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Biology Model Answers > Topic 2 > Flashcards

Topic 2 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Describe the structure of a nucleotide

A

Made of a phosphate, Pentose andnitrogenous base
Joined by a condensation reaction
Phosphodiester bonds form
Bases A,T pair and G,C pair
Held together by H bonds
Creates double helix

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2
Q

Why is DNA replication described as semi conservative/ why was the semi conservative model accepted (Melson and Stahl)?

A

Semi conservative accepted / conservative rejected
Generation 1 has single band halfway between 14N and 15N
Because the DNA has one strand containing 14N and one containing 15N
In semi conservative further generations would have no band at 15N

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3
Q

What happens in DNA replication

A

Semi conservative
BOTH strands replicate
DNA nucleotides line up against both strands
DNA polymerase joins them creating phosphodiester bonds
Then winds back up into double helix

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4
Q

What happens in transcription

A

DNA unzips because of helicase
RNA nucleotides line up against template strand due to complementary base pairing
RNA nucleotides joined by RNA polymerase
New phosphodiester bonds form between nucleotides
MRNA strand is formed and leaves nucleus

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5
Q

What happens in translation

A

MRNA attaches to ribosome
Triplet bases called codons are exposed within the ribosome
Amino acids attach to a binding site on specific tRNA molecules
Trna transports specific amino acids to ribosome
Anticodon in trna pairs with complementary codon on mRNA
Peptide bonds form by condensation reaction
Trna released from mRNA into cytoplasm

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6
Q

How is mRNA edited between transcription and translation

A

Non coding introns are removed and the remaining exons can be sliced together
Different proteins can then be made from one length of mRNA

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7
Q

Compare transactions and DNA replication

A

Both involve the unwinding of DNA by breaking H bonds
Transcription uses RNA nucleotides whereas DNA replication uses DNA nucleotides
Transcription nucleotides line up against anti sense strand whereas in replication nucleotides line up against both strands

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8
Q

How do mutations lead to nonfunctional proteins

A

Mutation could cause change in the primary structure
As there would be different R groups and different Positions/types of bonds e.g ionic, disulphide, hydrophobic interactions, hydrogen
Tertiary structure changes as protein fold

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9
Q

Compare DNA and RNA

A

Both are made up of nucleotides joined by phosphodiester bonds
DNA is double stranded whereas RNA is single stranded
DNA contains deoxyribose sugar whereas RNA contains ribose sugar
DNA contains the bases adenine, thymine, guanine and cytosine whereas RNA contains adenine, guanine, cytosine and uracil

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10
Q

Describe the function of enzymes

A

biological catalysts that lower activation of enemy
Increase rate of reaction
Specific to each reaction
Specific shape determined by amino acid sequence and R groups
This determines primary structure which therefore determines tertiary and therefore the function

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11
Q

How can mutations CF?

A

It is caused by a mutation to the CFTR protein
The primary mutation Occurs on an ATP binding site
ATP therefore can not bind to the CFTR channel
Phosphate is not relaxed and no phosphorylation of the protein can occur
This allows the channel to open
Therefore no transport of chloride can occur across the channel

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12
Q

What is a gene

A

Sequence if bases in the DNA that determine the sequence if amino acids in polypeptide chain

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13
Q

What is an allele

A

An alternate form of gene that is at the same locus on the chromosome

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14
Q

How does the expression of a gene mutation in people with CF impair the digestive system?

A

Thick and sticky mucus blocks the ducts in the pancreas that secrete digestive enzymes
Less enzymes are therefore available for digestion in the intestine
Therefore food doesn’t get disgusted properly leading to less absorption of nutrients

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15
Q

How does the expression of a gene mutation in people with CF impair the function of the gaseous exchange?

A

Thick and sticky musics increase the length of the diffusion pathway for gas exchange
According to flicks law the rate of gas exchange is inversely proportional to the light of the diffusion pathway
As the length increase the rate if gas exchange decrease
The mucus also blocks up the alveoli which decreases surface area for gas exchange
As flicks law states the rate of gas exchange is proportional to the surface area
Therefore a decrease in surface area leads to a decrease rate in gas exchange

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16
Q

How does the expression of a gene mutation in people with CF impair the function of the reproductive system?

A

CF affects the reproductive system by causing the sperm ducts to be blocked or not present in males
In female it results in thicker vaginal mucus making it harder for the sperm to reach the egg cell

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17
Q

What are the ethical issues with genetic screening?

A

Can pose emotional stress to parents
Can be seen as unethical to screen an embryo
Genetic abnormalities found can be stressful to parents
False positive may lead to termination of healthy baby
Designing a baby of Chaucer is considered unethical in some religions/cultures

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18
Q

What are some mammalian adaptations that increase the rate of diffusion?

A

The lungs contain many alveoli which increase the surface area for gas exchange which increase rate of diffusion
The walls of the alveoli are one cell thick which decreases the length of the diffusion pathway and increase rate of diffusion
The lungs have a large capillary network which maintain a concentration gradient

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19
Q

Describe the structure and function of the cell membrane?

A

Fluid mosaic model
Phospholipid bilayer
Hydrophilic head and hydrophobic fatty acid tails
Intrinsic proteins which span bilateral
Extrinsic proteins which are embedded in heads of phospholipids
Channel proteins span the bilayer and allow movement of substances
Glycoproteins which act as receptions

20
Q

What is osmosis

A

Net movement of water from an area of high concentration to a low area of congregation
Through a partially permeable membrane

21
Q

What is diffusion

A

Movement of particles from an area of high concentration to an area of low concentration

22
Q

What is facilitated diffusion?

A

Movement of particles from an area of high concentration to low concentration sung channel/carrier proteins

23
Q

What Is active transport?

A

Movement of particles from an area of low concentration to high using ATP
Energy is required

24
Q

What Is exocytosis?

A

Movement of a large number of molecules out of the cell
Contained within a vehicle which moves towards the cell membrane

25
Q

What is endocytosis?

A

Movement of a large number of molecules form outside the cell to the inside of the cell
A vesicle forms containing the substance
Vesicle pinches of the cell membrane and is taken into the cell membrane

26
Q

Compare and constant endocytosis and exocytosis?

A

Similarities
both contain vesicles
Differences
Exocytosis - out the cell
Endocytosis - into the cell

27
Q

CPAC 3:
Outline the procedure to investigate the effect of temperature on permeability of the cell membrane:

A

IV - temperature
DV - absorbance
Cut beetroot into identical cubes using a scalpel
Place each cube in a different test tube with equal volumes of distilled water
Place each test tube into water baths ranging from 30-80°C, leave it for 20 mins
Filter out each solution into a cuvette and measure the absorbance using a colourimeter

28
Q

Explain the effect of temperature on membrane permeability

A

Increasing temperature results in an increased membrane permeability
As high temperatures denature some of the membrane proteins
Creating gaps in membrane for molecules to pass through

29
Q

What is the effect of increasing ethanol concentration on membrane permeability?

A

Increased ethanol concentration leads to an increased membrane permeability
As the ethanol causes the membrane to rupture
Forming gaps for molecules to pass through

30
Q

CPAC 4:

What are the 4 factors that effect enzyme activity?

A

Temperature
pH
Enzyme concentration
Substrate concentration

31
Q

What is the effect of enzyme concentration on enzyme activity?

A

As the concentration of enzymes increases, the number of enzyme substrate complexes formed increase as successful collisions are more frequent
So the rate of reaction increase to an optimum
After the optimum, the rate of reaction plateaus

32
Q

CPAC 4

Describe an experiment that could be carried out to investigate the effect of enzyme concentration on the initial rate of reaction

A

IV - range of enzyme concentrations
DV - volume of oxygen produced
CV - temp, pH, size of potato disks
mix hydrogen peroxide with potato discs in a boiling tube.
initial rate must be soon after mixing: plot and calculate from a graph
use a gas syringe to measure the volume of O2 produced in 10 seconds for 2 minutes for each concentration of enzyme.
repeat to improve reliability

33
Q

MATT starts AUGust can u? - translation

A

mRNA leaves nucleus and
Attaches to ribsone subunit
tRNA line up
tRNA binds to ribosome oppoasite mRNA
Start codon - AUG
Complementary anticodon
UAC will pair up

34
Q

Uncle Tim Might Join Him Before

A

Unzips (dna helix unzips)
Template for each strand
Mononucleotides that are free floating join to OG stand
Joined together by DNA polymerase
H bonds form
Both strands are identical

35
Q

Ryan Has To Take Real Cash And Play Monopoly Deal - transcription

A

Rna polymerase attaches to dna
H bonds break
Template strand is
T transcribed
RNA nucleotides pair up with
Complementary dna bases
Attach to dna
Phosphodiester bonds form between rna nucleotide
mRNA produced
Detaches from dna and leaves nucleus

36
Q

What is ficks law

A

Fick’s Law is used to determine the rate of diffusion and it states that the larger the surface area, difference in concentra on and shorter the diffusion distance the quicker the rate.

37
Q

What’s the difference between globular and fibrous proteins

A

Glob - circular, physiological function, soluble in water , haemoglobin is example
Fibrous - long strands, structural function, insoluble , collagen is example

38
Q

Types of genetic screening

A
  • Pre-implanta on gene c diagnosis – embryos created through IVF are tested for gene c disorders before they are implanted into the woman’s uterus.

-Chronic villus sampling – this test is carried out at 8 to 12 weeks of pregnancy. A sample of embryonic ssue is taken from the placenta and the DNA is analysed. This form of tes ng is quicker than amniocentesis

-Amniocentesis – carried out at 14-16 weeks. A sample of amnio c fluid, which contains foetal cells, is obtained using a needle. The DNA is then analysed. Results are available a er 2-3 weeks, as foetal cells need to be grown in culture first.

39
Q

What is a gene

A

a piece of DNA which has a specific sequence of bases. Each gene codes for a specific protein

40
Q

What is substitution

A

Change in one base

41
Q

What is insertion

A

Adding another base

42
Q

What is deletion

A

Taking base out

43
Q

What is duplication

A

Adding same base more than once

44
Q

What is a protein

A

-Amino acids are the monomers from which proteins are made.
-Amino acids contain an amino group, a carboxyl group, and a variable R group which is a carbon-containing chain.
-There are 20 different amino acids with different R groups.
-Amino acids are joined by pep de bonds -formed in condensa on reaction

45
Q

What are some key features of the genetic code

A

● The gene c code is non-overlapping, meaning that each triplet is only read once and triplets
don’t share any bases.
● The gene c code is degenerate, meaning that more than one triplet codes for the same
amino acid.
● The gene c code is a triplet code - each three bases codes for one amino acid.
It also contains start and stop codons which either start or stop protein synthesis.

Biology Model Answers (8 decks)

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