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Flashcards in Chemistry of Life Deck (54):
1

pH of life

7.2 - 7.4

blood has to be slightly basic to accomodate for carbonic acid

2

What elements is life mostly composed of?

Carbon, oxygen, hydrogen, and nitrogen

3

4 macromolecules and function

Lipids: membranes, hormones, communication

Nucleic acids: store genetic information (can act as catalysts)

Proteins: structure, function, catalyst

Carbohydrates: store energy, indentification

4

Valence shell

Outermost shell of electrons

5

What is the bonding point?

Unpaired valence electrons

6

4 main types of bonds

1. Covalent
2. Polar covalent
3. Hydrogen
4. Ionic

7

Covalent bonds

Shared electrons

8

A single covalent bond has...

2 electrons

9

Nonpolar covalent bonds

electrons are shared equally

electrons are halfway between the two atoms

atoms have no charge

10

Polar covalent bonds

Electrons are not shared equally due to electronegatively

11

Why is water a polar molecule?

Oxygen has high electronegativity that attracts electrons. This gives it a partial negative charge and hydrogen gets a partial positive charge

12

What is CH4?

Methane

nonpolar covalent

13

What is NH3?

Ammonia

14

Electronegativity

chemical property that describes the tendency of an atom to attract electrons

15

What factors affect electronegativity?

Atomic number (# of protons)

Greater positive charge will attract more electrons

16

Label the 3 atoms of life in terms of increasing electronegativity

H, C, O

17

Strength of bonds

Nonpolar covalent are hardest to break (methane, hydrogen)

Polar covalent (water, ammonia)

Ionic bonds (NaCl) are easiest to break

18

Ionic bonds

have full charge

19

-OH functional group

hydroxyl, probably some type of alcohol

20

What does a functional group with oxygen probably indicate?

The molecule is probably polar

This means that it is hydrophilic

21

Hydrophilic substances

can interact with water through their charges

if it has a partial or full charge

22

Hydrophobic substances

cannot interact with water through these partial charges

Ex: hydrocarbons have no charge

23

What drives protein folding?

Interactions between hydrophilic and hydrophobic molecules

24

Where are there hydrogen bonds in the hydrogen atom?

Between two different water molecules

(polar covalent is actually in the molecule)

25

Hydrogen bond

an attractive interaction between polar molecules

Hydrogen bonds to atoms with a high electronegativity

26

What does hydrogen bonding lead to?

Cohesion

High specific heat

27

Cohesion

water can stick to itself

surface tension

28

Why is water's high specific heat important?

It makes a good buffer in temperature which is important for life

29

Adhesion

water can stick to other things

capillary action

30

Why does water expand when it freezes?

the orientation of hydrogen bonds

water molecules are spaced further apart in ice lattice structure (less dense)

31

Why is water a great solvent?

The partial negative and partial positive charges can break apart substances

Ex: Na+Cl-
Na is attracted to negative oxygen
Cl is attracted to positive hydrogen

32

How does water act as a pH buffer?

It can dissociate itself into H+ and OH-

33

H+

hydronium

34

OH-

hydroxide

35

What is the basis of the pH scale?

Proton (hydrogen ion) concentration

more hydrogen ions = lower pH

36

Acids

molecules that donate H+

makes sense that more hydrogen ions = lower pH, because acids are the ones that donate H+

Ex: HCl

37

Bases

molecules that remove H+

raise pH

Ex: NaOH

38

Is water an acid or a base?

It can act as both because it can pick up and remove hydrogen ions

39

Veins

carry oxygen depleted blood to the heart

40

Arteries

carry oxygen rich blood away from the heart

41

Where is CO2 high in the body?

Veins and tissues

This reduces the affinity of hemoglobin for oxygen. Hemoglobin will release more oxygen to tissues

42

How is CO2 transported in the body?

Dissolved in blood as carbonic acid that water has to buffer

43

What happens when affinity of hemoglobin is lowered?

Hemoglobin is more likely to release oxygen, since it cannot carry as much

44

Where is CO2 low in the body?

Arteries and lungs

Hemoglobin has a high affinity for oxygen. It does not need to release oxygen in these places. It needs to carry it.

45

What happens when CO2 levels in the blood increase?

more H+ is produced from forming carbonic acid

lowers pH

hemoglobin has a lower affinity for oxygen when pH lowers because it indicates high CO2

46

When does hemoglobin's affinity for oxygen increase?

When pH is high

This indicates less H+ ions and correspondingly less CO2

47

Carbonic acid

an unstable intermediate molecule that will quickly dissociate into HCO-3 and H+

48

If an atom has 4 electrons in its valence shell what kinds of covalent bonds can it form?

single, double, or triple

49

When atoms in a covalent bond have the same electronegativity what type of bond form?

Nonpolar covalent

Molecule is not charged

50

How many other water molecules is one water molecule bonded to?

4

51

Hydronium ion

a water molecule with an extra H+

forms from water gaining a H+ from another water molecule

has a +1 charge

52

Why do all living things need pH buffers?

Amino acid side chains have many carboxyl and amino acid groups

53

A solution with a pH 5 has how many more hydrogen ions in it than a solution with pH 7?

100x

54

What happens to HCl in water?

It is a strong acid, so it dissociates completely and produces lots of H+ which lowers the pH