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ST2 Biology > DNA & Proteins > Flashcards

DNA & Proteins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are living things made out of?

A

All living things are made out of proteins or products of proteins

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2
Q

state what proteins are made out of and state their function

A
  • made out of amino acids
  • function: determine the structure and function of a cell
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3
Q

Describe the following 4 types of functional proteins in terms of function and description

enzyme
hormone
receptor
antibodies

A

Enzyme
function: Catalyse chemical reactions

description: Shape of enzyme active site is complementary to the shape of the substrate

Hormone
function: Pass on chemical messages

description: Shape of hormone is complementary to the shape of the receptor protein (on the surface of a cell’s cell membrane)

** Receptor **
function: Receive chemical messages

description: Shape of the receptor protein is complementary to the shape of the signalling molecule or protein

Antibodies
function: Target and recognise foreign cells

description: Shape of antibody is complementary to the shape of the antigens on the surface of foreign cells

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4
Q

Describe the induced fit model

A
  1. Enzyme has an active site that is complementary in shape to substrate
  2. Complementary binding b/w enzyme and substrate
  3. Enzyme active site changes shape slightly to best fit substrate
  4. This strains the bonds b/w substrate to reduce activation energy
  5. Breakdown or synthesis reaction is carried

6, Enzyme remains unchanged to catalyse another reaction

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5
Q

Describe pH affect on enzyme activity

A

Enzyme work/function best at their optimum pH. Thus, returning pH closer to optimum will increase enzyme activity/function

Change (increase or decrease) in H+ concentrations (in other words pH) will disrupt the weak bonds in tertiary structure; hence this will change the shape of the enzyme active site, hence making it no longer complementary to substrate
- Structural change is temporary

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6
Q

describe effect of Concentration of substrate on enzyme activity

A

Increase in substrate concentration will increase number of substrates available to partake in the reaction, this increases the chances of successful collisions b/w enzyme and substrate, thus increasing the frequency of complementary binding b/w enzyme and substrate
This consequently increases enzyme activity hence rate of reaction

The rate of reaction is limited by the number of enzymes available
- There is a certain point in time, where all enzyme active sites will be occupied, hence increasing substrate conc. will not increase enzyme activity and rate of reaction will remain constant

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7
Q

Concentration of enzyme effect on enzyme activity?

A

increase in enzyme concentration will increase the number of active sites available, this increases the rate of successful collisions b/w enzyme and substrate, consequently increasing frequency of complementary binding b/w enzyme and substrate, this increases enzyme activity hence rate of reaction

Enzyme activity is limited by the number of substrates available
- Increasing enzyme concentration will not increase rate of reaction
- Rate of reaction will decrease once all substrates (reactants) have been turned into products

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8
Q

Temperature effect on enzyme activity

A

Increase in temperature to the optimum, increases particles kinetic energy, consequently increasing the chances of successful collisions b/w enzyme and substrate. This increases the frequency of complementary binding b/w enzyme and substrate, hence increasing enzyme activity hence rate of reaction

Increase pass optimum temperature disrupts the weak hydrogen bonds in secondary, tertiary, and quaternary structure, this permanently changes the shape of the enzyme (denatured) hence the enzyme active site no longer complementary to the substrate, this prevents the substrate from binding. Consequently, no complementary binding b/w enzyme and substrate can occur, therefore rate of reaction and enzyme activity decreases

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9
Q

Inhibitor effect on enzyme activity

A

**Competitive inhibitor **
- Similar shape to substrate hence it is complementary in shape to enzyme active site
- Binds to enzyme active site to prevent substrate from binding
- Hence, decreases enzyme activity and rate of reaction

**Non-competitive inhibitor **
- Binds to the alternative site (allosteric site) on the enzyme
- This changes the shape of the enzyme active site, making it no longer complementary to the substrate
- Substrate is unable to bind, hence enzyme activity and rate of reaction decreases

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10
Q

What is the function of DNA?

A

Store and transmit genetic information

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11
Q

State why it is possible for genes in a different type of cell to function in another organism?

A

DNA is universal in almost all living things – it functions the same

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12
Q

Describe features of the structure of the DNA molecule.

A

Double stranded helix structure
Nucleotides – that join via complementary base pairing
Sugar-phosphate backbone

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13
Q

What is a gene and what’s its function??

A

A gene is a section of DNA with a unique base sequence that is the code for synthesis of RNA molecule or RNA molecule that gets turned into a protein

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14
Q

Describe the process of DNA replication

A
  1. Helicase unwinds DNA and breaks the hydrogen bonds holding the nucleotides together
  2. DNA molecule is separated into 2 strands, each strand act as templates
  3. DNA adds/binds free-floating DNA nucleotides to exposed bases on template DNA strands via complementary base pairing
  4. DNA polymerase joins the sugar phosphate backbone of DNA nucleotides, synthesising a new strand
  5. Thus, 2 DNA molecules are formed
    Each has 1 strand from the original strand, 1 strand from the newly synthesised strand
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15
Q

State where transcription occurs and describe its process

A

occurs in: nucleus

  1. At a specific gene
  2. Helicase unwinds DNA and hydrogen bonds are broken to separate strands into 2 single strands
  3. only 1 strand acts as template
  4. Free floating RNA nucleotides bind to exposed bases on template strand via complementary base pairing
  5. RNA polymerase joins nucleotides into RNA strand
  6. DNA rejoins
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16
Q

State where splicing occurs and describe it process

A

where: cytoplasm

  1. Removal of introns from primary RNA strand
  2. Joining of exons to form mRNA strand
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17
Q

state where translation occurs and describe its process

A

where: cytoplasm at the ribosome

  1. mRNA binds to ribosome
  2. Ribosome reads 1 codon (3 mRNA bases)
  3. tRNA carry amino acid corresponding to anticodon
  4. tRNA with anticodon complementary to mRNA codon binds via complementary base pairing
  5. tRNA adds/deposits amino acid to polypeptide chain in correct order
  6. Process repeats until full protein is formed
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18
Q

Describe the relationship b/w DNA base sequence, mRNA codon, tRNA, and amino acid

A

3 DNA bases (triplet) = 3 mRNA bases (codon) = 3 tRNA bases (anticodon) = 1 amino acid

During transcription, DNA base sequence acts as a template and is transcribed into RNA strand. In splicing, which involves the removal of introns, mRNA strand is formed. The mRNA nucleotide sequence is translated into an amino acid sequence using the tRNAs as adaptors to add each amino acid in the correct sequence to the end of the growing polypeptide chain.

19
Q

What is cell differentiation? Why do cells differentiate?

A
  • Cells differentiation occurs because cells are able to only express (transcribe and translate) only certain genes
  • All cells have the genes to be any type of cells
  • Cells become specialised through the switching off or on of certain genes
20
Q

What is epigenetics?

A
  • Are the different mechanisms that control gene expression
  • Changes in epigenetics can lead to changes in structure and function
21
Q

Describe how ‘ PRODUCTS OF OTHER GENES’ affect transcription and gene expression

A

Transcription factors
- Activator factor that binds to enhancer DNA sequence to promote gene expression
o Promotes transcription
- Repressor factor that binds to silencer DNA sequence to inhibit gene expression
o Suppresses transcription

22
Q

Describe methylation effect on gene expression and transcription

A
  • Methylation of cytosine
  • Methyl (CH3) binds to cytosine base on DNA sequence
  • High methylation at the start of a gene appears to inhibit transcription and decrease gene expression (gene is switched off) by the closing off of DNA structure
23
Q

Describe histone modification effect on gene expression and transcription

A
  • The covalent addition of groups of atoms to histone protein that affect the wrapping of DNA
    For instance, acetylation – the addition of acetyl group to histone protein
    Results in DNA wrapping to be loos, thus promoting transcription, hence gene expression
24
Q

Describe the enviroment effect on gene expression and transcription

A
  • Physical factors such as smoking, alcohol consumption, diet, and working a night shift can lead to epigenetic changes
25
Q

what is cancer?

A

– uncontrolled cell growth and multiplication

26
Q

What are oncogenes?

A
  • Genes that increase the spread of cancerous cells
27
Q

What are the 2 ways epigenetic may cause cancer?

A
  1. The switching off of genes that stop the spread of cancerous cells such as tumour suppressor
  2. The switching on of genes that increase the spread of cancerous cells such as oncogenes
28
Q

Define mutation.

A
  • Any change in DNA base sequence
29
Q

Compare the impact of addition and deletion mutation in comparison to substitution mutation

A

Addition and/or deletion will change the way codons are grouped (frame shift), this will cause a change in codons after mutation. This will change more amino acids, hence more likely to affect protein structure and function

Substitution will change 1 or 2 codons, hence will cause a change in 1 or 2 amino acids. This will have a less impactful effect on protein structure and function

30
Q

State and describe the physical and chemical factors that increase the frequency of mutations:

A
  1. Ionising radiation – exposure to UV light increases the frequency of mutation and leads to skin cancer
  2. Mutagenic chemicals – chemicals in cigarettes increase the frequency of mutation and lead to lung cancer
  3. Viruses – viruses increase the frequency of mutations. For instance, HPV (human papilloma virus) is associated with cervical cancer
31
Q

The effect of mutations varies as a result of where they occur, describe the effect on the following:

  1. Mutations in somatic cells
  2. Mutation in germ cells
A
  1. Mutations in somatic cells
    - Body cells
    - Mutations leads to things like cancer
    - Affects individual
    - don’t get passed down to next generation and lead to genetic disease
  2. Mutation in germ cells
    - Sex cells
    - Does not affect individual
    - However, if mutated gamete leads to zygote, then every cell in the new offspring will carry the mutation
    - Hence will be passed on to next generation and lead to genetic disease
32
Q

Describe electrophoresis

A

a) Electrophoresis
1. DNA sample is cut into fragments using restriction enzyme
2. DNA sample is loaded into a well in the gel with different colour dyes
3. Electric potential is applied
4. Negatively charged DNA fragments move towards positive end of gel
5. Smaller fragments move faster than larger fragments
6. Electric potential is turned off once the first dye reaches the end of the gel
7. DNA fragments are arranged from largest to smallest

33
Q

state the function and describe the process of PCR (polymerase chain reaction)

A
  • Used to amplify DNA
  • Can create many identical copies of DNA
  1. Mixture of DNA sample, Taq polymerase, primers, and DNA nucleotides
  2. DNA sample is heated to 95 Celsius degrees to separate strands into 2
  3. Mixture is cooled to 60 Celsius degrees and primers bind via complementary base pairing
  4. At 72 Celsius degrees, Taq polymerase adds and joins complementary nucleotides into new DNA strand
34
Q

How are STR (short tandem repeats) used in DNA profiling?

A
  • Individuals have non-coding regions that have a certain number of repeats of certain base sequences at a particular locus
  • These numbers of repeats are unique to the individual and can be used to identify a person
35
Q

State the features of probes that allow it to be used in DNA profiling?

A

 Single stranded
 Fluorescently labelled and radioactive (visible by x-ray)
 Complementary to specific DNA fragments

36
Q

Describe DNA sequencing

A
  • Determines the base sequence of the entire genome of an organism or species
  • Uses PCR and electrophoresis
  • Electrophoresis is used to sort fragments by size
  • Uses nucleotides labelled with different coloured dyes
  • An electropherogram is produced by a computer for interpretation
37
Q

State the 4 applications of DNA profiling

(need to know at least/just two )

A
  • Identify bodies
  • Connect suspects to crime scenes
  • Determine family relationships
  • Identify genetic conditions
38
Q

State the 5 of the risks of DNA profiling?

(need to know at least/just 2-3)

A
  • Contamination or corruption of DNA samples
  • Storage of genetic information
  • Privacy of genetic information
  • Storage of genetic information that may contribute to systematic racism and discrimination
  • Inequity of access to genetic information
39
Q

Describe the process of gene modification via bacterial plasmids
(transfer of genes)

A
  1. Cut gene with restriction enzyme
  2. Cut plasmid with same restriction enzyme (to create complementary sticky ends on plasmid and gene of interest)
  3. Insert gene into plasmid using DNA ligase
  4. Insert plasmid into bacteria cell
40
Q

Describe the process of gene modification via viruses
(transfer of genes)

A
  • used as a viral vector
  • viruses can be genetically modified to insert target genes into cells (plant and animal cells)
41
Q

Describe the process of gene modification via electroporation
(transfer of genes)

A
  1. electric potential applied to create temporary pores in cell
    membrane
  2. small pieces of DNA pass through the small pores into the cell
  3. cells ‘heals’ with inserted DNA inside
42
Q

Describe the process of gene modification via microinjection

A

used on eggs or zygote (animals cells) : direct injection of genes into the nucleus of a cell

43
Q

Describe the process of gene modification via CRISPR

A

CRISPR - consists of a guide RNA (has a strand that is complementary to the gene of interest) and cas9 (cuts gene of interest)

  1. CRISPR has guide RNA that is complementary to gene being edited
  2. CRISPR-cad9 complex is introduced into cell and binds via complementary base pairing
  3. Cas9 cuts gene of interest
  4. Cell repairs cut gene, and in doing so, the gene loses its function (gene is switched off)

ST2 Biology (4 decks)

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