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A Level Biology AQA > UNIT 1, Topic 1A & 1B - Biological Molecules > Flashcards

UNIT 1, Topic 1A & 1B - Biological Molecules Flashcards

1
Q

What are the 5 biological molecules groups?
(Carbon based compounds)

A

Carbohydrates, lipids, proteins, nucleic acids and water

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2
Q

Where are carbohydrates found in living organisms?

A

Used by cells as respiratory substrates
- form structural components in plasma membranes and cell walls.

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3
Q

How are lipids used in living organisms?

A

Including: bilayer of plasma membranes, some structural components in hormones and as respiratory substrates; also as signalling molecules

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4
Q

How are proteins used in living organisms?

A

Form many cell structures.
Enzymes, chemical messengers and components of the blood

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5
Q

How are nucleic acids used in living organisms?

A

Carry the genetic code for production of proteins.
- the genetic code is common to viruses and living things, EVIDENCE FOR EVOLUTION

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6
Q

How is water used in living organisms?

A

Used in metabolic/ chemical reactions & common component of cells

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7
Q

Give some examples of carbohydrates from GCSE

A

Starch, cellulose, glucose, sucrose, fructose

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8
Q

Give some example of nucleic acids from GCSE

A

DNA, RNA, ATP, mRNA

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9
Q

What is the function of lipids (fats)?

A

Energy storage, insulation (also flotation in animals; low density), protection, water proof layer (minimises water loss too) and to make cell membranes

  • as they dont dissolve in body fluids, they don’t have an osmotic effect (not disrupting the balance)
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10
Q

What’s the function of proteins generally?

A

For growth and repair of tissues. Transport and structure too.

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11
Q

What is the function of ATP molecule and how is it made?

A

Source of energy for cell.
- Energy released from glucose during resp. used to make ATP.

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12
Q

Chromosomes are made from this chemical…

A

DNA

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13
Q

Storage compound in plant cells

A

Starch

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14
Q

Storage compound found in animal cells

A

Glycogen is a storage polysaccharide

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15
Q

Give an example of an element that is also a molecule

A

H²

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16
Q

Answer the following questions for covalent bonding and ionic bonding…

A
  1. Between which atoms do they occur, describe the bonding.
  2. Give an example of a molecule bonded this way.
  3. Arrangement.

COVALENT:
- shared pair of electrons
IONIC:
- gains or loses electrons

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17
Q

What is a hydrogen bond?

A

The attractive forces which binds hydrogen atom of one molecule with the electronegative atom of another molecule. POLAR MOLECULE*
- bond is weak individually, but strong in masses. It’s basically intermolecular forces between molecules.

Hydrogen becomes slightly positive as electrons are pulled slightly more towards one atom (like a bigger, electronegative oxygen atom); hence, electrons arent evenly distributed.

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18
Q

What’s an disulfide bond?

A

A covalent link between 2 sulfur atoms (which may be attached to other main acids for example).
S-S bridge.

  • involved in stabilising structure of proteins.
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19
Q

What’s a macro molecule?

A

Large complex molecules

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20
Q

What is a polymer?

A

Meaning many.
A large molecule in one big structure made from repeating units called monomers.

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21
Q

What’s a monomer?

A

A single unit of a chemical which can be joined to be repeatedly linked into a polymer.

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22
Q

Polymeristaion defintion

A

The process of how a substance/monomers become a polymer.

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23
Q

What’s a polypeptide

A

A polypeptide isa continuous, unbranched chain of amino acids joined by peptide bonds.
The monomer here is a protein.

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24
Q

Nucleic acids are polymers, what are their monomers and give an example.

A

Nucleotides; DNA

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25
Q

Proteins are polymers, what are their monomers and give an example.

A

Amino acids; haemoglobin

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26
Q

Carbs are polymers, what are their monomers and give an example.

A

Monosacharrides (from polysaccharides); starch.

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27
Q

Making polymers involves joining monomers and making bonds. What reaction is used for this.

A

A condensation reaction (not strictly for polymers); polymer (AKA the new bond) and water are the products here.

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28
Q

What reaction is used to break down polymers?

A

Hydrolysis reaction, USES H²O molecule to break bond.

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29
Q

During which process are polymers hydrolysed in the body into monomers?

A

Digestion <3

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30
Q

Full chemical formula of glucose

A

C⁶H¹²O⁶

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31
Q

Practice drawing the forming and breaking of bonds of monosaccharides

A

… On tablet for extra guidance

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32
Q

A condensation reaction between 2 monosaccharides forms a …

A

Glycosidic linkage/ bond. FORMING a disaccharide

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33
Q

FINISH SENTENCES:
1. Glycogen and starch are formed by the condensation of …
2. Cellulose is formed by the condensation of…

A
  1. Alpha glucose
  2. BEAT GLUCOSE
  • These polysaccharides are formed from the condensation of many beta glucose units
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34
Q

Name the 3 main disaccharides

A

Maltose, lactose, sucrose

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35
Q

What’s an isomer?

A

2 (or more) compounds with the same molecular formula but different arrangements of atoms and properties.

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36
Q

Hello this is Theresa

A

Eva smells

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37
Q

Describe monosaccharides

A

Simple sugars, white crystalline solids, dissolve in water to form sweet tasting solutions.
- glucose, fructose and galactose

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38
Q

Why is glucose called a hexose sugar?

A

It has 6 carbons

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39
Q

Explain how a disaccharide is formed.

A

A condensation reaction between two monosaccharides occurs, water is produced and a glycosidic bond is formed. Example, maltose.

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40
Q

Name the monosaccharides making up the disaccharides:

  • maltose
  • lactose
  • sucrose
A

Maltose: glucose and glucose
Lactose: galactose and glucose
Sucrose: glucose and fructose

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41
Q

What enzymes are required for the hydrolysis of:

  1. Maltose
  2. Sucrose
  3. Lactose
A
  1. Maltase
  2. Sucrase
  3. Lactase
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42
Q

What are the 2 groups of lipids (fats) we learn about?

A

Triglycerides and phospolipids

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43
Q

What is an ester bond?

A

The bond formed from a condensation reaction between glycerol and a fatty acid (R-COOH)
- water by product

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44
Q

What are triglycerides?

A

A type of lipid: includes plant oils and animal fats.
One glycerol and 3 fatty acids.
Not polymers (as not one type of repeating monomer) and dont dissolve in water.

  • non-polar and hydrophobic molecules
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45
Q

What is R-COOH? (Lipids)

A

Carboxyl group is the COOH and the R tail is a hydrocarbon chain that’s hydrophobic
- AKA the rest of the fatty acid.
- see samsung notes for reaction with this molecule and glycerol.

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46
Q

Structure of triglyceride?

A

Glycerol molecule stays the same; difference in properties come from the variations in the fatty acids (the R group, as all fatty acids have a carboxyl group)

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47
Q

Difference between unsaturated and saturated fatty acids?

A

Saturated: every carbon atom is joined to another carbon by a single bond in the hydrocarbon chain

Unsaturated: one or more carbon-carbon bonds in chain is a double bond. Causes kinks in the chain.

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48
Q

Polyunsaturated

A

Fatty acid chain with many C=C double bonds

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49
Q

Describe an unsaturated triglyceride at room temperature

A

The fatty acid tails are not able to be tightly packed and this results in oils that are liquid

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50
Q

Describe a saturated triglyceride at room temperature

A

Fully saturated fatty acid tails can pack tightly against one another as the single bonds result in straight molecules; generating fats and candle wax that are solid (e.g. butter)

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51
Q

Structure of triglycerides relating to their functions:

A
  1. Have high ratio of energy storing C-H bonds to C-C bonds; good energy source when broken down (compared to carbs; here you have the same energy with less mass)
  2. Low mass to energy ratio, good storage molecules, lots of energy in small vol.
  3. (*)Large non-polar molecules; insoluble in water so storage of them has no osmotic effect on cells.
  4. High ratio of O to H atoms, releasing water when oxidised: portant source of water for organisms (in dry conditions).
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52
Q

Differences between a triglyceride and phospholipid

A
  • 2 fatty acids instead of 3
  • 2 ester bonds instead of 3
  • has a phosphate group attached, other doesn’t
  • hydrolysis of one only requires two water molecules
  • behave differently so have different function and form different structures, droplet or bilayer.
  • 3rd carbon rotated 180°, the phosphate group is attached to an alcohol
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53
Q

How is a phospholipid a polar molecule?

A

It’s made up of two sections/poles: hydrophobic tail and hydrophillic head.

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54
Q

Describe the (nonpolar) hydrophobic and (polar) hydrophilic components of phospholipids (also applicable to troglycerides)

  • FUN FACT: hydrogen bond is formed between the polar molecule of water
A

Phobic tail:
- fatty acid molecules repel water. Tail orients itself away from water BUT readily mixes with fat

Phillic head:
- phosphate molecules attract. The head is attracted to water BUT not fat.

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55
Q

Triglycerides form droplets in water. What do phospolipids form?

A

A phospolipid bilayer, which is found in cell membranes (acting as a barrier to water soluble substances, due to hydrophobic tails) OR micelles.

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56
Q

What are glycolipids?

A

Carbohydrate (chain attached) and phospholipid combined; cell recognition as function.

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57
Q

How many hydroxyl groups does a glycerol molecule have?

A

(OH), 3×

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58
Q

What is the specific name given to a condensation reaction between a glycerol molecule and a fatty acid to form an ester bond (and water by product)?

A

Esterification
- example of condensation reaction

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59
Q

Why are triglycerides used for waterproofing in aquatic birds?

A

They’re non polar molecules; so are hydrophobic and dont dissolve in water

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60
Q

Why is the head of phospolipids hydrophillic?

A

The phosphate group is a charged molecules (also contains an R group fun fact)

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61
Q

How do you test for lipids?
Qualitative or quantitative test?

A

Emulsion test
- Add ethanol to dissolve your sample
- shake
- add water
- shake
- a white emulsion appears when positive

Qualitative; looking simply at presence or absence of it, no numeric data

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62
Q

In a phospolipid, what happens to the last hydroxyl group of the glycerol?

A

Its bonded to the phosphate group by condensation reaction;
This head can then face the aqueous internal / external cellular environment

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63
Q

What is a lipid?

A

An organic compound group containing hydrocarbons.
Lipids arefatty, waxy, or oily compounds that are soluble in organic solvents and insoluble in polar solvents such as water.

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64
Q

Test for reducing sugars

A

Heat sample in a water bath with Benedict’s reagent / solution.
Positive: blue > brick red

  • concentration makes colour vary: green, yellow, orange
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65
Q

Which sugars are reducing sugars?

A

ALL monosaccharides (fructose, glucose…) ; SOME disaccharides (lactose and maltose)

  • they reduce other chemicals when in solution.
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66
Q

Test for non-reducing sugars; explain why each step is done

A
  • May get a mark for stating that reducing sugars test was done first to determine there were no reducing sugars.

Sample BOILED with hydrochloric acid: to hydrolyse it into its constituent monosaccharides (sucrose > fructose + glucose)

Add sodium hydrogencarbonate (SHC); neutralises sample.

Perform Benedict’s test now….
Same colours still.

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67
Q

Example of non-reducing sugar

A

Sucrose

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68
Q

Why do you need to neutralise the sample from a non-reducing sugars test before continuing?

A

Hydrogen carbonate is then added to neutralise the solution asBenedick’s reagent doesn’t work under acidic conditions.

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69
Q

How many naturally occuring amnio acid monomers

A

20

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70
Q

What are the 4 components of an amini acid?

A

Amine group, carboxyl group, R group (hydrocarbonchain, e.g. CH³), hydrogen atom

Central, ‘alpha’ carbon

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71
Q

What elements make proteins differ from lipids and carbohydrates

A

Nitrogen

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72
Q

What would happen if you changed the sequence of amino acids?

A

Changes the shape of the protein/ tertiary structure, now a different protein with different function.

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73
Q

What is formed when more amino acids are added to a dipeptide

A

Polypeptide

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74
Q

What’s a protein?

A

Polypeptide folds into complex 3D shape in order to carry out specific function

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75
Q

List the 4 components making up an animo acid

A

Amine, carboxyl, hydrogen atom, R group

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76
Q

When does a polypeptide chain become a protein?

A

Until it folds up into a distinct 3D shape and becomes functional

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77
Q

All proteins have a tertiary structure bit not all have a….

A

Quaternary structure

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78
Q

Describe the primary structure of a protein

A

Sequence of amino acids, peptide bonds.
Amine and carboxyl group at the ends

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79
Q

Describe the secondary structure of a protein

A

Polypeptide folded into alpha helix or beta pleated sheets held by hydrogen bond.

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80
Q

Describe the tertiary structure

A

Determines function of protein.
- disulfide, ionic and hydrogen.
- COOH & NH² at ends

Bonds occur between the R groups on the amini acids causing the alpha helices or beta pleated sheets to interact and fold by forming bonds.

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81
Q

Describe the quaternary structure

A

More than one polypeptide chain in a protein; collagen and haemoglobin
- forms fibrous or globular proteins

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82
Q

Test for proteins (2 answers)

A

Biuret reagent
Blue > lilac

Add dilute copper sulphate solution and then add sodium hydroxide solution (then shake); result.

Sodium hydroxide creates an alkaline environment so the test can work.

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83
Q

Explain why globular proteins are soluble in water

A

They have amino acids on the surface of the protein which are hydrophilic (the R group is), hence interact with water molecules; soluble therefore.
- whilst the hydrophobic amino a. are in the centre, away from water.

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84
Q

Describe how the structure of haemoglobin relates to its function

A

It has 4 sub units (2 alpha and 2 beta sub units). Haemoglobin in RBCs and role of binding to O² reversibly.
- binds to oxygen in lungs, releases in body tissues.

Each sub unit contains prosthetic group haem (hence a conjugated protein); each haem contains an Fe2+ ion WHERE oxygen binds to
- 1 haemoglobin molecule can bind to 4 oxygen then!

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85
Q

What polymer cannot be broken down by human digestion (only ruminants)?

A

Cellulose

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86
Q

Why is glycogen described as compact?

A

Its branched structure can coil; which makes it branched.

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87
Q

STRUCTURE: Starch is….. in shape, making it compact, it’s also… (2)

A

Helical
- insoluble (no affect on water potential), large so cant leave the cell

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88
Q

Name given to the hydrogen bonds between cellulose chains (forming the microfibrils)?

A

Crosslinks; provides rigidity

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89
Q

Why can’t humans digest cellulose?

A

Our digestive enzymes cant break the beta 1,4 glycosidic linkage in cellulose; requires a special enzyme absent in humans.

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90
Q

What kind of energy do lipids store?

A

Chemical

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91
Q

What is an emulsion?

A

When small droplets of a substance are suspended in another solution.

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92
Q

Describe how a triglyceride is formed

A

By condemnation reaction between hydroxyl (OH) group on glycerol and carboxyl (COOH) groups on fatty acids. Eater bond formed. Water molecule produced for each ester bond (so 3).

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93
Q

Is it true tgatvinteractions between the R groups form the 3D tertiary structure?

A

Yes

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94
Q

What does changing the pH do to an enzyme’s tertiary structure?

A

Changes number of hydroxide ions and hydrogen ions surrounding, so they may alter the hydrogen and ionic (weaker) bonds between the amino acids.

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95
Q

What structural level of proteins is functional and why

A

Tertiary: possesses geometric shape held by bonds (list them) showing the necessary loops and bends

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96
Q

Describe the nature of polysaccharides: examples too.

A

a polymer (which is large substance made up of many repeating monomer units). Many monosaccharides, more than 2: glycosidic bonds by condensation reaction (reverse hydrolysis where broken down into constituent monos.); water by-product.

  • starch (in plants and food sources), glycogen and cellulose.
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97
Q
A
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98
Q

Structure of cellulose

A

Long straight unbranched chains of beta glucose linked by glycosidic bonds (condensation).
Each chain linked by weak hydrogen bonds (crosslinks) that are only strong when in masses; they form microfibrils (strong fibres).

  • Providing strong structural support to cells in cell wall for example.
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99
Q

Function of cellulose in cell wall

A

Structural: Provide rigidity to plant cell as its unbranched and bonded by many H bonds (crosslinks) between the cellulose molecules AND prevents plant cell bursting as water enters by osmosis.

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100
Q

Starch is found in many parts of a plant in the form of small grains. Which parts of the plant may contain starch?

A

In the leaf (stroma of chloroplasts) or in underground storage organs like seeds
- seeds are abundant in oils and fats and starch.

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101
Q

Does the storage compound starch have an osmotic effect on the plant cell?

A

No because the structure allows it to be insoluble; unlike storing just glucose molecules that are soluble

  • Needed for respiration; (extra) good to store when needed for times of no photosynthesis, like new growth from seed or at night.
102
Q

Structure of starch

A

Mix of 2 polysaccharides: amylase & amylopectin.
Both made from long chain of alpha glucose linked by glycosidic bonds (during condensation).

103
Q

Structure of amylopectin

A

(1,6) which makes it branched and (1,4) glycosidic bonds, for the linear chains.
Long and BRANCHED; side branches allow enzymes to hydrolyse the glycosidic bonds easily as there are more ends exposed.
Alpha glucose released quickly when needed.

104
Q

Structure of amylose

A

Long and UNBRANCHED; coiled/ helical structure held by hydrogen bonds.
Good to store as can fit more in a small space; its compact.
(1,4) glycosidic linkages

105
Q

Complete hydrolysis of starch?

A

Check samsung notes

106
Q

Test for starch

A

Iodine dissolved in potassium iodide solution OR just iodine solution:
Added to a teat tube with sample.

Orange > blue/ black if present

107
Q

How does the structure of starch relate to its function?

A
  1. Large so won’t leave the cell
  2. Insoluble and can be stored, and hence has no osmotic effect on cell
  3. Hydrolysed into alpha glucose; easily transported then and readily used in respiration, producing ATP for cells.
  4. Branched; releasing many alpha glucose molecules at the same given time
  5. Compact due to amylose and hence easy to store in cells
108
Q

In what form (which polysaccharide) do animals and BACTERIA store their excess glucose?

A

As glycogen (an energy store), polysaccharide of alpha glucose

109
Q

Where is glycogen usually found in animals?

A

Muscle and liver cells

110
Q

Compare starch and glycogen

A

Starch has 2 polysaccharides, glycogen has 1.

Glycogen branches more frequently as this allow hydrolysis of more alpha glucose molecules per given time/ quicker for when the alpha glucose molecules are needed urgently for aerobic respiration: producing ATP. (They have a higher metabolic rate than plants)

  • glycogen stored in animals and bacteria; starch stored in plants
111
Q

All carbohydrates that are found in plants?

A

Starch, alpha/beta glucose & cellulose

112
Q

Why starch is good for storage?

A

Insoluble so can be stored this way; converted back into glucose until needed again (when insufficient glucose)

113
Q

Targets

A
  • mention where the polysaccharides are found in cells
  • mention their monosaccharides always!
114
Q

Where is starch found in cells?

A

In starch grains in cells

115
Q

Where is glycogen found in cells?

A

Vesicles/ in the form of granules in cytoplasm

116
Q

What are fibrous proteins? With examples

A

Fibrous proteins are formed from parallel polypeptide chains
held together by cross-links. These form long, rope-like fibres,
with high tensile strength and are generally insoluble in water.

Collagen, keratin and silk

117
Q

What are globular proteins? With examples

A

Globular proteins usually have a spherical shape caused
by tightly folded polypeptide chains.
Many globular proteins soluble in water.

Enzymes, hormones, transport proteins (haemoglobin)

118
Q

Describe the general structure of a globular protein and explain why

A

Spherical; soluble in water.
This is because hydrophillic (R groups in) amino acids are on the surface of the proteins; they can interact with H²O molecules, making them soluble.
The hydrophobic (R groups of some other) amino acids are found deep in the centre of the protein away from H²O molecules.

119
Q

Why are fibrous proteins generally insoluble in water?

A

They have a large proportion of amino acids with hydrophobic R groups; so insoluble.

120
Q

Where is collagen found?

A

In tendons, ligaments and in your skin

121
Q

Where is keratin found?

A

Hair, claws, nails

122
Q

What causes proteins to denature, and what happens to a protein when its denaturing?

A

Extremes of pHs or too high temperatures.
The BONDS between the R groups on individual amino acids are broken; the protein will stop working properly and is denatured.
In fibrous proteins this may look like losing their structural strength if the proteins are non functional.

123
Q

What does the tertiary structure provide for a polypeptide chain?

A

Stability (and function) due to its 3 types of bonds.

124
Q

Describe enzymes

A

Globular proteins (hence can change shape) which are biological catalysts, that lower the activation energy of a reaction and so speeding it up.

They can be re-used and can work on an intracellular and extracellular level (such as respiratory or digestive enzymes)

125
Q

Describe the active site

A

It’s a very small part of the enzyme that is involved in the reaction, that consists of only a few amino acids and had a very specific tertiary structure.

126
Q

What level of protein structure does an enzyme have (bonds included in description) and what determines this?

A

Tertiary (3 types of bonds); the specific amino acid sequence (determined by our DNA as protein synthesis occurs).
Denaturing changes this structure- non functional protein.

127
Q

Give the full hydrolysis of starch.

A

Starch (amylase) > maltose
Maltose (maltase) > 2 glucose molecules

128
Q

(For exam technique) compare a saturated and unsaturated fatty acid

A

A saturated fatty acid has only single bonds between every carbon atom (saturated with as many hydrogen as possible) in its fatty acid tail; unsaturated have carbon-carbon double bonds in their fatty acid tail.

129
Q

(For exam technique) Link the primary structure of a protein to its precise 3D shape

A
  • unique amino acid sequence (determined by DNA)
  • each among acid has an R group with hydrogen/ionic/disulfide bonds between them
  • causing the polypeptide chain to fold into a specific tertiary structure
130
Q

Why did scientists doubt that DNA carried the genetic code for organisms?

A

Because of the relative simplicity of DNA

131
Q

What are ribosomes made of?

A

RNA and proteins

132
Q

What is the name given to the monomer of a nucleic acid? Many forming together then to form a what?

A

Nucleotides; polynucleotide

133
Q

DNA abbreviation

A

Deoxyribonucleic acid

134
Q

RNA abbreviation

A

Ribose nucleic acid

135
Q

DNA function, where its found, and structure

A

Store genetic information, in nucleus (nucleolus), its double helical

136
Q

DNA bases

A

Adenine, thymine, guanine, cytosine

137
Q

RNA bases

A

Adenine, uracil, guanine, cytosine

138
Q

RNA function, where its found, and structure

A

Transcription and translation (some in protein synthesis later on), found in the nucleus- then travels through cytoplasm out of nucleic pore into ribosome.
A single strand that’s relatively short (a copy of a DNA segment).

139
Q

Compare DNA to RNA

A
  1. The base thymine vs uracil (UTI, uracil thymine interchangeable)
  2. Single strand that doesn’t have hydrogen bonds joining complementary bases vs 2 strands (double helix)
  3. Large polymer vs relatively short polynucleotide chain
  4. Deoxyribose sugar vs ribose sugar in nucleotides.
  5. RNA travels and is used in ribosomes.
140
Q

Suggest why the chain of polynucleotide is described as having a sugar phosphate backbone

A

Adjacent nucleotides are joined together (by phopshodiester bonds) through the alternating deoxyribose sugars and phosphate groups, so forming what looks like an alternating backbone

141
Q

Why are the base pairings only complementary to one other base (A,T/u and C,G)?

A

They have specific shapes that fit into each other, forming hydrogen bonds between them.
Complementary base bonded on antiparallel strand.

142
Q

What are the number of hydrogen bonds between the base pairings of DNA

A

A,T - 2
C,G - 3 hydrogen bonds

143
Q

Why are the 2 polynucleotide chains said to be antiparallel?

A

Because the sugar phosphate backbone has an opposite orientation

144
Q

Why is DNA a stable molecule?

A

Large number of hydrogen bonds (between complementary base pairings) MEANS they’re strong together

145
Q

What can be determined about the proportions of each of the bases in a DNA sample?

A

Complementary bases have the same proportion on OPPOSITE strands.

146
Q

State structure of DNA and how each one relates to its function.
(5 points)

A
  1. The molecule contains complementary base pairings and 2 strands that can unwind; this allows it to replicate itself accurately.
  2. Sugar phosphate backbone protects the bases and bonds between them.
  3. Complementary bases are joined by lots of hydrogen bonds; this makes it a stable structure.
  4. (Histones) The molecule is helical; can be compact and lots stored in a small space.
  5. It’s a large polymer so can store a lot of information
147
Q

Describe how a DNA double helix is formed from 2 polynucleotide strands

A

The 2 antiparallel strands are joined by the hydrogen bonds formed between the complementary bases (2 between AT, 3 between CG). The strands also twist around each other to form a helical structure.

148
Q

What is the purpose of DNA replication and when would a DNA molecule be replicated

A

To allow new cells to be made with exactly the same copy of DNA instructions (unless a mutation occurs).
Prior to cell replication; in the synthesis phase of inter phase (in the cell cycle).

149
Q

What is genetic continuity?

A

Where chromosomes must copy themselves perfectly accurately to ensure daughter cells receive the correct identical genetic information

150
Q

A mistake made during the replication process is know as…

A

A mutation

151
Q

What does semi conservative replication entail/mean?

A

It is a copy of a DNA molecule which contains one original template strand and a new complementary strand.

152
Q

Explain the process of semi-conservative replication (maybe write it down)

A

See Samsung notes for full explanation with diagrams

153
Q

What does each strand on a DNA molecule end with. Try to add detail

A

3 and 5 prime ends.
The 3’ is a hydroxide group (OH).
The 5’ is a phosphate group.

The prime ends are on opposite ends in comparison to the other complementary strand due to the fact they’re antiparallel in structure; (casual explanation) this means that the DNA polymerase works towards different prime ends depending on if its the new or template strand (opposite directions)

154
Q

2 models to explain enzyme action

A

Lock and Key Model, Induced Fit Model

155
Q

Explain in 3 steps the lock and key model

A
  1. The substrate binds to the complementary active site of the enzyme, its fixed.
  2. The binding at the active site creates a lock and key appearance to form an enzyme substrate complex. Bonds form temporarily between certain amino acids of the active site and R groups on the substrate molecule.
  3. Pressure put on (substrate?) bonds to break it into its products by hydrolysis. Enzyme remains unchanged and products leave the active site
156
Q

Why was the model reviewed?

A

Proteins were discovered to not be completely rigid structures; a bit of movement can occur

157
Q

Explain the Induced fit model in a few steps

A
  • Initially, the shape of active site is not exactly complementary to substrate
  • Active site changes shape, moulds itself around substrate
  • After the reaction is hydrolysed/ finished, products leave and the active site returns to its shape
158
Q

What is activation energy, link it to emzymes

A

The minimum amount of energy required for a reaction to start. Enzyme lower Ea.

  • GIVE DEFINITION IN EXAM! Lost a mark for this one 🤧
159
Q

Enzyme acting outside of cell

A

Extracellular enzyme

160
Q

What determines the shape of an enzyme active site

A

Tertiary structure

161
Q

6 factors affecting enzyme activity

A
  1. pH
  2. Temp
  3. Conc. Of substrate
  4. Conc. Of enzymes
  5. Conc. Of competitive inhibitors
  6. Conc. Of non-competitive inhibitors
162
Q

How is enzyme activity measured?

A

Using a balance, change in mass or using a gas syringe.

Calculation: products/ reactants used up over time taken (something like that)

163
Q

Enzyme activity graphs

A

Look on Samsung Notes.

164
Q

Explain the impact of temperature on enzymes

A
  1. ^ temp gives substrates AND enzymes more Ke.
  2. ^ chance of substrate molecules colliding and then binding with enzyme active site.
  3. ^ temp, molecules vibrate more
  4. High temps with excessive vibrations START to break some of the bonds holding tertiary structure in place (SUCH AS hydrogen, even ionic and disulfide).
  5. Shape of active site permanently changes as its denatured and substrates can’t bind; not complementary.
  6. No enzyme-substrate complex can form (affecting rate of reactions)
165
Q

Naturally occurring enzymes that break down foods and are in products have an optimum temperature of…

A

37°C

166
Q

Control variable to monitor temperature

A

Thermostatically controlled water bath to keep temp the same AND a (digital) thermometer to MONITOR temp

167
Q

Explain the impacts of pH on enzymes

A
  1. pH of a solution is a measure of its H+ concentration
  2. All enzymes have a pH at which they catalyse the best (optimum)
  3. (MOST metabolic enzymes have am opt. Of 7)
  4. Extreme pHs (lots of H+ or OH- ions) cause ionic and hydrogen bonds in enzymes to be disrupted.
  5. Tertiary structure of enzyme changes (including active site, making it functional), substrate no longer fit.
  6. No enzyme substrate complexes can form.
  7. Enzyme denatured and no longer functions permanently.
168
Q

How is pH of 2 achieved in stomach?

A

Dilute HCl

169
Q

What would you use if you wanted the pH to be a control variable in an experiment

A

A buffer solution keeping the solution at a particular pH
- Y13: calculated using a formula

170
Q

What is the effect if substrate concentration on the rate of reaction?

A
  1. The higher the substrate concentration, the higher the rate of reaction; theres a higher chance of collision.
  2. This only holds up to the V max/saturation point, may be called intermediate substrate conc.
    (V max. = when all enzyme active sites are occupied at any one time)
  3. important beyond this, adding more substrate will not increase the RoR as all active sites are occupied.
  4. Now the concentration of enzyme has become the limiting factor.

Graph plateaus = constant RoR

171
Q

What is the effect of enzyme concentration on the rate of reaction?

A
  1. The more enzyme molecules in a solution, the more likely a substrate molecule is to collide with the active site and form an enzyme substrate complex. SO increasing the concentration of enzymes increases the rate if reaction.
  2. But, if the amount of substrates is limited, at one point there will be more than enough enzyme molecules to react with the available substrate (they may be in excess), so adding more enzyme molecules has no effect.

Graph plateaus when substrate is limited but, the graph would continue and steadily increase if more substrates were added (as the previous ones have been catalysed).

172
Q

what are inhibitors? 2 types.

A

substances which reduce enzyme activity: competitive and non competitive

173
Q

how can the impact of competitive inhibitors be reduced?

A

increase the concentration of substrates (compared to inhibitors to lower chance of binding)

174
Q

Describe how competitive inhibitors effect enzyme activity (4)

A
  1. inhibitors have a similar shape to the substrate
  2. it COMPETES with substrate for the active site
  3. With the inhibitor occupying the a. site of enzyme, substrate cannot bind; ESCs can’t be formed
  4. *** competitive inhibitor molecules move in and out of the active site
175
Q

what happens if you increase the substrate concentration while non-competitive enzymes are present?

A

no effect: once the (non) inhibitor binds, the enzyme remains inhibited and the active site is permanently changed, no enzyme substrate complexes can be formed with these affected enzymes.

176
Q

what is the effect of non-competitive inhibitors on enzyme activity? (3)

A
  1. these molecules bind yo another part of the enzyme away from the active site
  2. this produces a change in the shape of the active site so substrate molecules no longer fit and cant bind so ESCs can’t be formed (see graph for impact on rate of reaction)
  3. This change is irreversible
177
Q

What is meant by the saturation point in an enzyme controlled reaction?

A

(V. max, aka velocity maximum) The point at which all enzyme active sites are filled with substrates at a given point AND the rate of reaction is ar its highest

178
Q

Explain what happens to the rate if reaction of an enzyme-controlled reaction when the substrates concentration is increased after the saturation point.

A

the rate of reaction stays constant, and all active sites stay occupied so increasing the substrate concentration has no effect.

179
Q

An enzyme-controlled reaction is inhibited by substance X. Suggest a simple way in which you could tell whether substance X is acting as a competitive or non-competitive inhibitor.

A
  1. Addition of more substrate concentration.
  2. If non- competitive inhibitor, rate of reaction will not continue as active site is altered.
  3. If Competitive inhibitor, rate of reaction will increase as great probability of substrate binding to active site over inhibitor.
180
Q
A
181
Q

What does ATP stand for and what are its components (tip it’s a nucleotide derivative)?

A

Adenosine triphosphate
made up of adenine, ribose and 3 phosphates.

182
Q

what’s a nucleotide and which group of bio molecules does it belong to

A

it’s a monomer of nucleic acid polymer like DNA
- nucleic acids

183
Q

What processes that have been studied so far (year 12) requires energy released from aerobic respiration?

A

active transport, DNA replication and protein synthesis (synthesizing macro molecules)

184
Q

ATP can be produced and energy is released. So what is ATP in terms of energy if it’s not actually energy itself?

A

It is but a store of energy (and temporary yet IMMEDIATE as cant be stored long term)

185
Q

Name the 5 main uses of ATP in energy requiring processes (within cells)
mnemonic: MAMAS

A
  1. Metabolic processes
  2. Movement
  3. Active transport
  4. Secretion of cell products
  5. Activation if molecules
186
Q

How is ATP involved in metabolic processes?

A

ATP provides the energy needed to build up macromolecules from the basic units such as making starch from alpha glucose through a condensation reaction

187
Q

How is ATP involved in movement?

A

ATP provides the energy for muscle contraction for filaments of muscle to then slide past one another and therefore shorten the overall length of the muscle fiber, Y13 work.

188
Q

How is ATP involved in active transport?

A

ATP provides energy to change shape of carrier proteins in plasma membrane, allowing ions/ molecules to be moved against conc. grad.

189
Q

How is ATP involved in secreting cell products?

A

ATP needed for forming the lysosome necessary to secrete cell products.

190
Q

How is ATP involved in the activation of molecules (on cellular level)?

A

An organic phosphate release during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make the more reactive, thus lowering the activation energy such as in enzyme catalyzed reactions.
(Y13), another example: the addition of phosphate to glucose molecules at the start of glycosis.

191
Q

Why is ATP known as a nucleotide derivative?

A

It has a similar structure and is a modified form of a nucleic acid nucleotide

192
Q

What are some differences and similarities between a molecule of ATP and DNA nucleotide?

A

Differences include the number of phosphates; ribose against deoxyribose; adenine base against 4 different types of bases (but clarify one per nucleotide).

Similarities include that they both have a phosphate group, a pentose sugar, and a base.

193
Q

Define respiration (aerobic)

A

The release of energy from glucose (and water) in cells.
- is respiration hydrolysis?

194
Q

Leading on from the definition of respiration: why can’t a cell get its energy directly from glucose?

A

It just simply can’t so the energy released from the glucose in respiration is then used to make ATP (which stays in the same cell it was made).

195
Q

Describe what happens after ATP has been made, where does it go?

A

ATP diffusers to the part of the cell that needs energy. The energy is stored in high energy bonds between the phosphate groups, which are unstable and have a low activation energy.
This means they are easily broken BY hydrolysis, but release a considerable amount of energy.

196
Q

word equation for th breakdown of ATP

A

ATP&raquo_space;> ATP hydrolase + H²O&raquo_space;> ADP + Pi ( + energy! )

• inorganic phosphate

197
Q

what does ADP stand for

A

adenosine diphosphate

198
Q

word equation for the resynthesis of ATP from ADP? What kind of reaction is it?

A

condensation reaction.
ADP + Pi ( + energy supplied from respiration )&raquo_space;> ATP synthase&raquo_space;> ATP + H²O

199
Q

What is useful about (the hydrolysis of) ATP in relation to other reactions?

A

ATP hydrolysis can be coupled to other energy requiring reactions in the cell which increases efficiency, and this is because energy can be used directly to make the coupled reaction happen rather than energy being lost as heat.

200
Q

In dehydrolysis of ATP, what can iorganic phosphate be used for?

A

Added to another compound, often making it more reactive, hence lowering the activation energy of reaction.
This is phosphorylation.

201
Q

Uses of phosphorylation?

A

• make compounds more reactive, and so lower Ea.
• change in shape of a molecules; enzymes can be de/activated by phosphorylation- change in shape of active site can make it be complementary to substrate (OR vice versa).
\ This also applies to carrier proteins during active transport.

202
Q

Explain how ATP is described as an immediate energy store

A

• fairly unstable so not suitable as long term energy store
• immediate source of energy within cell as can be re-formed/ synthesised very rapidly
• cannot be stored so must be continually made by mitochondria via respiration.
• ATP cannot be transferred to other cells.

203
Q

Reas

A

ATP synthesized during reactions that release energy and its hydrolysed to provide energy for reactions that require it.

204
Q

Why do parts of the body, such as the small intestine have lots of mitochondria?

A

Lots of respiration and lots of energy released from glucose so that it can be used to synthesise ATP.
ATP must be hydrolysed to release energy from this kind of energy store, for active transport.

Note: from this you realised as a constant cycle involving ATP and its products, vice versa.

205
Q

does photosynthesis require energy?

A

yes from the hydrolysis of ATP also

206
Q

ATP is sometimes referred to as an immediate energy source. Explain why.

A

Because energy is released directly for the cell and rapidly to be used immediately, and because it’s an unstable molecule.

207
Q

Why is ATP a good source of energy?

A

Releases energy in small amounts (so no energy wasted)
Small, soluble molecule (easily transported around cell)
Energy easily released (unstable phosphate bond, low activation energy)
Can transfer phosphate group to other molecule (makes more reactive, lowers its activation energy)

208
Q

Roles of ATP in plant cells?

A

Cell division
Phosphorylation of carrier proteins, active transport (activation of molecules)
Building up macromolecules

  • photosynthesis produces ATP
209
Q

Explain how ATP can make an enzyme catalyzed reaction to take place more readily

A

its hydrolysis produces ADP+ Pi, phosphorylation, and changes enzyme shape to be complementary to substrate (or vice versa)/ makes it more reactive, lowering Ea, less energy needed for reaction and so happens more readily

210
Q

The movement of calcium irons across a cell membrane can occur via the energy requiring process of active transport. This movement of ion is coupled to the breakdown of ATP, suggest why.

A

The energy requiring reaction can directly receive the energy released from the hydrologists of ATP for active transport in the carrier protein.
[3 marks]

211
Q

What type of bond exists between the oxygen and hydrogen atoms within the water molecule? and contrastingly what type of bond exists between different water molequestion?

A
  1. Covalent
  2. Hydrogen bonds
212
Q

What is meant by the term polar?

A

Molecules that have an uneven distribution of charge due to uneven distribution of electrons within it.
The slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules and this attraction is called hydrogen bonding.

213
Q

Important fact about hydrogen bonds

A

Weak but collectively strong

214
Q

Water : metabolite.
Explain this property and how it is important in a living organism.

A

Water is a reactant and product in many reactions ; hydrolysis.
Allows for metabolic reactions like respiration, condensation reactions to build up macromolecules, and photosynthesis.

215
Q

Water : solvent.
Explain this property and how it is important in a living organism.

A

Ability to dissolve many substances, easier to transport them through organism to where required, through blood plasma/ xylem. Due to polarity; ions will be attracted to different parts of the water (slightly positive hydrogen, slightly negative oxygen - they attract correspondingly).
- Other polar molecules such as glucose dissolve in water, as hydrogen bonds are actually formed between them and the water molecules.
Especially useful in bodies of water that can contain dissolved oxygen (O2) for aquatic life to absorb and use in respiration.

216
Q

Water : high specific heat capacity.
Explain this property and how it is important in a living organism.

A

Meaning a lot of energy is required to raise the temperature of the water. And this is because most of the heat energy is used to break hydrogen bonds between a water molecule.
This also?
Allows water to act as a buffer against rapid temperature change.

This is useful to organisms, as it means temperature of water remains fairly stable even if external temperatures fluctuate. Therefore, internal temperatures of plants and animals should remain relatively constant due to the fact a large proportion of the organism is water. And this is also important so enzymes do not denature.
- Stable environment in terms of temperature for aquatic organisms.

217
Q

Water : latent heat a vaporisation.
Explain this property and how it is important in a living organism.

A

Amount of heat energy required to evaporate water.
Animals cool themselves w/o losing lots of water : during sweating, heat energy is used to evaporate water from the surface of the skin, allowing cooling.

218
Q

Water : cohesion.
Explain this property and how it is important in a living organism.

A

This is where water sticks together due to the hydrogen bonds between the molecules.
For example, it allows long columns of water to travel in xylem tubes, it’s an ideal transport medium in plants.
Cohesion also causes surface tension… See other cards.

219
Q

Water : surface tension.
Explain this property and how it is important in a living organism.

A

Although it’s closely linked to cohesion, this is where the surface of water meets air, allowing the surface of water to act as a habitat for some animals such as insects.
It’s a force where its water molecules are pulled inwards at its surface.

220
Q

Latent heat

A

The heat energy required to change a substance from one state to another, breaking its bonds

221
Q

Metabolite

A

The substance involved in a metabolic reaction.

222
Q

compression

A

the ability for particles to be squashed or decrease their volume

223
Q

adhesion

A

tendency of molecules to be attracted to other molecules of a different type

224
Q

viscosity

A

the result of intermolecular forces between various molecules

225
Q

more acidic means… (name a molecule)

A

more H+

  • think it’s like fiesty on it’s own, whilst OH- molecule is more soft so more alkali, or the minus for decreasing in acidity.
226
Q

more alkali means… (name the molecule)

A

more OH-
- aka hydroxide, hydroxyl is the name given to the functional groups attached to other components.

227
Q

ion?

A

charged particle; cation or anion

228
Q

use of sodium in humans

A

to co transport glucose and amino acids

229
Q

ion found in haemoglobin

A

iron

230
Q

what’s an iorganic ion? Where can they be found in an organism such as humans?

A

one that doesn’t contain carbon: there are inorganic ions in solution in the cytoplasm of cells and in the body fluids of organisms (such as the blood/ xylem for plants)

231
Q

Read…

A
  • watch a video, theres an 8 min clip on how the body regulates ion conc. too

Each ion has a specific role depending on its properties and its role also determine whether it is found in high or low concentrations (in certain areas).

232
Q

polar molecule

A

uneven distribution of charges causing some parts of the molecule to be slightly more positive or negative
(links to how ions dissolve in water as the water molecules will orientate themselves specifically depending on charges - might want to watch a video)
— When ions are completely surrounded by water they are said to be completely dissolved as water acts like a solvent.

233
Q

where is the inorganic ion of phosphate found in body and its role? (2)

A

DNA and ATP (here energy is stored between groups/ phosphates) and RNA, even cell membrane.
Phosphorylation.

234
Q

what’s the role of the inorganic ion of iron in the body?

A

Used to bind to O² in RBCs in the protein haemoglobin (haem is the functional group, read up on this):
each polypeptide chain has an iron at its centre.

235
Q

what’s the role of the inorganic ion of sodium in the body?

A

co transport (glucose and amino acids) and links to the nervous system, linked to communication between neurons (Y13 other topics)

236
Q

role of inorganic ion hydrogen in the body?

A

Maintain and regulates pH (such as maintains low stomach pH), and help with aerobic respiration.
The more H+ ions, the more acidic.

  • check if correct info: needed for ATP synthesis and can denature.
237
Q

Explain the action for DNA polymerase, why it goes in the direction it does.

A
  • 5’ (phosphate group) and 3’ (OH group of pentose sugar) ends of polynucleotide strands of DNA have different shapes.
  • active site of DNA polymerase only complementary to 3’ end of the NEW DNA strand being formed.
  • DNA joins adjacent nucleotides together forming phosphodiestee bonds.
  • DNA nucleotides added by DNA polymerase to extend 3’ (OH group) end of the strand; new strand hence made in the 5’ to 3’ ens direction.
  • 2 antiparallel TEMPLATE starnds so 2 DNA polymerase enzymes working in opposite directions at the same time.

— Meaning, on the template strand it appears as though the enzyme is working from their 3’ end to 5’ and but of course the enzyme doesn’t do work on the template one.

238
Q

6 sentences. What’s the evidence for semi conservative replication?
- How to aet up the experiment

A
  1. 2 samples of bacteria grown in 2 nutrient broths; one containing light nitrogen and the other heavy.
    Asexual reproduction, taking up nitrogen from broth to make nucleotides for new DNA. Nitrogen gradually becoming part of bacterial DNA.
  2. Sample of DNA taken from each, into centrifuge. DNA from heavy nitrogen bacteria settled lower down centrifuge tube than DNA from light bacteria- as its heavier.
  3. Bacteria grown in heavy nitrogen broth taken into new broth with only light nitrogen. Left for one round of DNA replication, then sample of DNA taken again and spun.

NOW 4. If semi conservative, new bacterial DNA molecules would contain one stand of old DNA. containing the heavy nitrogen, and one strand of new DNA containing light nitrogen. Would settle between were 100% light and 100% heavy strands would.
5. If conservative, original heavy DNA, which would still be together, settle at bottom & new light DNA settle at top.

  1. Results shows DNA settled in the middle; DNA molecules contained a mixture of heavy and light nitrogen.

Bacterial DNA had replicated semi-conservatively IN light nitrogen they were placed in secondly.

239
Q

where is MRNA formed

A

nucleus

240
Q

sugar found in nucleotides

A

pentose

241
Q

phenotype

A

Physical and functional characteristics of an organism, partly determined by its genes

242
Q

protein production is controlled by
…

A

DNA and RNA

243
Q

Anticodon

A

determines which amino acid transfer RNA binds to
- used to describe 3 tRNA molecules

244
Q

The base that replaces thymine (found in DNA) in any general RNA

A

uracil

245
Q

first stage of protein synthesis

A

translation in nucleus

246
Q

gene

A

A sectioned base sequence of DNA that codes forthe amino acid sequence of a polypeptide.

  • Anda functional RNA (including ribosomal RNA and tRNAs).
247
Q

where can RNA be found?

A

both the nucleus (alike DNA) AND the cytoplasm

248
Q

Why may viruses have an uneven ratio of complementary base pairings

A

unlike DNA, it’s not double stranded so cannot form complementary base pairs.
Single stranded genetic material

249
Q

Describe how the structure of DNA enables it to replicate semi-conservatively

A
  • 2 antiparallelstrands that can be separated to make template strands
  • they are joined by weak hydrogen bonds between complementary base pairs (broken by DNA helicase)
  • free floating DNA nucleotides can be bonded (can mention bonds) to their complementary bases on the template strand to generate 2 identical DNA molecules.
250
Q

a gene occupies…

A

a fixed position, called locus (loci) on a particular DNA molecules

A Level Biology AQA (6 decks)

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