Molecules and Cells- Chapter 1 Flashcards
(162 cards)
1
Q
What 6 elements are present in the largest proportions in living organisms?
A
Carbon, hydrogen, oxygen, nitrogen, phosphorus an sulphur (1st 3 are the most abundant)
2
Q
How does most oxygen and hydrogen exist in organisms?
A
As Water
3
Q
What is an ion?
A
An atom or molecule that have an electrical charge due to the number of protons and electrons not balancing.
4
Q
What are the 7 Biologically important ions?
A
- Calcium (Ca2+)
- Iron (Fe2+)
- Magnesium (Mg2+)
- Potassium (K+)
- Nitrate (NO3-)
- Phosphate (PO43-)
- Hydrogen Carbonate (HCO3-)
5
Q
What is the formula of ions: calcium, iron, magnesium, potassium, nitrate, phosphate and hydrogen carbonate
A
Ca2+, Fe2+, Mg2+, K+, NO3-, PO43-, HCO3-
6
Q
What is the function of Ca2+ ?
A
- Calcium pectate is an essential component of middle lamella of plant cell walls
- Component of bones and teeth
- Essential in blood clotting and muscle contraction.
7
Q
What is the function of Fe2+ ?
A
- In Haem group of haemoglobin
- Constituent of election carriers in respiration
8
Q
What is the function of Mg2+ ?
A
- Essential in giving chlorophyll its light-absorbing properties
9
Q
What is the function of K+ ?
A
- Maintains electrical gradients across neurons
10
Q
What is the function of NO3- ?
A
- A component of amino acids, nucleic acids and chlorophyll.
11
Q
What is the function of PO43- ?
A
- As phospholipids, it is the main component of cell membranes.
- Component of other important biological molecules> ATP and Nucleic acids
12
Q
What is the function of HCO3- ?
A
- Important as a natural buffer
13
Q
Why do atoms of the elements found in living organisms combine?
A
- To form biologically important molecules linked by strong covalent bonds
14
Q
Explain the hydrogen bonds in water…
A
- In a H20 molecule, each hydrogen atoms shares a pair of electrons with the oxygen atom, forming a covalent bond.
15
Q
Why is water molecule described as being polar?
A
- As the molecule has an uneven distribution of charge..
16
Q
Why is water an excellent solvent?
A
- As it can dissolve a wide range of inorganic and organic substances.
17
Q
What % of cells does water form in living organisms?
A
Between 50% to over 90%
18
Q
What 3 points values water as a solvent?
A
- Most of a cell’s reaction takes place in aqueous solution.
- Transports medium in living organisms
- The different effects it has on hydrophilic and hydrophobic molecules.
19
Q
What does hyrdophilic mean?
A
Water loving
20
Q
What does hydrophobic mean?
A
Water Hating
21
Q
What are buffers?
A
- Chemicals or substances that resist changes to pH and ensure that a particular environment maintains a particular pH
22
Q
Why are atoms of metals positively charged?
A
As they tend to lose electrons
23
Q
Why are atoms of non-metals negatively charged?
A
As they tend to gain electrons
24
Q
What are organic molecules? +examples
A
- Complex carbon-containing molecules
- E.g- Carbohydrates, proteins and lipids
25
What are many organic molecules formed of?
- Sub-units called monomers
26
What do monomers join together to form?
- Larger polymers through the process of polymersation
27
What charge does hydrogen and oxygen hold in a water molecule?
Hydrogren- delta positive
| Oxygen- delta negative
28
What are carbohydrates?
- A group of substances used as both energy sources and structural materials in organisms
29
What 3 elements do carbs contain?
Carbon, hydrogen and oxygen ( C6H12O6)
30
What is the ratio of hydrogen to oxygen atoms in carbs?
2:1
31
What are monosaccharides?
- These are simple sugars with general formula = ( CH2O)n n=3-7
32
What are 3 examples of monosaccharides?
- glucose, fructose and galactose.
33
What are disaccharides?
- These are double sugars formed from 2 monosaccharide monomers
34
What are 2 examples of disaccharides?
-Maltose and sucrose
35
What are polysaccharides?
- These are large molecules formed from many monosaccharides
| - Complex carbohydrates which often form very long chains
36
What are 3 examples of polysaccharides?
-Cellulose, starch and glycogen
37
What is a hexose monosaccharide?
Glucose - C6H12O6
38
Why are some substances like monosaccharide known as being isomers of eachother?
- As the have the same molecular formula but different structural formula
39
How are disaccharides formed?
-When 2 monosaccharides( hexoses) react together in a chemical reaction known as a condensation reaction
40
what type of reaction is a condensation reaction and why?
- A reversible Reaction
| - As a disaccharide molecule can be broken down into its constituent monosaccharide monomers in a hydrolysis reaction
41
What happens to the water during condensation?
- 1 molecule of water is lost
42
What happens to the water during hydrolysis?
- 1 molecule of water is gained
43
What is a glycosidic bond?
-The bond that is formed between 2 hexose sugars in the formation of a disaccharide
44
What general formula do all disaccharides have?
- C12 H22 O11
45
How is maltose formed?
- when 2 a-glucose molecules are linked through a condensation reaction.
- Formed when starch is digested
46
How is sucrose formed?
- When an a-glucose molecule condenses with fructose molecule.
47
what does maltose require further digestion to form?
- The monomer glucose
48
what is sucrose?
- The form in which carbohydrate is transported through phloem in plants
49
What reaction forms polysaccharides?
Condensation reactions joining large number or monomers together to make complex polymers
50
What is the general formula of polysaccharides?
(C6 H10 O5)n
51
What is starch?
a polymer of a-glucose. starch consists of a mixture of 2 types of chains
52
How are the a-glucose molecules linked in Amylose?
by 1,4 glycosidic bonds
53
What type of bonds does amylose form?
As only 1,4 bonds are involved, amylose forms long unbranched chains. Chains are coiled to form a spiral
54
how much starch is formed form amylose?
20%
55
How does amylopectin link it’s a-glucose monomers together?
by a-1,4 glycosidic bonds, + a-1,6 glycosidic bonds form side branches to produce a branched molecule
56
How much starch is in amylopectin form?
80%
57
what is the benedict’s test used to detect?
Reducing sugars
58
How do you test for reducing sugars?
-Add an equal volume if benedict’s reagent to the test solution and heat to atleast 80degrees in water bath
59
Describe the positive colour change in Benedict’s test..
blue-green-yellow-orange-brick red precipitate
60
Why would the benedict’s test stop at the green or yellow stage?
If there’s only a small amount of sugar present
61
Why is the benedict’s test Semi-quantitative?
As it can only approximate quantities
62
How can a non-reducing sugar be identified by the benedict’s test?
- Test for reducing sugar (negative)
- The hydrolyse the rest of the sample by heating with dilute hydrochloric acid in water bath
- Once cooled, neutralise with sodium hydrogencarbonate
- Test with benedict’s solution(positive)
63
Why is starch such a good storage molecule?
- Molecules of amylose and amylopectin are very compact (Rich store of glucose in small space)
- Insoluble
- Large molecule
- The branching nature of amylopectin
64
Why does insoluble make starch a good storage molecule?
-It won’t affect the water relations of the cell. If carb were stored as glucose a lot of water would enter by osmosis
65
How does being a large make starch a good storage molecule?
-Can be retained in cell and won’t easily pass through cell membrane
66
How does branching make starch a good storage molecule?
- It creates many terminal ends that are easily hydrolyse
67
Where is glycogen found?
The storage carbohydrate found in animal and fungal cells
68
In what form is glycogen stored?
Small granules
69
Describe the glycogen structure?
- Similar to amylopectin
- Formed of chains of a-glucose monomers
- Has 1,4 and 1,6 glycosidic bonds but chains more branches and shorter
70
Where is glycogen stored?
-In liver and muscle cells in mammals
71
What are 3 properties of glycogen?
- compact
- insoluble
- proportionally more terminal ends, enabling faster hydrolysis
72
what is the role of cellulose?
-Not a storage polysaccharide, it’s rôle is structural
73
What monomers is cellulose made of?
B-glucose
74
What occurs when two B-glucose molecules join together?
-Form B-1,4 glycosidic bonds, alternate molecules are rotated through 180degrees
75
What 2 effects does the flipping of adjacent glucose monomers have?
- The unbranched chains are straighter
| - Hydrogen bonds can form cross-linkages between adjacent chains
76
What are cellulose chains grouped together in?
microfibrils
77
What is formed with cellulose microfibrils?
- Plant cell walls.
| - Put into many planes in lattice structure to increase its tensile strength
78
Are lipids soluble?
- Not soluble in water (hydrophobic)
| - Soluble in organic solvents, ether and ethanol
79
What is a fatty acid made up of?
Long hydrocarbon tails linked to a carboxyl group
80
What is the formation of a triglyceride?
One glycerol molecules is joined with 3 fatty acid molecules
81
Explain what occurs during the reverse reaction of a triglyceride…
Hydrolysis of triglyceride happens during lipid digestion. Uses 3 molecules of water and produces 3 fatty acids and one molecules of glycerol
82
How are the carbon atoms linked in saturated fatty acids?
By C-C single bonds
83
How are carbon atoms linked in unsaturated fatty acids?
By atleast one C=C double bond
84
What type of fatty acid is it if there’s one double bond?
Monounsaturated
85
What type of fatty acid is it when there’s more than one double bond?
Polyunsaturated
86
Give two examples of unsaturated fatty acids…
- Oleic acid and linoleic acid
87
Give one example of a saturated fatty acid…
Stearic acid
88
What type of fatty acid is fat?
Saturated fatty acids
89
What type of fatty acid is oil?
Unsaturated hydrocarbon chains
90
Why are triglycerides excellent energy stores?
As they release more energy per unit mass than carbohydrate
91
What are the functions of fat?
Important for insulation, store in a layer below the body surface in many animals.
- Body organs are protected by a layer of fat
92
What do lipids form?
Large molecules (macromolecules) - insoluble
93
What are the 4 main types of lipids?
- Triglycerides, phospholipids, waxes and steroids
94
How are triglycerides formed?
Through combination of glycerol and fatty acid molecules
95
Describe the structure of a triglyceride…
One glycerol molecule is joined with 3 fatty acids by 3 condensation reactions
96
When does hydrolysis of triglyceride occur?
Reverse reaction- During lipid digestion
97
What is used and made during hydrolysis of triglyceride?
3 H2O molecules- produces 3 fatty acids and 1 glycerol molecule
98
What 5 elements do proteins contain?
Carbon, hydrogen, oxygen, nitrogen and sulfur
99
What are proteins?
Large polymers formed from amino acid sub-units
100
How many types of amino acids are there? What does this mean for protein?
- 20
| - Infinite number of arrangements in a protein
101
What is the shape of a protein determined by?
- by the sequence of the amino acids in the protein
102
What bonds are amino acids linked by?
Peptide bonds
103
What do 2 amino acids joined together form?
A dipeptide
104
What is formed when many amino acids join together?
- Polypeptide
105
What 3 elements do lipids contain?
-Carbon, hydrogen and oxygen
106
What is the ratio of hydrogen and oxygen in lipids?
2:1
107
What is the general formula of glycerol?
C3H8O3
108
How is the formation of a triglyceride formed?
By 3 condensation reactions
109
what is the state of fats at room temp.?
-Solid
110
What is the state of liquids at room temp.?
- Liquid
111
What bond is formed with each condensation reaction in a triglyceride?
Ester bond
112
What is the primary structure of a protein?
- The sequence of the amino acids in the polypeptide chain
| - usually formed by hundreds of amino acids linked by peptide bonds
113
What 2 groups do the amino acids in a polypeptide contain?
-NH and -C=O
114
How is the formation of hydrogen bonds in secondary structure enabled?
By the O of the -C=O >négative and H of -NH >positive
115
What are the two most common types if secondary structures?
- a-helix
| - B-pleated sheets
116
Where are hydrogen bonds formed in a-helix?
-Between amino acids occurring at regular intervals in the sequence.
117
What does the tertiary structure involve?
- The further folding of the secondary structure.
| - This gives each protein its unique 3D shape
118
What 4 roles does proteins have
- Structural- Main component of body tissues, muscle, skin, ligaments and hair
- Catalytic- all enzymes are proteins, catalysing
- Signalling- Many hormones and receptors are proteins
- Immunological-all antibodies are proteins
119
What are the four levels of a protein structure...
- Primary
- Secondary
- Tertiary
- Quaternary
120
What 4 types of bonds will hold the tertiary structure in place?
- Ionic bonds
- Hydrogen Bonds
- Disulfide bonds (bridges)
- Hydrophobic interactions
121
Where are hydrophobic interactions found?
-Between non-polar sections of a protein
122
Where does a disulfide bond occur?
- Between 2 cysteine amino acids
| - One of the strongest and most important bonds
123
What are 3 fibrous proteins?
- Collagen
- Keratin
- Silk
124
What is collagen?
- Consists of 3 identical polypeptides.
| - The main component of connective tissue like ligaments, tendons and cartilage.
125
Describe the structure of Globular proteins..
-A spherical shape caused by tightly folded polypeptide chains
126
Why are the chains folded in Globular proteins?
- So hydrophobic groups are on the inside and hydrophilic groups are on the outside> makes them soluble in water
127
What are 3 examples of globular proteins?
- Transport proteins(haemoglobin)
- Enzymes( lipase and DNA polymerase)
- Hormones (Oestrogen and insulin)
128
What does the additional folding of tertiary structure do?
Give each protein it’s unique 3D shape and is a consequence of the range of bonds formed between R-Groups of amino acids
129
Describe hydrogen bonds…
-Are numerous but weak and easily broken
130
Describe Ionic bonds…
-Formed between amino and carboxyl groups in some amino acid R groups ( stronger then H bonds but damaged by change in pH)
131
Describe disulfide bonds…
- Covalent bonds formed between R-groups of sulfur containing amino acids (cysteine)
- Strong bonds and give strength to structural fibrous proteins like collagen
132
Describe the secondary structure of protein a-helix…
- H2 bonds formed between amino acids.
- Bonds twist the chain into helical shape.
- Held by H2 bonds
133
Describe the secondary structure of protein B-pleated sheets…
- More rigid and less flexible
- Formed by sections of polypeptide chain
- Orientated in opposite directions lying adjacent to each other
- Hydrogen bonds form C=O and NH groups
134
What term is used to describe the structure of unsaturated fatty acids?
- A kink
135
Where are lipids stored in?
- Adipose tissue
136
What does the polar nature of the phosphate group in phospholipids mean?
- the 'head' end of the phospholipid is attracted to water (hydrophilic)
137
What does the non-polar nature of the fatty acids in a phospholipid mean?
-The 'tail' end of the phospholipid is repelled by water (hydrophobic)
138
What is the nature of phospholipids?
- Amphipathic, as molecule has both hydrophobic and hydrophilic sections
139
What test tests for lipids?
- Emulsion test
140
Describe the emulsion test:
- Ethanol added to sample
- Test tube shaken
- Lipids dissolve in ethanol as non-polar
- Added to pure water once dissolved >insoluble
- white cloudy emulsion formed
141
What 3 groups make up an amino acid?
- Amino group
- Carboxyl group
- R Group> defines amino acid
142
What is a quaternary structure?
- proteins that have more than one polypeptide chain
143
What is the non-amino acids part called in conjugated proteins?
-prosthetic group
144
What are fibrous proteins formed from?
- Parallel polypeptide chains held together by cross-links
145
What are fibrous proteins (3 points)?
- long rope-like fibres
- Insoluble in water
- high tensile strength
146
When does a protein become denatured?
-If the bonds that maintain the proteins shape are broken the protein will stop working properly
147
What 3 points can denature a protein?
- Changes in temp.
- pH
- Salt concentration
148
How do fibrous proteins change when they become denatured?
-Lose their structural strength
149
How do globular proteins change when they become denatured?
-Insoluble and inactive
150
What test is used to detect proteins (peptide bonds)?
- Biuret Test
151
Describe the stages of the Biuret test...
- A few drops of Biuret reagent, blue copper(II) sulfate (cu2+ ions) and sodium hydroxide are added
- Shake
- Solution will change colour in presence of peptide bonds
152
What is the positive colour change in Biuret test?
-Blue to Mauve/lilac
153
Why does it turn mauve/lilac when positive?
- Due to the Cu2+ ions bonding to adjacent pairs of -CO-NH- groups in peptide bonds
154
What are prions?
A particular type of protein found in mammals and some other animal groups
155
Where are prions found in mammals?
Nervous system involved in synaptic transmission
156
What occurs if a disease causing prion is present in an individual?
-Acts as a template causing other normal prions to convert. Leads to a chain reaction and disease causing prions increase
157
What is the symbol for normal and disease-causing prions?
```
Disease= PrPsc
Normal= PrP/ PrPc
```
158
Describe the structure of disease causing form…
Higher proportion of beta pleated sheets
159
What are two key features of disease causing prions?
-Replicate and infectious
160
How long is the incubation period for prions?
5 to 20 years
161
In what three ways can the disease causing prion increase?
- Normal prion can spontaneously adopt PrPsc form
- Mutations in DNA codes for prion, disease causing can be passed to offspring
- Eating contaminated food that contains disease causing form
162
What are the 3 prion diseases?
- Scrapie in sheep
- Bovine Spongiform encephalopathy (BSE) in cattle
- Variant Creutzfeldt-Jakob disease- human version by eating contaminated food
