Study Guide Bio Test 1

Hypothesis

A testable, falsifiable explanation for an observation

prediction

A specific outcome you expect if the hypothesis is correct.

Observation leads to Hypotheses

true

Testing Hypotheses:

Through experiments or observations that collect data to support or refute the hypothesis.

Steps of Scientific Inquiry:

Observation → Question → Hypothesis → Prediction → Experiment → Data Collection → Analysis → Conclusion.

controlled experiments

.An experiment where only one variable is changed; all others are kept constant.

Observational

No manipulation, only observation of natural occurrences.

test group

Receives the treatment.

control group

Does not receive treatment; used for comparison.

independent variable

What you change.

dependent variable

what you measure

control variables

kept constant

theory

Broad explanation supported by large body of evidence.

hypothesis

Narrow, testable statement.

element

Substance made of one type of atom.

atom

Smallest unit of an element.

proton

+ charge, in nucleus.

neutron

No charge, in nucleus.

electron

– charge, orbits nucleus.

Atomic Number

# of protons.

atomic mass

Protons + Neutrons.

Isotopes:

Atoms of the same element with different neutron numbers.

Example: Carbon-12, Carbon-14.

Electron Energy Levels:

Electrons closer to nucleus = lower energy; outer electrons = more reactive.

Nonpolar Covalent

Equal electron sharing.

Polar Covalent

Unequal sharing

Ionic

Electron transfer.

Water Molecule Properties:

a. Polar due to unequal sharing between O and H.

b. Can form 4 hydrogen bonds.

Water Properties (due to H-bonds):

Cohesion

Adhesion

High specific heat

Ice is less dense than liquid water

Hydrophilic

Water-loving (polar)

Hydrophobic

Water-fearing (nonpolar).

pH

Measures H+ concentration

Acid

Donates H+

Base

Accepts H+

pH scale

Ranges 0–14. Lower = acidic, 7 = neutral, higher = basic.

Carbon’s Versatility:

4 valence electrons = forms 4 covalent bonds; allows complex molecules.

Carbon Skeleton Variation:

Vary in length, branching, double bonds, rings → molecular diversity.

isomers

Same formula, different structure.

proteins functional group

amino

carbohydrates functional groups

hydroxyl

lipids functional group

carboxyl

nucleic acid functional group

phosphate

Proteins

Structure, enzymes

carbs

energy

lipids

membranes, energy

nucleic acids

genetic info

monomers

single unit

polymer

chain of monomer

Protein Structure:

Amino acids (monomers) → polypeptides (via peptide bonds)

Amino Acid Structure:

Central carbon, amino group, carboxyl group, R group, hydrogen.

DNA Structure:

Double helix, antiparallel strands, base pairing (A–T, G–C)

Nucleotide Components:

Sugar + phosphate + nitrogenous base; linked via phosphodiester bonds.

Pyrimidines

1 ring (C, T, U)

Purines

2 rings (A, G)

5’ vs. 3’:

Direction of sugar-phosphate backbone

DNA

Double, stable, thymine

RNA

Single, uracil

mono

Simple sugars (glucose)

poly

Complex (starch, cellulose)

Storage Polysaccharides

starch

Structural polysaccharide

cellulose

Monosaccharide Bond:

Glycosidic linkage.

Triacylglycerol:

Energy storage

Phospholipids

Membranes

Steroids

Hormones, membrane structure

Saturated

No double bonds, solid

Unsaturated

Double bonds, liquid

Prokaryotic

no nucleus

Eukaryotic

Has nucleus and organelles

Phospholipid Structure:

Amphipathic (hydrophilic head, hydrophobic tail)

Shorter or unsaturated tails =

more fluid

Cholesterol =

buffer (less fluid at high temp, more at low)

Peripheral:

surface

integral

Embedded in membrane

Membrane Protein Functions:

Transport, signal transduction, cell-cell recognition, attachment

Channel

Open pores

carrier

Change shape to move molecules

Diffusion

Passive movement down concentration gradient.

Simple:

No protein

Facilitated

Uses protein

Diffusion:

solutes

osmosis

water

Primary

uses atp

secondary

uses gradient

Large hydrophobic

simple difussion

gases

simple diffusion

large polar

endocytosis

ions

Active or facilitated transport

Electrochemical Gradient:

Chemical gradient + electrical gradient

Nucleus Role:

Houses DNA; controls cell activities.

Endomembrane Pathway:

Nucleus → ER → Golgi → Vesicles → Membrane

Endomembrane System Importance:

Produces and transports proteins/lipids.

Endomembrane Components:

Nucleus, ER, Golgi, vesicles, lysosomes, plasma membrane.

smooth er

Lipid synthesis, detox

rough er

Has ribosomes, makes proteins

cis

receives

trans

ships

Lysosome Functions:

Digestion & recycling of cell components

Mitochondria vs. Chloroplasts:

Both: Have DNA, make energy

Mitochondria: ATP (animals/plants)

Chloroplasts: Photosynthesis (plants)

Cell Shape Structures:

Cytoskeleton, cell wall (plants), membrane proteins

Plant vs. Animal Cells:

Plant: Cell wall, chloroplasts, central vacuole

Animal: Centrioles, lysosomes