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Biology > Breadth > Flashcards

Breadth Flashcards

1
Q

2016
A DNA molecule contains 2 polynucleotide chains
Describe how these two chains are held together

A

There are phosphodiester bonds in the phosphate backbone. Hydrogen bonding occurs between bases. Nitrogenous bases are split into two categories- purine and pyrimidine which bond to each other e.g. AT and CG. There are 2 hydrogen bonds between AT and 3 between CG.

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2
Q

Explain one advantage and disadvantage of lack of nuclei to mammalian enthrocytes

A

An advantage is that there is more space for Hb

A disadvantage is that the lack of mitochondria means they respire anaerobically

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3
Q

Explain why enthrocytes do not make use of the oxygen that they are transporting

A

Oxygen is bound to Hb whilst being transported and the lack of mitochondria means they respire anaerobically

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4
Q

A nucleotide is a molecule that consists of what (3)

A
  • A 5-carbon sugar
  • A phosphate group
  • A nitrogenous base
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5
Q

What are the phosphate and nitrogenous base joined to pentose (5-carbon) sugar by?

A

The phosphate group is joined to C5 and the nitrogenous base is joined to C1

These are joined together by a covalent phosphodiester bond which are formed by a condensation reaction and broken down by hydrolysis

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6
Q

Name the four nitrogenous bases

A

Adenine

Thymine

Guanine

Cytosine

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7
Q

Adenine and guanine are both example of what?

A

PURINES

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8
Q

Thymine and Cytosine are both examples of what?

A

Pyrimidines

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9
Q

What type of bond and how many bonds are there between AT?

A

2 hydrogen bonds

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10
Q

What type of bond and how many bonds are there between CG?

A

3 hydrogen bonds

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11
Q

What are two differences between an RNA molecule and a DNA molecule?

A
  • RNA is usually stranded

* In RNA, adenine binds to uracil instead of thymine

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12
Q

Describe the stages of DNA replication (4)

A
  • The first stage of DNA replication is UNWINDING of DNA which is catalysed by enzyme GYRASE
  • Next, the 2 strands are UNZIPPED thanks to enzyme HELICASE which breaks the hydrogen bonds holding the bases together
  • New strands of DNA are SYNTHESISED by DNA polymerase
  • In this stage, free nucleotides are joined to their complementary bases and each other by forming HYDROGEN bonds and PHOSPHODIESTER bonds.
  • They’re added in the 5’ to 3’ directional
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13
Q

What enzyme catalysed the unwinding of DNA (1 mark)

A

ENZYME GYRASE

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14
Q

What enzyme catalyses the unzipping of DNA (1 mark)

A

DNA HELICASE

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15
Q

What enzyme synthesised new strands of DNA during replication (1)

A

DNA POLYMERASE

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16
Q

What is the number of DNA nucleotide bases that code for an amino acid and why (3)

A

It’s 3 because the information in genes is read in 3’s

Furthermore, TAC, GAT, and TTG are referred to as a codon

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17
Q

There is a maximum of 64 different base combinations in DNA that could code for each amino acid.
How are these combinations calculated and why (2)

A

The combination are calculated by 4 to the power of 3 because codons are 3 letter genetic words e.g. TTG and the language of genes use for letters (nitrogenous bases)

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18
Q

Why is DNA replication considered to be semi-conservative (1)

A

Because there is one strand from original DNA and one newly formed strand

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19
Q

What nucleotide bases are both common to DNA and RNA?

A

A C Got

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20
Q

How is a nucleotide bass sequence in a gene used to synthesise a polypeptide (6)

A
  • In transcription, DNA is transcribed to mRNA
  • whereby free RNA nucleotides line up by complimentary base-pairing
  • to one DNA strand e.g. AT, CG, and AU
  • this reaction is catalysed by RNA polymerase
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21
Q

What does a gene code for (1)

A

A gene is a section of DNA that codes for the production of a polypeptide

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22
Q

What is the name of the molecule that copies a gene and carries the information to a ribosome (1)

A

RNA

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23
Q

When a colour is added to a suspension of yeast cells why won’t some cells stain at low temperature (1)

A

Because at low temperature, the membrane structure is still in tact/ less fluid and so the cell membrane is impermeable or isn’t respiring so no ATP can take up the stain

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24
Q

Why do stain cells lose their colour at exceedingly high temperatures (1)

A

At temperatures exceeding optimum level, the membrane structure becomes damaged and so the stain can diffuse out of the cell

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25
Q

Name the effects of high temperature on membrane structure (4)

A
  • Membrane structure is damaged
  • Phospholipid bilayer is more fluid
  • Proteins in the membrane become denatured
  • Membrane becomes more permeable
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26
Q

What evidence shows yeast cells take up pigment via active transport (2)

A
  • At low temperature, all stain remains in cell (state figures)
  • Whereas at high temperatures, the stain is not held in the cell because the high temperature denatures the enzymes in the cell meaning no ATP can be generated for active transport
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27
Q

Describe the role glycoproteins play in the membrane structure (4)

A

1) Glycoproteins in the membrane act as antigens
2) and are involved in the recognition of cells being foreign or self
3) and also enables cell signalling to occur whereby communication between cells is maintained
4) It further acts as a receptor/binding site for hormones

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28
Q

What is the function of cholesterol in the membrane structure (1)

A

Cholesterol stabilises the membrane’s stability by giving mechanical support

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29
Q

What function do protein channels have in the membrane structure (1)

A

Protein channels allow communication across the membrane

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30
Q

Describe cell signalling (2)

A

Cell signalling refers to communication between cells whereby cell recognition of foreign or self matter occurs and cells work together to coordinate a response

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31
Q

Explain how glycoproteins act as receptors (3)

A

The tertiary structure of the receptor is specific and is only complementary to the shape of the trigger molecule and so the trigger molecule binds to the receptor

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32
Q

Describe water potential (3)

A

Water potential refers to water moving out of a cell via osmosis because the cell has a higher water potential than its surrounding solution and so water moves down the water potential gradient from high to low water potential

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33
Q

Describe the effect high temperature has on a yeast cell’s membrane (4)

A

Phospholipids have more kinetic energy and so the phospholipids move around more which this creates gaps in the membrane as so the bilayer becomes more fluid and proteins denature at temperatures exceeding optimum

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34
Q

Describe the structure of a phospholipid bilayer (4)

A

Phospholipid bilayer has a hydrophilic region facing outwards and a hydrophobic region facing onwards

Glycoproteins and glycolipids stick out of the bilayer and cholesterol is between phospholipids

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35
Q

State two functions of cell membranes within cells (2)

A

1) They separate the contents of organelles from the cytoplasm
2) They control what substances enter or leave an organelle
3) They provide a surface for attachment of ribosomes

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36
Q

Outline how vesicles are moved from one organelle to another (2)

A

1) Cytoskeleton provide pathways for movement and the vesicles move along microtubules

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37
Q

Suggest how proteins ensure that a vesicles is transported to the correct target organelle (2)

A

A receptor is only found on a target organelle and a protein has a specific shape and that only the correct receptor can fit into

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38
Q

Describe how extracellular enzymes are secreted from the cells (2)

A

Exocytosis enables vesicles to fuse with the plasma membrane which results in the releasing of enzyme to the exterior

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39
Q

Describe the term active transport (2)

A

The movement of substances from low to high concentration using ATP and occurs through transport proteins

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40
Q

Describe the linear / and curve ( or plateau — part of the graph means with regard to enzyme activity (5)

A

Linear part /
• There are more successful collisions with amylase active site at increasing substate concentration

• More enzyme-substrate complexes form at increasing starch concentration

Curve ( or plateau — means
• Most active sites are occupied by substrates

  • and so enzymes are working near maximum capacity
  • thus meaning a further increase in starch concentration has no effect on the rate of the reaction
  • and so enzyme concentration becomes a limiting factor
41
Q

Why does pH concentration need to be kept constant for enzyme activity to occur (3)

A

1) so the charges in the active site do not change
2) resulting in ionic bonds being unaffected
3) so the tertiary structure of the active site is unaltered
4) resulting in the enzyme not denaturing
5) and the substrate can still be complementary to the active site of the enzyme

42
Q

Explain the term biological catalyst (2)

A

Enzymes are proteins used in metabolism which alter the rate of chemical reactions by lowering the activation energy required to start them

43
Q

Explain the effect of increasing the concentration of substrate on the rate of a reaction without an inhibitor (3)

A
  • There are more successful collisions between substrate and active site
  • Thus resulting in more ESCs forming
  • When the concentration is low, not all active sites will be occupied but at high concentration all active sites will be occupied
  • This means that enzymes cannot work any faster
44
Q

Explain the effect of increasing the concentration of substrate on the rate of a reaction with an inhibitor (2)

A
  • The inhibitor can bind to an active site and occupied it temporarily
  • which results in fewer active sites available for substrate
45
Q

Describe how an enzyme breaks down a substrate (5)

A
  • The substrate binds to the active site of the enzyme which is nearly complementary to the substrate shape
  • This is known as the induced fit hypothesis which refers to the shape of the active site as not being exactly complementary but in fact accommodates to and changes shape in the presence of a specific substrate to become complementary
  • This leads to the formation of temporary ESCs whereby there’ll soon be a destabilisation of bonds in the substrate which result in the formation of an enzyme-product complex where products leave the active site
46
Q

Which lipid compounds contain only the elements of carbon, hydrogen, and oxygen (2)

A

Triglycerides

Cholesterol

47
Q

Which lipid compounds are insoluble in water (3)

A

Triglycerides

Phospholipids

Cholesterol

48
Q

Which lipid compounds contain glycerol (2)

A

Triglycerides

Phospholipids

49
Q

Which lipid compounds contain water bonds (2)

A

Triglycerides

Phospholipids

50
Q

Which lipid compounds are important in membrane structure (2)

A

Phospholipids

Cholesterol

51
Q

Which lipid compounds contain fatty acids (2)

A

Triglycerides

Phospholipids

52
Q

Describe how to do the emulsion test for lipids and how a positive result would be identified (2)

A

Add ethanol and water and wait for the solution to turn cloudy / milky in colour

53
Q

State two things that describe the primary level of protein structure (2)

A

B) Peptide bonds

D) The sequence of amino acids

54
Q

State two things that are found in secondary level of protein structure that are not present in the primary structure (2)

A

A) Hydrogen bonds

E) The initial folding of the polypeptide chain

55
Q

State two things that are found in the tertiary level of protein structure that are not present in the secondary structure (2)

A

F) The overall 3D shape

G) Ionic bonds

56
Q

State one thing that is only found in the quaternary level of protein structure (1)

A

C) The alpha and beta subunits

57
Q

Describe the formation of a hydrogen bond between two molecules of water and explain why water can form these bonds (3)

A

1) Between O and H of adjacent molecules
2) The Hydrogen molecule is slightly positive whereas the Oxygen molecule is slightly negative
3) which results in the water molecule being polar

58
Q

Why is the ability of water to act as a solvent important for the survival of organisms (3)

A

Metabolic reactions can occur in water

Water also has the ability to dilute toxic substances

59
Q

State the name given to the sequence of amino acids in a protein molecule (1)

A

Primary structure

60
Q

State one property of collagen that makes it a useful component of blood vessel walls (1)

A

It is insoluble

61
Q

Describe the structure of the collagen molecule (6)

A

There are peptide bonds between amino acids whereby every 3rd amino acid is the same and they spiral around each other

62
Q

State one function of haemoglobin (1)

A

To transport blood carrying oxygen

63
Q

Name the polymer formed from a chain of amino acids (1)

A

A polypeptide

64
Q

Name the bond that is formed when 2 amino acids are joined together and describe the formation of this bond (3)

A

The peptide bond is formed between the amine group of one amino acid and carboxyl group of another

A Hydrogen molecule from the amine group combined with OH from the carboxyl group and this occurs during a condensation reaction

65
Q

Give 3 examples of where hydrogen bonds are found in biological molecules (3)

A

1) between chains of cellulose
2) Between bases in DNA
3) between mRNA and tRNA

66
Q

State two roles of cholesterol in living organisms (2)

A

Regulates fluidity of phospholipid bilayer / supports structure of membrane

Is involved in the making of bile (salts)

67
Q

Identify one way in which the molecular structure of cholesterol and similar to the structure of a carbohydrate (1)

A

Contains OH groups

68
Q

Explain why glycogen is a good storage molecule (3)

A

1) Insoluble
2) Does not affect water potential
3) It is compact and so stored a lot of energy

69
Q

What molecule is being tested when the reagent if Benedict’s solution is being used (1)

A

To test to see if a reducing sugar is present

70
Q

What molecule is being tested when the reagent of biuret 1 and 2 are used (1)

A

To test to see if a protein is present

71
Q

What molecule is being tested when the reagent of iodine solution is used (1)

A

To test to see if starch is absent

72
Q

Describe the structure of a tryglyceride molecule (3)

A

There is an Ester bond between one glycerol and 3 fatty acids

73
Q

State 3 roles of lipid in living organisms (3)

A

1) They provide thermal insulation
2) Act as an energy store
3) The phospholipid bilayer in membranes control what substance enter and exit the membrane

74
Q

What is the function of the smooth endoplasmic recticulum (1)

A

It’s involved the transportation of fats and processes toxins

75
Q

What is the function of lysosomes (1)

A

Contain hydrolysing enzymes

76
Q

What is the function of a ribosome (1)

A

It’s involved in protein synthesis

77
Q

Name 2 features of plant cells that are not featured of animal cells (2)

A

Cell wall

Chloroplasts

78
Q

Name one structure present in animal cells that is not present in plant cells (1)

A

Lysosomes

79
Q

Describe the roles of the cytoskeleton (3)

A

It provides support and stability to the cell

It enables the movement of flagella

And are involved in the movement of chromosomes

80
Q

Outline how the organelles in pancreatic cells work together to produce and release protein molecules from the cells (5)

A

The nucleus is the site of transcription and the ribosomes are a site of protein synthesis

The vesicles then transport proteins and the Golgi apparatus packages them so that the vesicles can fuse to the plasma membrane

81
Q

What is the function of mitochondria (1)

A

Produces ATP for respiration

82
Q

What is the function of the SER (1)

A

Involved in the transport of lipids

83
Q

What is the function of the Golgi apparatus (2)

A

It modifies and packages proteins into vesicles

84
Q

Name the 3 groups present in the general structure of an amino acid and the molecules within the group (6)

A

AMINE GROUP - 2 hydrogen molecules bonded to a nitrogen molecule via peptide bonds

R GROUP - 1 Carbon molecule bonded to a hydrogen molecule

CARBOXYL GROUP - 1 Carbon molecule bonded to 2 oxygen molecules and 1 Hydrogen molecule

85
Q

State a feature for an efficient gaseous exchange surface (1)

A

The layers are thin for a short diffusion distance

86
Q

What happens to the formation of phosphodiester bonds in DNA replication

A

The formation of phosphodiester bonds will occur in the same direction on each strand during DNA replication

87
Q

Name a factor that applies to both transpiration and evaporation

A

It occurs at the surface of leaves

88
Q

Explain why diastole follows systole in the mammalian heart (1)

A

Cardiac muscle takes a short time to repolarise after being stimulated

89
Q

Name a similarity in the way ATP is made in respiration and photosynthesis (1)

A

They both involve proton gradients

90
Q

What type of diabetes is Type 2 most similar to and why (2)

A

GESTATIONAL because beta cells are still working and insulin is still being produced

91
Q

Name 2 tissues where glucose is removed from the blood in response to insulin (1)

A

Liver tissue and skeletal muscle

92
Q

Explain why glucose is required for the contraction of skeletal muscles (3)

A

Glucose is used in respiration the production of ATP and skeletal muscle contraction is a process in which ATP is needed for myosin to detach from actin

93
Q

Describe two adaptations of thylakoids stacks (2)

A

The membranes within the stacks containing the pigments have a large surface area for absorbing light

There is a large surface area for the electron transport chain

94
Q

Name the 2 types of epithelial tissue found in the lungs and airway (2)

A

Ciliates and squamous

95
Q

Adaptions of alveoli (5)

A

1 Cell Thick

Contain squamous cells which provide a short diffusion pathway

Large number of alveoli which provide large surface area

Alveolus walls contain elastic fibres to help them recoil during ventilation

96
Q

Outline transcription (4)

A

1) DNA Helicase unwinds the double
strand.

2) RNA nucleotides complimentary
base pair with the DNA template
strand whereby Thymine bases are replaced with
uracil in mRNA

3) RNA polymerase forms the sugar
phosphate backbone/ phosphodiester bonds.

4) and mRNA produced.

97
Q

How is the genetic code interpreted by the cell in a way that determines the order of amino acids? (2 marks)

A

In a series of codons/triplets –consisting of three nucleotides whereby each one codes for an amino acid

98
Q

What is a stop codon and how does it work? (2 mark)

A

Nucleotide triplet/3 bases at the end of the mRNA tells the ribosome to end
translation.

99
Q

Why does translation occur in the cytoplasm and not the nucleus? (1 mark)

A

The ribosomes/enzymes involved are not required/confined not in nucleus.

Biology (8 decks)

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