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Histology II > Cell Structure 1 > Flashcards

Cell Structure 1 Flashcards

0
Q

What are cells organized into?

A

A collection of cells is known as Tissue. Tissue generally has a single function.

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1
Q

What is the basic unit from which all other things are built?

A

The cell! Humans begin as a single fertilized ovum. Differentiate into 200 different types of cells.

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2
Q

What are the four types of tissue?

A
  1. Nervous
  2. Epithelial
  3. Connective
  4. Muscle
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3
Q

What germ layer does Nervous tissue originate from?

A

Ectoderm

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4
Q

What germ layer(s) does epithelial tissue originate from?

A

All three. Ectoderm, Endoderm and Mesoderm.

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5
Q

What germ layer does connective tissue originate from?

A

Mesoderm.

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6
Q

What germ layer does muscle tissue originate from?

A

Mesoderm.

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7
Q

What do two or more tissues form?

A

Organ. Organs have multiple tissues and multiple functions.

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8
Q

What is the circulatory system an example of?

A

An organ system. The heart, arteries, veins and capillaries all function to circulate blood throughout the body. Several organs serve a unifying function.

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9
Q

What does the Neutrophil Chase movie show?

A

A blood smear in the 1950s, found a neutrophil and added a staph bacteria. Neutrophil (macrophage) moves around chasing the bacterium. Notice the leading edge on the neutrophil where the movement is taking place. Eventually absorbs bacteria and lysosomes in the cell fuse and break down the bacteria.

Take away: different cells do different things; ability depends on various organelles inside them.

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10
Q

What are described as “living” components of the cell?

A

Organelles, which take part in metabolic activity and synthesis.

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11
Q

What are inclusions?

A

Considered as “non” living parts of the cell. Not involved in metabolic/synthetic activity. Includes glycogen droplets, lipid droplets, storage granules.

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12
Q

What is the role of the cytoskeleton?

A

Made up of fibrous proteins, provides mechanical support, anchors organelles in their locations (location is important to function), movement.

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13
Q

What do organelles do?

A

Compartmentalize different processes.

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14
Q

What is the nucleus surrounded by?

A

A double membrane structure known as the nuclear envelope.

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15
Q

Where are ribosomes synthesized?

A

Nucleolus

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16
Q

What % of the plasma membrane is made up of lipids? What makes up the remainder?

A

50% lipids
50% proteins either within membrane or on surface (mediate many functions: recognition, movement across membrane, regulation of binding of receptor to ligand)

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17
Q

What is meant by “amphphipathic” when describing plasma membrane?

A

Lipid molecules have both polar and non-polar regions (fatty acid tails). Form a bilayer.

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18
Q

What can permeate the plasma membrane freely?

A

Can pass: small non-polar (O2, N2); small polar (H20, CO2)

Can’t: charged ions

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19
Q

What type of diffusion is allowed in plasma membrane?

A

Lateral only. Plasma membrane is fluid and allows lateral diffusion of membrane proteins and lipids. Proteins can’t flip.

20
Q

What is the general % make-up of membrane lipids?

A

50% phospholipids
~50% cholesterol
5-10% glycolipids (present only in the outer leaflet because of the way they are synthesized)

21
Q

What is the backbone of phospholipids? What is the polar head group composed of?

A

Glycerol backbone with two fatty acid chains. Polar groups represent phosphate (-) bridge bound to an amino alcohol (+). Hydrophobic and hydrophilic regions.

22
Q

How is the name of a phospholipid derived?

A

Named after amino-alcohol that forms head group. Example: phosphatidylcholine

23
Q

What is the relevance of the kink in fatty acid chain of phospholipid?

A

Caused by double bonds (unsaturation). Helps maintain membrane fluidity. Prevents from packing too closely together, created minimum distance between adjacent molecules.

24
Q

What is the structure of cholesterol found in the plasma membrane?

A

Steroid ring structure, polar head group is a simple hydroxyl and non-polar hydrocarbon tail. Integrates between phospholipids filling in spaces.

25
Q

What is the function of cholesterol in plasma membrane?

A
  1. Reduces permeability to small molecules (h20)
  2. Stiffens membrane and provides mechanical strength
  3. Provides further resistance to packing-membrane fluidity buffer

As you add cholesterol fluidity decreases, but only up to a certain point. Once you have maxed out the system doesn’t get any less fluid. Establishes a minimum level of fluidity; interferes with actions between fatty acid chains of phospholipid molecules.

26
Q

What are lipid rafts?

A

Areas of high concentration of cholesterol. Act like little islands within sea of cholesterol, concentrated specific types of proteins important in cell-cell interactions.

27
Q

What do glycolipids contribute to?

A

The glycocalyx: sugar coating on the extracellular surface of the cell.

28
Q

What is the structure and function of glycolipids?

A

Phospholipid with sugar in head group. PMS stain can see them. Contribute to glycocalyx. Important because a defect in metabolism of these molecules can cause disease.

29
Q

What symptoms would a patient suffering from Tay Sachs disease exhibit?

A

Enzyme defect causing inability to turn over gangliosides (type of glycolipid), which begin to build up on neurons. Cognitive impairment. Typically die by the age of 2 or 3.

30
Q

What are the main functions of membrane proteins? What are the two types and where are they located?

A

Two types of proteins:

  1. Integral (transmembrane typically) and
  2. Peripheral proteins

Function:

  1. transport of ions and molecules (pores, channels)
  2. cell-cell recognition and adhesion
  3. signal transduction
31
Q

During freeze fracture of the plasma membrane, what side are you more likely to see integral membranes?

A

On the p face (protoplasmic). There is a tendency for integral proteins to stay with cytoplasmic leaflet, anchored somehow with cytoplasmic skeleton.

E face (extracellular) will have holes.

32
Q

Where is the glycocalyx located?

A

Only present on cell surface. The glycocalyx is a sugar coating on the extracellular surface of the cell. Composed of carbohydrates associated with lipids and carbohydrates associated with proteins.

33
Q

What are the main functions of the glycocalyx?

A
  1. Protects against infection.
    How: Extremely negatively charged because sugars carry negative charge (anionic). This prevents invasion by bacteria because bacteria coated in antibody are negatively charged and will be repelled by the glycocalyx.
  2. Protects cell from chemical and mechanical damage.
    How: barrier above phospholipid membrane.
  3. Cell-cell specific interactions
    important for cell-cell recognition.
34
Q

Movement of macromolecules and particulate matter across cell membrane is controlled by?

A
  1. Endocytosis and

2. Exocytosis

35
Q

What are the three types of endocytosis (bringing things into cell)?

A
  1. pinocytosis (cell drinking)
  2. receptor mediated endocytosis
  3. phagocytosis
36
Q

What are the main steps involved in pinocytosis?

A

Pinocytosis is bulk fluid uptake into clathrin coated endocytic vesicles. Driven by clathrin. Clathrin begins to accumulate on cytoplasmic surface, interactions between clathrin molecules drive invagination.
Pinching off of vesicles driven by a collar of GTPase protein called
dynamin. Pinches off, endocytic vesicle, goes inside cell and fuses with lysosome.
Process is ongoing, all cells are doing it all the time. Constitutive.
Take up material present in extracellular and take it into intracellular environment.

37
Q

What is the main purpose of pinocytosis?

A

Helps meet general cell requirements for nutrients.
Ongoing process that takes up material from extracellular environment, captures nutrients for cells. Part of cells ability to turn over membranes, components of membrane get broken down continuous cycling of old membrane being taken out.
Important for maintaining membrane surface area, shape and size of cell.

38
Q

If pinocytosis removes things from the plasma membrane, what adds to it? (equilibrium)

A

Exocytosis.

39
Q

What process uses clathrin coated pits and receptors to bring molecules into the cell?

A

Receptor mediated endocytosis.

40
Q

What causes uncoupling of ligand and receptor within an endosome during receptor mediated endocytosis?

A

A low pH; acidic environment.

41
Q

After receptors are returned to the cell surface, what happens to the LDL inside the endosome?

A

Moves to the lysosome for degradation.

42
Q

What endocytosis process is not clathrin driven?

A

Phagocytosis. Driven by rearrangement of actin
cytoskeleton (clathrin independent). Process of engulfing particulate matter. Triggered by binding to receptors
in cell membrane.

43
Q

What is exocytosis?

A

Constitutive pathway important for replacing membranes and
membrane proteins as well as secreting materials synthesized by
cell. Fusion of membrane bound cytoplasmic vesicle with cell
membrane.

44
Q

A patient inherits a defect in LDL receptor gene resulting in decrease in affinity of the receptor for LDL. What do you expect to see?

A

Large amounts of cholesterol build up in the blood. Cholesterol is unable to be taken up into the cells. Receptor mediated endocytosis is dysfunctional.

45
Q

During familial hypercholesteremia (FH) you see high levels of circulating LDL and early onset artherosclerosis. What are some possible treatments for heterozygous (mild) and homozygous mutations?

A

Heterozygous: statins and low cholesterol diet
Homozygous: dialysis or liver transplant (liver has 50% or more of LDL receptors, captures a lot of LDL)

46
Q

During exocytosis what happens to the integral membrane contained in vesicles?

A

They now become part of the cell membrane. Way to replace materials that are being removed by pinocytosis.

47
Q

What is an example of a constitutive pathway?

A

Constantly working; unregulated; such as secretion of mucus by goblet cells.

Histology II (4 decks)

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