biology exam 1

cell

the basic unit of structure and function; the lowest level of organization that can perform all activities required for life

• are enclosed by a membrane

• use DNA as their genetic information

Chromosomes

_____________ contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid)

genes

are the units of inheritance that transmit information from parents to offspring; are expressed and form functional molecules such as proteins

Feedback mechanisms allow biological processes to ___________

self-regulate

prokaryotic cell

a type of cell that lacks a membrane-enclosed nucleus and membrane-enclosed organelles; dna floats freely

• simpler and usually smaller than eukaryotic cells

• characteristic of organisms in domains Bacteria and Archaea (kingdoms)

• circular dna

eukaryotic cell

a type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles; contains mitochondria

• larger and more complex than prokaryotic cells

• characteristic of organisms in domain Eukarya (protists, plants, fungi, and animals - kingdoms)

• linear dna

negative feedback

a control mechanism that “damps” its stimulus and stabilizes an issue ; plays a major role in homeostasis in animals.

• Ex: when you exercise vigorously, you produce heat, which increases your body temperature. Your nervous system detects this increase and triggers sweating. The evaporation of sweat from your skin then cools your body, helping return body temperature to its set point and eliminating the stimulus

positive feedback

a control mechanism that amplifies the stimulus; help drive processes to completion by causing more movement (making it extreme)

• Ex: during child-birth, the pressure of the baby’s head against sensors near the opening of the mother’s uterus stimulates the uterus to contract. These contractions result in greater pressure against the opening of the uterus, heightening the contractions and thereby causing even greater pressure, ultimately causing the baby to be born

Taxonomy

branch of biology that names and classifies species into groups of increasing breadth

Charles Darwin

published “On the Origin of Species by Means of Natural Selection in 1859”

modification

Darwin’s Two Points

• Species showed evidence of “descent with _____________” from common ancestors

• Natural selection is the mechanism behind “descent with modification”

Darwin’s theory, produced

explained the duality of unity and diversity (evolution unifies biology)

• Individuals in a population have traits that vary, many of which were heritable

• More offspring are __________ than survive

• Species are generally suited to their environments

element

a substance that cannot be broken down to other substances by chemical reactions

compound

a substance consisting of two or more elements in a fixed ratio (sodium chloride)

C, H, O, and N

96% of living matter

Ca, P, K, and S

Most of the remaining 4% consists of

Trace elements

required by an organism in minute quantities

• Makes up less than .01% of human body weight

oxidation

Copper makes blood blue, Iron makes blood red through _______

Atoms

are composed of subatomic particles (neutrons, protons, elections); elements are consisted of them

Isotopes

are two atoms of an element that differ in number of neutrons

radioactive isotopes

decay spontaneously, giving off particles and energy; fossil dating, tracing metabolic processes, and diagnosing medical disorders

energy

the capacity to cause change

• frozen energy = matter

potential energy

is the energy that matter has because of its location or structure; the top of a hill

electron shell

an energy level or region surrounding an atom's nucleus where electrons are located; The layer closest to the center has the lowest energy. Layers further out have higher energy.

• energy absorbed goes away from nucleus

• energy lost goes to nucleus

valence electrons

are those in the outermost shell, or valence shell

• The chemical behavior of an atom is determined by the distribution of electrons in electron shells

orbital

the three-dimensional space that an electron occupies 90% of the time

incomplete

Atoms with __________ valence shells can share or transfer valence electrons with certain other atoms

covalent bond

sharing of a pair of valence electrons by two atoms; strongest bonds in organisms are _____________ that form a cell’s molecules

molecule

consists of two or more atoms held together by covalent bonds

• Ex: diatomic hydrogen (H2) H:H

nonpolar covalent bond

the atoms share the electron equally

polar covalent bond

one atom is more electronegative, and the atoms do not share the electron equally

electronegativity

is an atom’s attraction for the electrons in a covalent bond

Ionic Bonds

Atoms sometimes strip electrons from their bonding partners; an attraction between an anion and a cation

• An example is the transfer of an electron from sodium to chlorine (now both valence shells complete)

cation

a positively charged ion

anion

a negatively charged ion

ionic compounds, or salts

Compounds formed by ionic bonds; Salts, such as sodium chloride (table salt), are often found in nature as crystals

ionic bonds in water and hydrogen bonds

What are the weak chemical bonds

hydrogen bond

forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom

electronegative

In living cells, the _____________ partners are usually oxygen or nitrogen atoms

If electrons are distributed ____________ in molecules or atoms, they can result in “hot spots” of positive or negative charge

asymmetrically

Van der Waals interactions

attractions between molecules that are close together as a result of these charges

valence orbitals

Molecular shape is determined by the positions of its atoms’ _____________

Molecular specificity

_________________ based on molecular shape. Molecules with similar shapes can have similar biological effects

chemical reactions

are the making and breaking of chemical bonds

Sunlight

___________ powers the conversion of carbon dioxide and water to glucose and oxygen

lewis dot diagrams

shows the valence electrons (outer shell electrons) of a molecule or atom

• Dots show unshared electrons (lone pairs).

• Lines show shared pairs of electrons in a covalent bond (one line equals two shared electrons).

• The Octet Rule guides the drawings, meaning most atoms want eight electrons in their outer shell to feel stable. Hydrogen only wants two

water

All living organisms require _______ more than any other substance; Most cells are surrounded by water, and cells themselves are about 70–95% water

polar

Water molecules are _______ because they’re constructed from two polar covalent bonds

• makes water a versatile solvent

Multiple, reform

This polarity and the ”V” geometry of the water molecule allow for:

• Water polarity and H-bonding

• _________ hydrogen bonds

• Liquid water H-bonds break and ______

• Bond “flickering”

Cohesive, temperature, expansion, solvent

Four of water’s (emergent) properties that facilitate an environment for life are:

1. __________ behavior

2. Ability to moderate _________

3. __________ upon freezing

4. Versatility as a _________

cohesion

hydrogen bonds hold water molecules together

Adhesion

an attraction between different substances, for example, between water and plant cell walls

absorbs, stored

Water _________ heat from warmer air and releases ________ heat to cooler air

heat bank,

Water functions as a _________, it can absorb or release a large amount of heat with only a slight change in its own temperature

• Total thermal energy (kinetic energy)

• Temperature is a measure of heat intensity (average kinetic energy, regardless of volume)

specific heat

the amount of heat that must be absorbed or lost for 1 g of a substance to change temperature by 1ºC

• Ex: Water is 1 cal/g ºC – this is relatively high

resists

Water ________ changing its temperature because of its high specific heat

• Water will change its temperature less as it absorbs or loses heat relative to other materials (like a metal pot on the burner)

hydrogen bonding, break

Water’s high specific heat can be traced to _____________

• Heat is absorbed when hydrogen bonds _______ (absorbed heat must break bonds before accelerating water molecules)

• Heat is released when hydrogen bonds form

evaporation

is transformation of a substance from liquid to gas

• Some evaporation occurs at any temperature

evaporative cooling

As a liquid evaporates, its remaining surface cools, a process called ______________

• helps stabilize temperatures in organisms and bodies of water (sweating)

Heat of vaporization

the heat a liquid must absorb for 1 g to be converted to gas

less dense (spread out)

Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice ____________

4°C

Water reaches its greatest density at ______ • If ice sank, all bodies of water would eventually freeze solid, making life impossible on Earth

solution, solvent, solute

A ___________ is a liquid that is a homogeneous mixture of substances

• _________: dissolving agent (Aqueous solution if water is the solvent)

• ________: The substance that is dissolved

hydrophilic

substance is one that has an affinity for water (can combine w/ water)

hydrophobic

substance is one that does not have an affinity for water (does not combine w/ water; oil)

• Molecules are hydrophobic because they have relatively nonpolar bonds

A hydrogen atom in a hydrogen bond between two water molecules can ______ from one to the other

shift

hydrogen ion, hydronium, hydroxide

• The hydrogen atom leaves its electron behind and is transferred as a proton, or ___________ (H +)

• The molecule with the extra proton is now a __________ ion (H 3O+), though it is often represented as H +

• The molecule that lost the proton is now a ___________ ion (OH-)

concentrations

Changes in ___________ of H + and OH – can drastically affect the chemistry of a cell’s Amino acids, proteins, enzymes, and other molecules are affected

• Adding certain solutes, called acids and bases, modifies the concentrations of H + and OH –

equal

Concentrations of H + and OH – are ________ in pure water (10^-7M at 25°C)

acid

any substance that increases the H + concentration of a solution (HCl)

• HCl → H+ + Cl-

base

any substance that reduces the H + concentration of a solution (NH 3)

• NH₃ + H+ <-> NH₄+

• NaOH → Na+ + OH-

constant

aqueous solution at 25°C the product of H + and OH – is _______

pH

The ______ of a solution is defined by the negative logarithm of H + concentration, written as: pH = –log [H +]

neutral

For a __________ aqueous solution: [H +] is 10 –7 = –(–7) = 7

Acidic, Basic

• ________ solutions have pH values less than 7

• ______ solutions have pH values greater than 7

14

At room temperature (25°C) the sum of pH and pOH is always _____

molar concentration conversions

for questions asking to find pH solution w/ a concentration of M

7

The internal pH of most living cells must remain close to pH ___

Buffers

_________ are substances that minimize changes in concentrations of H + and OH – in a solution

hydrogen

Most buffers consist of an acid-base pair that reversibly combines with _________

carbonic acid

One major blood buffer is ___________/H₂CO₃ (dissociates to bicarbonate and H+)

• Add 0.01 mol of strong acid to water and pH goes from 7 to 2

• Add same amount of acid to human blood and pH goes from 7.4 to 7.3

Organic chemistry

__________ is the study of compounds that contain carbon

• Although cells are 70–95% water, the rest consists mostly of carbon-based compounds

• Most organic compounds contain hydrogen atoms in addition to carbon atoms

Miller’s 1953 experiment

tested whether complex organic molecules could arise spontaneously under conditions thought to have existed on the early Earth

abiotically

Organic molecules may have been synthesized __________ (through non-living physical and chemical processes) on the early Earth

3 special traits of carbon

1. Has many possible bonding partners

2. Makes single or double bonds (and more)

3. Forms chains, branches and rings

hydrogen, oxygen, nitrogen

has many bonding partners such as

methane, ethane, and ethene

Makes single or double bonds (and more) such as

skeletons

Forms chains, branches and rings; Carbon chains form the _________ of most organic molecules

hydrocarbons

organic molecules consisting of only carbon and hydrogen; they are not prevalent by themselves in organisms

• Many organic molecules, such as fats, have components of it (gray circles in the diagram)

• can undergo reactions that release a large amount of energy

Isomers

are compounds with the same molecular formula but different structures and properties

• Ex: (C₆H₁₂O₆​) = glucose and fructose, glucose contains an aldehyde group (an aldose) while fructose contains a ketone group (a ketose)

Structural isomers

isomers that have different arrangements of their atoms

cis-trans isomers

isomers that have the same covalent arrangements but differ in spatial arrangements

• cis = same side

• trans = opposite side

Enantiomers

are isomers that are images of each other

components

• Distinctive properties of organic molecules depend not only on the carbon skeleton but also on the molecular __________ attached to it

• A number of characteristic groups are often attached to skeletons of organic molecules

functional groups

are the components of organic molecules that are most commonly involved in chemical reactions

• The number and arrangement give each molecule its unique properties

• hydroxyl, carboxyl, amino, sulfhydryl, phosphate, methyl

hydroxyl

(-OH) Polar due to electronegative oxygen; forms hydrogen bonds with water

• gives larger molecules the ability to mix with water, makes them polar, creates alcohol

carboxyl

(-COOH) acts as an acid

• act as a weak acid by donating a hydrogen ion and to make molecules polar and water-soluble; lowers pH,

amino

(-NH₂) acts as a base

• serve as a key building block for proteins in living things, accepts protons, changes charge, raises pH

sulfhydryl

(-SH) Two -SH groups can react, forming a “cross-link” that helps stabilize protein structure

• active participant in chemical and antioxidant reactions

phosphate

(-OPO₃^2-) Contributes negative charge; when attached, confers on a molecule the ability to react with water, releasing energy

• stores energy, builds DNA and RNA, makes cell membranes (phospholipids), signals and regulates chemical reactions, helps molecules dissolve