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Foundations of Medicine I > Structures of Cells and Tissues; Cell Cycle and Cell Death > Flashcards

Structures of Cells and Tissues; Cell Cycle and Cell Death Flashcards

1
Q

LO: Describe the structure and primary function of the plasma membrane

A

Structure: Tri-laminar structure formed by a phospholipid bilayer with hydrophilic head facing outward and a hydrophobic core.

Primary function: Selective permeability

Secondary functions: Endocytosis, exocytosis, cell-cell communication

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2
Q

LO: 3 major components of the cytoskeleton

A

Microtubules, intermediate filaments, and microfilaments

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3
Q

LO: Explain the structures and functions of the major nuclear components

A
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4
Q

LO: Predict a cell’s relative activity based on the structural characteristics of nuclear components

A
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5
Q

LO: Describe the process of cell death (necrosis, apoptosis)

A
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6
Q

LO: Explain the cell cycle process (mitosis, meiosis)

A
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7
Q

What form of microscopy must be used to see the plasma membrane?

A

Electron microscopy

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8
Q

Name the biochemical components of the plasma membrane

A

Lipids: cholesterol, phospholipids, glycolipids

Proteins: Integral proteins, peripheral proteins

Carbohydrates: linked to proteins and lipids, form glycocalyx

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9
Q

Function of cholesterol in the plasma membrane

A

Regulating fluidity.

Higher concentration of cholesterol (like at the site of lipid rafts) reduces membrane fluidity

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10
Q

Describe the distribution of the four different phospholipids in the PM

A

Sphingomyelin and phosphatidyl-choline are near extracellular surface.

Phosphatidyl-ethanolamine and phosphatidyl-serine are more concentrated at the intracellular surface

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11
Q

Where are glycolipids located in the PM?

A

Only on the extracellular (outer leaflet) of the bilayer

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12
Q

Differentiate between integral proteins and peripheral proteins

A

Integral proteins traverse the membrane whereas peripheral proteins are anchored to either the intracellular or extracellular membrane

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13
Q

State the makeup, location, and functions of the glycocalyx

A

Connections of carbohydrates on the extracellular surface of the PM that aids in cell adhesion and recognition

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14
Q

Define Fluid Mosaic Model

A

This model explains the proteins clustered in the lipid bilayer of the PM, but are mobile within the bilayer

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15
Q

PM Membrane Asymmetry

A

Proteins tend to stay on respective sides of the PM

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16
Q

PM Membrane Mobility

A

Proteins can move around the membrane or may be held stable by intracellular structures

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17
Q

Types of endocytosis

A

Phagocytosis, pinocytosis, and receptor-mediated endocytosis

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18
Q

Clathrin

A

Slight depression in the PM where endocytosis is about to occur and then forms a cage-like scaffolding for the invagination

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19
Q

Membrane receptors are mainly ______proteins

Name the four main functions of membrane receptors

A

Glycoproteins

Functions: control PM permeability, regulate entry of molecules into cells, bind ECM molecules to cytoskeleton via integrins, act as transducers to translate extracellular events into an intracellular response via second messenger systems

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20
Q

The three types of membrane receptors:

A

Channel-linked, enzymatic, and G protein-coupled receptors (GPCRs)

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21
Q

Common type of enzyme that is present in enzymatic receptors in PM

How is this type of receptor activated and what does it do?

A

Protein kinases

Activation upon ligand binding. Catalytic activity is induced in associated peripheral proteins

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22
Q

Activated GPCRs trigger a ______ involving a second messenger (and many more after that).

Name 3 common second messengers

A

Signaling cascade

cAMP, Ca2+, and inositol phospholipid-signaling pathway

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23
Q

Describe the molecular and systemic implications or familial hypercholesterolemia.

What causes this condition?

A

Cells have a decreased ability to take in LDL from the blood stream. Leads to build up of cholesterol in the blood stream and accelerated development of atherosclerosis

Cause: inherited genetic defect disabling synthesis of LDL receptors or synthesis of functional LDL receptors

24
Q

What do Venoms do to the PM?

A

Inactivation of acetylcholine receptors of skeletal muscle sarcolemma at NMJ (neuromuscular junction)

25
Q

How do autoimmune diseases affect the PM?

A

In the disease state, autoantibodies are produced that specifically bind to and activate certain membrane receptors on the PM

26
Q

Effect of cholera toxin on the PM and its larger scale consequences

A

The exotoxin alters G proteins to the point that it is unable to hydrolyze its GTP molecule.

In effect, cAMP builds up in the intestinal cells and causes excessive loss of water and electrolytes as diarrhea

27
Q

Effect of the pertussis toxin on the PM and its larger scale consequences

Where does the toxin attach?

A

Toxin inserts ADP-ribose into the alpha-subunits of trimeric G proteins –> inactivates GPCRs

In effect, irritation of mucosa of the bronchial passages, causing whooping cough

Toxin attaches in the upper respiratory system

28
Q

What are the two pathways of protein synthesis in the cell?

A
  1. Nucleus –> ribosomes in rough ER –> Golgi complex –> vesicle packaging of proteins
  2. Nucleus –> free ribosomes –> cytoplasmic proteins
29
Q

Describe the structure of the mitochondria from inside to outside

A

Intercristae space/matrix: enclosed by inner mem, contains Ca2+
Cristae: folds in inner membrane
Intermembrane space
Outer membrane

30
Q

Functions of the mitochondria

A

Pyruvate oxidation: pyruvate –> acetyl CoA

Citric acid cycle: oxidizes acetyl CoA

Electron transport chain & oxidative phosphorylation: produces ATP (more than 100/second in each protein complex!)

31
Q

Chemiosmotic process involved in ATP production

A

Characteristic of oxidative phosphorylation in forming ATP - electrochemical gradient across the inner membrane facilitates activation of ATP-synthase

32
Q

When and how does the mitochondria induce apoptosis?

A

In response to cell stress, mitochondria release cytochrome c from intermembrane space into the cytoplasm.

Cytochrome c activates proteases that degrade all cellular components

33
Q

Name an effective stain for displaying ribosomes

A

Hemaotoxylin (and other basic dyes)

34
Q

Describe structure of the rough ER

A

Comprised of tubular system of membranes + ribosomes attached; continuous with unit membrane of nucleus

35
Q

Describe the functions of the rough ER (3 broad ones)

A
  1. Synthesis and modification of proteins
  2. Isolation of synthesized proteins from cytosol
  3. Packaging for transport to Golgi apparatus
36
Q

Modifications of proteins that could take place in the rough ER

A

Glycosylation, sulfation, phosphorylation, cleavage, assembly of proteins

37
Q

What is the Agranular ER?

A

A network of membranes within the cell.

AKA: smooth ER

38
Q

Functions of the smooth ER (5)

A
  1. Detoxification
  2. Steroid hormone synthesis and cholesterol metabolism
  3. Regulation of Ca2+ concentration in the cell
  4. Glycogen breakdown
  5. Lipid and lipoprotein synthesis; phospholipid synthesis
39
Q

Where are phospholipids synthesized?

A

Smooth ER

40
Q

Describe the structure of the Golgi Apparatus

A

The Golgi app is made of stacked cisternae with vesicles budding off cisternae. Molecules coming in are received at the cis-face and molecules exiting do so through the trans-face

41
Q

Name the 3 functions of the Golgi

A
  1. Receives proteins and lipids from rough ER
  2. Continuation of protein glycosylation, sulfation, phosphorylation, and proteolysis
  3. Packaging of proteins and dispatch to various destinations
42
Q

Lysosomes (in general)

A

Spherical membrane-enclosed vesicles that function as sites of intracellular digestion

43
Q

Primary lysosomes

A

Freshly made by the Golgi, unused

44
Q

Secondary lysosomes

A

Activated upon fusing with vesicles containing phagocytic materials (phagosomes)

45
Q

Residual bodies

A

Membrane-encased debris of lysosome activity; contain lipofuscin

46
Q

Proteasomes

A

Constitutive pathway for degradation of cellular proteins

47
Q

Describe the role of ubiquitin in proteasomes

A

Proteins are conjugated to ubiquitin by ubiquitin ligase, then poly-ubiquinated proteins are targeted for proteolysis by the proteasome

48
Q

Peroxisomes - location, contents, and function

A

Buds off of ER

Contains oxidative enzymes (amino acid and hydroxyacid oxidases) catalase (to get rid of hydrogen peroxide)

Functions:
1. Production and breakdown of hydrogen peroxide
2. Lipid metabolism
3. Bile salt synthesis
4. Detoxification

49
Q

What is the role of secretory granules?

A

They are small granules containing neurotransmitters, hormones, growth factors, and enzymes that are released into the external environment of cells

50
Q

What are inclusions in the PM? Provide 3 examples

A

They are NOT organelles; they have little-no metabolic activity, but contain accumulated metabolites and other substances not enclosed by membrane. Ex: fat droplets, glycogen granules, pigment deposits

51
Q

Name the four pigments deposits that are found in inclusions in the PM

A

Melanin, Hemosiderin, Lipofuscin, and Bilirubin

52
Q

Function of the cytoskeleton

A

Structural support and cell/organ motility

53
Q

Three main components of the cytoskeleton

A

Microtubules (alpha and beta tubulin), intermediate filaments (cell-specific), and microfilaments (actin)

54
Q

Key features of Microtubules

A

Polymerization occurs at the leading edge.

Can be structurally cross-linked by microtubule-associated proteins

Can be randomly distributed in a cell or form specialized structures: centrioles, cilia and flagella, basal bodies, mitotic spindles

55
Q

Functions/features and types of Intermediate Filaments

A

Smaller diameter that microtubes, provides structural support.

Types (vary by cell): cytokeratins, desmin, glial-fibrillary acidic proteins, lamins, peripherin, vimentin

56
Q

Features and function of Microfilaments

A

Smallest diameter in cytoskeleton, involved in cell contraction, motility, movement of cytoplasmic components, microvilli contraction

Foundations of Medicine I (3 decks)

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