Found inside plasma membrane in cytoplasm or nucleus. The ligand crosses the membrane (it’s hydrophobic), like the steroid hormone testosterone
Cell Cycle: Life of a cell from its formation until it divides into 2 cells
Functions of Cell Division:
Reproduction
Growth and development
Tissue renewal
Genome - All of a cell’s genetic info (DNA)
Prokaryote - Single, circular chromosome
Eukaryote - More than one linear chromosome
Ex: Human - 46, Mouse - 40, Fruit fly - 8
Each chromosome must be duplicated before cell division
Duplicated Chromosome - 2 sister chromatids attached by a centromere
Somatic Cells:
Mody cells
Diploid (2n) - 2 of each type of chromosome
Divide by mitosis
Humans - 2n = 46
Gametes:
Sex cells (Sperm / Egg)
Haploid (n) - 1 of each type of chromosome
Divide by mitosis
Humans - n = 23
Checkpoint: Control point where stop / go signals regulate the cell cycle
Major Checkpoints:
G1 (Most important)
Controlled by cell size, growth factors, environment
‘Go’ → Completes whole cell cycle
‘Stop’ → Cell enters nondividing state (Go phase)
Nerve muscle cells stay at go; liver ells called back from go
G2
Controlled by DNA replication completion, DNA mutations, and cell size
M-Spindle
Check spindle fiber (microtubule) attachment to chromosomes at kinetochores (anchor sites)
Kinetochore - Protein associated with DNA at centromere
Kinases - (Cyclin-dependent kinase, CDK) Protein enzyme controls cell cycle; active when connected to cyclin
Cyclin - Proteins which attach to kinases to activate them; levels fluctuate in the cell cycle
External Regulator Factors:
Growth - Proteins released by other cells to stimulate cell division
Density Dependent Inhibition - Crowded cells normally stop dividing; cell-surface protein binds to adjoining cell to inhibit growth
Anchorage Dependence - Cells must be attached to another cell or ECM (extracellular matrix) to divide
Transformation:
Process that converts a normal cell to a cancer cell
Tumors - Mass of abnormal cells
Benign - Lump of cells remain at original site
Malignant - Invasive and impairs functions of 1+ organs
Metastasis - Cells separate from tumor and travel to other parts of the body
G Protein-Coupled Receptor:
A membrane receptor that works with the help of G protein
The ligan or signaling molecule has bound to the G protein-coupled receptor. This causes conformational change in the receptor so that it may now bind to an inactive G protein, causing a GTP to displace the GDP. This activates the G protein.
G protein binds to a specific enzyme and activates it. When the enzyme is activated, it can trigger the next step in a pathway leading to a cellular response. All the molecular shape changes are temporary. To continue the cellular response, new signal molecules are required.
Intracellular Receptors:
Bind hydrophobic ligands
Hydrophobic ligands can easily cross the plasma membrane
Main class of intracellular receptors are nuclear receptors
Insulin / Glucagon:
Insulin (decreases blood sugar) and glucagon (increases blood sugar) are antagonistic hormones that help maintain glucose homeostasis
Pancreas has clusters of endocrine cells called pancreatic islets with alpha cells that produce glucagon and beta cells that produce insulin
Target Tissue:
Insulin reduces glucose levels by
Promoting cellular uptake of glucose
Slowing glycogen breakdown in the liver
Promoting fat storage, not breakdown
Glucagon increases glucose levels by
Stimulating conversion of glycogen to glucose in the liver
Stimulating the breakdown of fat and protein into glucose
Phases of Cell Cycle:
The mitotic phase alternates with interphase
G1 → S → G2 → Mitosis → Cytokinesis
Interphase (90% of cell cycle)
G1 - Cell grows and carries out normal functions
S - Duplicates chromosomes (DNA replication)
G2 - Prepares for cell division
M Phase (Mitotic)
Mitosis - Nucleus divides
Cytokinesis - Cytoplasm divides
Mitosis:
Prophase → Metaphase → Anaphase → Telophase
Continuous process with observable structural features
Chromosomes become visible (Prophase)
Alignment at the equator (Metaphase)
Separation of sister chromatids (Anaphase)
Form 2 daughter cells (Telophase and Cytokinesis)
Cytokinesis:
Cytoplasm of cell divided
Animal Cells - Cleavage furrow
Plant Cells - Cell plate forms