9th grade bio
Photosynthesis
Three reactants
Sun (light energy), carbon dioxide, water
Creates glucose
C6H12O6
Glucose formula
6CO2+6H2O —-> glucose
Photosynthesis takes place in the chloroplast
Grana - stacks of pancakes in the chloroplast
Thylakoid - one singular layer (pancake)
Stroma - liquid in between the thylakoids and grana
Light dependent reactions
To turn the sunlight energy into ATP and NADPH
Happens in the grana (thylakoid membrane)
Chlorophyll absorbs blue and red and reflects green
Summary
Energy from the sun is passed down the electron energy transport chain and is stored in the bonds of ATP and NADPH
Oxygen is released as a waste product
Light independent reactions
Stroma - next stage of the process
Purpose
Using ATP and NADPH to create glucose
Location - occurs in the stroma
Cellular Respiration
Goal
Convert energy in food to chemical food in in storage through ATP
Equation
C6H12+6O2 —> 6H2O + 6CO2 + Energy (ATP)
Opposite of the equation for photosynthesis
Mitochondria
2 main parts
Inner membrane
Folded membranes /////
Matrix
Fluid like substance that fills the space on the inside
Glycolysis
The breakdown of glucose
Purpose
Split the 6 carbon molecule of glucose in half to form 2 3 carbon molecules called pyruvate
Occurs in the cytoplasm, and requires no oxygen
This means it is anaerobic
Produces 2 ATP total and a 2 NADH
Decision time
If there is oxygen, it will go through aerobic respiration
If there is not oxygen, it is anaerobic (fermentation)
These both create energy
Aerobic respiration
Citric Acid Cycle (Krebs Cycle)
Location
Mitochondrial Matrix
Process
Takes 2 pyruvate molecules from glycolysis and converts them into 2 ATP and sometimes NADH and FADH2
Carbon dioxide is the waste product
Electron transport chain
Location
Inner membrane of the mitochondria
Process
Series of reactions using the e- and hydrogen bonds formed in the Krebs cycle
Makes 34 ATP AND H20
MOST ATP COMES FROM THIS STEP
Anaerobic respiration
When there is no oxygen, it will go through this process
It can go through two types of fermentation
Lactic acid fermentation
Occurs in bacteria and muscles
Pyruvate from glycolysis is converted into lactic acid and 2 ATP
Alcohol fermentation
Occurs in yeast when oxygen is not available
Pyruvate from glycolysis is broken down into alcohol, CO2, and 2 ATP
TOTAL ATP PRODUCED
Aerobic Respiration = 36-38 ATP
2 ATP from glycolysis
2 ATP from Krebs cycle
34 ATP from Electron Transport Chain
Anaerobic Respiration = 2-4 ATP
Photosynthesis vs. Cellular Respiration
Cell Theory
1. All living things are made of cells. 2. Cells are the basic unit of life. 3. All cells come from other cells
Organisms can be Unicellular - composed of one cell
Multicellular - made of multiple cells
Cells are the most basic unit of life
Smallest part of an organism that is still capable of all of life’s processes
They are VERY diverse
Every cell has
Genetic material
Cytoplasm
Cell membrane
Ribosomes
Organelles
Specialized structures within the cell that work together to make the cell function
Cell Transport
Things going through the plasma membrane
Major part of this is homeostasis
Cells react to stimuli and signals in ways that maintain your body in very narrow limits
These include
PH, cell hydration, blood sugar, and body temperature
Much of homeostasis is controlled by the cell membrane on the top which allows things to come in and out of the cell.
Cell membrane is selectively permeable
Allows certain things in and some things out
Things that pass easily through = passive transport
Small, nonpolar, hydrophobic, and water
Cannot pass through = active transport
Polar and/or large molecules
Cell (plasma) membrane
Phosopholipid by layer
Made of fats (phospholipids)
Have hydrophilic heads and hydrophobic tails
Cell transport
Passive transport
Requires no extra energy in order to get inside of the molecule
The molecules move from high concentration to low concentration areas with a concentration gradient
Examples
Simple diffusion, facilitated diffusion, and osmosis
Active transport
Requires energy (ATP) to be spent to bring materials into the cell or expel materials out of the cells moving from low to high concentration against the concentration gradient
Good way to remember this is swimming upstream takes energy while swimming downstream you can just float
Words to know
Solute - what gets dissolved (lemonade powder)
Solvent - what does the dissolving (water)
Solution - uniform mixture of two or more substances (lemonade)
Concentration - amount of solute dissolved in the solvent
Symbol for concentration - [ ]
Concentration gradient - difference in concentration of a substance from one location to another
Passive transport
Simple diffusion
Simple diffusion is one type of passive transport
Spreading out of molecules across a membrane until a equilibrium is reached
Equilibrium - equally concentrated on both sides of the membrane
Molecules move down a concentration gradient, from high [] to low []
Facilitated diffusion
A transport protein helps to facilitate the diffusion if the molecules that normally couldn’t pass through the cell membrane
These act like a channel or a carrier
Molecules move down from high [] to low []
Ex. large molecules like glucose and polar molecules like calcium
Osmosis
Simple diffusion of water across the cell membrane
Water molecules will always move down a concentration gradient, from high water to low water until a equilibrium is reached
High water concentration means low solute concentration
Low water concentration means high solute concentration
The reason the equilibrium looks so weird is because it is the concentration, not the amount of water
Hypertonic solutions
Water [] is lower than the cell’s cytoplasm
Net movement of water out of cell —> cell shrivels
Hypotonic solutions
Water [] is higher than the cell’s cytoplasm
Net movement of water into a cell —> cell swells
Isotonic solution
Identical water [] to the cells cytoplasm —> cell stays the same
Active Transport
Molecular Pumps
When a cell uses energy to pump molecules across the membrane against the [] gradient through a protein channel
Allows the cell to concentrate key molecules and remove waste quickly
Using vesicles
Endocytosis
Uses vesicles to move large particles into the cellis
Exocytosis
Uses vehicles to export materials out of the cell
This can be waste or neurotransmitters to talk with another cell
Levels of organization
1. Cell
2. Tissue
3. Organ
4. Organ System
Cellular Communication
Uses chemical cells to pass signals from one cell to another
A cell must have a receptor for the signaling molecule to bind to it
Cancer Cells Vs. Normal Cells
Healthy Cell
Large Cytoplasm
Single nucleus
Small nucleoli
Fine chromatin
Cancer Cell
Small cytoplasm
Multiple Nucleus
Multiple and large nucleoli
Coarse chromatin
Cell division through mitosis is gives rise to many identical cells
Differentiation is a process that creates specialized structures and functions
Specialized cells —> tissues —> organs —> systems
How often do cells divide?
It depends on what the cell needs
Internal lining of intestines - 5 days
Skin - 2 weeks
Red blood cells - 4 months
Liver cells - 1 year
Why do our body cells divide?
They divide for growth and repair
Cell Cycle
A repeated pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells.
Three main phases
Interphase - cell growth
3 parts
Gap 1 phase - cell grows and makes proteins
Synthesis phase - DNA replication occurs = doubling the amount of chromosomes
Gap 2 phase - more growth and protein synthesis
At the end of this process there is 2 full sets of chromosomes
Mitosis - Cell division
1 cell becomes 2 identical cells
4 steps
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis - Cytoplasm separation
Regulation
Checkpoints
Critical point where ‘stop’ and ‘go’ signals regulate the cycle
G1 - checks there is enough materials to continue / no damage to the cells
G2 - Checks that cells are ready to divide and no DNA duplication or replication errors
M - Checks spindle fibers attached to chromosomes correctly during metaphase
Cancer
Cancer - uncontrolled cell division
When the cell cycle regulation breaks down and stops working, cancer cells divide much more often than healthy cells
This causes tumors
Tumors
Benign
Abnormal cells that typically remain clustered together
Harmless and can be removed easily
Malignant
Cancer cells that break away from the tumor and move to other parts of the body
This creates more tumors
Metastasize - spreading of disease from one organ to others
DNA and RNA
Both made of nucleic acids
Contains genes
These are sections of DNA that serve as the instructions for making proteins
Nucleotides
Monomer of nucleic acids
Have 3 parts
Sugar
Deoxyribose (DNA)
Ribose (RNA)
Phosphate
Nitrogen
Adenine
Guanine
Cytosine
Tjumine (DNA)
Uracil (RNA)
DNA Structure
Double helix like a twisted ladder
Sugar and phosphate from the “sugar phosphate backbone”
Nitrogen bases bond in the middle with weak hydrogen bonds
All other bonds are strong covalent bonds
Nitrogen bases only bond to their complimentary base pair with hydrogen bonds
A—T
G—C
RNA Structure
Single strand of nucleotides with exposed bases
RNA bases bind with DNA bases
A’s bind with U’s
C’s bind with G’s
DNA Vs. RNA
A, T, C, G
A, U, C, G
ribose
deoxyribose
single strand
double helix
Basics of Heredity
Chromosomes = tightly coiled strands of DNA
Different organisms have different numbers of chromosomes
Ex. Humans have 23 pairs (46 total – 23 from mom and 23 from dad)
Ex. Dogs have 37 pairs (74 total – 37 from mom and 37 from dad)
Gene = a section of DNA that has instructions to code for one protein
One chromosome can contain thousands of genes linked together!
So, genes are pieces/sections of DNA. Chromosomes are long strands of DNA all bunched up.
DNA Replication
Background
When a cell is ready to divide, it must first copy its DNA. The process of making an identical copy of DNA is called DNA Replication.
This happens in the nucleus during the S Phase (Synthesis) of Interphase.
DNA Replication ensures that each new cell made will have exactly the same DNA as the original cell.
Steps
Unzip the DNA.
Enzymes help find complementary bases and bind them according to base-pairing rules (A-T and C-G)
Two identical DNA molecules are formed, each with an “old” strand and a “new” strand.
Additional Info
It is considered to be Semi-Conservative Replication (because part of the molecule is conserved/
Each parent strand is now a template (pattern) that determines the order of the new bases
Forms a “complementary” strand to original strand
The newly synthesized double helix is a combination of one “old” (or original) and one “new” DNA strand.
Meiosis
Somatic cells = Body cells
These are diploid (2n)
Ex. Blood cells, lung cells, muscle cells, heart cells, etc.
Gametes = Sex cells
These are haploid (n)
Ex. Egg and sperm
Diploid Cells = 2 full sets of chromosomes
2N
A set from mom and one from dad
Haploid Cells
1 full set of chromosomes
There is only one set, and it is a combination of chromosomes from mom and dad
Karyotype
Diagram that shows the number and visual appearance of chromosomes in a cell.
Autosomes
Cary traits that make you who you are
This is in the 1st 22 pairs of chromosomes
Sex chromosomes
Carry traits that make you who you are and determine your biological gender
This is in the 23rd pair of chromosomes
Babies can’t happen without pregnancy.
Pregnancy can’t happen without fertilization.
Fertilization can’t (naturally) happen without copulation.
Copulation can’t result in offspring without an egg and a sperm.
Meiosis
The process of cell division that makes gametes in the gonads
Produces eggs in females and sperm in males
Sexual reproduction cannot happen without meiosis!!
Fertilization
The fusion of the egg and sperm to form a zygote.
During sexual reproduction, the number of chromosomes is very important!!!
Homologous Chromosomes
Chromosomes pairs that have the same type of genes
Sister chromatids
2 identical copies of the chromosome
Meiosis is the process of creating gametes – sex cells that have HALF the normal number of chromosomes (only 1 set).
To do this, cell division happens twice.
Meiosis I: separation of homologous chromosomes
A reduction from diploid duplicated chromosomes to haploid duplicated chromosomes.
Meiosis II: separation of sister chromatids
Duplicated chromosomes from Meiosis I divide into individual chromosomes.
Before meiosis 1
Interphase = the growth phase of the cell cycle.
3 parts:
G1 phase = Gap 1 phase = cell grows and makes proteins
S phase = Synthesis phase = DNA replication occurs, doubling the number of chromosomes
G2 phase = Gap 2 phase = more cell growth and protein synthesis
At the end of the interphase, the cell has 2 duplicated copies of every chromosome.
Prophase
Nuclear membrane breaks down
Centrioles separate and make spindle fibers
Homologous chromosomes pair
Tetrad
Cluster of 4 chromatids
Crossing over can happen between the chromosomes.
During Prophase 1 homologous chromosomes are lined up together.
Sometimes chromosomes can cross over each other and get “tangled”.
When this happens, they swap pieces of DNA.
This process creates new combinations of genes – chromosomes that are “part mom/part dad”.
Metaphase 1
Homologous chromosomes are lined up in the middle of the cell in pairs
Anaphase 1
Homologous chromosome pairs separate, one chromosome (2 sister chromatids) pulled away to each side of the cell.
Sister chromatids remain attached.
Telophase 1 and cytokinesis
Chromosomes gather at the sides of the cell
Nuclear membranes will reform
Cytokinesis
Cell divides into 2 cells
End result
2 haploid daughter cells with duplicated chromosomes that are different than the original diploid cell.
Prophase 2
Nuclear membrane breaks down (if they reformed).
Spindle fibers form and attach to the centromeres of the sister chromatids.
Metaphase 2
Nuclear membrane breaks down (if they reformed).
Spindle fibers form and attach to the centromeres of the sister chromatids.
Anaphase 2
Sister chromatids separate and are pulled away from each other to each side of the cells.
Telophase 2 and cytokinesis
Nuclear membranes form around each set of chromosomes.
Spindle fibers dissolve.
Cytokinesis = cytoplasm divides each cell into 2 cells.
End result = 4 haploid daughter cells that are genetically unique.
Mitosis vs. Meiosis
MITOSIS | MEIOSIS | |
What | Creation of diploid somatic cells | Creation of haploid sex cells |
When | Throughout your life | Females: before you are born; Males: throughout life |
Where | Throughout body | In ovaries and testes |
Why | For growth and repair | To make babies |
How | PMAT once | PMAT twice |
Result | 2 identical diploid somatic cells | 4 unique haploid gametes |
Type of Reproduction | Asexual | Sexual |
Genetic Terminology
Chromosome:
Organized packaged DNA found inside the nucleus of animal and plant cells.
DNA:
Hereditary material found in humans and almost all other organisms.
Gene:
Segments of DNA that carry hereditary information.
Humans have 23 pairs of chromosomes or 46 in total. (23 from each parents)
We have two copies of each chromosome: a maternal and a paternal copy, together referred to as homologues.
Greek: homos (same) + logues (ratio)
Chromosomes in a homologous pair contain the same type of genes that code for the same characteristics, such as eye color.
Each chromosome in the pair, however, may have a different version of the gene.
Each different version of a gene is called an allele.
This is a much more complicated system but it is simplified here
Dominant
These are always expressed because there is only one copy need
Ex. Brown eyes
Recessive
Less common because two copies of the allele are needed to be present
Ex. Blue eyes
Pedigree
Cystic Fibrosis
Genetic disorder that primarily affects the lungs.
Thick mucus fills the airways and makes it difficult for gas exchange to occur.
The diagram on the right is a pedigree chart. It describes this family.
Mom and Dad do not have the disorder (white circle and square) but two of the sons do (gray squares).
We know that cystic fibrosis is inherited. Children get it from their parents.
Pedigrees allow us to make scientific predictions about the chance of having a child with albinism.
A pedigree shows three things:
male or female
family relationship
with or without disorder
Pedigree Symbols
Squares = male
Circles = female
Gray = has disorder
White = does not have disorder
Evolution
A change in the genetic makeup of a population of a speaciers over many generation
Five causes
Mutations
Natural selections
Genetic drift
Gene flow
Non-random mating
Charles Darwin’s Ideas
Natural selection
Organisms with the best traits for their environment will live longer and reproduce more than others, causing changes in the population over time by acting on traits that are inheritable
Evolution
The process of biological change in populations over time that makes descendants genetically different from their ancestors.
Two Types
Evolution can occur on a small scale affecting a single population (microevolution).
Evolution on a large scale affecting changes in species across populations (macroevolution).
Charles Darwin
English Naturalist
Went on a voyage to the Galapagos Islands.
Saw that different species of finches/tortoises/etc. lived on different islands and had specific characteristics for that island.
Developed his theory of natural selection to serve as the mechanism for how evolution occurs.
Natural Selection: organisms with the “best” traits (adaptations) will live longer and reproduce more than others, causing changes in the population over time by acting on traits that are heritable.
Survival of the fittest
Fitness = a measure of how well you can survive in your environment
Based on:
Overproduction of offspring
Variation
Adaptation
Descent with modification
The Principles
Overproduction of Offspring
Lots of offspring and limited resources causes competition for those resources
Variation
Variation: differences in the physical traits of organisms
Sources of Variation:
Random mutations = ultimate source
Genetic recombination during meiosis (crossing over)
Migration (gene flow)
The Principles
Adaptation
A feature that allows an organism to better survive in its environment.
Beneficial traits (adaptations) will become more common over time because organisms should live longer and thus be able to reproduce more!!
This changes the gene pool = the combined alleles of all individuals in a population.
Descent with Modification
A change in gene frequency over time.
Natural selection leads to populations with new phenotypes adapted to new situations.
Their traits come from their ancestors.
Beneficial traits should become more common over time.
3 Modes of Selection
Directional Selection: increases the expression of an extreme version of a trait in a population.
Disruptive Selection: a process that splits a population into two groups; removes individuals with average traits and favors the 2 extremes.
Stabilizing Selection: eliminates extreme expressions of a trait when the average expression leads to higher fitness.
Allele Frequencies
Each allele has a frequency in a population’s gene pool.
Allele frequency = # of times the allele appears in a population (how common it is).
The higher the frequency, the greater the allele is there (and the more common the trait is).
It shows how frequently the allele (usually dominant or recessive) appears in the gene pool.
Remember: gene pool = the combined alleles of all individuals in a population.
All frequencies can be calculated.
p = Frequency of the dominant allele
q = Frequency of the recessive allele
In a given population with only 2 versions of a gene (alleles), meaning a dominant (p) version and a recessive (q) version, then:
Mechanisms of Microevolution
Mutations
Natural Selection
Genetic Drift
Gene Flow
Non-random Mating (Sexual Selection)
Mutation
any change in a DNA sequence.
Creates new genotypes and thus new phenotypes.
Changes the allele frequency in a population (how common the allele is in the gene pool).
Increases variation, which is a driving force of evolution.
Can be harmful, beneficial, or neutral.
Natural selection
Organisms more fit for their environments will survive and reproduce more offspring.
Beneficial traits (adaptations) will thus become more common over time.
Genetic drift = random change in the frequency of alleles in a population over time.
Rare alleles in a pop. will decrease in frequency, while others increase.
Often results in a loss of genetic variation.
Changes may be more apparent in smaller populations.
Gene flow = movement of genes into/out of a population.
Occurs during migration.
Results in an increase in genetic variation in the population.
Sexual Selection
Also known as non-random mating.
The selection of traits that aren’t necessarily good for survival fitness, but without them, you can’t pass on your genes at all because you can’t reproduce.
Genetic Equilibrium
Genetic equilibrium (Hardy-Weinberg equilibrium)
When there are NO changes in the allele frequencies in a population over time.
Evolution will NOT occur if:
Population is large.
Must be random mating.
No migration.
No mutations.
No natural selection.