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BIOL1020 > Cells > Flashcards

Cells Flashcards

1
Q

What is the endoplasmic reticulum?

Smooth vs rough?

A

ER is an organelle in eukaryotic cells that has ribosomes attached, and is involved in the synthesis of lipids and proteins

Rough ER: Has ribosomes attached to outer surface which decode RNA to produce the amino acid chain of proteins

Smooth ER: synthesis of lipids (e.g. cholesterol and phospholipids)

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2
Q

How do alpha and beta bonds differ in glycosidic bonds?

A

Alpha bonds OH is ‘below the plane,’ like a u shape, beta is above the plane like a z shape
Beta glycosidic linkages are indigestible by animals, as we do not have the enzymes required to break this link

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3
Q

Describe differences between saturated and unsaturated fats.

A

Saturated fatty acids do not have any double bonds, whereas unsaturated ones do. This means that the saturated fats are more linear in shape, allowing them to be compacted tighter. The bent shape of unsaturated fats limits how tightly it compacts, meaning that enzymes can easily get into the gaps and break the molecule down. The intermolecular forces in saturated fats are much stronger (due to proximity), which makes the bonds harder to break.
Room temperature= saturated - solid, unsaturated - liquid

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4
Q

How are cis and trans unsaturated fats different?

A

Cis - hydrogen on same side either side of the double bond = more repulsion, more bent in shape

Trans - hydrogen on opposite sides = less repulsion, more straight in shape and therefore acts more like a saturated fat

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5
Q

Discuss peptide bonds.

A
  • forms between the amino group of one molecule and the carboxyl group of another
  • dehydration reaction
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6
Q

What are the 3 different components of amino acids?

A
  1. N terminus = the amino end (-NH2)
  2. C terminus = carboxyl end (-COOH)
  3. R group = different for each amino acid, determines different properties

All are connected to the alpha carbon in the centre. Also has a single hydrogen attached to it, completing carbons’ outer ring.

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7
Q

Describe the 4 different structures of a protein.

A
  1. Primary = the amino acid sequence
  2. Secondary = folding and coiling of polypeptides due to the charged properties of the R group
  3. Tertiary = globular configuration, folding of the folds
  4. Quarternary = the combination of multiple polypeptides to form a complete protein
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8
Q

What are the 5 nucleotides and what are they made of?

A

Adenine, guanine, cytosine, thymine and uracil (RNA only - replaces T)
Purines = A & G
Pyrimidines = U,T and C
Made up of:
A phosphate group, a pentose sugar and a nitrogenous base

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9
Q

Describe the bonding between nucleotides.

A

A binds to T (or U)
C binds to G
The 2 strands of DNA are held together by hydrogen bonds between the nucleotides. A-T has two hydrogen bonds, whereas C-G has three, making it a stronger bond and harder to break.

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10
Q

Where, and when, does DNA replication occur?

A

The cell replicates it’s DNA before beginning the division process
Where:
- prokaryotes = cytoplasm
- eukaryotes = nucleus

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11
Q

Discuss the role of the enzymes topoisomerse and helicase in DNA replication.

A

Topoisomerase - relieves the supercoiled DNA and prevents supercoiling during replication

Helicase - ‘unzips’ the DNA by breaking the hydrogen bonds between the nucleic acids of each strands ahead of the replication fork

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12
Q

Discuss the role of primase and polymerase III in the DNA replication process.

A

Primase - synthesises short RNA molecules that work as primers, which work as the starting point of replication

Polymerase III - starting from the primers, it copies each strand. It is a continuous process on the leading strand, but broken up into Okazaki fragments on the lagging strand

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13
Q

What is the role of Polymerase I and Ligase in DNA replication?

A

Polymerase I - replaces the RNA primers with DNA nucleotides

Ligase - joins everything up - joins the Okazaki fragments together in the lagging strand.

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14
Q

Why is the replication on the lagging strand not continuous?

A

Lagging strand = 5’ to 3’, therefore replicated strand must be 3’ to 5’, however polymerase III can only build in the 5 to 3 direction, therefore it has to keep returning to the replication fork, meaning little gaps are left in between sections (Okazaki fragments)

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15
Q

What is the role of the Golgi apparatus?

A

Packages proteins and lipids into vesicles for delivery to specific locations

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16
Q

What is the central dogma?

A

Process of: DNA > RNA > Protein

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17
Q

What is Gibbs free energy (G)?

A

The amount of energy in a system that can be used to do work while pressure and temperature are constant.
Delta G = G initial - G final

18
Q

Describe the differences between endergonic and exogonic reactions as well as catabolic and anabolic?

A

Exergonic and Catabolic = negative delta G
These reactions break down molecules and release energy

Endergonic and anabolic = positive delta G
These reactions synthesise molecules and therefore need to consume energy

19
Q

What is the role of an enzyme and activation energy in metabolic reactions?

A

Activation energy is a barrier that must be overcome in order for the reaction to proceed.
Enzymes assist by lowering the activation energy, meaning it is easier to overcome and therefore quicker.

20
Q

What are coupled reactions?

A

Reactions that need energy (anabolic / endergonic) coupled with ones that release energy (catabolic / exergonic) to allow the process to occur. For example.. DNA polymerisation

21
Q

What is the electron transport chain?

A 
Byproducts of sugar metabolism donates high energy electrons to the electron transport chain. As the electrons move along the chain, they release energy and create a proton gradient across the inner mitochondrial membrane.
Once the electrons have travelled down the chain, the final electron acceptor is oxygen, which binds to hydrogen to fork water.  
Uses NADH (complex 1) which donates its electron and becomes NAD+
Complex 2 uses FADH2 which donates electrons to become FAD 
Donation of electrons = oxidation
22
Q

What would stop oxidative phosphorylation from happening?

A
  • no NADH or FADH2 present

^ no need these to donate their electrons to allow the entire process to occur

23
Q

What is chemiosmosis

A

The ATP synthase that uses the proton gradient across the inner membrane of the mitochondria to produce high amounts of ATP.
The protons travel down their gradient through atp synthase, and this energy is used to catalyse ADP becoming ATP. The massive proton gradient produced by the electron transport chain means the ATP output is very large.

24
Q

What is oxidative phosphorylation?

A

Electron transport chain + chemiosmosis = oxidative phosphorylation

25
Q

What are the first 2 stages of mitosis after interphase?

A

Please Pee on the MAT

Prophase - chromosomes start to condense and the mitotic spindle begins to form

Prometaphase - mitotic spindle microtubules grows and begins to ‘capture’ chromosomes
- the nuclear membrane starts to break down

26
Q

What happens during interphase / the cell cycle?

A

G1 - checks the cell has enough resources to replicate, and that replication is necessary
#
S - DNA duplicates
G2 - checks the quality of the DNA before the cell enters the M phase and prepares for division
M - mitosis stage - checkpoint ensures the chromosomes are correctly attached to the spindle to ensure even distribution into the daughter cells

27
Q

What are the third and fourth stages of mitosis?

A
  1. Metaphase - the chromosomes on the spindle line up in the middle of the cell
  2. Anaphase - sister chromatids are pulled apart, to opposite poles of the cell
    - this is controlled by microtubeles contraction, and ensures there is identical copies of the genetic material at each pole of the cell.
28
Q

What is the final stage of mitosis?

A
  • telophase - the cell splits into two by cytokinesis, each with a set of chromosomes
    Cytokinesis is the physical splitting of the cell, which occurs by action forming a ring around the middle of the cell and contracting, thereby pinching the cell to form a cleavage furrow
29
Q

Why do different cells divide at different rates?

A

It is relative to their function.
E.g. nerve cells do not continually divide, as this would interrupt the neurotransmitters
Skin cells also do not regularly divide, but can do so in response to injury - needs to provide a stable barrier from the outside

30
Q

What is PCR?

A

Polymerase Chain Reaction
A method used by scientists to create billions of copies of a specific DNA sample
It is very fast, precise and efficient
The amount of DNA increases exponentially. 2^n where n = number of cycles

31
Q

What are the 3 stages of PCR?

A
  1. Denaturation
    Heat is applied which seperates the DNA double helix into single strands. The heat breaks the hydrogen bonds
  2. Annealing
    Short DNA primers attach to the single stranded DNA
  3. Extension
    The new DNA strand is extended as a DNA Taq Polymerase incorporates new dNTPS (nueleotides) to reform the double stranded DNA
32
Q

Which enzymes involved in regular mitosis are not required for PCR?

A
  1. Helicase and topoisomerase - the DNA is separated using heat
  2. Ligase - no Okazaki fragments
  3. DNA Primase - primers are added into the PCR so not needed
33
Q

Explain cyclin and CDK

A

Cyclin - regulatory unit
CDK - Cyclin dependent kinase
When these two bind together, they are activated and form MPF (Maturation promoting factor). MPF concentration allows the cell to pass the G2 checkpoint and continue to M phase

34
Q

Explore the concentration of MPF throughout the cell cycle.

A

Cyclin production begins during S phase
Continues to increase during G2 and M. Once M is over, MPF breaks down and cyclin is degraded p, leaving CDK inactive. CDK does not get degraded, but rather recycled, so the cell can preserve some energy

35
Q

What is cancer?

A

Uncontrolled proliferation / division of cells

36
Q

What is an oncogene?

A

Proto-oncogene = a gene that promotes cell division

Oncogene = when a proto-oncogene isn’t ‘turned off’ at the right time, it becomes an oncogene

37
Q

What is a tumour suppressing gene (TSG)?

A

A gene that typically inhibits cell division. If mutated, can lead to cancerous division

38
Q

What is the role of p53 and how can it lead to cancer?

A
  • typically, this TSG induces apoptosis if the DNA cannot be repaired
    If mutated, the cells with damaged DNA are allowed to continue to proliferate, potentially leading to tumorous growths
39
Q

How can cancer drugs work?

A

Inhibit certain stages of the cell cycle to stop rogue division.

40
Q

What is RNA Splicing?

A

Splicing removes the introns (non-coding region) of a DNA segment.
It cuts the intron out, and rejoins the exons using an enzyme

41
Q

What is alternative splicing?

A

The splicing and rearranging of introns and exons, altering the function of the mRNA and resultant protein

BIOL1020 (4 decks)

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