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Fubmed > Cell biology > Flashcards

Cell biology Flashcards

1
Q

How is DNA stored in the nucleus?

A

Chromatin, DNA + Histones

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2
Q

Where does transcription occure?

A

Nucleus

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3
Q

What is the nuclear envelope compose of?

A

2 lipid bilayer membranes which surround the nucleus

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4
Q

What does each membrane layer of the nuclear envelope produce?

A

Inner layer- Nuclear lamina

Outer membrane- Continuous with the endoplasmic reticulum

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5
Q

What is heterochromatin?

A

Tightly packed form of DNA

Consists of genetically inactive sequences and many Gene’s are repressed

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6
Q

What is euchromatin?

A

Tightly packed form of chromatin
often under active transcription
92% of human genome is euchromatin

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7
Q

What is the location and function of the nucleolus?

A

sits in the nucleus
Makes rNA
Made of proteins, DNA, RNA

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8
Q

What is the nuclear pore? What is its function?

A

Protein complexes found on the nuclear envelope

Allows the transport of molecules across nuclear membrane:
e.g,
mRNA and ribosomal proteins to the cytoplasm

carbohydrates, signaling molecules and lipids into the nucleus.

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9
Q

What causes laminopathies?

A

When nuclear lamina is defective, Heterochromatin’, can be transcribed (usually inactive)

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10
Q

Give examples of laminopathies

A

muscular dystrophy and Progeria syndrome.

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11
Q

Describe the condition Progeria syndrome.

A

Premature ageing
Nuclear lamina is weakened
This limits the ability of the cell to divide.

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12
Q

What is the function of the rough ER and its ribosomes?

A

(Protein production)

Translates RNA into protein.
Labelles and sorts proteins
Foldes and modifies proteins

Synthesize proteins from amino acids to make peptides, then polypeptides and complete proteins.

Glycosylates proetins

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13
Q

Which conditions are caused by protein misfolding?

A

Cystic fibrosis,Type 1 diabetes, Alzheimer’s disease

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14
Q

What is the function of the smooth ER?

A
  1. Responsible for the synthesis and breakdown of lipids, synthesis of carbohydrates,
  2. Acts as a store for calcium.
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15
Q

Which conditions are caused by Disorder of smooth ER?

A

obesity & jaundice.

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16
Q

What is the function of the Golgi apparatus?

A

Stack of membranes that package and modify proteins from the rough ER into membrane bound vesicles

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17
Q

What is glycosylation? Where does it occure?

A

Attachment of sugar monomers to proteins.

Occurs in the Rough ER and golgi apparatus

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18
Q

what is the function of the plasma membrane?

A

Anchores the skeleton

Allows constant exchange of molecules between the cell and its surrounding

19
Q

Why is the plasma membrane described as a fluid mosaic?

A

Lipid molecules in the membrane are very mobile and constantly moving past one another

20
Q

What effect can receptors on the plasma cell membrane have on the nucleus?

A

They can signal changes in gene expression

21
Q

What is exocytosis?

A

Form of active transport as energy is required

Contents of a cell is released into the exterior through fusing with the cell membrane

22
Q

How do cells insert membrane proteins, ions channels , receptors and lipids onto the cell membrane?

A

Exocytosis

23
Q

What are the two types of exocytosis?

A

1) Ca2+ triggered non-constitutive (i.e., regulated exocytosis)
2) non-Ca2+ triggered constitutive (i.e., non-regulated).

24
Q

What is the difference between non-constitutive and constitutive exocytosis?

A

Constitutive- carried out by all cells and transfers molecules from the Golgi network to the outer surface of the cell
N
on-constitutive (regulated)- occurs in response to specific conditions (clathrine coat), signals or biochemical triggers, and is the process underlying the release of cytokines, hormones, neurotransmitters and other small signalling molecules

25
Q

What is endocytosis?

A

cell transports molecules (such as proteins) into the cell from the plasma membrane by engulfing them in an energy-using process.
The engulfed components are either broken down to simple components and recycled back to the surface or targeted for degradation by lysosomes

26
Q

What are lysosomes? What is there function?

A

vacuoles containing hydrolytic enzymes that break down biological material into its constituent parts to provide food for the cell
They can also fuse with phagocytes to digest material such as bacteria
So they:
Defense against disease.
Autophagy – clean up of organelles
Autolysis after cell death

27
Q

What is Lysosomal Storage Diseases?

A

A group of 50 rare inherited metabolic disorders.
Characterized by an abnormal build-up of various toxic materials in the body’s cells as a result of lysosomal enzyme deficiencies.
1 in 5000 live births
Life expectancy 15 years.

28
Q

Give an example of a Lysosomal Storage Diseases?

A

Tay Sachs disease

29
Q

What is the function of Peroxisome? Where does it originate from?

A

It breaks down very long chain fatty acids through beta-oxidation

Originates from the rough ER and contain 50 different enzymes

30
Q

What is the function of catalse?

A

An enzyme produced by peroxidase which breaks down the toxic hydrogen peroxide into water

31
Q

What are peroxisomes?

A

Sites of synthesis of several enzymes found in the liver and kidney

Those in the liver produce bile

32
Q

What produces bile in the liver?

A

Peroxisomes

33
Q

What is Peroxisome biogenesis disorder?

A

autosomal recessive developmental brain disorders that also result in skeletal and craniofacial dysmorphism, liver dysfunction, progressive sensorineural hearing loss, and retinopathy

34
Q

What are mitochondria?

A

organelles which take in nutrients, breaks them down, and oxidises them into ATP.

35
Q

How does the mitochondria initiate cell death?

A

Pores are formed in the inner mitochondrial membrane due to cellular damage.
Then the mitochondria releases cytochrome C to starts the apoptotic cascade

36
Q

What are Mitochondrial diseases, give examples

A

Present themselves as neurological disorders

e.g. Parkinson disease, cardiac dysfunction, heart failure and autism

37
Q

How does the mitochondria contribute to aging?

A

Leakage of the high-energy electrons in the respiratory chain with time forming reactive oxygen species. Oxidative stress leads to mitochondrial DNA mutation.

38
Q

What is the cytoskeleton?

A

network of three types of proteins:
1. Microfilaments (formed from actin);

  1. Intermediate filaments ( fibrous proteins with similar properties)
  2. Microtubules (formed from the tubulin).

Each filament associates with proteins to conduct function

They are responsible for the cells change in shape, position, and movement.

39
Q

Describe the structure and function of actin microfilaments

A

Thinest filament protein
Organised into bundles
Cores of actin filaments are bound by villin protein.

They support finger like projections of the cell membrane (filopodia and microvilli)

F-Actin and myosin cross-bridges in non-muscle cells supply the motile force involved in cell division, cell movement and the uptake of external material by cells (endocytosis).

40
Q

What do genetic diseases of actin microfilaments result in?

A

congenital hearing loss and skeletal and cardiac myopathies

41
Q

Describe the structure and function of Intermediate filaments

A

Provide strength
highly-tensile, yet flexible cables, that penetrate the entire cell.
Found in durable structures like hair, fingernails
10 mmin diameter

42
Q

Name of Intermediate filaments found in the nucleus, connective tissue, muscle cells nerve cells and skin

A 
Nucelus- Lamins
Connective tissue- Vimentin
Nerve tissue-Neurofilaments
Muscle tissue- desmins
Epethilal tissue- Keratins
43
Q

Consequence of mutations in keratin?

A

weaken skin causing blistering with the slightest contact from birth

44
Q

Describe the structure and function of Microtubules

A

20-25nm in diameter.
Hollow tube made from tubulin
Help to produce movment in flagella and cilia using dynein which links adjacent microtubules and allows the to side over each other

also form the framework of the mitotic spindle during chromosomes division.

Fubmed (13 decks)

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