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Biology > Nucleic Acids, Mitosis And ATP > Flashcards

Nucleic Acids, Mitosis And ATP Flashcards

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1
Q

What are nucleic acids?

A

Biologicalmolecules that carry important information. They are molymers of many monomers called nucleotides

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2
Q

Describe the roles of DNA and RNA

A

DNA stores genetkc information inside the cell
RNA transferes the genetic information from DNA to ribosomes

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3
Q

What are the components of DNA nucleotides

A

4 bases (adenine, thymine, guanice, cytosine)
Deoxyribose sugar
Phosphate group

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4
Q

Describe the structure of DNA polynucleotides

A

Poly nucleotides join during a dindensation reaction
each nucleotide is held by strong covalent bonds called phosphodiester bonds between the phosphate group of one and the sugar of another.
Creates a sugar-phosphate backbone

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5
Q

Descrobe the structure of a DNA molecule

A

Two polynucleotides running anti-parallel to eachother
Twist to form a double helix
Complimentary base paring- hydrogen bonds between the complimentary bases of each strand

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6
Q

Describe what complimentary base pairing is

A

Adenine and thymine join with 2 hydrogen bonds
Guanine and cytosine join with 3 hydrogen bonds

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7
Q

What is the difference between pyramidines and purines, give examples of each

A

Puramidines are smaller bases (thymine and cytosine)
Purines are larger bases (guanine and adenine)

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8
Q

Give the adaptations of the structure of DNA

A

Double helix with many hydrogen bonds- stable molecule
Sugar-phosphate backbone- strong
Complimentary base pairing- allows DNA to replicate via semi-conservative replication (as weak hydrogen bonds can break)
Long and compact- stores lots of info in a small space
Precise genetic coding- allows protein synthesis

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9
Q

What is the only way that polynucleotides can differ from eachother?

A

Different sequences of bases in the polynucleotide

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10
Q

Describe the structure of RNA and its components

A

RNA is a ribonucleic acid, it is short singke stranded polynucleotide made lf RNA nucleodide monomers
Each nucleotide contains a phosphate group, nitrogen containing bases (adenine, uracil, cytosine, guanine) and a ribose sugar

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11
Q

What is semi-conservative replication?

A

DNA replication where half of the origional DNA molecule is conserved, and the other half is newly synthesised

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12
Q

Describe the process lf semi-conservative replication

A

enzyme DNA helicase unwinds double helix by BREAKING the hydrogen bonds between bases. separates polynucleotide strand
Each exposed strand now acts as template
Single DNA nucleotides found free in nucleoplasm are attracted to exposed bases, and attach by complimentary base pairing with new hydrogen bonds
Enzymes DNA polymerase joins the new nucleotides together with phosphodiester bonds in comdensation reaction. This forms new polynucleotide,

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13
Q

When and by which scientists what evidence for semi-conservative replication discovered?

A

1958
Stahl and Meselson

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14
Q

Explain the evidence for semi-conservative replication

A

Cultures of E-coil bacteria grown in medium of 15N (heavy isotope)
All DNA becomes labelled with 15N
Transfered and grown in medium with 14N (lighter/ normal isotope)
Samples taken, each generation of DNA was extracted and centrifuged

Gen 0- DNA all heavy
Gen 1- two hybrid molecules of DNA
Gen 2- 50% light, 50% hybrid
Gen 3- 75% light, 25% hybrid

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15
Q

What is a chromosome?

A

Long, linear structures consisting of DNA and histone proteins

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16
Q

What are a homologous pair of chromosomes?

A

A pair pf chromosomes containing the same gene in the same position, each derived from a different parents gamete

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17
Q

How many homologous pairs of chromosomes does a human cell contain?

A

23

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18
Q

What is the diploid number of chromosomes?

A

The total number of chromosomes in a normal cell

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19
Q

What is the diploid number of chromosomes in a human cell?

A

46

20
Q

State and describe the 4 stages in the cell cycle

A

G1- cell prepares for replication (respires, grows, produces new organelles and proteins)
S- DNA replicates by semi-conservatove replication
G2- cell grows and prepares for mitosis
M- mitosis

21
Q

What three stages in the cell cycle can be described as interphase?

A

G1, S and G2

22
Q

What does it mean if a cell is in stage G0 of the cell cycle?

A

Some cells within multicellular organicms are soecialised to not divide, so are in G0

23
Q

How does the diration of interphase indicate the rate of cell division?

A

The shorter the interphase stage, the more rapid the rate of division

24
Q

Explain the stages of mitosis

A

Prophase- chromosomes shorten and become visible. Nuclear envelope breaks down
Metaphase- chromosomes line up along the equator of the cell and attach to spind fibres by their centromeres
Anaphase- centromere divides, spindle fibres contract to pull apart sister chromosomes to opposite okles of the cell
Telophase- chromosomes uncoil, become thread like again and not visible.new nuclear envelope forms around each set of daughter chromosomes.

25
Q

Explain the process of cytokinesis

A

After mitosis, the cell pinches itself in two and a cell membrane forms in the middle.
The cell membrane from one side of the cell joins that of the opposite side, the cell splits and creates two daughter cells

26
Q

What is the mitotic index and what is its equation?

A

A ratio that shows the number of cells undergoing mitosis compared to the total number of cells

= number of cells in mitosis/ total number of cells

27
Q

State and explain how prokaryotic cells divide

A

Binary fission:
Replicate circular DNA and plasmids
The cell memnrane grown between the two main circular DNAs and pinches inwards, dividing the cytoplasm in two
A new cell wall forms, forming two daughter cells each with one main circular DNA and variable number of plasmids

28
Q

Why can prokaryotic cells not divide by mitosis?

A

They have no nucleus, therefore have no histone proteins so DNA cannot coil and chromosomes cannot be made)

29
Q

Explain how viruses divide

A

They attach to host cells using attachment proteins that are complimentary to the host cells antigens
They inject their nucleic acids into the host cell, which uses the nucleic acids to produce viral compoments that can be assembled into new viruses

30
Q

What is cancer and how is it caused?

A

Results from mutations in genes that cause uncontrolled and rapid cell division of cells by mitosis
Forms a mass of abnormal cells called a tumour
Tumours dont respond to signals from nerves or hormones, so cannot undergo programmed cell death

31
Q

What are treatments lf cancer?

A

Drugs can be used so that parts of the cell (such as DNA replication or spindle fibre formation) can be blocked to control/ stop the rate of division

32
Q

What is ATP?

A

ATP is an immediate source of energy used by all cells to drive their metabolic reactions

33
Q

What are the components of an ATP nucleotide?

A

3 phosphate groups
Organic base adenine
Ribose sugar

34
Q

Explain how ATP is synthesised

A

By the addition of ADP to an inorganic phosphate (Pi)
This is a condensation reaction that is catalysed by the enzyme ATP synthase, it occurs during respiration and requires an input of energy

35
Q

What is the reaction called when ATP is synthesised?

A

Phosphorylation

36
Q

Explain the breakdown of ATP

A

The phosphate- phosphate bond between the 2nd and 3rd phosphate is broken during a hydrolysis reaction, using the enzyme ATP hydrolase. This removes one inorganic phosphate group and releases energy. ATP becomes ADP

37
Q

Between which bonds is useful energy stored in ATP?

A

Between the phosphate- phosphate bond between the second and third ohosphates. This is because it is very unstable and easily broken

38
Q

What is the use of ATP, give examples of when it is used?

A

Energy is released during its hydrolysis, which can be used in metabollic reactions that require energy:
Active transport
Exocytosis
Synthesis of substances
Movement of muscle cells
Activation of other molecules

39
Q

What are benefits of ATP as an intermediate energy source compared to glucose?

A

Hydrolysis of ATP is a single reaction, so energy is immediately available. Glucose hydrolysis uses more reactions
ATP is soluble, so can easily move around cells without passing through cell membranes. Glucose is insoluble
ATP releases small amounts of energy. Glucose releases large amounts of energy that are not needed, so is less efficient

40
Q

What is the ATP cycle?

A

The condensation of ATP from ADP and Pi and the hydrolysis of ATP is a reversable reaction, so described as a cycle

41
Q

why is ATP not s good long term energy source?

A

Due to the instability in the phosphate group bonds

42
Q

What are chromatids?

A

One of two threads of a chromosome, formed after DNA replication

43
Q

What is a centromere?

A

Holds together two identical sister chromosomes, in the centre of the chromosome

44
Q

What are chromatins?

A

a substance formed from DNA and proteins together

45
Q

Which two scientists proposed the DNA structure and replication?

A

James Watson and Francis Crick

Biology (13 decks)

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