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

Histology Cell Structure and Division Flashcards

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?

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
Q

What is the nuclear lamina?

A

a network of protein filaments that support the nuclear envelope

26
Q

What do the nuclear pores on the nuclear envelope do?

A

Actively transport selected molecules to and from the cytoplasm

27
Q

What is the Nucleolus?

A

the region of the nucleus where different chromosomes carrying genes for ribosomal RNA cluster (1 per nucleus)

Contains both granular and fibrous material

28
Q

What is chromatin?

A

A complex of DNA, histones and nonhistone proteins from which chromosomes are made

29
Q

Is chromatin basophilic or acidophilic? In other words how will it stain?

A

basophilic

30
Q

What are the 2 types of chromatin?

A

Heterochromatin

Euchromatin

31
Q

What is heterochromatin?

A

a highly condensed form of interphase chromatin which is transcriptionally inactive

Stains very intensely!

32
Q

What is euchromatin?

A

the least condensed extended state of chromatin

known as active chromatin - transcriptionally active

Stains very lightly!

33
Q

What are the characteristics of a Leptochromatic Nucleus?

A

Mostly Euchromatin

Actively Metabolically and Mitotically

34
Q

What are the characteristics of a Pachychromatic Nucleus?

A

Mostly Heterochromatin

Not very active metabolically

35
Q

What is the cell cycle?

A

the reproductive cycle of the cell - the orderly sequence of events by which a cell duplicates its contents and divides into two.

36
Q

In order for a eukaryotic cell to divide into two, the two into four, etc. two processes must alternate…

What are these two processes?

A

doubling: doubling of DNA in S phase of the cell cycle
halving: of that genome during mitosis (M phase)

37
Q

What are the 4 stages or broad phases of the cell cycle?

A

M phase

G1 Phase

S Phase

G2 Phase

38
Q

What happens during M phase of mitosis?

A

Chromosomes are condense

Nucleus and cytoplasm divide

39
Q

What is the division of the nucleus in M phase called?

A

mitosis

40
Q

What is the division of the cytoplasm in M phase called?

A

cytokinesis

41
Q

What happens during G1 phase of the cell cycle?

A

also called the gap phase, it’s the interval between completion of mitosis and the beginning of S phase

42
Q

What happens during G2 phase of the cell cycle?

A

It’s the interval between the end of S phase and the beginning of mitosis

43
Q

What are the G1, S and G2 phases (together) termed?

A

interphase

44
Q

What is the purpose of interphase (G1, S and G2)?

A

to allow the cell additional time to grow and duplicate its centrosomes

45
Q

What are the 6 stages of Mitosis?

A

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

Cytokinesis

46
Q

Summarize the events of Prophase

A

1st Stage of Mitosis

Chromosomes are condensed but not yet attached to the mitotic spindle

47
Q

Summarize the events of Prometaphase

A

Starts with the disassembly of the nuclear envelope

Microtubules from the mitotic spindle bind to specialized protein complexes (kinetochores) and capture chromosomes

48
Q

Summarize the events of Metaphase

A

The chromosomes align along the equatorial plate of the spindle

49
Q

Summarize the events of Anaphase

A

connections between sister chromatids are cut by proteolytic mechanisms

Daughter chromosomes migrate to opposite poles of the spindle

50
Q

Summarize the events of Telophase

A

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
Q

Summarize the events of cytokinesis

A

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
Q

What are the main players in animal cells in relation to the cell cycle?

A

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
Q

What can happen if cells progress to the next phase of the cell cycle before the previous phase is properly completed?

A

Catastrophic genetic damagge can occur

54
Q

What is the purpose of a cell cycle checkpoint?

A

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
Q

What do mitogens do in the cell cycle?

A

They stimulate cells to enter G1

56
Q

Summarize the initial (pre-replication) steps of the cell cycle including major players (factors, cyclins, CDKs and checkpoints)

A

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
Q

Summarize the events of the cell cycle including the major players (cyclins, factors, etc) after the initial early-response gene induction —> restriction point

A

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
Q

What was the term “tumor” formerly used to denote?

A

any localized swelling in the body caused by inflammation or abnormal cell proliferation

Now we use it as a synonym for neoplasm

59
Q

What are neoplasms?

A

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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