Transcript Importance of Food

Chemistry of Life
Life Science Book pp.66-73
The Importance of Food
 Living things need food for
building tissue and for energy.
What is not used is eliminated
from the body as waste.
 Example: Muscle Tissue
What Substances Make Up Food?
 Sugars
 Vitamins
 Minerals
 Proteins
 Water
 Waste
What happens when food is
eaten?
 The substances in food break apart from one another.
 First the teeth and tongue break the food into smaller
pieces manually.
 Second, chemicals such as enzymes and acids break the
food down chemically into small molecules.
What are molecules?
 Molecules are two or more
atoms chemically bonded to
each other.
What is an atom?
 Atoms are the basic building
blocks of all substances, both
living and non-living.
 Consists of:
 Nucleus that contains:
 Positively charged protons
 Neutral neutrons
 Electron cloud that contains:
 Negatively charged
electrons
Elements
 A substance made up of only one type of element.
 Can’t be broken down into a simpler form by chemical
reactions.
 Arranged in a chart known as Periodic Table of Elements.
Elements That Make Up the Human
Body
Symbol
Element
Percent
O
Oxygen
65.0
C
Carbon
18.5
H
Hydrogen
9.5
N
Nitrogen
3.2
Ca
Calcium
1.5
P
Phosphorous
1.0
K
Potassium
0.4
S
Sulfur
0.3
Na
Sodium
0.2
Cl
Chlorine
0.2
Mg
Magnesium
0.1
Other elements
0.1
Most Common Elements in Human
Body
 Six elements listed on the table make up 99% of living
matter.
 Oxygen – O
 Carbon – C
 Hydrogen – H
 Nitrogen – N
 Calcium – Ca
 Phosphorus – P
What can we learn about an
element from the periodic table?
 http://education.jlab.org/beamsactivity/6thgrade/tableofelements/tableo
felementsc.pdf
 Metal or Non-metal
 State at room temperature
 Mass of the atom (# protons + # neutrons)
 Number of protons (= atomic number)
 Number of electrons (= atomic number)
 Number of neutrons ( = atomic mass – # protons)
 And more!
Use the periodic table to learn
about Mg
 Name is magnesium
 Atomic mass = 24 amu (atomic mass units)
 Atomic number = 12
 Metal
 In column 2, row 2 – Will have 2 shells and 2 electrons in outer shell
 Number of protons = 12
 Number of electrons = 12
 Number of neutrons = (24 – 12)
What would a model of
magnesium look like?
Placement of Electrons
 Electrons travel in shells around the nucleus of an atom.
 Each shell represents an energy level. The further from the
nucleus, the higher the energy level.
 Within each shell are orbitals. Each orbital is a different energy
level. Electrons fill shells from least energy level to greatest.
Sometimes this means putting electrons in the next shell before
completely filling the previous shell.
Electron Filling Order
Shell / Orbital
Max. Number of Electrons
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
3d
10
4p
6
5s
2
4d
10
5p
6
6s
2
4f
14
5d
10
6p
6
7s
2
5f
14
Examples
Potassium
K
 Maximum 1st shell can hold is 2.
 Maximum 2nd shell can hold is 8.
 Maximum 3rd shell can hold is 18 but only has 8.
 1 electron goes into shell 4 because 4s is lower energy
than 3d.
Strontium Sr

Strontium has 38 electrons

1s 2

2s 2

2p 6

3s 2

3p 6

4s 2

3d 10

4p 6

5s 2
1
s
2
2
3
s
2
4
s
p 6
5
2
s
p 6
d
10
f
2
p 6
d
s 2
Atoms Combine to Form
Compounds
 Definition: A compound is a substance made up of two or
more elements in exact proportions.
 Example: H2O – water is always made up of 2 atoms of
hydrogen bonded to 1 atom of oxygen.
 Compounds have properties different from the elements
they are made of.
Two Types of Compounds
 Molecular (covalent) – compounds form when atoms share
electrons.
 Example: Each atom of hydrogen in a water molecule shares 1
atom with the oxygen atom.
 Ionic compounds – form when positively and negatively charged
atoms (ions) are attracted to each other.
 Chlorine gains an electron from sodium and becomes negatively
charged: Cl1 When sodium loses an electron, it has one more proton than
electron and has a positive charge: Na1+
 Na1+ + Cl1-  NaCl
Important Compounds in Living
Things
 Organic Compounds – Always contain carbon and
hydrogen and generally associated with living things:
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids
Carbohydrates
 Supply energy for all cell processes
 Contain the elements carbon, oxygen and hydrogen
 Examples: sugars, starches, cellulose
Lipids
 Store and release even more energy than carbs.
 Do not mix with water.
 Made up of carbon, oxygen, hydrogen, and phosphorus
 Examples: fats, oils, phospholipids, cholesterol
Proteins
 Building blocks of many structures, such as muscles, in the
body.
 Proteins called enzymes regulate most chemical reactions
in cells.
 Made up of small molecules called amino acids.
 Contain the elements carbon, oxygen, hydrogen,
nitrogen, and sulfur.
Nucleic Acids
 Store important information in cells.
 Example: DNA and RNA
 Contains the elements carbon, hydrogen, oxygen,
nitrogen, and phosphorus
Inorganic Compounds
 Most are made from elements other than carbon.
 Usually smaller than organic compounds.
 Examples:
 Calcium phosphate – gives strength to bones
 Hydrochloric acid – breaks down food in stomach
 Sodium bicarbonate – helps digestion occur
 Salts containing sodium, chlorine and potassium – helps send
messages along nerves
 Water – makes up blood; most chemical reactions occur in water.
Characteristics of Water
 H end of water molecule has a + charge and O end has a – charge. The
(+) end of one water molecule attracts the (-) end of another water
molecule. This allows small insects to walk on water.
 When substances are heated, the molecules start to move. Water
molecules don’t move as easily because of the attraction noted above;
therefore; water temperature does not change quickly.
 In living things, water acts as an insulator, helping to keep
temperature constant.
 Ice floats when frozen. This ice protects water animals from extremely
low temps.
Wrap Up
 Food is made up of molecules.
 We break down these molecules and separate out what we need
from what we don’t need.
 Some of the molecules are used to rebuild tissue, bones, etc.
 Some are used as fuel for energy.
 Water plays an important role as a key ingredient of blood that
allows it to break down and transport nutrients throughout the
body and to regulate temperature.