Cell Membrane Sec.3.3,3.4,&3.5

The cell membrane is the barrier that separates the cell from the external environment.

It is composed of 2 fat layers called a phospholipid bilayer

Polar Head (hydrophilic/water loving)& Nonpolar Tail(hydrophobic/water fearing)

The cell membrane is known to be selectively permeable (only selected molecules can pass through it or leave from it)

Attached within the cell (intracellular receptors) which are proteins receptors that allow specific molecules in and out of the cell.

When a substance (ligand) attaches to the correct receptor it is allowed in.

Membrane Receptors: are located in the membrane and binds to molecules that cannot cross the membrane, change in shape transmits the message to the cell interior

Take a look....

This is the Fluid Mosaic Model : describes the arrangements of molecules making up a cell membrane. (membrane is flexible like FLUID and has a variety of molecules like the variety of tyles in a mosaic.

Other Molecules found in the membrane:

cholesterol: strengthens membranes

carbohydrates aid cell identification

Check it out!

Recap and Intro

Lets assess your knowledge....

Cell Membrane Quiz Section 3.3

Section 3.4

There are 2 methods of  transporting molecules across a membrane....

Passive Transport

No ATP,Energy, required because molecules are moving from areas where there are many [High] to areas where there are less [Low] known as down a concentration gradient.

-Diffusion (molecules moving from [High] --> [Low])

Diffusion Video

-Osmosis (H2O moving from [High] --> [Low])

Osmosis Video

So why does this matter?...

(Review vocabulary solute vs solvent vs solution)

Your cells (animal cells) function at a specific concentration concentration. Too much/too little of a solution can have deadly effects

Gummy Bear Lab

-Facilitated Diffusion (moving large molecules across using the help of integrated proteins)

Lets assess your knowledge....

Diffusion & Osmosis Quiz Section 3.4

Section 3.5

Active Transport 

ATP required because we are moving molecules against what they tend to normally do.

-Similar to facilitated diffusion but in the opposite direction [Low] --> [High] up a concentration gradient.

Two different ways of active transport are....

Endocytosis (into cell)

Exocytosis (out of cell)

Lets watch this video

Lets assess your knowledge....
Active Transport,Endocytosis,Exocytosis Sec 3.5

Cell Theory and All About Cells

Cell Theory States:

• All living organisms are composed of cells. They may be unicellular or multicellular.
• The cell is the basic unit of life.
• Cells arise from pre-existing cells.

Wacky History

2 Types of Cells:



Prokaryotic Cells (Bacteria)

• No nucleus only free DNA
• No membrane-bound organelle (except ribosomes)
• Unicellular organisms

Eukaryotic Cells (Plant, Animal, Fungi, Protist)

• Nucleus present
• Specialized structures that work together called organelles.
• Most are multi-cellular organisms

What do Prokaryotes and Eukaryotes have in common?....

• both are cells
• both contain a deoxyribonucleic acid
• both have a cell membrane as a protective barrier
• both have ribosomes for protein synthesis
• both have cytoplasm, a jelly-like substance inside their membrane.

A cell can be compared to a city....
each organelle functioning as a part of a whole.



Each organelle has its role in the cell....




Lets assess your knowledge....Cell Quiz Section 3.1

For extra help please access the online book at my.hrw.com
(Access code needed)

Chemical Reactions and Enzymes

What are Chemical Reactions?

Changing substances to different substances by breaking or forming chemical bonds.

.


         Reactants go in        ---->       Products come out

Example:

In order for reactions to occur energy is required known as activation energy.

Some reactions absorb energy than they release (Endothermic Reactions) 

Some reactions release more energy than they absorb (Exothermic Reactions)

So why does this matter?

At this moment your body is going through many chemical reactions at a cellular level with the help of ENZYMES.

What are Enzymes?

All Enzymes are proteins but not all proteins are enzymes.

What????? It's kinda like....

Enzymes are made up of proteins. But not all proteins function as enzymes.

 How Does It Work?....

Enzymes are known as catalyst because they lower the energy needed for a reaction to take place.

Reactions happen at a faster pace with enzymes.

Check this out....

Some enzymes allow reactions to occur quick and require less energy but require a optimal temperature and/or pH.

Other enzymes break items down like Amylase in your saliva. 

 Amylase is an enzyme that catalyzes starch into sugars in your mouth.

Helpful tip: Enzymes can be identified by the ending of -ase. (ex: amylase, lipase, etc...) there are exceptions like pepsin and trypsin which are proteins used for digestion.

So how do enzymes work?....

Enzymes have a specific site where specific substances attach. So enzymes are specific kind of like a lock and key.

What happens to enzymes once they complete their task?

Lets Review

Lets assess your knowledge....Enzyme Quiz Section 2.4

For extra help please access the online book at my.hrw.com
(Access code needed)

Carbon The Magical Element

Carbon-Based Molecules

To understand basis of life we must analyze an important element at the molecular level....

  
Carbon's outermost shell can hold 8 electrons so this means carbon can bond with 4 other atoms....

  

Carbon has a been called the molecule of life because most living things are composed of carbon. Its atomic composition is unique and essential. The 3 basic structures of carbon-based molecules are straight chain, branched chain, and ring. 

The 4 electrons in its valence shell (outermost shell) allow this element to covalently bond to 4 other elements including other carbons. STRUCTURE IS RELATED TO FUNCTION.

 Top Left to Right: Branched Chain, Ring, Straight Chain.
Bottom Left to Right : All are Branched Chain.

Sometimes carbon forms long chains made up of small sub-units....





There are 4 main types of carbon-based molecules found in all living things known as BIOMOLECULES....

Carbohydrates (aka sugars and starches)
















Carbs are composed of 3 elements Carbon, Hydrogen, and Oxygen or (CHO) and are one of the sources for chemical energy.

Helpful tip: many science terms ending in -ose are considered carbohydrates. Ex: Glucose, Fructose, Sucrose, Cellulose.....Starch?....this is one exception. An easy way of identifying some carbs is by their ring structure

Simple carbs (monomer) are known as monosaccharides (mono=1 and saccharide=sugar)



Complex carbs (polymer) are composed of many monosaccharides linked together to form a chain .....polysaccharides (poly=many)





Lipids (aka fats, oil, cholesterol) 



These biomolecules are composed of Carbon, Hydrogen, and Oxygen or (CHO), but look different than carbohydrates.
Lipids are very important because they make up the membrane of your cells.

 

Helpful tip: fats can be identified by their structure....look at this


 an exception is cholesterol.... 


Proteins

These biomolecules are composed of Carbon, Hydrogen, Oxygen, and Nitrogen or (CHON)

There are 22 essential amino acids all similar in structure....







            



A monomer of a protein is known as a amino acid. A polymer is known as a protein and are grouped together by bonds known as peptide bonds.





Nucleic Acids

These biomolecules are composed of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus or (CHONP)

The 2 examples are Deoxyribonucleic Acid and Ribonucleic Acid

The monomer for a nucleic acid is called nucleotide and is composed of a....


A polymer looks like this.....and is called a nucleic acid