Transcript Presentation

Biology
Chapter 6- Chemistry
Chemistry-science that studies the
composition of matter and its changes
Matter-anything that takes up
space and air
The units that make up matter are called atoms
atoms have 3 parts:
Protons-positive charge
(in nucleus)
Neutrons-no charge
(in nucleus)
Electrons-negative charge
(in clouds around nucleus)
States of matter
Matter is divided up into 3 forms (states) based
on the movement of the particles in them:
1.
2.
3.
solid-particles vibrate in place but do not move around
(little kinetic energy, a lot potential energy) ex. ice
Liquid-particles move slightly apart (some potential
and some kinetic energy) ex. Liquid water
Gas- particles move rapidly and bounce off each other
(little potential energy and a lot of kinetic) ex. Water
vapor
Changes is states of matter
•
•
•
•
Melting- change from a solid to a liquid
Freezing- change from a liquid to a solid
Evaporaton- change from a liquid to a gas
Condesation- change from a gas to a
liquid
Energy is grouped into 2
categories:
• Kinetic energy- energy of moving objects
ex. Water running
• Potential energy- energy of position
(no movement)
ex. Water behind a dam
Electrons surround the nucleus
of an atom
Electrons float around the nucleus in shells called
orbitals
Each shell holds a certain number of electrons
1st shell---max of 2 electrons
2nd shell---max of 8 electrons
3rd shell---max of 18 electrons
example: phosphorus
Element-matter that can not be broken down into a
simpler substance
There are 92 known elements and all are shown of the periodic table
Each element has a symbol ex. H-hydrogen
Elements differ from one another by the number of protons they have
(atomic number)
(example: hydrogen has 1 proton/carbon has 6 protons)
periodic table
Atomic number= number of protons (ex. 2)
Atomic mass= number of protons + neutrons (ex.
4.003)
Electrons = protons
Different atoms bond (attach to each other)
to make a molecule
ex. NaCl (salt)
Na + Cl >> NaCl
Chemical formula- tells the number of elements present and how many of
each element
example water has 2 hydrogen and 1 oxygen
chemical reaction- the combining or breaking apart of atoms
example Na + Cl >>
NaCl (salt)
There are 2 kinds of chemical reactions:
1.
2.
synthesis reaction- atoms combine to make new product
(elements that combine are called reactants and new
substance made is called products)
-gives off energy (exothermic)
decomposition reaction- atoms break apart
energy is needed (endothermic)
Types of bonds in chemical reactions:
1.
Covalent bond- bond in which 2 atoms share a pair of electrons
ex. H-H
2.
Ionic bond- bond in which an atom donates electrons to another
ex. Na-Cl
All reactions are classified into
2 groups:
1. Endothermic reaction- energy is needed for a
reaction to occur
activation energy- amount of energy needed
for a reaction to start
2. Exothermic reaction- energy is given off when
the reaction occurs
Enzymes-the protein molecules in living things
that regulate chemical reactions in the body
Why do chemical reactions occur?
All atoms want to have 8 electrons in their outer most
shell (valence shell)
(all except hydrogen and helium-they want to have 2 in
outer shell)
If they do not, atoms will attach to other atoms to get
their electrons.
If they do have 8 electrons, they will not attach to
anything. They are not reactive (stable).
Example: neon has 8 electrons in outer shell so it will not
react/attach to anything.
Chlorine has 7 in outer shell, so it will get 1 from another
element.
What determines the rate of a
chemical reaction?
•
•
•
•
1. type of substance reacting
2. concentration of the substance
3. temperature of the substance
4. enzymes reacting in the substance
Enzyme- proteins that speed up chemical
reactions
What is the difference between a mixture
and a solution?
Mixture-elements combine and each retains its own
properties (ex. Mix sugar and salt)
Solution- elements combine by one dissolving into the
other
(ex. Sugar, kool-aid and water)
Solution is made of 2 parts:
1. solute-what is being dissolved
ex. Sugar
2. solvent- what is dissolving the solute
it is usually water hence water is called the
“universal solvent”
What is the difference between an acid and
base?
Acid-a compound that releases a hydrogen
ion when placed in water (H +)
Base-a compound that releases an
hydroxide ion when placed in water (OH-)
Buffer- solution that resists changes to pH
when an acid or base is added
pH scale shows the concentration of hydrogen ions in
something (range is 1-14)
example pH of 1 has many hydrogen ions and a pH
of 14 has few
The lower the pH the more acidic it is.
Neutral pH is 7 (water)
Why is water so important to life?
1. Absorbs heat to keep the temperature
stable
2. Good lubricant (ex. Tears in eyes)
3. Needed for reactions
4. Dissolves a lot of substances (universal
solvent) ex. Water in blood
transports nutrients
Organic molecules- contain carbon
(except Carbon dioxide)
types of organic macromolecules in humans
1.
2.
3.
4.
Carbohydrates
Lipids-fats
Proteins
Nucleic acids
Carbohydrates
• Composed of C, H, O
• Monosaccharides are the simplest units that
make them up
2 monosaccharides form disaccharide
many monosachharides form
polysachharides
Lipids- fats
• Composed of C, H, O, N, P
• Glycerol-smallest units that
make up lipids
2 types of lipids:
Saturated-all carbons have a single
bond
Unsaturated-all carbons do not have
single bond (easier to break
2 types of fats:
• Saturated fat- all
carbons have a
single bond
• Unsaturated fatall carbons do not
have a single
bond
(easier to break
down)
Proteins
• Made of C, H, O, N, S
• Amino acids are the smallest
unit that makes them up.
There are 20 amino acids
putting these in different
combinations results in
different proteins
Enzyme- protein that speeds
up reactions
Nucleic acids
• Made of C, H, N, O, P
• Nucleotides-smallest
unit that makes up
nucleic acids
There are 2 kinds of Nucleic
acids:
DNA (deoxyribonucleic acid)
RNA (ribonucleic acid)
DNA and RNA
DNA- genetic material of the cell
-controls the cells activities
-found in the nucleus
RNA- protein synthesis
(makes proteins)
-found in ribosomes
DNA structure– consists of a double
RNA structure- consists of
helix (2 strands of nucleotide
coiled together)
1 strand of nucleotides