UCLA LS7A - Midterm 1 Study Guide

polarity

unequal sharing of electrons

what is the electronegativity trend?

increases up and to the right

what is the most electronegative element?

Flourine

covalent bond

a bond formed when atoms share one or more pairs of valence electrons, valence electrons farthest from nucleus and are at the highest energy level

nonpolar covalent bond

a covalent bond in which the electrons are shared equally by the two atoms

which three elements are the most electronegative?

N, O, F

which bonds are never polar

C-H bonds

what determines atomic number?

number of protons

what determines mass of atom?

protons + neutrons

electronegativity

ability of protons to attract electrons

polar covalent bond

when electrons are shared unequally, partial charges on atoms

breaking a bond is ________

endothermic, energy is required

forming a bond is _______

exothermic, energy is released

bond energy

the strength of a covalent bond

stronger the bond to be broken, more/less energy is required/released ?

more required

On the Morse Curve, explain what point 1 conveys

At a larger internuclear distance, THERE IS NO POTENTIAL ENERGY, ZERO, which means there is no interaction, or they are not bonded to each other

On the Morse Curve, explain what point 3 conveys

The relative potential energy is low, PERFECTLY BONDED ATOMS HAVE A LOWER POTENTIAL ENERGY because they dont want to move away from each other, the internuclear distance is closer, meaning that the atoms protons are perfectly countering the electrons of the other atom.

On the Morse Curve, explain what point 4 conveys

Even though the internuclear distance is closer, THE POTENTIAL ENERGY IS HIGHER because the energy is repulsive and the energy of the two atoms is very high

out of the atoms H, C, O, N, which pairs have similar electronegativities

H and C have similar electronegativities, and O and N have similar electronegativities, H and C have lower electronegativies than O and N

ionic bond

Formed when one or more electrons are transferred from one atom to another due to the attraction of opposite charges

hydrogen bond

A weak bond between a hydrogen atom in one molecule and an electronegative atom in another molecule (such as F, O, N)

in a hydrogen bond, the hydrogen molecule has to be slightly __________

positive

any hydrogen bonded to a ___________ cannot hydrogen bond

carbon

decreasing tempterature ---->

slows everything down

increasing tempterature ------>

atoms move around

van der waals forces

electrostatic interactions between atoms that have a temporary partial change

order of strength of bonds

1. covalent 2. ionic (in water) 3. hydrogen 4. van der waals

hydrophilic

"water-loving"; polar molecules; class of molecules in which water can undergo hydrogen bonding

hydrophobic

"water-fearing"; nonpolar molecules; poorly able to undergo hydrogen bonding

hydrophobic effect

The exclusion of nonpolar molecules by polar molecules, which drives biological processes such as the formation of cell membranes and the folding of proteins.

structure of triglyceride

3 fatty acids and 1 glycerol

structure of a phospholipid

glycerol attatched to a phosphate-containing head group and two fatty acid tails; hydrophilic head, hydrophobic tail

the head of a phospholipid is _________

hydrophilic, polar

the tail of a phospholipid is ____________

hydrophobic, nonpolar

cell membranes are made of a ___________________

phospholipid bilayer

amphipatic

having both a hydrophilic region and a hydrophobic region (describes a phospholipid)

double bond in an unsaturated fatty acid creates a _______

kink, meaning the acids cannot stack on top one of another

structure of a saturated fatty acid

stacked neatly on top of one another and mostly solid at room temperature

structure of an unsaturated fatty acid

contains a double bond between carbons and results in a kink meaning the acids cannot stack neatly on top of one another and are mostly liquid at room temperature

main component of cell membrane

phospholipid bilayer

structure of proteins in cell membrane

embedded in or associated with a cell membrane and perform important functions such as transporting molecules

glycolipids

carbohydrates in cell membrane attached to lipids

glycoproteins

proteins that have carbohydrates covalently bonded to them in cell membrane

selectively permeable

lets some molecules in ad out freely, lets other in and out only under certain conditions, prevents others from coming in at all

function of cholesterol in cell membrane

increases or decreases membrane fluidity depending on temperature and maintains a consistent state of membrane fluidity by preventing any dramatic transitions from fluid to solid

at temperatures normally found in a cell, cholesterol _________

decreases membrane fluidity because interaction of cholesterol's rigid ring structure with phospholipid fatty acid tails reduces mobility of phospholipids

at low temperatures, cholesterol

increases membrane fluidity because it prevent phospholipids from packing tightly with other phospholipids

transporters

membrane proteins that move ions or other molecules across the cell membrane

receptor

a molecule on cell membranes that detect critical features of the environment; sometimes found in the cytoplasm

enzyme

protein that functions as a catalyst to make rate of a chemical reaction faster; critical in determining which chemical reactions take place in a cell

anchor

A membrane protein that attaches to other proteins and helps to maintain cell structure and shape

integral membrane protein

A protein that is permanently associated with the cell membrane and cannot be separated from the membrane experimentally without destroying the membrane itself

peripheral membrane protein

A protein that is temporarily associated with the lipid bilayer or with integral membrane proteins through weak noncovalent interactions

transmembrane proteins

Proteins that span the entire lipid bilayer; most integral membrane proteins are transmembrane proteins

fluid mosaic model

A model that proposes that the lipid bilayer is a fluid structure that allows molecules to move laterally within the membrane and is a mosaic of two types of molecules, lipids and proteins.

prokaryote

an organism whose cell(s) lack a nucleus

eukaryote

an organism whose cell has a true nucleus

organelle

any one of the several compartments in eukaryotes tht divide the cell contents into smaller spaces specialized for different functions

cytoplasm

contents of the cell other than the nucleus

cytosol

region of the cell inside the plasma membrane but outside the organelles, jelly-like stuff

mitochondria

make energy for the cell from chemical compounds like sugar and convert it to ATP

What kind of cell does not have a mitochondria

A red blood cell; one of the main functions of these cells is to transport oxygen

chloroplast

an organelle that converts energy of sunlight into chemical energy by synthesizing simple sugars ONLY IN PLANT CELLS

nucleus

compartment of cell that houses the DNA in chromosomes

nucleoid

A dense region of DNA in a prokaryotic cell.

Endoplasmic Reticulum (ER)

synthesizes or combines chemicals to create proteins and lipids

golgi apparatus

Modifies, sorts, and packages proteins and lipids for storage or transport out of the cell

lysosome

contains enzymes that BREAK DOWN macromolecules

vacuoles

maintain turgor pressure against cell walls ONLY FOUND IN PLANT CELLS

diffusion

random motion of individual molecules, with net movement occuring where there are areas of higher and lower concentration of molecules

how do molecules move in diffusion

from high concentration to low concentration

explain how chemical properties of a phospholipid bilayer allow it to act as a semipermeble membrane

result of combination of lipids and embedded proteins of which it is composed; HYDROPHOBIC INTERIOR prevents ions, charged/polar molecules from diffusing freely across membrane; large macromolecules are too big to cross on their own; gases, lipids, small polar molecules can move freely across lipid bilayer; protein transporters in membrane allow export and import of molecules that cannot cross on their own

tonicity

ability of an extracellular solution to make water move into or out of a cell by osmosis

osmosis

the net movement of a solvent, such as water, across a selectively permeable membrane toward the side of higher solute concentration

hypertonic

higher solute concentration

hypotonic

lower solute concentration

isotonic

equal solute concentration

Where does the electron transport chain occur?

mitochondria

Simple diffusion

diffusion across the lipid bilayer

What kind of molecules diffuse the easiest across the bilayer?

small nonpolar molecules

Facilitated diffusion

diffusion through a membrane, bypassing the lipid bilayer

Active transport

the "uphill" movement of substances AGAINST a concentration gradient REQUIRING the input of energy

Primary active transport

active transport that uses the energy of ATP directly

Secondary active transport

active transport that uses the energy of an electrochemical gradient to drive the movement of molecules

Electrochemical gradient

A gradient that combines the charge gradient and the chemical gradient of protons and other ions

Metabolism

Chemical reactions occuring in cells that convert molecules to other molecules and transfer energy

Catabolism

Chemical reactions that BREAK DOWN molecules into smaller units and produce ATP to meet energy needs of cell

Anabolism

Chemical reactions that BUILD molecules from smaller units REQUIRING an input of energy usually in ATP and produce net energy storage in cells

Energy

capacity to do work

Kinetic energy

energy of motion

Potential energy

stored energy that is released by a change in the object's structure or position

An electrochemical gradient is a form of ____________ energy

potential

Chemical energy

a form of potential energy that is held in the chemical bonds between atoms in a molecule

First Law of Thermodynamics

Energy is conserved, it cannot be created or destroyed, can only be transformed from one form into another

When kinetic energy changes to potential energy the amount of energy _______________

always remains the same

Second Law of Thermodynamics

transformation of energy is associated with an increase in the degree of disorder in the universe

Gibbs free energy (G)

amount of energy available to do work

Exergonic

Releases energy

Exergonic is a -ΔG or a +ΔG

-ΔG

Endergonic

requires input of energy