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Histology Lecture 2 Cell Structure and Division > Histology Cell Structure and Division > Flashcards

Histology Cell Structure and Division Flashcards

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1
Q

What is a Cytoskeleton?

A

A highly dynamic (changes rapidly) system of protein filaments in the cytoplasm of a eukaryote that gives the cell a polarized shape and the capacity for directed movement

The supporting mechanism for the cell

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2
Q

What is diapedesis?

A

The crawling of cells along a surface

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3
Q

What are the functions of the cytoskeleton?

A

Responsible for:

Large-scale cellular movements such as the crawling of cells along a surface

Contraction of muscle cells

Changes in cell shape that accompany embryonic development

Provides machinery for intracellular movements

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4
Q

What are the 3 intracellular movements that involve the Cytoskeleton?

A

Transport of organelles from one place to another

Segregation of chromosomes into 2 daughter cells (mitosis)

Pinching apart of animal cells at cell division

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5
Q

What are the three types of protein filaments within the cytoskeleton?

A

Microtubules

Intermediate Filaments

Actin Filaments

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6
Q

What are the characteristics of Microtubules?

A

They are…

long stiff, cylindrical intracellular structures

20nm diameter

composed of tubulin protein

grow out of the centrosome and create a system of tracks for vesicles, organelles and other cells components to move through

Utilize motor proteins for movement of organelles

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7
Q

What are motor proteins?

A

proteins that bind to organelles within a cell and move them along microtubules (and sometimes actin filaments)

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8
Q

What are the characteristics of Intermediate Filaments?

A

Intermediate in size

10nm in diameter

Stable rope-like polymers

Made of fibrous proteins which give mechanical strength

STRONGEST OF THE 3 CYTOSKELETON PROTEINS!

Also found in the nucleus under the nuclear envelope (forming the nuclear lamina)

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9
Q

Which type of protein filament is rope-like and forms a nuclear lamina under the nuclear envelope of a cell - therefore strengthening the envelope?

A

Intermediate filaments

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10
Q

True or False

Protein filaments participate in cell junctions

A

True

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11
Q

What are the characteristics of Actin Filaments?

A

Small

7nm in diameter

made of filamentous protein

formed from a chain of globular actin molecules

Found in cross-linked bundles and networks (stronger)

Forms cell cortex

used in muscle contraction

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12
Q

What are integrins?

A

Cell surface receptors that attach cells to the extracellular matrix and mediate mechanical and chemical signals

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13
Q

Which protein filament type forms the cell cortex?

A

Actin Filaments in a network of cross-linked bundles

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14
Q

What are Cell Inclusions?

A

temporary structures in cells that can be cell products or ingested material

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15
Q

What are the 4 types of cell inclusions?

A

Glycogen

Lipids

Pigment Granules

Secretory Granules

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16
Q

What is glycogen?

A

a large branched polysaccharide found in the cytoplasm of several cell types including liver and muscle

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17
Q

What are lipids?

A

non-membrane bound droplets in the cytoplasm that vary in size

Require special stain to see with LM

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18
Q

What are the 2 types of lipid cell inclusions?

A

Neutral

Metabolic

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19
Q

Give an example of Neutral Lipid Cell Inclusions and where they are found in the body

A

Triglycerides

stored in adipose tissue

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20
Q

Give an example of metabolic lipid cell inclusions and where they are found in the body

A

Steroids as a substrate for estrogen or cortisol

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21
Q

What are pigment granules?

A

Melanin (to block UV damage)

heme (oxygen transport)

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22
Q

What are secretory granules?

A

membrane bound vesicles that contain inactive enzymes, proteins and neurotransmitters

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23
Q

Which organelle is the most prominent in the eukaryotic cell and contains DNA organized into chromosomes?

A

Nucleus

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24
Q

What is the nuclear envelope?

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A

The envelope surrounding the nucleus which consists of 2 lipid bilayer membranes and is perforated by nuclear pores

the membranes are continuous with the ER (although structurally different)

25
What is the nuclear lamina?
a network of protein filaments that support the nuclear envelope
26
What do the nuclear pores on the nuclear envelope do?
Actively transport selected molecules to and from the cytoplasm
27
What is the Nucleolus?
the region of the nucleus where different chromosomes carrying genes for ribosomal RNA cluster (1 per nucleus) Contains both granular and fibrous material
28
What is chromatin?
A complex of DNA, histones and nonhistone proteins from which chromosomes are made
29
Is chromatin basophilic or acidophilic? In other words how will it stain?
basophilic
30
What are the 2 types of chromatin?
Heterochromatin Euchromatin
31
What is heterochromatin?
a highly condensed form of interphase chromatin which is transcriptionally inactive Stains very intensely!
32
What is euchromatin?
the least condensed extended state of chromatin known as active chromatin - transcriptionally active Stains very lightly!
33
What are the characteristics of a Leptochromatic Nucleus?
Mostly Euchromatin Actively Metabolically and Mitotically
34
What are the characteristics of a Pachychromatic Nucleus?
Mostly Heterochromatin Not very active metabolically
35
What is the cell cycle?
the reproductive cycle of the cell - the orderly sequence of events by which a cell duplicates its contents and divides into two.
36
In order for a eukaryotic cell to divide into two, the two into four, etc. two processes must alternate... What are these two processes?
doubling: doubling of DNA in S phase of the cell cycle halving: of that genome during mitosis (M phase)
37
What are the 4 stages or broad phases of the cell cycle?
M phase G1 Phase S Phase G2 Phase
38
What happens during M phase of mitosis?
Chromosomes are condense Nucleus and cytoplasm divide
39
What is the division of the nucleus in M phase called?
mitosis
40
What is the division of the cytoplasm in M phase called?
cytokinesis
41
What happens during G1 phase of the cell cycle?
also called the gap phase, it's the interval between completion of mitosis and the beginning of S phase
42
What happens during G2 phase of the cell cycle?
It's the interval between the end of S phase and the beginning of mitosis
43
What are the G1, S and G2 phases (together) termed?
interphase
44
What is the purpose of interphase (G1, S and G2)?
to allow the cell additional time to grow and duplicate its centrosomes
45
What are the 6 stages of Mitosis?
Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis
46
Summarize the events of Prophase
1st Stage of Mitosis Chromosomes are condensed but not yet attached to the mitotic spindle
47
Summarize the events of Prometaphase
Starts with the disassembly of the nuclear envelope Microtubules from the mitotic spindle bind to specialized protein complexes (kinetochores) and capture chromosomes
48
Summarize the events of Metaphase
The chromosomes align along the equatorial plate of the spindle
49
Summarize the events of Anaphase
connections between sister chromatids are cut by proteolytic mechanisms Daughter chromosomes migrate to opposite poles of the spindle
50
Summarize the events of Telophase
Final stage of mitosis Nuclear envelope re-assembles around each group of chromosomes to form two daughter nuclei Nucleus expands and the condensed chromosomes decondense into their interphase state
51
Summarize the events of cytokinesis
Process by which the cytoplasm is cleaved in two Begins in anaphase involves a transient structure made of actin filaments (contractile ring) contractile ring attaches to the membrane-associated proteins on the cytoplasmic face of the membrane
52
What are the main players in animal cells in relation to the cell cycle?
Early Response Transcription Factors like c-fos and c-jun Cyclins (G1, S-phase, and M-phase cyclins) - which rise and fall with the stages of the cell cycle CDKs (G1 CDKs, S-phase CDKs, M-phase CDKs) - levels remain fairly stable, each must bind to the appropriate cyclin in order to be activated Cell cycle checkpoints
53
What can happen if cells progress to the next phase of the cell cycle before the previous phase is properly completed?
Catastrophic genetic damagge can occur
54
What is the purpose of a cell cycle checkpoint?
Control mechanisms at such checkpoints make sure the cell progresses through the cell cycle - completing each step in order (otherwise castastrophic genetic damage can occur)
55
What do mitogens do in the cell cycle?
They stimulate cells to enter G1
56
Summarize the initial (pre-replication) steps of the cell cycle including major players (factors, cyclins, CDKs and checkpoints)
Early response genes are induced and encode transcription factors such as c-Fos and c-Jun - which stimulate transcription of the delayed-response genes such as cyclins and CDKs. Mitogens form - which stimulate cells to enter G1 Combination of the two above drive cell past the restriction point Cell now committed to complete the entire mitotic division
57
Summarize the events of the cell cycle including the major players (cyclins, factors, etc) after the initial early-response gene induction ---\> restriction point
A rising level of G1 cyclins signals cell to prepare for replication Checkpoint - if DNA damaged process will halt until repaired Rising level of S-phase promoting factor (SPF) prepares cell to enter S phase and duplicate DNA and centrioles S-phase cyclins degraded M-phase promoting factor inititates assembly of mitotic spindles, breakdown of the nuclear envelope, condensation of the chromosomes (metaphase) Checkpoint - if DNA damaged process will halt until repaired Checkpoint - improper assembly of mitotic spindle leads to arrest in anaphase M-phase promoting factor also activates the anaphase promoting complex (APC) which allows sister chromatids at the metaphase plate to separate and move to poles
58
What was the term "tumor" formerly used to denote?
any localized swelling in the body caused by inflammation or abnormal cell proliferation Now we use it as a synonym for neoplasm
59
What are neoplasms?
abnormal mass of tissue formed by uncoordinated cell proliferations Can be benign or malignant depending on their growth rate and invasiveness

Histology Lecture 2 Cell Structure and Division (1 decks)

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