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Ellie's Medical Cell Biology And Genetics > Sesh 1: Cell Ultrastructure and Function > Flashcards

Sesh 1: Cell Ultrastructure and Function Flashcards

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1
Q

When viewed under an electron microscope, heterochromatin in the nucleus appears ____ and euchromatin appears ____.

A
  1. Dark

2. Light

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2
Q

How can the structure of euchromatin be described?

A

As beads on a string. More unfolded structure than heterochromatin, therefore DNA is available for transcription and translation- genes are expressed.

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3
Q

How can the structure of heterochromatin be described?

A

In a solenoid 30nm fibre form. Genes are not expressed, as the DNA is tightly wrapped.

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4
Q

What is a nucleosome?

A

DNA wrapped around a histone protein core. Resemble ‘beads on a string’.

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5
Q

What is a solenoid?

A

It is formed by the coiling of the ‘beads on a string’- nucleosomes linked by linker DNA.

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6
Q

Define the limit of resolution.

A

The minimum distance at which 2 objects can be distinguished as separate.

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7
Q

The limit of resolution is directly proportional to the __________________.

A

Wavelength i.e. As wavelength decreases, resolution improves

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8
Q

How do prokaryotic cells differ from eukaryotic cells?

A
  1. No separate nucleus
  2. Cell wall
  3. No internal membranes- all biochemical processes of the cell occur in the same compartment.
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9
Q

What is the glycocalyx?

A

A glycoprotein-polysaccharide coating on the plasma membrane of some cells, involved in cell recognition.

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10
Q

What model describes biological membranes?

A

The fluid mosaic model. Describes the lipid bilayer and proteins embedded within it.

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11
Q

How do the RER and SER differ in structure?

A

The RER has flat cisternae with ribosomes on the surface.

The SER is tubular and has no ribosomes.

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12
Q

What are the functions of the Golgi apparatus?

A
  1. To modify, sort, concentrate and package proteins made on the RER.
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13
Q

From which face are vesicles secreted from the Golgi apparatus?

A

The trans face.

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14
Q

Which face of the Golgi is closest to the RER?

A

The cis face.

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15
Q

What is the function of lysosomes?

A

Produced by the Golgi apparatus, and contain hydrolytic enzymes to fuse with material to digest it within an acidic pH.

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16
Q

What’s the function of peroxisomes?

A

Detoxification of long chain fatty acids e.g. Alcohol, phenols, formic acid and formaldehyde via beta oxidation reactions, as contain catalases. Therefore abundant in the liver.

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17
Q

Folds of the mitochondrial inner membrane are called _________.

A

Cristae.

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18
Q

What are on the inner mitochondrial membrane?

A

Enzymes for the oxidation reactions of the respiratory chain.

19
Q

In steroidogenic cells, mitochondrial cristae are typically ________.

A

Tubular.

20
Q

Mitochondria contain their own ___ and can _________.

A
  1. DNA

2. Divide

21
Q

What’s the primary function of mitochondria?

A

To generate ATP by oxidative phosphorylation. They are the site of the cell’s energy production.

22
Q

What protein are microfilaments made of and where are they normally distributed?

A

Made of actin, and mainly found cortically. Run through cell and upwards.

23
Q

What are microtubules?

A

Long hollow cylinders of tubulin. Help give shape and movement of structures and found in e.g. Mitotic spindle, cilia and flagella.
They are the biggest cytoskeletal component.

24
Q

How are microtubules arranged in a cilium or flagellum?

A

In a ‘9+2’ arrangement. 2 central singlet microtubules are surrounded by 9 outer doublet microtubules.

25
Q

Is there more euchromatin or heterochromatin in the nucleus?

A

Euchromatin- more, the more active the cell is in gene expression.

26
Q

Once made by ribosomes on the RER, proteins go into the ___________ _______.

A

Intracisternal space of the RER.

27
Q

What is the difference between constitutive and regulated secretion?

A 
Constitutive= contents released straight away.
Regulated= requires signal for secretion.
28
Q

What is the difference between primary and secondary lysosomes?

A

Primary- contain hydrolytic enzymes.

Secondary- already fused with bacterium and hydrolysed it.

29
Q

What is the endosymbiosis theory?

A

Proposes that mitochondrion were formed when an ancestral eukaryote endocytosed an external bacterium (prokaryote).

30
Q

What proteins make up intermediate filaments?

A

Can be various proteins, e.g. Keratin- gives strength.

31
Q

What can mutations in keratin lead to?

A

Blistering diseases- skin loses strength and epidermis comes away from the dermis.

32
Q

What is meant by the term ‘amphipathic’?

A

Part of the molecule is hydrophilic, and part is hydrophobic.

33
Q

Give 2 definitions of pH.

A
  1. -log [H+]

2. Measurement of hydrogen ions, giving a value between 1-14, indicating whether a substance is an acid or base.

34
Q

Why do metabolically active tissues cause a localised decrease in blood pH?

A

Aerobic respiration produces H+ and CO2, which dissolves in blood to form carbonic acid.
If respiring anaerobically, tissues produce lactate.

35
Q

How can hyperventilation cause an increase in blood pH (alkalosis)?

A

Breathing out more CO2 than is being produced by cells, so less CO2 dissolved in the blood (hypocapnia).

36
Q

What effect would pulmonary obstruction e.g COPD have on blood pH?

A

Less CO2 would be blown off than is being produced, so CO2 builds up and forms more carbonic acid, which dissociates into H+, giving rise to an acidosis.

37
Q

Lysosomes appear _______ on an electron micrograph, as they are _________ _________.

A
  1. Dark
  2. Electron
  3. Dense
38
Q

What are the main functions of the SER?

A

Steroid hormone, lipid and phospholipid synthesis, and metabolism.

39
Q

Cytoplasmic extensions and lysosomes aid what cellular function?

A

Phagocytosis.

40
Q

What type of vesicles arrive at the Golgi’s cis face?

A

Protein vesicles from the ER, to be processed.

41
Q

What type of vesicles emerge from the Golgi’s trans face?

A

Secretory vesicles.

42
Q

Where in the body may SER be abundant?

A
  • Adrenal cortex (production of mineralo/glucocorticoids)
  • Testes (production of testosterone)
  • Skeletal and cardiac muscle (sarcoplasmic reticulum=specialised form of SER- Ca2+ storage and release)
43
Q

What is pinocytosis?

A

The ingestion of substances into a cell by the budding of small vesicles from the cell membrane.

Ellie's Medical Cell Biology And Genetics (12 decks)

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