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Biol112 > Week 2 > Flashcards

Week 2 Flashcards

1
Q

What is the role of the smooth endoplasmic reticulum ?

A

Most cell types have relatively little smooth ER (SER)

•Phospholipid, fat and steroid (including sex hormones) manufacturer
•Carbohydrate metabolism

•In hepatocytes, breaks down stored glycogen to release glucose

•Detoxifies lipid-soluble drugs such as barbiturates
–Adds charged water-soluble groups such as sulphate or glycuronic acid

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2
Q

Describe the sarcoplasmic reticulum

A

Found in muscle cells

➢Network of tubular sacs

➢Transmits electrical signals

➢Sequesters calcium ions from the cytosol

➢The level of intercellular calcium regulates muscle contraction in muscle cells.

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3
Q

What zone shortens within a sarcomere during contraction ?

A

The H zone/line

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4
Q

What does the release of Ca2+ do in muscle contraction ?

A

Ca2+ causes a conformational change in troponin, changing of position of tropomyosin, allowing myosin to bind to its binding sites on actin

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5
Q

What is the motor end plate in muscle cells?

A

It receives the electrical signal, before it travels to the SR and Ca2+ is released

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6
Q

What do proteins have to have to do with

A
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7
Q

What does a ribosome require of the desired protein (the mRNA) for it to attach to the RER?

A

A specific signal peptide sequence

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8
Q

What is glycosylation ?

A

The addition of sugars or oligosaccharides

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9
Q

What face is the receiving side of the Golgi ?
Which is it exit face ?

A

Cis face
Trans face

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10
Q

Why is glycosylation important for mucus ?

A

The long oligosaccharide chains are essential for a highly hydrated gel like material

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11
Q

What was found when respiratory cells were looked at in healthy and cystic fibrosis patients ?

A

There was a lot more mucus in CF patients (more marker MUC5AC in airway )
There was more epithelial B-tubulin in airway of healthy person , less in CF

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12
Q

Roughly how many hydrologic enzymes do lysosomes use ?
What happens when a lysosome fuses with a target ?

A

60
H+ ions pumped into secondary lysosomes to bring down the pH and activate the enzymes

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13
Q

What is an example of a disease , which is caused by a lysosome disease?

A

Tay-Sachs - deficiency in hexosaminidase A enzyme leads to the accumulation of the lipid ganglioside , in nerve cells , usually die by 2-3 years old

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14
Q

What are the types of endocytosis ?

A

Phagocytosis
Pinocytosis
Receptor mediated endocytosis

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15
Q

For protein synthesis in the RER what is the signal sequence cleaved off with ?

A

The enzyme signal peptidase

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16
Q

What similarities are there between mitochondria and bacteria ?

A

Own circular genome
Double membrane
Similar in size to prokaryotic cell
Divide by binary fission

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17
Q

What type of cell contains around 2500 mitochondria when most have several hundred?

A

Liver cells

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18
Q

How are mitochondria moved inside cells?

A

They are moved by the microtubules of the cytoskeleton

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19
Q

What is the major protein component of the outer membrane of mitochondria ?

A

Porin —-> large aqueous channels

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20
Q

What are the 3 major types of membrane complexes in the inner mitochondrial membrane ?

A
  1. Electron transport chain
  2. ATP synthase
  3. Specific transporters of metabolites which vary according to cell/tissue type
21
Q

What does the mitochondrial matrix contain ?

A

Enzymes which catalyse Krebs cycle and fatty acid oxidation
Ribosomes
Mitochondrial DNA

22
Q

What type of phosphorylation does glycolysis generate?

A

Substrate level phosphorylation

23
Q

Why is cyanide one of the most dangerous and fast acting poisons ?

A

It blocks the passage of electrons from one of the cytochromes thereby blocking the electron transport chain

24
Q

Why is 2,4-Dinitrophenol so dangerous (DNP)?

A

makes the inner membrane leaky to H+ so that a gradient cannot be established
electron transport chain still works but energy is released as heat
“ Cooks “ you from the inside

25
Q

Describe how ATP drives muscle contraction briefly

A

1)Myosin cross bridge attaches to the actin myofilament
2)ADP and Pi released. Working stroke - myosin head pivots and bends as it pulls on the actin filament , sliding it towards the M line
3) as new ATP attaches to the myosin head pivots, the cross bridge detaches
4) As ATP is split into ADP and Pi, cocking of the myosin head occurs, allowing more power strokes to occur

26
Q

Where do the high energy electrons used by mitochondria derive from ?

A

Organic molecules

27
Q

Does FADH2 or NADH transfer electrons at a higher energy level ?

A

NADH

28
Q

What is attached to many of the proteins in the electron transport chain ?

A

Prosthetic groups

29
Q

What is the Fo portion of ATP synthase?
F1 portion ?

A

An H+ channel
Site of ATP synthesis

30
Q

What does movement of H+ through Fo do?

A

Causes rotation of the rotor and central stalk , while the stator keeps the enzymatic F1 stationary
Forces sequential conformational changes in the central stalk and F1. Provides the energy for ATP synthesis. 10H+ moving back into the matrix generates around 3 ATP molecules

31
Q

What is the function of the mitochondria in brown fat ? Which people is it found in large quantities?

A

To produce heat
In newborn babies

32
Q

What is MERRF?
What gene is the mutation in ? So affects what ?
Which system does it primarily affect ?

A

Myoclonic epilepsy and ragged-red fibre disease
Mitochondrially encoded tRNA Lys gene . Proteins encoded by the mitochondria
Multi system disease but mainly affects muscles and nerves—-> epilepsy and general muscle weakness

33
Q

What new IVF technique has been developed which avoids passing on defective mitochondria?

A

The embryo has 3 genetic parents

34
Q

What are grana composed of ?

A

Individual thylakoid membranes

35
Q

What wavelengths work most efficiently for photosynthesis?

A

Those of red and blue light

36
Q

In chlorophyll a and b what part is the light absorbing ‘head’ of the molecule ?

A

Porphyria ring

37
Q

What is the only difference between chlorophyll an and b ?

A

The chlorophyll has a CHO in chlorophyll b and CH3 in chlorophyll a

38
Q

What happens when light hits a chlorophyll molecule and there are pigments adjacent to it?

A

The excited electrons cause energy to be released as heat or fluorescence whereas if no adjacent pigments , the electrons fall back to the ground state

39
Q

What wavelength is photosystem 1 best at absorbing ? What’s it name ?

A

700nm, reaction centre is called P700

40
Q

Ideal wavelength for photosystem 2? Name ?

A

680nm , p680

41
Q

Which photosystem cannot split water?

A

PS1

42
Q

The cyclic electron flow only produces what molecule ?

A

ATP

43
Q

In the Calvin cycle , what does Carbon enter in the form of ? What does it leave in the form of ?
What is the energy source?
What is the source of high energy electrons ?

A

CO2
Sugar
ATP
NADPH

44
Q

What does the Calvin cycle produce ?

A

Hexose phosphates for starch (storage )
Cellulose ( cell walls )
Sucrose (translocations )
Lipids (cell membranes )
Amino acids (protein synthesis)

45
Q

What do the carriers become progressively more of in the electron transport chain ? Which carriers are very similar in mitochondria and chloroplasts ?

A

More electro-negative
Quinones and cytochromes

46
Q

What is one reason why mitochondria and chloroplasts have similar characteristics ?

A

Both are thought to have evolved from bacteria via the endosymbiotic theory

47
Q

What are the components of the cytoskeleton ?

A

Intermediate filaments
Spindle fibres
Microfilaments and microtubules
Actin filaments

48
Q

What are some examples of membrane proteins ?

A

Transport channels
Hormones
Receptors
Enzymes
Antigenic markers

49
Q

What is a kinetochore ?

A

A protein complex at the centre of sister chromatids

Biol112 (4 decks)

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