AP Bio Unit 1

What are the 6 general steps of the scientific method?

1. Make an observation

2. Ask questions

3. Form a hypothesis

4. Design an experiment

5. Collect data

6. Draw a conclusion

Null Hypothesis

A hypothesis stating that there is no effect or difference between two groups of data.

Alternative Hypothesis

A hypothesis stating that there IS a relationship, effect, or difference between two groups of data.

Independent Variable (IV)

The variable or factor that is CHANGED or manipulated by the experimenter, plotted on the x-axis.

Dependent Variable (DV)

The variable or factor that is MEASURED and AFFECTED by the independent variable, plotted on the y-axis.

Constants

Factors kept CONSISTENT for ALL groups during an experiment.

Controls

Groups used for COMPARISON to the experimental group to increase confidence in conclusions.

Positive Control

When a group is not exposed to the independent variable but exposed to a treatment known to have an expected effect.

Negative Control

A group not exposed to any treatment or exposed to a treatment known to have no effect.

Descriptive Statistics

Statistical methods used to summarize or describe observations or samples.

Inferential Statistics

Statistical methods that use observations to make estimates or predictions from a sample to a wider population.

Central tendencies

Summary value representing the average (mean), middle (median), or typical point (mode) of a dataset.

Type based on shape of distribution

Mean

Average; typically used in an approximately normal distribution.

Median

The middle number of a dataset; used in datasets with abnormal values such as extreme high and low outliers or skewed distributions.

Mode

The value that appears most often in a dataset; used for categorical data or bimodal data with two or more distinct peaks.

Range

A measure of variability representing the total spread from the highest to the lowest values in a data set.

Standard Deviation

A measure of variability that represents the average amount by which all values deviate from the mean.

Interquartile Range (IQR)

A measure of variability that measures the spread of the middle $50\text{\%}$ of a data set.

Is data more reliable with low or high standard deviation? Why?

Low SD: Data is closer to the mean , meaning it’s less scattered/spread out

Standard Error of the Mean (SEM)

A measure used by researchers to assess how accurately the sample mean estimates the population mean.

If standard error bars overlap, is the difference between the means significantly different? Why or why not?

No, observed differences are due to chance, don’t always mean they are entirely different

Chi-Square

A form of statistical analysis used to compare actual counts or frequencies observed with expected counts or frequencies.

Identify elements that make up nearly all living matter

C, H, N, O, P, S

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

Element

A substance that cannot be broken down into other substances by chemical reactions.

Atomic Number

The number at the top of an element on the periodic table, representing the number of protons.

Atomic Mass

The number at the bottom of an element on the periodic table, representing the number of protons plus neutrons averaged over all isotopes.

Octet Rule

Principle stating that elements will gain, lose, or share electrons to complete their valence shell and become stable like noble gases.

Chemical Bonds

Attractions between two atoms resulting from the sharing or transferring of valence electrons.

Electronegativity

A measure of an atom's ability to attract electrons to itself.

Solute

Substances being dissolved in a solution.

Solvent

The dissolving agent in a solution.

Solution

A homogeneous mixture of two or more substances.

Covalent Bonds

Bonds formed when two or more atoms (usually two nonmetals) share electrons to form molecules and compounds.

EX: H2O (polar), O2 (non-polar)

Nonpolar Covalent Bonds

Covalent bonds where electrons are shared equally between two atoms.

Polar Covalent Bonds

Covalent bonds where electrons are NOT shared equally between two atoms.

Ionic Bonds

Attraction between oppositely charged atoms (ions), usually formed between a metal and a nonmetal.

EX: NaCl, LiF

Hydrogen Bonds

Intermolecular bonds formed between molecules with partial positive and partial negative charges that do not share or trade electrons.

How does electronegativity affect the interactions between water molecules?

Causes oxygen to pull shared electrons away from hydrogen making molecules polar (stick together)

Imagine if O and H had the same electronegativity, what would that do to the properties of water?

Water would become non-polar (share electrons equally) and lose ability to form hydrogen bonds because they can no longer stick together

Cohesion

The attraction of molecules for other molecules of the same kind.

ex: H2O to H2O, water stick together

Adhesion

The attraction of water molecules to other molecules that are polar or charged.

ex. H2O to other molecules; allows water to cling to cell walls against gravity

Capillary Action

The upward movement of water due to forces of cohesion, adhesion, and surface tension, occurring when adhesion is greater than cohesion.

ex: plants absorbing/pulling up water from soil into rest of plant for nutrients and energy

Temperature control (high specific heat/high heat of vaporization)

Water resists charges in temperature, heat absorbed to break hydrogen bonds and released to form bonds

ex: Coastal oceans maintain a mild temp between summer and winter

Density

As water solidifies it expands and becomes less dense from hydrogen bonds

ex: Ice floats on top of frozen lakes and in a glass of water

Water as a solvent

Water is a universal solvent, dissolves many polar and ionic substances

ex: Salt completely dissolves in a glass of water

Buffer

A solution that resists changes in pH when an acid or base is added.

Organic Chemistry

The study of compounds containing covalently bonded carbon.

What makes carbon such a versatile element?

Has four valence electrons

Can form single, double, AND triple covalent bonds

Single carbon can form up to four covalent bonds

How do functional groups affect the structure and behavior of organic molecules?

Attached to the carbon skeleton that participate in chemical reactions

Organic compounds

Contain carbon and hydrogen BUT also can include other elements

Hydrocarbon

A specific type of organic compound containing ONLY carbon and hydrogen atoms.

Macromolecule

A large, complex molecule built of smaller repeating subunits known as polymers covalently bonded together.

Four types: Carbohydrates, Proteins, Nucleic acids, and Lipids

Monomers

The repeating units that make up polymers.

Hydrolysis Reaction

A reaction that BREAKS covalent bonds in a polymer by adding water ($H_2O$).

Dehydration Reaction

A reaction that covalently bonds two monomers together with the loss of water ($H_2O$).

Polysaccharides

Polymers containing many sugars (monosaccharides-their monomers) joined together via dehydration reactions.

What important roles do polysaccharides play in animals? Plants?

Animals: Store glycogen (polymer of glucose) in liver and muscle cells

Plants: Store starch (polymer of glucose monomers) to store excess glucose

Disaccharide

Two monosaccharides joined together by covalent bonds.

Cellulose

A tough substance made of polysaccharides that forms plant cell walls.

Where can a phospholipid be found in a cell and what is their role

Found in cell membranes (major component)

Form structural foundation of membranes and assemble as a bilayer in water

Lipid

A class of biological molecules that do NOT include true polymers.

Fat

A molecule composed of glycerol and fatty acids (long carbon chains) that provides energy storage, supports cell function, and provides insulation.

Saturated Fatty Acid

A fatty acid containing only single bonds between carbons in the chain and maximum hydrogen atoms.

Unsaturated Fatty Acid

A fatty acid containing one or more double bonds, causing the fatty acid tails to form kinks.

What forms the “backbone” of DNA?

Alternating chain of deoxyribose (sugar) and phosphate groups linked together 

What does it mean that DNA is antiparallel? Why are they?

Two strands of DNA double helix run down side-by-side in OPPOSITE directions

Why?: The strands composed of sugar-phosphate groups give each a distinct direction, wouldn’t be able to form hydrogen bonds and molecules would repel each other →5’ ends opposite of each other, 3’ opposite, 5’ runs to 3’ vice versa

 Identify the three components of a nucleotide.

1. Nitrogenous base

2. Five carbon sugar 

3. Phosphate group(s)

Nucleoside

A nucleic acid monomer that is lacking a phosphate group.

Nitrogenous bases found in nucelotides

Pyrimidines and purines

Pyrimidines

Nitrogenous base structures consisting of one ring with 6 atoms.

Purines

Nitrogenous base structures consisting of one ring with 6 atoms bonded to one ring with 5 atoms.

Compare and contrast DNA and RNA.

DNA: Consists of TWO polynucleotides (C-G) (A-T)

RNA: Single stranded polynucleotide, variable in shape (A-U (C-G)

Where can DNA be found in a cell? What about RNA?

-ost DNA stays in nucleus, RNA moves between nucleus and working areas of the cell; cytoplasm and ribosomes

What functional group defines the 5’ end?

Phosphate group

What functional group defines the 3’ end?

Hydroxyl (-OH)

How many bonds connect adenine and thymine? How does this differ from cytosine and guanine?

Two hydrogen bonds connect adenine and thymine, three hydrogen bonds connect cytosine and guanine 

What determines the primary structure of a protein?

Gene/genetic sequence

 How does the primary structure of a protein affect the other structural levels?

Specific order/sequence of amino acids determines hydrogen bonds, acts as blueprint

What interactions occur in the secondary structure? Tertiary structure? Quaternary structure?

 Secondary: Hydrogen bonding within polypeptide backbone: creates folding pattern

- Tertiary: Hydrophobic interactions, hydrogen bonds, ionic interactions, and disulfide bridges of side chains: creates 3D folding 

- Quaternary: Same as tertiary, association of 2 or more polypeptides

How many monomers of proteins are there?

20

How do the R groups of amino acids contribute to protein structure?

Determine unique side chains and chemical properties of each AA to determine stabilization and folding of protein from bonds