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Histology > Lecture 1: Cell Structure > Flashcards

Lecture 1: Cell Structure Flashcards

1
Q

What is a cell?

A

It is the basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane

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2
Q

Define tissue

A

it is an organized assembly of specialized cells subserving a generalized function

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3
Q

What is histology?

A

the study of tissues?

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4
Q

What is a system?

A

it consists of several organs whose functions are interrelated

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5
Q

What is an example of a system?

A

the urinary system which is composed of the kidneys, ureters, bladder, etc.

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6
Q

What are the basic components of a cell?

A

the plasma membrane, the nucleus, the cytoplasm, and the cytoskeleton

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7
Q

Define Plasma Membrane

A

a biomolecular leaflet of phospholipids between two protein coats

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8
Q

Define Nucleus

A

it is the most prominent organelle in a eukaryotic cell and is enclosed by two concentric membranes that form the nuclear envelope

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9
Q

What is the nuclear envelope made up of?

A

two layers of phospholipid

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10
Q

Define cytoplasm

A

it is the transparent substance around the nucleus that fills the rest of the cell’s interior

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11
Q

What makes up the cytoplasm?

A

it consists of cytosol and a large number of membrane bound organelles

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12
Q

Why does the cytosol behave more like a water-based gel than a liquid?

A

it contains a host of large and small molecules that crowd together closely

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13
Q

Define cytoskeleton

A

It is a system of protein filaments in the cytoplasm of the eukaryotic cell that gives a cell a polarized shape and the capacity for direct movement

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14
Q

What are the cytoskeleton’s most abundant components?

A

actin filaments, microtubles, and intermediate fiaments

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15
Q

Why are the protein filaments important?

A

they are responsible for maintain/changing the plasma membrane of the cell

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16
Q

What is the lipid bilayer of a protein comprised of?

A

phospholipid molecules with hydrophobic tails pointing inward and hydrophilic heads pointing outward

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17
Q

What are some examples of membrane proteins?

A

transporters, linkers, receptors, and enzymes

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18
Q

What is significant about membrane proteins?

A

carries out most membrane functions

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19
Q

What reinforces the plasma membrane?

A

the cell cortex

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20
Q

What is the cell cortex?

A

a specialized layer of cytoplasm consisting of a meshwork of fibrous proteins that is attached to the inner face of the plasma membrane

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21
Q

Define glycocalyx

A

a sugar coating of oligosaccharides and polysaccharides found on the exterior of the cell membrane

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22
Q

What is significant about a glycocalyx?

A
  1. it appears as a “fuzzy coat” at the ultrastructural level
  2. serves to protect and lubricate the cell, may contain enzymes(intestine)
  3. Is important in cell-cell recognition and adhesion
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23
Q

Define a ribosome

A

They are 10-20nm cytoplasmic particles composed of ribosomal RNAs and ribosomal proteins that associate with messenger RNA and catalyze the synthesis of proteins

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24
Q

Where are ribosomes found?

A

in clusters as polyribsomes or associated with membranes of the ER

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25
Q

Why are ribosomes important?

A

ribosome biogenesis and translation are regulated at multiple levels and are associated with accurate cell growth and proliferation.

26
Q

What are signal sequences?

A

a relatively short amino acid sequence that directs a protein to a specific location within a cell (to a particular organelle)

27
Q

How many amino acids does a signal sequence contain?

A

15-60

28
Q

What are two other names for a signaling sequence?

A

a signal peptide or a targeting sequence

29
Q

What is significant about the amino acid sequence in a signaling sequence?

A

it isn’t so much important what the sequence of the amino acids are but where the charged amino acids appear in the sequence

30
Q

Define the Endoplasmic Reticulum

A

it is a membrane-bounded compartment in the cytoplasm of eukaryotic cells where lipids are secreted and membrane-bound proteins are made

31
Q

Define RER

A

rough ER; region of the ER associated with ribosomes that is involved in the synthesis of secreted and membrane-bound proteins

32
Q

Define SER

A

smooth ER; region of the ER not associated with ribosomes

33
Q

What are the three main functions of the SER?

A
  1. involved in the synthesis of lipids(steroids)
  2. metabolism of lipid soluble substances
  3. regulates the concentration of calcium in muscle cells
34
Q

What are the differences between the appearance of SER and RER when staining?

A

SER does not stain

35
Q

Define Golgi apparatus

A

it is a membrane bound organelle in eukaryotic cells where the proteins and lipids made in the ER are modified and sorted

36
Q

Where are the Golgi usually located?

A

in the cell nucleus but sometimes distributed throughout the cytoplasm

37
Q

What does the Golgi apparatus consist of?

A
  1. cisternae
  2. a cis face (or entry)
  3. an exit face (or trans)
38
Q

What are cisternae?

A

a collection of flattened, membrane-bound sacs, piled up like stacks of place in the Golgi Apparatus

39
Q

What are transport vesicles?

A

the mode of transport from the ER to golgi and the golgi to the other compartments of the endomembrane system

40
Q

What do golgi apparatuses look like with H&E and triple stains?

A

clear and referred to as the golgi vacuole

41
Q

Define lysosome

A

membranous sacs of hydrolytic enzymes that carry out the controlled intracellular digestion of both extracellular materials and worn-out organelles

42
Q

Three pathways involving lysosomes

A
  1. phagocytosis
  2. autophagocytosis
  3. hydrolytic enzymes
43
Q

Define phagocytosis

A

internalization of large particles like bacteria or of small macromolecules and the vesicles fuse with the lysosome

44
Q

Autophagocytosis

A

degradation of internal organelles

45
Q

Hydrolytic enzymes

A

secreted to digest extracellular components

46
Q

Why are lysosomal membrane proteins highly glycosylated?

A

the sugars, with cover much of the protein surfaces facing the lumen protect the proteins from digestion by the lysosomal proteases

47
Q

What are secondary lysosomes?

A

they are endosomes fused with primary lysosomes

48
Q

Define Autolysis

A

the digestion of cell contents when lysosomal membranes rupture(in the absence of oxygen) releasing the hydrolytic enzymes

49
Q

Define mitochondria

A

the chief energy source of the cell that are similar in size and shape to bacteria; they contain their own DNA and RNA and a complete transcription and translation system including ribosomes

50
Q

What is shape of mitochondria?

A

varies from rods to spheres

51
Q

How many membranes does mitochondria have?

A

two, an outer and an inner

52
Q

What is the inner membrane of mitochondria responsible for?

A

has tubular folds termed cristae that serve to increase its surface area for metabolic activity and is also the site of enzymes associated in electron transport and phosphorylation

53
Q

What is the outer membrane of mitochondria responsible for?

A

contains proteins involved in mitochondrial lipid synthesis and is permeable to all molecules of 5000 daltons or less

54
Q

The matrix of the mitochondria

A

large internal space containing highly concentrated mixture of hundreds of enzymes including those required for the oxidation of fatty acids an pyruvate during the citric acid cycle

55
Q

What is the function of the mitochondrial matrix granules?

A

to bind cations (especially CALCIUM)

56
Q

What are the main functions of mitochondria?

A
  1. ATP production and electron transport
  2. role in calcium sequestration
  3. participation in the apoptosis cascade that results in the neurodegeneration and cell death
57
Q

Define Proteasome

A

a large multifunctional protease complex in the cytosol that degrades intracellular proteins marked for destruction by attachment of multiple ubiquitin molecules.

58
Q

What is the function of a proteasome?

A

degrades a variety of endogenous protons including transcription factors, cyclins, proteins encoded by viruses and other intracellular parasites, and proteins that are folded incorrectly

59
Q

What is it important that proteasomes degrade cyclins?

A

they must be destroyed so that the next step of the cell cycle can occur

60
Q

Why is the ubiquitin-proteasome system significant?

A

essential for cell viability and abnormalities of the system can lead to degenerative diseases and some types of cancer.

61
Q

Structure of a proteasome

A

cossets of a core particle in the form of 4 rings and 2 regulatory particles that have binding sites to recognize the protein ubiquitin

62
Q

What happens to proteins that are destined for destruction?

A

they are bound to the ubiquitin molecule and unfolded by ATPases associated with the regulatory particle –> the unfold protein is translocated into the central cavity of the core particle –> several active sites in the core particle break various specific peptide bonds of the protein

Histology (4 decks)

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