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A Level Biology OCR > Chapter 3- DNA (Bio Mol cont.) > Flashcards

Chapter 3- DNA (Bio Mol cont.) Flashcards

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1
Q

What is a special property of Nucleic Acids?

A
  • Ability to be copied
  • Ability to carry instructions
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2
Q

What are the components of a nucleotide?

A
  1. Nitrogen containing base
  2. Pentose Sugar (5 carbon atoms)
  3. Phosphate Group

e.g. DNA, RNA = polymers

individual nucleotides = monomer that build up polynucleotides

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3
Q

What are the 5 nitrogenous bases?

A
  • A = adenine
  • T = thymine
  • U = uracil
  • C = cytosine
  • G = guanine
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4
Q

What is a Purine and Pyrimidine? Which bases go under which?

A

Purines (LARGER):

  • double rings of carbon an nitrogen atoms
  • Adenine
  • Guanine

Pyrimidines (smaller):

  • single ring of carbon and nitrogen atoms
  • Thymine
  • Uracil
  • Cytosine

In complementary base pairing- 1 purine always opposite 1 pyrimidine.

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5
Q

What is the difference between RNA and DNA?

A

DNA:

  • double stranded
  • thymine as base with adenine
  • different sugar - deoxyribose
  • double helix

RNA:

  • single stranded
  • uracil as base with adenine
  • different sugar - ribose
  • single helix
  • can leave nucleus!
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6
Q

Explain how nucleotides are added to a chain and what kind of bond is formed:

A
  • A phosphodiester bond occurs between nucleotides (monomers that build nucleic acid)
  • forming the sugar-phosphate backbone.
  • Phosphodiester bond formation occurs by the removal of a water molecule when 2 hydroxyl groups from 2 different sugars bond with a phosphate group
  • = a condensation reaction

Both DNA and RNA undergo condensation reaction to form phosphodiester bonds to form polymers.

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7
Q

What is the role of mRNA (brief):

A

mRNA transfers genetic info from nucleus to ribosome

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8
Q

What is the role of rRNA (brief)?

A

rRNA makes up ribosomes where translation occurs.

rNA directs catalytic steps of protein synthesis

sometimes called a ribozyme

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9
Q

What is the role of tRNA (brief)?

A

tRNA molecules bring AAs to ribosome.

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10
Q

Explain the formation of sugar-phosphate backbone:

A
  1. 2 stands side-by-side running in opposite directions (anti-parallel)
  2. 2 strands are held together by weak H-bonds (twisted into coil = double helix)
    1. Look at image below for last steps:
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11
Q

Why does DNA replication occur?

A
  • When cells divide, daughter cell must receive exact copy of genetic material from parent cell
  • In order for this to occur, DNA in parent cell must be replicated.
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12
Q

Describe the stages of Semi-conservative DNA replication:

A
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13
Q

What are Okazaki Fragments? Draw and describe the process of formation:

A
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14
Q

What is translation in basic terms (not all the the stages, just what it does)

A

Translation is process where mRNA code is ‘read’ + translated into protein

Occurs in ribosomes

Process involves another type of RNA molecule = tRNA (transfer RNA)

After mRNA is made, leaves nucleus through nuclear pore.

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15
Q

What occurs in Transcription?

A
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16
Q

Describe all the stages of translation (protein synthesis):

A
17
Q

Why do we need energy (ATP)?

A

Metabolism

Movement

Active Transport

Maintenance, Repair + division of cells

Maintenance of body temperature

Nerve Impulse Conduction

18
Q

Where does energy come from and how do we get it?

A

Light energy is converted by plants into chemical energy during photosynthesis

The chemical energy from photosynthesis (organic molecules) is converted into ATP during respiration

ATP is used by cells to perform useful work.

19
Q

What is ATP?

A
20
Q

How does ATP release energy?

A
  1. 3 phosphate groups are joined together by 2 high energy bonds
  2. ATP can be hydrolysed to break a bond which releases a large amount of energy
  3. Hydrolysis of ATP to ADP (diphosphate) is catalysed by enzyme ATPase.
  4. ATP + H2O —-→ ADP + Pi ( + energy = 30 kJmol-1
21
Q

Describe Phosphorylation:

A

(regeneration of ATP from ADP)

22
Q

What are some properties of ATP that are useful for survival?

A

Properties of ATP:

  • Instant Source of energy in the cell
  • Releases Energy is small increments as needed
  • It is mobile + transports chemical energy to where it is needed in cell
  • Universal energy carrier + can be used in many different chemical reactions.
23
Q

What is a problem with ATP as a source of energy?

A
  • ATP is highly unstable- so it cannot be stored
  • It will want to break down all the time
  • Instability of bonds means ATP not good for Long Term storage of energy
  • Fats and Carbohydrates better source of Long Term energy storage.
  • Cells do not store large quantities of ATP, so…
    • production of ATP needs to be constantly occurring in all living cells.

A Level Biology OCR (23 decks)

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