Chapter 2 The Molecules of Cells Pages 19-44. Matter - a substance that occupies space and has...
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Transcript of Chapter 2 The Molecules of Cells Pages 19-44. Matter - a substance that occupies space and has...
Chapter 2
The Molecules of CellsPages 19-44
Matter- a substance that occupies space and has ________;
- a substance composed of _________
Atom- the smallest unit of an _________
that possesses all the characteristics of that element
- unit of an element that is not easily divisible by ordinary chemical means
Atom• Composed of :
1 or more _________ (positive charge),usually 1 or more neutrons (no charge),and 1 or more __________
(negative charge)
Often the number of protons and electrons are equal. The resulting atom has no net charge.
similar to Fig. 2.2
____________• a pure substance composed of only one kind
of atom
e.g. hydrogen (H), carbon (C), oxygen (O)
(See Blackboard for a list of chemical symbols you should know.)
Different elements MUST have a different number of protons in the nucleus
Isotope• an atom of an element that differs in the
number of ____________ in the nucleus
e.g. Carbon 12 (12C) and Carbon 14 (14C)
both are carbon, must have 6 protons
12C has 6 protons and 6 neutrons
14C has 6 protons and 8 neutrons
____________ Isotope• an unstable isotope; an atom that will
decay (change) into a different element as subatomic particles are lost from the nucleus
e.g. 14C 14N + 1e-
6p + 8n 7p + 7n
Ion• an atom of an element that has gained
or lost one or more ___________
e.g. H+, Na+ - both have lost one electron
Cl- - has gained one electron
outer electron is lost
_____________• a substance composed of two or more
atoms; the atoms may be identical or may be different elements (compound).
e.g. water H2O
glucose C6H12O6
oxygen gas O2
Chemical Bond• an attractive force between two atoms
• Three different types:
__________
______________
_____________
Ionic Bond• the chemical bond that results from the
attractive force between two oppositely charged _________
e.g. table salt Na+- Cl-
Ionic bonds are not extremely strong.
Fig. 2.7
Covalent Bonds
• chemical bonds that result from two atoms sharing one or more pairs of ____________;produces a relatively strong bond
• Two types of covalent bonds:Nonpolar covalent bond – the pair(s) of
electrons are shared equallyPolar covalent bond – the pair(s) of
electrons are not shared equally
Nonpolar covalent bondChlorine atoms share 1 pair of electrons
similar to Fig. 2.8
Polar covalent bondsO and H do not share electrons equally
similar to Fig. 2.9
O and H have partial charges due to polar covalent bonds
Pg. 26
OH H
_____________ Bond• an attractive force between two atoms
with opposite partial charges
• The atoms are not ions, the partial charges result from the atoms being polar covalently bonded to some other atom.
• weak bonds, but very important in living systems
O forms hydrogen bonds with H BETWEEN water molecules
Fig. 2.9
Properties of water
• very good __________ for polar substances
• water molecules are adhesive and cohesive
• takes a lot of energy to warm (high heat capacity) or vaporize (high heat of vaporization) water
• ice (solid water) is ________ dense than liquid water
________________- the substance is attracted to
water; will form H bonds with water; contains some polar covalent bonds
________________- the substance is repelled by
water; will not form H bonds with water; contains mostly nonpolar covalent bonds
Hydrophilic – e.g. glucoseO-H bond is polar covalent
A fatty acid – all the C-C and C-H bonds are nonpolar covalent
Will this molecule form any H bonds with water?
see also Fig. 2.20
See page 110 in Chapt. 6
____________ – the loss of one or more electrons from an atom or molecule
_____________ – the gaining of one or more electrons from an atom or molecule
Usually linked; referred to as oxidation/reduction (redox) reactions
Oxidation/reduction is important in living systems because energy is transferred from molecule to molecule with the electrons.
Oxidation – loss of e- and _______
Reduction – gaining of e- and energy
NADox + e- + H+ NADHre
lower energy higher energy
Acid- a substance that releases _________ ions when placed in solution
e.g. HCl H+ + Cl-
________- a substance that combines with H+ or releases OH- when placed in solution
e.g. HCO3- + H+ H2CO3
NaOH Na+ + OH-
_____- a measure of the hydrogen ion concentration of a solution
- ranges from 0 to 14 0 – the most acidic, lots of H+ 14 –
the least acidic, very few H+ (most alkaline or basic)
7 – neutral, neither acidic or basic
pH is the negative logarithm of the hydrogen ion concentration
Based on logarithms, each whole number change represents a 10-fold change in H+.
pH 6 is ______ more acidic than pH 7
Negative log is why larger pH numbers represent lower acidity.
100 = 1 10-1 = 0.1 10-2 = 0.01 10-14 = 0.000,000,000,000,01
__________- a substance, that within a certain range, maintains a constant pH by combining with H+ when mixed with an acid, or releasing H+ when mixed with a base
- Buffers do not necessarily maintain a pH of 7.
H2O + CO2 H2CO3 HCO3- + H+
Organic Chemistry “Organic chemistry nowadays almost drives me mad. To me it appears like a primeval tropical forest full of the most remarkable things, a dreadful endless jungle into which one does not dare enter for there seems to be no way out.”
Fredrich Wohler 1835
Organic Chemistry- the study of ___________ containing compounds
Organic molecule- a molecule synthesized by living organisms (no longer useful)- a molecule containing 2 or more carbon atoms (What about methane, CH4?) - a molecule containing at least the elements ________ and __________
Functional Groups- parts of organic molecules
• Hydroxyl group -OH
• Methyl group -CH3
• Carboxyl (acidic) group -COOH
• Amino group -NH2
• Phosphate group -PO3
Can you identify the functional groups?
Can you identify the functional groups?
_____________, -COOH
Can you identify the functional groups?
__________, -CH3
Can you identify the functional groups?
_____________, -OH
Can you identify the functional groups?
______________, -PO3
Can you identify the functional groups?
__________, -NH2
Families of Organic Molecules
• Carbohydrates
• Lipids
• Proteins
• Nucleic AcidsNote – this list does not contain all the different
kinds of organic molecules
____________________• Contain only C, H and O• Lots of hydroxyl groups• Three groups we’ll look at
Monosaccharides – simple sugars
Disaccharides – made from 2 simple sugars
Polysaccharides – polymers of simple sugars
_____________- a large molecule composed of repeating subunits, monomers
e.g. polysaccharides, proteins, DNA, plastics, etc.
Monosaccharides – simple sugars• Contain only C, H, and O
• Ratio of these three elements is:
___C : ___H : ___O
• Lots of hydroxyl groups, -O-H
• Dissolve easily in water. Why?
e.g. glucose or fructose, C6H12O6
ribose, C5H10O5
_________________• Composed of 2 simple sugars bonded
together
• C:H:O ratio not quite 1:2:1
e.g. sucrose, C12H22O11, made from joining glucose and fructose, both C6H12O6
Easily digested to simple sugars
Fig. 2.16
Dehydration aka
______________________• Contain only C, H and O
• Ratio not 1C:2H:1O, but still contains
lots of O
• Size limits solubility in water
e.g. starch and cellulose are both polysaccharides made from only glucose
starch – easily digested
cellulose – undigestible by most organisms
similar to Fig. 2.17
similar to Fig. 2.19
__________• Usually contain only C, H and O
• Ratio of C:H:O nowhere near 1:2:1
lots of C and H, relatively little O
• 4 types we’ll look at:
Fatty Acids Glycerides
Phospholipids Steroids
Fatty Acids• Consist of a carboxyl group and a
____________________ chain
similar to Fig. 2.20
________________ Fatty Acids
• at least 2 H atoms bonded to each of the C in the hydrocarbon chain
Common in animal fats; solid at room temperature
from Fig. 2.20
_________________ Fatty Acids
• One or more C atoms in the hydrocarbon chain have less than 2 H atoms bonded to them.
Common in vegetable oils; liquid at room temp.
Trans fats - partially hydrogenated vegetable oils, not typically made by living organisms
from Fig. 2.20
Glycerides• Glycerol and 1, 2 or 3 ________ _____
(mono-, di-, or triglycerides)
How are they synthesized?
How do you digest them?
When did your great grandmother use hydrolysis of
triglycerides?
similar to Fig. 2.20
Dehydration
Will this molecule form any H bonds with water?
Is it hydrophilic or hydrophobic?
Fig. 2.20
________________• A diglyceride + phosphate group + R group
• Lipid end is hydrophobic
• Phosphate and R group end is hydrophilic
• Form the basic structure of all cell membranes
similar to Fig. 2.21
Steroids• Non-fatty acid lipids• Contain only lots of C, H and little O• Behaves like other lipids• e.g. _________________• Absolutely necessary –
e.g. cell membranes, sex hormones
similar to Fig. 2.22
Proteins• Contain __________, in amino groups
• Made from long chains of amino acids
• Very diverse group of molecules;
very diverse functions
• Shape is extremely important
Amino Acids• An _________ group and a
____________ group bonded to the same carbon atom
• Differ in the R group attached to the central carbon atom
Amino Acids• All proteins made from different
combinations of the same 20 amino acids
• Humans have 8 (children 9) _____________ amino acids – must be present in diet
similar to Fig. 2.23
Polypeptide• A small polymer of ______ _____;
part of a protein molecule.
• Peptide bonds – a covalent bond between the carboxyl group of one amino acid and the amino group of the following amino acid.
• Synthesis? Digestion?
similar to Fig. 2.24
Dehydration
_______________• A change in the shape of a molecule.
• Shape is very important in organic molecules, especially proteins.
e.g. frying an egg; sickle-cell anemia
_____________ _______
• An organic molecule composed of long chains of nucleotides.
e.g. DNA, RNA
Nucleotides• An organic molecule composed of:
1 or more phosphate groups,
a 5-carbon sugar,
and a _______________ base
similar to Fig. 2.26
Adenosine Triphosphate - ______
• A nucleotide involved in most of the reactions in which energy is transferred in living organisms
• Composed of Adenine (N-base), 5-C sugar and three phosphate groups
similar to Fig. 2.27