Chemistry and CellsImportant Definitions:

Define these terms (5 word definitions or less)

What are you made from?

Atom:- smallest unit of matter; unable to be cut into smaller units and still remain the same.

But what do you get when you cut an atom in half?Proton: +-positively charged

Neutron: -neutral charge (no charge)

Electron: -- negative charge

What is an element?

Element:- a group of atoms with the same structure and properties.

What happens when an atom has more neutrons than it is supposed to?

It creates an Isotope

Isotopes: - an isotope is an atom with more, or less neutrons than other atoms of its element.

“Normal” Carbon 12Carbon 12

6 Protons6 Neutrons6 Electrons

Radioactive Carbon 14Carbon 14

6 Protons8 Neutrons6 Electrons

What happens when you put two elements together?

Compounds are formed.

Compound:- two or more elements that are combined in specific proportions.

Ex - NaCl

a.k.a………. Salt

Water, Water, Everywhere………….Water: – the universal solvent

Polar (polarity) : having a definite positive and negative region on/in a molecule.

+

-That means that a water molecule is like a little magnet!

Anything that is magnetic (polar) will stick to water!!

Carbon CompoundsCarbon: An element that is used

by organic life forms to make molecules of the body.

Macromolecule:Macro = large or manyMolecule = arranged atoms

Def: a large molecule composed of many units, or smaller molecules

Ex: Glucose

A single 6 carbon ring

But if I add a lot of them together, I get:

Complex Carbs

`

A single unit is a MONOMER

Having multiple units is a POLYMER

First Carbohydrates

What is a Carb?

Chemical Structure of a Carbohydrate:

C

O

H

H

Carbohydrates are ALWAYS found in the Ratio of :

1 Carbon to 2 Hydrogen to 1 Oxygen

1:2:1

Glucose (simplest carb):

C6H12O6Usually found in a ring

What do we use Carbohydrates for?Energy

Both short term and long term

Short term

Simple SugarsLong term

Complex carbs like pasta

What can you eat that has more energy than Carbs?

Second Molecule: Lipids (fats) can store enough energy that they can even hold a flame!

Plants store fat as liquids.

Animals store fat as solids

Lipid Composition:

A Glycerin Molecule

This acts as a connector for:

Three Fatty acids The fatty acids contain several carbon groups that store energy in their bonds.

What are the main types of Lipids?Neutral Fats

Saturated and Unsaturated fatsUsed for long term energy storage!

PhospholipidsThese make the cell membrane

SteroidsThese are messages carried all about the body!They are NOT only the illegal drugs

Third Molecule:Nucleic Acids: The cells BlueprintDNA & RNA

The building block” that makes nucleic acids are NUCLEOTIDES

DeoxyriboNucleic Acid & RiboNucleic Acid

Phosphate group

Ribose Sugar

Nitrogen Base

DNA: Contains all the genetic material that is needed by the cell. It is found in a “Double

Helix”, two twists in a clockwise spiral.

RNA:A single strand of Nucleotides that carries genetic material out of the nucleus to be processed.

Proteins

Forth Molecule: Proteins are used as structural

components in all cells!

Amino acids: - 20 different molecules that combine to make all proteins

These are just two

Protein Uses:

Construction:

Proteins build components inside and outside our cells

Enzyme reactions:Enzymes are special proteins that build or break down materials inside or outside the cells

What happens to the food you eat?

Enzymes break down the food by acting as a Catalyst

Catalyst – anything that makes a reaction take place without being changed itself

Enzyme (catalyst)

Food particle (substrate)

The enzyme attaches to the food at the

“active site”

The enzyme breaks the food into smaller usable

pieces (products) and releases them

CellsCells are the basic

units of life All organisms are

composed of cells.The activity of the

body’s cells determines the both the structure and the function of the body.

What we’ll be concentrating on is how things move in and out of cells.

Plasma MembraneThe membrane separates the

cell interior (the cytoplasm) from the cell exterior (extracellular or interstitial fluid).

Both the cytoplasm and the exterior are aqueous, or water based.

The membrane is a bilayer (double layer) of phospholipids.

A phospholipid is a molecule made of a glycerol backbone to which 2 fatty acids and one phosphorous-containing group are attached.

2 PM’s as seen w/ an electron microscope

Cartoon representation of the PM

Plasma MembraneBecause the cell has water inside and water outside, the phospholipids have to line up in two lines to protect the fatty (hydrophobic) tails

This structure has important implications for how things travel thru this membrane.

Notice that the membrane is made up of more than just phospholipids.

Proteins are found either embedded within the membrane itself (membrane proteins), or weakly associated with either the interior or exterior face of the membrane (peripheral proteins).

The membrane also has molecules of cholesterol embedded among the phospholipids. Cholesterol increases the temperature range over which the membrane can function.

Some integral proteins protrude into the ECF and have sugars attached. These are called glycoproteins.Glycolipids often function as markers that label the cell as “self,” i.e.,

not foreign.

Other integral proteins function as:Enzymes Transport molecules Channels Structural supports

The membrane is a fluid structure. There is a lot of lateral movement of phospholipids and unanchored proteins.

B/C of its gel-like nature and the fact that it’s made up of many different parts, we say the membrane is a fluid mosaic.

Crossing the MembraneNutrients must get in and

wastes must get out.Signaling molecules

received by a cell may need to get in, while signaling molecules sent by a cell need to get out.

Fluid must be able to get in and out.

Certain ions must be able to get in and out.

Types of transport:Passive Transport:

Either by simple diffusion or through a membrane protein

Requires NO Energy

Active Transport:

Requires Energy - ATP

Always happens through a membrane protein and uses ATP to force a molecule across a membrane against concentration grandient

Big Stuff?Membrane Proteins are adequate for bring

small molecules into the cell or out of the cell.However, a different kind of active transport

is necessary to move large things into/out of the cell – vesicular transport.

There are 2 types of vesicular transport:

exocytosis and endocytosis

Exocytosis Exocytosis literally means “out of the cell” It accounts for hormone secretion,

neurotransmitter release, mucus secretion, and, sometimes, ejection of wastes. Inside the cell, the substance to be exported is enclosed

in a membranous sac called a vesicle. The vesicle will migrate to the PM fuse with it, and then

rupture, spilling the contents into the extracellular space.

EndocytosisReverse of exocytosis. Allows macromolecules to enter

cells.The substance is progressively enclosed by an enfolding

portion of the plasma membrane.This forms a vesicle which will pinch off the plasma membrane

and enter the cytosol where it is typically digested.Types of endocytosis are:

PhagocytosisPinocytosis (a.k.a. bulk-phase endocytosis)Receptor-mediated endocytosis

PhagocytosisLiterally “cell-eating.”Cytoplasmic extensions

called pseudopods “reach out and grab” large, solid material such as a clump of bacteria or cell debris, and then engulf it.

The resulting vesicle is called a phagosome.

Usually, the phagosome fuses with a lysosome, a membranous organelle that contains digestive enzymes, and its contents are digested.

Macrophages and white blood cells are the most phagocytic cells in the body.

PinocytosisLiterally means “cell-drinking.”A bit of infolding plasma membrane

surrounds a droplet of extracellular fluid containing dissolved molecules. This creates a tiny membranous vesicle.

Most cells routinely perform this.Unlike phagocytosis, pinocytosis is

unselective!

DiffusionMany molecules have the capacity to

diffuse right through the phospholipid bilayer.Nonpolar molecules move thru w/ ease

b/c they do not mind the hydrophobic interior of the plasma membrane. Such molecules include O2, CO2, steroid

hormones, fat soluble vitamins, and alcohol.What governs whether these molecules

will move into or out of a cell? Its CONCENTRATION GRADIENT.

Hydrophilic molecules must diffuse thru special protein channels in order to get thru the cell membrane.

This type of transport through the plasma membrane is termed simple diffusion.

Based on the concept of diffusion.Random molecular

movement (due to KE) results in molecules moving from areas where their concentration is high to where their concentration is low. Note: Concentration

is defined as how many molecules of a substance are present in a certain volume of liquid.

The dissolved particles are the solutes while the fluid in which they’re dissolved is the solvent. Together, they create a solution.

Note that in the above diagram, molecules are moving down their concentration gradient!

DiffusionSome polar molecules enter cells via diffusion. They cannot

go straight through the nonpolar lipid bilayer, so they require the assistance of proteins that act as carrier molecules.

These carriers bind the substance (glucose and other simple sugars are the best examples) on one side of the plasma membrane and then change their conformation and release the substance on the other side of the PM.

This is known as facilitated diffusion.

OsmosisOsmosis is the diffusion of water

through a semipermeable membrane.A membrane that is semipermeable

allows some molecules to pass thru, but does not allow others.

Water will diffuse from an area of high concentration to an area of low conc.

It’s important that you understand the following:An area that has a high [water] has a low

[dissolved particles].An area that has a low [water] has a high

[dissolved particles].

Right: Water molecules (black dots) move to the right since they are high in conc. on the left and low on the right.

Water will diffuse from a solution with low a concentration into a solution of high concentration if they are separated by a semipermeable membrane.This is simply

another way of saying that water will flow down its concentration gradient.

(Permeable to water only)

TonicityTonicity is defined as the ability of a

solution to change the shape of a cell immersed in it due to changes in the cell’s water volume.

A solution with the same concentration of non-penetrating solutes as those found in cells are isotonic, i.e., “the same tonicity.”

Cells exposed to such solution retain their normal shape and exhibit no net gain or loss of water.

Most intravenous solutions are isotonic (e.g., 0.9% saline or 5% glucose). Why is this necessary?

TonicitySuppose you placed a cell in a solution, and the cell shrank (the technical term is crenated):The cell must have

lost water which means that, the [non-penetrating solutes] was higher outside the cell.

Thus, the solution was hypertonic (hyper means greater than usual).

Red blood cells in a hypertonic environment

TonicitySuppose you put a cell in solution and the cell burst (lysed):The cell must have

gained water which means that the [non-penetrating solutes] was higher inside the cell.

Thus the solution was hypotonic (hypo means less than usual).

Do you think pure water is hypertonic to cells or hypotonic to cells?

RBC’s in a hypotonic environment

Cell Junctions:How do cells connect?Gap Junctions:

These are the way cells communicate with cells adjoining them. They are semi-permeable and allow many things across the boundary

Desmosomes:Anchors holding cells to neighboring cells.

Tight Junctions:Creates a water-tight bond between the cells like rivets.