Download 5-Chemical Organization of the Cell

Taft College Human Physiology
5-Chemical Organization of
the Cell
Chemical Bonds and Energy
Storage
Chemical Bonds and Energy
Storage
• Molecules and compounds are held together by
chemical bonds.
• It takes energy to form bonds and a lot of the
energy is stored in this bond as potential energy.
• When bonds are broken, potential energy is
released.
• Example: ATP is the main energy source in
living cells. It releases energy from high energy
phosphate bonds.
• ATP
ADP + Phosphate + Energy
• A-P-P~P
A-P-P + P + Energy
Chemical Bonds and Energy
Storage
• When you eat sugar, chemical bonds in
the sugar are broken providing energy.
• Energy stored in a chemical compound is
measured in terms of calories.
• These are not the same as dietary
calories.
• The relationship is:
1 dietary calorie = 1000 chemical calories.
Food Energy
• In terms of food energy, the food we eat
has the following chemical equivalents:
• In chemical calories
• Carbohydrates
=4000 calories per gram
• Fats
=9000 calories/gram
• Proteins
=4000 calories per gram
= about same as carbohydrates.
• You can see value of low fat diet!
The Chemical Composition of
the Cell
• Important Elements in the Cell
• Of 100 or so elements we know of,
4 elements makeup about 96% of the body.
• These 4 elements are:
C Carbon
18%
H Hydrogen
10%
O Oxygen
65%
N Nitrogen
03%
• these 4 =
96% of your body’s atoms
The Chemical Composition of
the Cell
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Other important elements include
P
Phosphorus
S
Sulfur
These 2 (P+S) plus 4 above account for 99%
Mg Magnesium
Ca Calcium
Na Sodium
K
Potassium-You can remember these by ‘mechanic’ (mgcanak)
Fe Iron
I
Iodine
Cl Chlorine
6 of these elements, CHNOPS will combine in many ways to form
most of the molecules found in living systems.
Important Molecules of Living
Systems = Biomolecules
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Biomolecule
Water- H2O
Protein (amino acids) C,H,O,N,S
Lipids (fats) C,H,O
Carbohydrates (sugars) C,H,O
Other (nucleic acids C,H,O,N,P + certain
radicals, minerals, ions)
total
% of body weight
60%
17%
17%
1%
5%
100%
= significant difference
male female
62
59
18
15
14
20
1
1
5
5
Important Molecules of Living
Systems = Biomolecules
• Water - Important Functions
• Water is the most abundant substance in living
organisms (60% in humans)
• 1. Solvent function of water.
• Water is the solvent of our bodies.
Solvent = a dissolving medium.
The reason it is such a good solvent is that it is a polar
molecule. The term "polar" means that one side of the
molecule is slightly positively charged (hydrogen) and
the other side is slightly negatively charged (oxygen). In
the case of water it looks like this:
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Water as a Solvent
(-)
(+)
= Polar Molecule
Unequal sharing of electrons takes place in water
Electrons spend most time with Oxygen causing Oxygen end of the
molecule to be ( - ) and the hydrogen end to be (+)
Na+Cl-
Water as a Solvent
(-)
(+)
Na+
Cl-
= Polar Molecule
Na+ will be attracted to Oxygen side of the molecule which is ( - )
Cl- will be attracted to the Hydrogen side of the molecule which is (+)
The Na+ and Cl- ions are now dissolved in solution
Important Functions of Water
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1. Water serves as the Solvent of the body
2. Water is the body’s medium for transport. Fluids are pumped
or otherwise distributed throughout the body to transport nutrients
and wastes.
3. Water helps maintain cells at a constant temperature.
Water is a good retainer of heat.
It is difficult to change the temperature of water.
This helps maintain homeostasis of body temperature.
Much heat can be removed by sweating since water contains heat
energy and it is dissipated as sweat evaporates.
4. Water participates in chemical reactions.
Hydrolysis and dehydration synthesis of biomolecules.
5. Water serves as the body’s lubricant.
Examples: Mucous, lubricates the chest, abdomen, & joints.
Electrolytes in Water
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Within the water of the body we will find electrolytes.
Electrolytes- substances that can dissociate into ions = (electrically charged atoms).
+ charged ions = cations. As they are attracted to a negatively charged pole or
electrode (cathode = negative pole ( - )).
- charged ions = anions. As they are attracted to a positively charged pole or
electrode (anode = positive pole (+)).
Main electrolytes of the body:
cations
Na +
+ = Anode (Positive)
K+
Ca + +
Mg + +
Battery
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anions
Cl HPO4 -SO4 -- sulfate
HCO3 -bicarbonate
- = Cathode (Negative)
Function of Electrolytes
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1. Necessary for Osmotic gradients. Example: Na
2. Influence enzyme activity. Examples: Mg, P
3. Components of buffer systems. Example: phosphates,
bicarbonate.
What is Buffer?
Buffers maintain pH in close limits.
What is pH?
pH measures acid/base balance
pH Scale
Scale: 0-14
<7 = acid
(7 = neutral)
> 7 = basic or alkaline
4. Electrolytes carry electrical current = Excitability (membrane
potentials) (Necessary for muscle and nerve activity, Na, K, Ca)
pH Scale = Acid / Base Scale
• The pH scale is a measure of H+ ion or
OH- ion concentration.
pH Values of Selected Substances
Acidic
Gastric Juice
Lemon Juice
Vinegar
Soft Drink
Vaginal Fluid
Coffee
Urine
Saliva
Basic
1.2-3.0
2.3
3.0
3.0-3.5
3.5-4.5
5.0
4.6-8.0
6.3-6.8
Distilled Water
Blood
7.3-7.5
Semen
7.2-7.6
CSF
7.4
Pancreatic juice 7.1-8.2
Bile
7.6-8.6
Milk of magnesia 10.5
Lye
14
7.0 = Neutral
Red denotes substances in human body
Important Molecules of Living
Systems
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Carbohydrates
Carbohydrates are compounds made of C, H, O.
The term:
carbo (C)
hydrate (H2O) or ‘watered carbon’
tells you a lot about the make up of carbohydrates.
Carbohydrates are molecules containing carbon, hydrogen and
oxygen in a ratio close to the ratio of 1:2:1, or CH2O.
Examples: sugars and starches (animal starch = glycogen, plant
starch = cellulose).
Mainly used for energy but can be structural as in DNA, RNA.
Sugars are formed by photosynthesis. We cannot make them
ourselves.
Carbohydrates have 3 major
properties:
• 1. Have a high caloric value and a
principal energy source for most living
systems.
• 2. Are the basic materials from which
many other types of molecules are made.
• 3. They are soluble in water (except
polysaccharides).
Where does the body get it’s
energy?
• 1st – ATP, but you can only store enough for about 6
seconds.
• 2nd – Carbohydrates, but only about 1% of your body
weight is carbohydrates.
• 3rd – Lipids = main storage form of energy.
• As humans we are very well adapted for storing energy
in this form – maybe too good!
• Will you use fat (burn fat) if carbohydrates are readily
available from your diet?
• 4th – Protein
• In starvation, you see nothing left but skin and bones –
the fat and protein (muscle) has been used as an energy
source.
There are 3 recognizable forms of
carbohydrates:
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Monosaccharides, Disaccharides, Polysaccharides.
Mono = 1,
Di = 2,
Poly = many;
saccharide = sugar.
1. Monosaccharides- "single sugars".
Example: glucose (main energy molecule), (deoxy)ribose, fructose, galactose (in
milk).
2. Disaccharides- "2 sugars". 2 sugar molecules bonded together.
Example: maltose- malt sugar (2 glucoses joined), lactose- milk sugar (glucose plus
galactose). Sucrose- table sugar (glucose plus fructose) sugar most common in
plants.
Find disaccharides primarily as intermediates in protein synthesis or breakdown of
other carbohydrates.
3. Polysaccharides- "many sugars".
Examples: cellulose and starches (glycogen- animals main storage form). Made of
many hundreds or thousands of monosaccharides linked together in a long chain.
They makeup a storage form of sugar: Glycogen in liver and muscle.
Polysaccharides also play a structural role: Cellulose in plant cell walls. Cellulose is
not digestible by humans.
Important Molecules of Living
Systems
• Lipids (fats)
• Lipids are most commonly fats, waxes,
or oily substances. Lipids contain C,H,O
like carbohydrates but not in a 1:2:1 ratio.
There is much less oxygen in lipids than
in sugars.
Major Functions of Lipids
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1. Protection – they cushion the body
2. Insulation for Thermoregulation
3. Major energy storage form
4. As a component of membranes
2 Major Characteristics of Lipids
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1. Are water insoluble. Are soluble in solvents like ether, alcohol,
and chloroform, nonpolar solvents.
2. Have C-H bonds in greater proportion than other organic
compounds.
This leads to their ability to store more than 2x the energy than an
equivalent amount of carbohydrates or protein.
Fats = 9000 calories/gram
Carbohydrates and Proteins = 4000 calories/gram
Therefore, lipids are very important sources of energy.
Lipids are stored in cell mostly as fat. Lipid is synthesized from
sugar. You see many foods that say “fat free”. These are often
carbohydrates that your body can use to make lipids.
Therefore they are only truly “fat free” if they stay in the package!!!!
3 Major Types of Lipids
• 1. Simple Lipids
• 2. Phospholipids
• 3. Steroids
Simple Lipids
• 1. Simple Lipids- include fats, waxes, and oils.
• These are the triglycerides, composed of 3
fatty acids bonded to a molecule of glycerol.
• Triglycerides are the major storage form of fat.
• They compose the adipose tissue of the body
and are the primary lipids to metabolize for
energy by the body.
Formation of a Simple Lipid = Triglyceride
= Glycerol + 3 Fatty Acids
Simple Lipids
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A fatty acid may be saturated or unsaturated.
Saturated fatty acid- means every carbon in the hydrocarbon tail has its
full complement of hydrogens (=2). In other words, all carbons are joined by
single bonds.
O HHHHHH
OH
HH
HO-C-C-C-C-C-C-C-ETC.
VS.
HO-C-C=C-C=C-C-C-etc.
HHHHHH
H
HH
• Example of saturated fats: animal fats (lard), palm oil, coconut oil.
• Unsaturated fatty acid- has doubled or triple bonds between 2 or more of
the carbons in a chain. In other words, it doesn't have as many hydrogens
as is possible or it could have.
• Polyunsaturated fats contain more than one double bond.
• Examples: corn oil, safflower oil, or canola oil.
• Saturated fats have a higher energy content (more calories) than
unsaturated fats.
• They are also more solid at the given temperature.
• Most animal fats are saturated while most vegetable fats are
unsaturated. What are the dietary implications?
• Saturated fats and atherosclerosis are linked in diet studies. This leads to
arteriosclerosis.
Phospholipids
• 2. Phospholipids- a lipid portion and a
non-lipid portion attached to a glycerol
backbone.
• Phospholipids are the main component in
cell membranes.
Phospholipid =
Lipid + a non-lipid portion
Non-lipid
Lipid portion
Steroids
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3. Steroids- sterol and steroids.
Steroid structure differs considerably from the triglycerides but they
are nonpolar, fat soluble molecules. They have four rings of carbon atoms.
Examples: cholesterol, sex hormones, cortisol, bile salts, vitamin D.
Cholesterol can contribute to fatty build-up in atherosclerosis but also
serves as the starting material for synthesis of other steroids.
Cholesterol can be synthesized by the liver or received from your diet.
Important derivatives of it included the sex hormones: estrogen,
progesterone, testosterone.
Cholesterol has definitely been implicated in one form of heart disease
known as atherosclerosis where it clumps together in blood vessels to form
crystals and is deposited there.
The cholesterol crystals may block the flow of blood.
End Note- Easy way to identify a lipid is by high proportion of C-H
bonds with relatively little oxygen.
Steroids
Cholesterol, which is synthesized in the liver, is the starting material
for synthesis of other steroids in the body
How does the body digest fats?
• Bile salts, which are made in the liver as
cholesterol derivatives have this responsibility.
• Bile salts act like detergents to break fat into
small droplets (emulsify fats) and allows fats to
be absorbed and digested in the body ..
• Bile salts work the same way that detergents
do in getting grease off of clothing, etc.
• It’s important for us to look at how a detergents
works.
How Detergents (Soaps) or Bile Salts Work?
Lipids in an aqueous solution, will go to the top of the water as a film.
Note- these are lipid salts (soap), so have a polar end.
The situation looks something like this:
uncharged tail
Hydrophobic
charged head
lipid molecule
Hydrophyllic
lipid (oil) forms layer on top of water
Water
uncharged tail
A detergent molecule looks like this:
CH2-CH2-CH2-CH2-CH2....
Head Charged (+)
charged head
Hydrocarbon Chain detergent molecule
Hydrophobic
Hydrophyllic
Like dissolves like
The head end is charged meaning it is soluble in water (water is a polar substance and charged molecules, ions, or
parts of molecules will be soluble in it).
The long hydrocarbon chain that forms the tail is not charged and will not be soluble and water.
However, when detergents are added to lipids in water, the detergent molecules will react with lipid molecules to
form microscopic droplets. This is how lipids are made soluble.
Bile salts act like detergents to break fat
into small droplets (emulsify fats) and
allows fats to be absorbed and digested in the
body.
Detergent micelle