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Higher Human Biology > Division & Differentiation In Human Cells > Flashcards

Division & Differentiation In Human Cells Flashcards

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1
Q

What happens rather than each cell carrying out every function?

A

A DIVISION OF LABOUR in multicellular organism and cells become differentiated

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2
Q

What is differentiation?

A

Differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell

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3
Q

All the genes at the embryonic stage are either ______ or have the _____ to be ______

A

Switched on

Potential

Switched on

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4
Q

How do specialised cells arise?

A

From the differentiation of unspecialised cells during embryonic development

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5
Q

Once a cell becomes differentiated…

A

It only expresses the genes that code for specific proteins

Eg nerve cell - genes for neurotransmitters switched on/ genes for mucus production switched off

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6
Q

What are somatic cells?

A

Body cells

Any differentiated cell (except reproductive cells)

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7
Q

What does DNA do during mitosis and what does it produce?

A

DNA replicated and the cells divide during mitosis to produce two identical daughter cells with the full chromosome complement

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8
Q

Where are germline cells found?

A

In sex organs

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9
Q

What do germline cells do?

A

Lead to the formation of gametes

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10
Q

What process do germline cells go through to produce haploid gametes?

A

Meiosis

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11
Q

Describe the process of meiosis

A
  • 1st division - separating homologous pairs
  • 2nd division - separating chromatids

Genetic material is divided between 4 nuclei and each receives a single set of 23 chromosomes

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12
Q

What are stem cells?

A

Stem cells are unspecialised (undifferentiated) cells that can:

  • reproduce (self renew) themselves by repeated mitosis and cell division while remaining undifferentiated
  • then differentiate into a diverse range of specialists cells when required to do so
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13
Q

What is a blastocyst?

A

An early embryo consisting of a ball of embryonic stem cells

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14
Q

All of the genes in an embryonic stem cell are _______

A

Switched on

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15
Q

How many cell types are there in the body?

A

> 200

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16
Q

How many cell types can embryonic stem cells differentiate into?

A

They are pluripotent which means they can turn into any cell type

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17
Q

Where are tissue stem cells found? Include examples

A

Tissue stem cells are found in small numbers in the tissues and organs of adults and children including the brain, bone marrow, skeletal muscle, and skin

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18
Q

What are tissue stem cells involved in?

A

The growth, repair, and renewal of the cells found in that tissue

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19
Q

How many types of cells can tissue stem cells differentiate into?

A

A much more limited range of specialised cell types.

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20
Q

Why can tissue stem cells only differentiate into a limited range of specialised cell types?

A

Because many of their genes are already switched off

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21
Q

Cell types that tissue stem cells can differentiate into and their origin tissue

A
  • Epithelial - cheek cells
  • Connective - blood, bone, cartilage
  • Muscle - Skeletal, cardiac or smooth
  • Nerve - sensory or motor nerves
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22
Q

What is a model organism?

A

One that is suitable for laboratory research because it’s biological characteristic are similar to those of a group of related (but often unavailable) organisms eg mice used for research into human conditions

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23
Q

Stem cells can be used in research as model cells to investigate:

A
  • The means by which certain diseases and disorders develop

* the responses of cells to new pharmaceutical drugs

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24
Q

Therapeutic uses of stem cells?

A
  • In the treatment of diseases eg leukaemia (bone marrow transplant) and heart disease
  • In medicine, including skin grafts for burns and stem cells grafts for cornea repair
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25
Q

What does the regulation of stem cells ensure?

A

This ensures that the quality of the stem cells used and the safety of the procedures carried out are of the highest order and that abuses of the system are prevented

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26
Q

What is a cancer?

A

An uncontrolled growth of cells

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27
Q

Cancerous cells do not respond to ______ ______ that normally control cell division

A

Regulatory signals

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28
Q

Cancer cells ______ __________ to produce a mass of abnormal cells called a _____

A

Divide uncontrollably

Tumour

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29
Q

What is a tumour?

A

A mass of abnormal cells

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30
Q

When is a tumour described as benign?

A

If it remains as a discrete growth of abnormal cells in one place, within an otherwise normal tissue

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31
Q

When is a tumour said to be malignant?

A

If it invades nearby tissues.

Some of its cells can lose the surface molecules that keep them attached to the original cell group.

These can enter the circulatory system and spread through the body.

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32
Q

Where do most cancers originate from?

A

From a cell that has undergone a succession of mutations to the genes involved in the control of cell division

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33
Q

How is the risk of mutation increased?

A

By exposure to agents that cause genetic damage such as smoking, pollution and excessive exposure to of skin to ultraviolet radiation

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34
Q

Why is cancer particularly common in skin, lung and bowel tissue?

A

As theses cells have a high frequency of division so the mutation rate is higher than normal

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35
Q

What tissues are more likely to have cancerous mutations?

A

Skin

Lung

Bowel

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36
Q

What does a molecule of DNA consist of?

A

Two strands of repeating units called nucleotides

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37
Q

What is a nucleotide made up of?

A
  • a deoxyribose sugar
  • a phosphate group
  • a base
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38
Q

What type of sugar is on a nucleotide?

A

Deoxyribose sugar

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39
Q

What type of bond forms between the phosphate group of one nucleotide and the carbon (3) of the deoxyribose sugar on another nucleotide forming a sugar phosphate backbone?

A

Strong peptide bond/ strong chemical bond

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40
Q

Name the nucleotide bases

A

Adenine

Guanine

Cytosine

Thymine

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41
Q

What nucleotide bases pair together?

A

Adenine bonds with Thymine

Cytosine bonds with Guanine

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42
Q

How are the two strands of nucleotides joined together?

A

Weak hydrogen bonds

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43
Q

Why is DNA described as being anti-parallel?

A

Because the 2 sugar phosphate backbones rum in opposite directions

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44
Q

Where is the 5’ end of a DNA molecule?

A

On a phosphate group

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45
Q

Where is the 3’ end of a DNA molecule?

A

On a deoxyribose sugar

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46
Q

Which end do DNA nucleotides add on to?

A

The 3’ end

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47
Q

Why is DNA a unique molecule?

A

Because it is able to direct its own replication and ensures an exact copy of genetic information is passed from cell to cell during growth and from generation to generation during reproduction

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48
Q

What does semi-conservative mean?

A

This means that each raw strand of DNA is composed of one original strand and one new strand

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49
Q

When does DNA replication begin?

A

When a starting point on DNA is recognised

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50
Q

Describe the formation of the leading DNA strand

A

1) The enzyme DNA Helicase unwinds - separates the two strands by breaking the weak hydrogen bond between base pairs (‘unzips’)
2) These template strands became stabilised and expresses the bases at a Y-shaped replication ark
3) A short sequence of nucleotides known as a primer bond at the ‘3’ end of the template flow strand
4) Once nucleotides have aligned with complementary base pairs, replication of leading strand begins. The enzyme DNA polymerase adds nucleotides to the ‘3’ end in one direction.

The leading strand is synthesised as a single strand (continuously) from the point of origin towards the opening replication ark

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51
Q

Describe the formation of the lagging DNA strand

A

DNA polymerase is only able to add nucleotides to the ‘3’ end of a growing strand.

The DNA parental template strand that has the 5’ end has to be replicated in fragments, each starting at the 3’ end of a primer

Each fragment must be primed to enable the DNA polymerase to bind individual nucleotides together

Once replication of a fragment is complete, its primer is replaced by DNA.

Finally, the enzyme ligase (which acts like a glue) joins the fragment together.

The strand formed is called the lagging strand and the formation is described as discontinuous.

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52
Q

Describe DNA replication

A

1 - The parental double helix unwinds forming replication forks

2 - The DNA molecule becomes stabilised as two template strands

3 - DNA polymerase promotes formation of the single leading strand on a 5’ to 3’ direction (DNA can only grow from the 3’ end)

4 - The DNA polymerase bonds a nucleotide to a primer

5 - DNA polymerase promotes the formation of a fragment of the lagging strand of replicating DNA

6 - Ligase joins fragments together on the lagging strand of replicating DNA

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53
Q

For DNA replication to occur, what must the nucleus contain?

A
  • DNA ( to act as a template)
  • Primers
  • Free DNA nucleotides (A,C,G,T)
  • Enzymes (DNA polymerase and ligase)
  • ATP
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54
Q

What is a Polymerase Chain Reaction (PCR)?

A

Procedure used to amplify DNA using primers (short strands of DNA complementary to specific target sequences at the two ends of the region of DNA to be amplified

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55
Q

What can PCR be used for?

A

To help solve crimes, settle paternity suits and diagnose genetic disorders

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56
Q

Describe the stages of PCR

A
  • Solution containing DNA template, primers, heat tolerant polymerase, and free nucleotides added to test tube
  • DNA is heated (92-98 °C) to separate the strands - DENATURING
  • Cooling (50-65 °C) allows primers to bind to target sequences - ANNEALING
  • Heated between (70-80 °C) to allow heat tolerant DNA polymerase to add nucleotides to primers and replicate regions of DNA - EXTENDING
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57
Q

What does PCR allow for?

A

Allows DNA to be screened for the presence/ absence of a specific sequence characteristic to a genetic disease.

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58
Q

Medical applications of PCR?

A
  • Eliminate the risk of disease onset by identifying mutations in the persons genome
  • Confirm a diagnosis of a suspected genetic disorder
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59
Q

Describe how PCR is used to test for a mutant allele

A

Testing for the mutant allele can be done using blood cells.

DNA is amplified and probes are used to test for the presence of the mutant allele.

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60
Q

What can be used to confirm genetic relationships?

A

PCR and gel electrophoresis

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61
Q

Why must every band in a DNA profile (genetic fingerprint) match one of the mother or father?

A

As 50% of our DNA is inherited from each parent

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62
Q

Forensic applications of PCR?

A

DNA samples from crime scenes of victims and suspects are amplified, separated by gel electrophoresis and compared.

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63
Q

What is a cell’s genotype determined by?

A

The sequence of the DNA bases in its genes

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64
Q

What is phenotype determined by?

A

The proteins produced as the result of gene expression

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65
Q

How many bases code for an amino acid?

A

Three (triplet)

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66
Q

How many of the genes in a cell are expressed?

A

Only a fraction

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67
Q

What determines a proteins structure, shape and ability to carry out its function?

A

The sequence of amino acids

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68
Q

How many strands does mRNA have?

A

One (single stranded)

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69
Q

What is on an mRNA nucleotide?

A
  • A ribose sugar
  • A phosphate group
  • A base
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70
Q

What are the mRNA bases?

A

Adenine

Guanine

Cytosine

Uracil

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71
Q

Sugar present in mRNA nucleotide?

A

Ribose

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72
Q

Sugar present in DNA nucleotide?

A

Deoxyribose

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73
Q

What is the function of mRNA?

A

Carries a copy of the DNA code from the nucleus to the ribosome

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74
Q

What is ribosomal DNA?

A

This RNA + proteins form the ribosome

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75
Q

What is transfer RNA?

A

3D shape

Folds due to complementary base pairing

Carries a specific amino acid to the ribosome

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76
Q

Definition of TRANSCRIPTION

A

Synthesis of mRNA from a section of DNA in the nucleus

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77
Q

What is the enzyme responsible for transcription?

A

RNA polymerase

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78
Q

Description of TRANSCRIPTION

A
  • RNA polymerase moves along the promoter, unwinding the DNA and breaking the hydrogen bonds between bases
  • Nucleotides are added
  • mRNA gets a nucleotide sequence complementary to one of the two DNA strands
  • The mRNA strand produces becomes separated from its DNA template and is called the primary transcript of mRNA
  • This mRNA carries a copy of the DNA code from the nucleus to the ribosome
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79
Q

What is a codon?

A

A triplet of based of mRNA which codes for a specific amino acid

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80
Q

Where does RNA polymerase add nucleotides to on a growing mRNA molecule?

A

Only the 3’ end

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81
Q

When does an mRNA molecule elongate until?

A

Till a terminator sequence of nucleotides is reached on the DNA strand

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82
Q

How long is the region of DNA transcribed to mRNA normally?

A

About 8000 nucleotides long

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83
Q

How many nucleotides are needed to code for an average sized polypeptide chain?

A

About 1200 nucleotides

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84
Q

What are introns?

A

Non-coding regions of DNA interspersed between the coding regions

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85
Q

What are exons?

A

Coding regions of DNA

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86
Q

Describe splicing

A

The introns are removed and the exons are spliced together to form a mature transcript with a continuous sequence of nucleotides

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87
Q

Definition of TRANSLATION

A

The synthesis of protein as a polypeptide chain at the ribosome

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88
Q

Where is tRNA found?

A

In the cytoplasm

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89
Q

Why does tRNA have a complex folded structure?

A

Due to hydrogen bonding between its bases

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90
Q

What does tRNA fold to form?

A

A triplet anticodon site, complementary to a codon

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91
Q

What does the triplet anticodon site correspond to?

A

A specific amino acid carried at the tRNA’s attachment site

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92
Q

How do anticodon bond to codons?

A

By complementary base pairing

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93
Q

Where does tRNA pick up its specific amino acid from?

A

The cytoplasm’s amino acid pool

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94
Q

Where does translation start and end?

A

Starts at a start codon and ends at a stop codon

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95
Q

Example of a start codon?

A

AUG
/
Methionine

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96
Q

Example of a stop codon?

A

UGA

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97
Q

Describe translation

A

1) Each tRNA picks up a specific amino acid molecule from the cytoplasm’s amino acid pool at its site of attachment and takes it to a ribosome.
2) Anticodons bond to codons by complementary base pairing ( hydrogen bonds form between anticodon and codon)
3) The amino acid is then added to the growing end of a polypeptide chain. Amino acids are held together by strong peptide bonds.
4) Each tRNA then leaves the ribosome as the polypeptide is formed (to pick up another amino acid)

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98
Q

What kind of bonds form between anticodon and codon?

A

Hydrogen bonds

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99
Q

The same primary transcript has the potential to produce _______ _______ _____ ________ depending on which exons are retained

A

Different mature mRNA transcripts

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100
Q

How can one gene code for several different proteins?

A

Alternative segments of RNA may be treated as exons and introns and produce several different mRNA molecules with a different sequence of bases coding for a different polypeptide

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101
Q

Describe how amino acids become proteins

A
  • Amino acids are linked by peptide bonds
  • Polypeptide chains fold to form a 3D shape of a protein, held together by hydrogen bonds and other interactions between individual amino acids
  • The sequence of amino acids determines the proteins final structure
  • Proteins have a variety of shapes which determine their function
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102
Q

What can influence phenotype?

A
  • The proteins hat are synthesised when the genes are expressed
  • Environmental factors eg diet linked to growth
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103
Q

Example of an environmental factor which influences phenotype?

A

Diet linked to growth

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104
Q

Describe enzymes and their function

A
  • Speed up chemical reactions

* Folded in such a way as to expose an active site ready to combine with a specific substrate

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105
Q

Describe structural proteins and their function

A

• One of the components that make up the cell membrane and plays a vital structural role in living cells

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106
Q

Describe hormones and their functions

A

• Chemical messengers transported in blood to target tissues to exert a regulatory effect on growth and metabolism

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107
Q

Describe antibodies and their function

A

• Y-shapes proteins produced by white blood cells to defend the body against foreign antigens

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108
Q

What are the building blocks of proteins?

A

Amino acids

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109
Q

Site of protein synthesis?

A

Ribosome

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110
Q

What is a mutation?

A

A random change in the structure or composition of an organism’s DNA that can result in the gene expressing a faulty protein or no protein at all

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111
Q

What’s the chromosomal abnormality for Down Syndrome?

A

An extra chromosome (21)

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112
Q

What can mutations vary from?

A

A tiny change in the DNA sequence of a gene to a large scale alteration in chromosome structure or number

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113
Q

Frequency of mutations?

A

In the absence of outside influences gene mutations arise spontaneously and at random but only occur rarely

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114
Q

What can mutation rate be artificially increased by?

A

Mutagenic agents

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115
Q

Examples of mutagenic agents?

A
  • certain chemicals (eg mustard gas)

- various types of radiation (eg gamma rays, x-rays, UV light)

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116
Q

What do single gene mutations involve?

A

The alteration of a DNA nucleotide sequence in the genes

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117
Q

Single gene mutations lead to ____ __ ____ _____ for one or more amino acids becoming _____ altered

A

One or more codons

Altered

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118
Q

What are the 3 different types of single gene mutations?

A

A single nucleotide is:

  • Substituted
  • Inserted
  • Deleted
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119
Q

How many types of single gene mutations are there?

A

3

SID

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120
Q

What is a substitution mutation?

A

In this type of mutation, one nucleotide is replaced by another

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121
Q

What can happen in a substitution mutation?

A

The change may be minor (one different amino acid) and the organism may be slightly affected or not at all, unless the different amino acid occurs at a crucial position in the protein then a major defect can arise

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122
Q

How many types of substitution mutations are there?

A

3

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123
Q

What are the 3 types of substitution mutations?

A
  • Nonsense mutations
  • Missense mutations
  • Splice-site mutations
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124
Q

What is a nonsense mutation?

A

As a result of a substitution, a codon that used to code for an amino acid is exchanged for one that acts as a stop codon.

Protein synthesis is stopped prematurely resulting in the formation of a shorter polypeptide chain that is unable to function

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125
Q

Example of a nonsense mutation?

A

DMD - Duchenne Muscular Dystrophy

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126
Q

What is a missense mutation?

A

Following a substitution, the altered codon codes for an amino acid but not the original amino acid.

This can produce non-functional protein OR may have little effect on the protein

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127
Q

Example of a missense mutation?

A

Sickle cell, phenylketonuria

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128
Q

What is splicing controlled by?

A

Specific nucleotide sequences + splice sites on those parts of introns that are next to exons

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129
Q

What is a splice site mutation?

A

If a substitution mutation occurs at one of these splice sites, the codon for an intron-exon splice may be affected

Some introns are retained and/o some exons are not included in the mature transcript, producing an abnormally functioning protein

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130
Q

Example of a splice site mutation?

A

Beta (b) thalassemia

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131
Q

What do nucleotide insertions and deletions both result in?

A

Frame-shift mutations

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132
Q

What is a nucleotide insertion mutation?

A

Extra nucleotide is inserted into sequence of bases

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133
Q

What is a nucleotide deletion mutation?

A

A nucleotide is deleted from sequence of bases

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134
Q

Why do nucleotide insertions and deletions lead to a major change?

A

As it causes all of the codons and all of the amino acids after the mutation to be changed

This leads to a very different and generally non-functional protein product

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135
Q

Example of a nucleotide insertion mutation?

A

Tay-Sachs syndrome

136
Q

Example of a nucleotide deletion mutation?

A

Cystic Fibrosis

137
Q

What makes Chromosome Structure Mutations lethal?

A

The substantial changes in chromosome structure (eg loss of several functional genes)

138
Q

How can the structure of a chromosome be altered?

A

As a result of a breakage of one or more chromosomes

139
Q

What are the 4 types of chromosome structure mutations?

A
  • Deletion
  • Inversion
  • Duplication
  • Translocation
140
Q

What happens in a chromosome deletion mutation? What does it result in?

A

A deletion occurs when a chromosome breaks in two places and the segment in between becomes detached.

The two end then join up, giving a shorter chromosome which lacks certain genes.

141
Q

Example of a chromosome deletion mutation?

A

Cri du chat syndrome - deletion of a section of chromosome 5

142
Q

What is a chromosome inversion mutation?

A

This mutation results in a set of genes being reversed
eg
GHI —> IHG

143
Q

Example of chromosome inversion mutation?

A

Haemophilia - a disease that inhibits the ability of blood to clot

144
Q

What happens in a chromosome duplication mutation?

A

A section of chromosome (deleted from the matching partner) becomes attached to its homologous partner resulting in a set of genes being repeated

145
Q

Example of a chromosome duplication mutation?

A

The duplication of certain genes is a common cause of cancer

146
Q

What is a chromosome translocation mutation?

A

Translocation involves a section of one chromosome breaking off and becoming attached to another chromosome that is not its homologous partner

Can bring about a major change in an individuals phenotype

147
Q

Example of a chromosomal translocation mutation

A

Familial Down’s Syndrome

Most common type of mutation associated with cancer eg Chronic Myeloid Leukemia (CML)

148
Q

What is a genome?

A

The genome of an organism is its entire hereditary information encoded in DNA

149
Q

What is a genome made up of?

A

Genes and other DNA sequences that do not code for proteins

150
Q

What is human genomics?

A

The study of the human genome

151
Q

What does human genomics involve?

A

It involves determining the sequence of the nucleotide base molecules all the way along the DNA (genomic sequencing) and then relating this genetic information to their information

152
Q

What does SNP stand for?

A

Single nucleotide polymorphisms

153
Q

What is a single nucleotide polymorphism?

A

SNPs (snips) are single nucleotide substitution point mutations and cause an alteration to the genome

154
Q

How much of all human genetic variations do SNPs make up?

A

Around 90%

155
Q

What does people affected by certain diseases always inheriting a group of SNPs that unaffected people do not suggest?

A

The gene for the disease is located near the group of SNPs

156
Q

What can we analyse if we know the location of SNPs?

A

Nearby genes

157
Q

Describe the process of sequencing DNA to find the genome

A
  • A portion of DNA with an unknown base sequence is chosen + many copies of the strand are synthesised
  • Modified nucleotides are incorporated into DNA strand halting synthesis
  • If carries out on a large enough scale, synthesis of complementary strand will have been stopped at every possible nucleotide position along the DNA template
  • The fragments of various lengths are separated by electrophoresis (shortest fragments travel the furthest distance)
  • Detection of the four dyes is linked to a computer which displays the sequence of bases in the DNA sample as a series of peaks
158
Q

How long did it take for the human genome to be unravelled?

A

13 years

159
Q

How many nucleotide bases make up the human genome?

A

3 billion

160
Q

Thanks to genome sequencing how many disease causing genes do we know exist?

A

300 disease causing genes

161
Q

Thanks to genome sequencing how many genes do we know each express several different forms of the protein they encode?

A

4000 genes

162
Q

What is bioinformatics?

A

A fusion of biology, computer technology and statistical analysis which allows for quick mapping and analysis of DNA sequences on a large scale

163
Q

What does bioinformatics allow for?

A

Quick mapping and analysis of DNA sequences on a large scale

164
Q

What is bioinformatics often used for?

A

To search for specific sequences such as known genes or promotors

165
Q

What is a complete sequencing of a person’s DNA bases called?

A

Personal genome sequence (personal genomics)

166
Q

What is pharmacogenetics?

A

The study of the effects (therapeutic, neutral, or adverse) of pharmaceutical drugs in the genetically diverse members of the human population

167
Q

What would the benefits of personalised medicine be?

A

It may be possible to select the most effective drugs and dosage to treat their disease as indicated by a person’s gene sequence.

Thus increasing drug efficiency and reducing side effects

168
Q

What fraction of drugs varies in effect depending on differences in a person’s DNA profile (SNPs) and example?

A

1 in 10 drugs (eg warfarin)

169
Q

What is cell metabolism?

A

The term used to describe all of the integrated, enzyme-controlled reactions which take place within a living cell

170
Q

What are the 2 types of metabolic pathways?

A
  • Catabolic pathways

* Anabolic pathways

171
Q

What is a Catabolic pathway?

A

Break down complex molecules into simple building blocks usually releasing energy

172
Q

What is an anabolic pathway?

A

Synthesise complex molecules from simple molecules usually requiring energy

173
Q

Anabolic and catabolic relationships _____ on each other to _____

A

Depend

Function

174
Q

Example of anabolic and carbolic pathways relying on each other

A

Aerobic respiration (catabolic) releases energy required for protein synthesis (anabolic)

175
Q

What is the importance of enzymes?

A

Without enzymes chemical pathways would proceed too slowly for life to exist

176
Q

What’s a metabolic pathway?

A

Integrated and controlled pathways, regulated by enzymes that catalyse specific reactions

177
Q

Why do pathways contain both reversible and irreversible stages?

A

to keep the process highly controlled

178
Q

Reversible and irreversible steps of respiration?

A

IRREVERSIBLE- glucose - intermediate 1 - maintains low concentration of glucose inside cell, promoting diffusion of glucose into cell

REVERSIBLE - intermediate 1 - intermediate 2. If more int.2 than cell requires then some can be converted back into int.1 and used in alternative pathway (eg build up glycogen)

179
Q

What do alternative metabolic routes allow?

A

Allows steps to be bypassed

180
Q

Describe the alternative route for respiration

A

Glucose bypasses the steps controlled by enzymes A,B, and C via an intermediate called sorbitol and returns to glycolysis later in the pathway.

This is used when the cell has a plentiful supply of sugar.

181
Q

What is the energy required to break chemical bonds in reactant molecules called?

A

Activation energy

182
Q

What is the transition state?

A

When the bonds of a molecule in the reacting have absorbed enough energy to make them unstable so they can break

183
Q

What is a catalyst?

A

A substance that:

  • lowers the activation energy required for a chemical reaction to proceed
  • speeds up the rate of a chemical reaction
  • takes part in the reaction but remains unchanged at the end of it
184
Q

What are enzymes?

A

Biological catalysts

185
Q

What are metabolic pathways controlled by?

A

The presence or absence of particular enzymes

186
Q

What is the affinity of a substrate?

A

It’s chemical attraction to the active site

187
Q

The active site is _____ and _____

A

Flexible and dynamic

188
Q

When a substrate binds to an enzyme, the ____ of the active site _____ ___ _____ to better fit the substrate

A

Shape

Changes very lightly

189
Q

What is induced fit?

A

When a substrate binds to an enzyme, the shape of the active site changes very slightly to better fit the substrate

190
Q

What does induced fit ensure?

A

This ensures that the active site is in very close contact with the substrate and increases the chance of a reaction taking place

191
Q

When the reaction involves two or more substances, what does the shape of the active site determine?

A

The orientation of reactants to ensure they are held together in such a way that the reaction can take place

192
Q

The substrate molecules have a __ _____ for the active site

A

High affinity

193
Q

The products have a __ _____ for the active site allowing them to ____ the active site

A

Low affinity

Leave

194
Q

Factors affecting enzyme action?

A
  • Temperature
  • pH
  • Substrate concentration
195
Q

Why is the reaction rate low at low concentrations of substrate?

A

There are too few substrate molecules for enzymes to bind to

196
Q

What does an increase in substrate concentration have on reaction rate?

A

Causes an increase in reaction rate until the reaction rate remains constant as all the active sites are occupied.

The rate is constant until more enzymes are added

197
Q

Some metabolic reactions are _____ and the presence of a _____ or the _____ of a product will drive a sequence of reactions in a particular ______

A

Reversible

Substrate

Removal

Direction

198
Q

If metabolite Y were to increase and X were to decrease, enzyme 2 could go into _____ and convert Y back into X until a _____ was _____

A

Reverse

Balance

Restored

199
Q

If the appropriate enzyme is present the metabolic pathway _____ ; if an enzyme is absent the pathway ____

A

Proceeds

Halts

200
Q

Why are some metabolic pathways only required to operate under certain circumstances?

A

To prevent waste of resources

201
Q

Genes coding for enzymes controlling each of the stages in a metabolic pathway are ‘_____ ___’ or ‘___’ as required

A

Switched on or off

202
Q

When is the only time E.coli can make use of glucose?

A

If it’s released from galactose

203
Q

When is the enzyme B-galactosidase switched on ?

A

When lactose is present

204
Q

What special gene does E.coli carry?

A

A genes which codes for the enzyme B-galactosidase which is switched on when lactose is present

205
Q

Describe what happens when lactose is present in a cell

A

1 - lactose (inducer) enters the cell

2 - transcription and translation to form a repressor protein molecule

3 - some lactose combined with repressor

4 - repressor unable to combine with operator

5 - operator free

6 - successful transcription and translation to form B-galactosidase

7 - enzyme digests lactose until supply runs out then repressor combines with operator and switches the gene off

206
Q

What is the system called that controls the coding of the enzyme B-galactosidase in E.coli cells?

A

LAC Operon System

207
Q

Describe what happens when no lactose is present in an E.coli cell

A

1 - transcription and translation to form a repressor protein molecule

2 - repressor combines with operator

3 - structural gene switched off

4 - no B-galactosidase produced

5 - bacterium conserves it’s resources

208
Q

Some metabolic pathways operate continuously so the genes that code for their enzymes are ___ _____ __

A

Always switched on

209
Q

Control of metabolic pathways which operate continuously is brought about by regulating the action of their enzymes with?

A
  • competitive inhibitors
  • non-competitive inhibitors
  • feedback inhibition by an end product
210
Q

What’s an inhibitor?

A

A substance which decreases the activity of an enzyme

211
Q

How do competitive inhibitors prevent the substrate from binding to the active site?

A

They’re of a similar shape to the substrate so bind to the active site

212
Q

How can a decrease in the rate of reaction due to competitive inhibitors be reversed?

A

By increasing the substrate concentration

213
Q

Where do non competitive inhibitors bind to?

A

A non active site (allosteric site)

214
Q

How do non competitive inhibitors work?

A

They bind to an allosteric site.

This changes the shape of the enzyme indirectly changing the shape of the active site and preventing the substrate from binding

215
Q

Describe the effect of no inhibitor on the rate of reaction

A

Increase in substrate concentration causes an increase in reaction rate until all active sites are occupied

216
Q

Describe the effect of a competitive inhibitor on the rate of reaction

A

Increase in substrate concentration causes gradual increase in reaction rate as substance and inhibitor compete for active sites

217
Q

Describe the effect of a non competitive inhibitor on the rate of reaction

A

Increase in reaction rate which quickly levels off as active sites become denatured

218
Q

What is inhibition by an end product?

A

The final product of the pathway acts an inhibitor for the first enzyme

When there is a large concentration of an end product it down regulated the pathway

219
Q

Describe feedback inhibition by an end product

A

As the concentration of metabolite Z build up, some of it binds to enzyme 1 and slows down the conversion of metabolite W to X to regulate the pathway.

As the concentration of Z drops, fewer molecules of enzyme 1 are affected

This controls the pathway and wasteful conversion and accumulation of intermediates are avoided

220
Q

The region of a DNA molecule which codes for a protein is called a ____

A

Gene

221
Q

Name 2 substances which are necessary for DNA replication

A

ATP

DNA polymerase

222
Q

Name a cellular process for which DNA replication is essential

A

Mitosis

223
Q

State the importance of DNA replication to cells

A

It ensures an exact copy of genetic information is passed from cell to cell during growth and from generation to generation during reproduction

224
Q

Name the component of a nucleotide which would be found at the 3’ end of a DNA strand

A

Deoxyribose sugar

225
Q

State the role of DNA ligase in the replication of DNA

A

DNA ligase bonds fragments of replicated DNA into the lagging strand of DNA

226
Q

Name the type of bond which links the primer to the DNA strand

A

Weak hydrogen bond

227
Q

Name the chemical group found at the 5’ end of a DNA strand

A

Phosphate

228
Q

State the function of PCR

A

Procedure used to amplify DNA using primers - used to help solve crimes, settle paternity suits and diagnose genetic disorders

229
Q

Where does the process of cellular respiration begin? What happens?

A

In the cytoplasm of a living cell with a molecule of glucose being broken down to form two pyruvate molecules

230
Q

Glycolysis consists of a series of ____-______ steps

A

Enzyme controlled

231
Q

What is the first half of the glycolysis pathway called?

A

Energy investment phase

232
Q

How many ATP are needed to start the process of glycolysis off?

A

2 ATP

233
Q

What is the 2nd half of the glycolysis pathway called?

A

Energy payoff phase

234
Q

How many ATP IN TOTAL are produced in glycolysis?

A

4 ATP

235
Q

What is the ATP net gain of glycolysis?

A

2 ATP

236
Q

Where does glycolysis take place?

A

Cytoplasm

237
Q

ATP is required for p_______ of glucose and i_____ during energy investment phase of glycolysis

A
  • phosphorylation

* intermediate

238
Q

What’s phosphorylation? (Glycolysis)

A

Occurs when a phosphate group is added to another molecule

ATP-ADP

239
Q

In glycolysis, hydrogen ions are released from glucose by __________ _____

A

Dehydrogenase enzymes

240
Q

What carries hydrogen ions from glycolysis to the final stage of cellular respiration?

A

Carried by NAD

Forms NADH

241
Q

In glycolysis, one molecule of glucose is broken down into p_____

A

Pyruvate

242
Q

In aerobic conditions pyruvate is broken down to an a_____ group and combines with c_______ A to form _____ ______ _ (AcoA)

A
  • acetyl
  • coenzyme
  • acetyl coenzyme A
243
Q

In the energy payoff phase of glycolysis what releases hydrogen ions from the substrate?

A

An enzyme called hydrogenase

244
Q

If ____ is present, aerobic respiration proceeds in ________

A

Oxygen

Mitochondria

245
Q

What is the inner membrane of the mitochondria folded into?

A

Many extensions (Cristae)

246
Q

What’s the purpose of the cristae of the mitochondria’s inner membrane?

A

Increases the surface area for ATP production

247
Q

In the citric acid cycle the acetyl group of acetyl coenzyme A combines with ___________ to form _____ and enter the citric acid cycle

A
  • oxaloacetate

* citrate

248
Q

The citric acid cycle consists of several enzyme-mediated stages, which occur in the ____ _____ of the mitochondria and result finally in the regeneration of __________

A
  • central matrix

* oxaloacetate

249
Q

In the citric acid cycle, __________ enzymes remove H+ ions from the respiratory substrate along with associated ____ _____ ______

A

Dehydrogenase

High energy electrons

250
Q

In the citric acid cycle, ___ is produced in one of the steps and ____ ____ is released in two of the steps

A
  • ATP

* Carbon dioxide

251
Q

A ____ of ____ ____ are attached to the inner membrane of the mitochondria

A

Series of carrier proteins

252
Q

What is the electron transport chain?

A

Electrons are passed along the electron transport chain releasing energy as they flow along the chain of electron acceptors

253
Q

What’s the energy from the electron transport chain used for?

A

Used to pump H+ ions across the inner membrane

254
Q

What drives the synthesis of ATP?

A

The return flow of H+ ions back through membrane protein ATP synthase

255
Q

How many ATP does the electron transport chain produce?

A

36 ATP

256
Q

How many ATP does cellular respiration produce?

A

38

257
Q

Describe the 2nd part of respiration (electron transport chain)

A
  • NADH releases hydrogen and electrons
  • flow of High energy electrons - electron transport chain
  • energy from electrons used to pump H+ across membrane
  • return flow of H+ makes part of the ATP synthase rotate
  • ADP + Pi ——> ATP
  • Finally hydrogen ions and electrons combine with oxygen to form water
258
Q

What does ATP stand for?

A

Adenosine Triphosphate

259
Q

What is cellular respiration?

A
  • series of metabolic pathways
  • brings about release of energy from a foodstuff
  • the regeneration of the high energy compound adenosine triphosphate (ATP)
260
Q

What is a molecule of ATP composed of?

A
  • Adenosine

* 3 inorganic phosphate (Pi) groups

261
Q

When is the energy stored in an ATP molecule released?

A

When the bond attaching the terminal phosphate is broken by enzyme action

262
Q

What’s the enzyme controlled process that requires energy to regenerate ATP from ADP + Pi called?

A

Phosphorylation

263
Q

The break down of ATP ____ energy and the build up of ATP ______ energy

A
  • releases

* requires

264
Q

What does phosphorylation from ATP do to a reactant in a metabolic pathway?

A

Adds energy - makes note reactive

265
Q

Often a step in a pathway can proceed only if a reactant becomes ____ and energised

A

Phosphorylated

266
Q

ATP acts as the ____ between catabolic energy releasing reactions (respiration) and anabolic energy consuming reactions (active transport)

A

Link

267
Q

What is the transfer of energy via ATP?

A

It is the means by which chemical energy is transferred from one cell type of reaction to another in a living cell

268
Q

ATP is ______ at the same time it is used up

A

Manufactured

269
Q

What’s the quantity of ATP in the human body?

A

Remains constant at 50g

270
Q

What’s the rate at which the human body uses up and regenerates ATP?

A

400g/h

271
Q

Under what conditions will pyruvate be converted to lactate (fermentation)?

A

During vigorous exercise, when the muscle cells do not get sufficient oxygen to support the electron transport chain

272
Q

What happens to the H+ from NADH produced during glycolysis in fermentation?

A

Transferred to pyruvate to produce lactate

273
Q

Explain the importance of NADH in aerobic respiration

A

Generates the NAD needed to maintain ATP production through glycolic

H+ from NADH transferred to pyruvate to produce lactate

274
Q

What does the accumulation of lactate cause?

A

Muscle fatigue

275
Q

When is the oxygen debt of fermentation repaid?

A

During recovery time when exercise stops

276
Q

What does the oxygen debt being repaid in fermentation allow for?

A

Allows respiration to provide the energy required to convert lactate back to pyruvate and glucose in the liver

277
Q

How much ATP does lactate metabolism (fermentation) produce?

A

2 ATP

278
Q

How much ATP does aerobic respiration produce?

A

38 ATP (2 in glycolysis and 36 in ETC)

279
Q

What are the 2 types of skeletal muscle fibres?

A
  • slow twitch muscle fibres

* fast twitch muscle fibres

280
Q

Describe the contractions of slow twitch muscle fibres

A
  • Contract relatively slowly
  • can sustain contractions for longer
  • good for endurance activities
281
Q

Examples of slow twitch muscle fibre activities

A
  • Long distance running
  • cycling
  • cross country skiing
282
Q

Energy source of slow twitch muscle fibres

A

Rely on Aerobic respiration to generate ATP

283
Q

Relative no.pf mitochondria of slow twitch muscle fibres

A

Many

284
Q

Blood supply of slow twitch muscle fibres

A

Large

285
Q

What protein do slow twitch muscle fibres have a high concentration of?

A

Oxygen storing protein myoglobin

286
Q

What is myoglobin?

A
  • oxygen storing protein
  • stronger affinity for oxygen than haemoglobin
  • able to extract oxygen from blood for use by muscle cells, particularly slow twitch muscle fibres
287
Q

What’s the major storage fuel of slow twitch muscle fibres?

A

Fats

288
Q

Describe the contraction of fast twitch muscle fibres

A
  • contract relatively quickly
  • over short periods
  • good for bursts of activity
289
Q

Example of fast twitch muscle fibre activities

A

Power activities

  • sprinting
  • weight lifting
290
Q

Energy source of fast twitch muscle fibres

A

Rely on glycolysis to generate ATP requirements

291
Q

Relative no.of mitochondria in fast twitch muscle fibres

A

Fewer

292
Q

Blood supply of fast twitch muscle fibres?

A

Lower

293
Q

Why do fast twitch muscle fibres have fewer mitochondria and a lower blood supply than slow twitch muscle fibres?

A

They rely on glycolysis for energy and so produce less ATP

294
Q

Major storage fuel of fast twitch muscle fibres?

A

Glycogen

295
Q

Example of muscle with mostly slow twitch muscle fibres

A

Muscles in the back which are responsible for posture

296
Q

Example of muscle with mostly fast twitch muscle fibres

A

Muscles that move eyeballs

297
Q

Sources of embryonic stem cells?

A
  • IVF

* Embryos

298
Q

Potential ethical issue with use of embryonic stem cells

A

Results in destruction of human embryo

299
Q

Define the term multi-potent

A

Capable of differentiating into a limited range of specialised cell types

300
Q

Define the term pluripotent

A

Capable of differentiating into all of the cell types found in the human body

301
Q

Two properties of cancer cells

A
  • do not respond to regulatory signals

* divide uncontrollably to produce rumours

302
Q

Describe the formation of a secondary tumour

A
  • some of a malignant tumour’s cells lose the surface molecules that keep them attached to the original cell group
  • these can enter the circulatory system and spread through the body
  • now tissues are invaded and a secondary tumour forms
303
Q

Two properties of stem cells?

A
  • can reproduce (self renew) themselves by repeated mitosis and cell division while remaining undifferentiated
  • can then differentiate into a diverse range of specialised cells when required to do so
304
Q

Tissue stem cells found in bone marrow will develop into?

A
  • red blood cells
  • platelets
  • phagocytes
  • lymphocytes
305
Q

Two locations of tissue stem cells?

A
  • bone marrow

* skin

306
Q

Name of the repeating units that make up a molecule of DNA?

A

Nucleotides

307
Q

The arrangement of the DNA strands is described as?

A

Antiparallel

308
Q

Explain why the leading strand of DNA is copied continuously

A
  • DNA polymerase can only add nucleotides to the 3’ end of a growing strand
  • the leading strand is replicated in a 3’ to 5’ direction so it can be synthesised as a single strand
309
Q

Name 5 substances that are required in order for DNA replication to take place

A

1) DNA (to act as a template)
2) Primers
3) Free DNA nucleotides (A,C,G,T)
4) Enzymes (DNA polymerase and ligase)
5) ATP

310
Q

Explain why the ‘lagging’ stand has to be copied in fragments

A
  • lagging strand goes in a 5’ to 3’ direction
  • DNA polymerase can only add DNA nucleotides in a 3’ to 5’ direction so the lagging strand has to be replicated in fragments, each starting at the 3’ end of a primer
311
Q

At what end of a DNA strand does DNA polymerase add new nucleotides?

A

3’

312
Q

The small section of DNA needed by DNA polymerase to start replication is called?

A

A primer

313
Q

Function of DNA polymerase in DNA replication

A

Bonds complementary nucleotides to the 3’ end of the DNA strand

314
Q

Function of ligase in DNA replication?

A

Bonds fragments of replicated DNA together on the lagging strand of DNA

315
Q

List 3 used of DNA amplified through PCR

A
  • help solve crimes
  • settle paternity suits
  • diagnose genetic disorders
316
Q

Site of translation

A

Ribosome

317
Q

A ribosome is formed from?

A
  • Ribosomal RNA

* proteins

318
Q

Differences between DNA and RNA

A

DNA
———-
• 1 nucleotide strand present in one molecule

  • uracil = complementary base partner of adenine
  • ribose = sugar present in a nucleotide

———-
RNA
———
• 2 nucleotide strands present in one molecule

  • thymine = complementary base partner of adenine
  • deoxyribose = sugar present in a nucleotide
319
Q

Site of transcription?

A

Nucleus

320
Q

Enzyme responsible for transcription?

A

RNA polymerase

321
Q

The 3D shape of a protein is held together by which type of bonds?

A
  • peptide bonds

* hydrogen bonds

322
Q

Give 4 different functions of proteins

A
  • enzymes
  • hormones
  • structural proteins
  • antibodies
323
Q

What is a cell’s phenotype determined by?

A

The proteins that are synthesised when the genes are expressed

324
Q

What does the shape of a protein determine?

A

The proteins function

325
Q

What’s a cell’s genotype determined by?

A

The sequence of the DNA bases

326
Q

Name 3 single gene mutations

A
  • substitution
  • insertion
  • deletion
327
Q

What type of mutation for insertion and deletion single gene mutations produce?

A

Frame shift mutations

328
Q

Computer programs can be used to identify base sequences by looking for…?

A
  • sequences that are similar/close to known genes

* sequences that are different to known genes

329
Q

Explain 2 ways that information about an individual genome could be used in personalised medicine

A

1) It may be possible to select the most effective drugs and dosage to treat their disease as indicated by a person’s gene sequence. Thus increasing drug efficiency and reducing side effects.
2) In the future people may be able to be forewarned of the possibility of disease in later life

330
Q

Explain why mutations in germline cells are potentially more serious than mutations in somatic cells

A

Mutations in germline cells can be passed to offspring (while mutations in somatic cells cannot)

331
Q

Describe what happens in the energy investment and energy payoff stages of glycolysis

A

INVESTMENT - ATP molecules are broken down/ used up - phosphorylation of phosphate to glucose/intermediates occur

PAY OFF - ATP molecules are produced

332
Q

What’s Preimplantation Genetic Diagnosis (PGD)?

A

During IVF treatment, it is possible to detect single gene disorders in fertilised eggs before they are implanted into the mothers womb

333
Q

State one way in which stem cells are used in research

A

To study diseases/drug testing

334
Q

Explain why embryonic stem cells can differentiate into all cell types?

A

All genes are switched on

335
Q

Describe the DENATURING star of PCR

A

DNA is heated (92-98°C) to separate the strands

336
Q

Describe the ANNEALING stage of PCR

A

Cooling (50-65°C) allows primers to bind to target sequences

337
Q

Describe the EXTENDING stage of PCR

A

Heated between (70-80°C) to allow heat tolerant DNA polymerase to add nucleotides to primers and replicate regions of DNA

Higher Human Biology (3 decks)

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