Homeostasis and cell protection, movement, nutrition, communication, energy production, renewal

Question 1

What is homeostasis?

Answer 1

Process of keeping internal variables within a normal range of values

Question 2

Give 3 examples of internal variables regulated by homeostatic mechanisms?

Answer 2

Blood glucose level, temperature, blood pressure

Question 3

When carbohydrates are eaten, how does homeostasis regulate blood glucose levels?

Answer 3

Pancreatic beta cells detect rise in blood glucose level

Pancreatic beta cells release insulin which binds to hepatocyte and skeletal muscle receptors

Cells take up extra glucose in blood and store it as glycogen, until blood glucose level is restored to a normal value

Question 4

How does a negative feedback loop work?

Answer 4

Stimulus changes variable so that value isn’t in normal range

Receptor detects change

Control centre compares change to reference value, instructs effector to make adjustment to restore normal value

Question 5

What 2 substances can’t pass through the phospholipid bilayer of the plasma membrane by passive diffusion?

Answer 5

Large molecules, charged/polar molecules

Question 6

Why can’t charged/polar molecules move through the phospholipid bilayer by passive diffusion?

Answer 6

They are repelled by the neutral, hydrophobic tails of the phospholipids

Question 7

Why can’t large molecules passively diffuse through the phospholipid bilayer?

Answer 7

They are too big to fit between the individual phospholipids

Question 8

What is a phosphatidylserine?

Answer 8

Negatively-charged phospholipid that faces outwards in a normal cell, and is important in signaling phagocytes

Question 9

How does phosphatidylserine signal to phagocytes that its cell is apoptotic?

Answer 9

The phosphatidylserine turns to face outwards, which attracts phagocytes

Question 10

In which condition are glycolipids on outside of the plasma membrane important?

Answer 10

Inflammation

Question 11

How can cell polarity be maintained

Question 12

Give 6 examples of substances that passively diffuse through the phospholipid bilayer?

Answer 12

Oxygen, carbon dioxide, urea, steroids, water, alcohol

Question 13

What size do ions/molecules need to be to require transport through fast channels and slow carrier proteins?

Answer 13

Over 75 daltons

Question 14

What does the Multidrug Resistant (MDR) Protein carry out of cells, and what is the consequence of this substance being removed from the cell?

Answer 14

Chemotherapy drugs pumped out of cell which causes cell to become resistant to treatment

Question 15

What does cytoplasm contain that increases cell osmolarity?

Answer 15

Charged metabolites

Question 16

What is cell osmolarity?

Answer 16

Process of measurement of solute concentration

Question 17

If cell cytoplasm has high osmolarity, what substance will diffuse into the cell?

Answer 17

High osmolarity attracts water

Question 18

How does a cell prevent lysis from excess water entering the cell?

Answer 18

Na-K ATPase pump constantly pumps sodium and chloride ions

Question 19

If a cell is injured and can’t produce energy, how will the Na-K ATPase pump be affected?

Answer 19

Pump will fail, so excess water will enter cell and lysis occurs

Question 20

What occurs in endocytosis?

Answer 20

Large molecule is taken into the cell by cell membrane invagination, which buds off to form an endosome (vesicle)

Question 21

After an endosome has fused with a lysosome and the extracellular material has been ingested, what happens to the receptors coating the endosome?

Answer 21

Receptors are recycled back to the cell plasma membrane

Question 22

What is another name for receptor-mediated endocytosis?

Answer 22

Claritin-dependent endocytosis

Question 23

What occurs in receptor-mediated endocytosis?

Answer 23

Large molecule binds to cell surface receptors then Claritin proteins are used to coat the forming endosome before it buds off

Question 24

Give 2 examples of extracellular ligands/molecules that use receptor-mediated endocytosis?

Answer 24

Transferrin (iron transporter), bad cholesterol

Question 25

What occurs in caveolin-mediated endocytosis?

Answer 25

Large molecule binds to cell surface receptors then Caveolin proteins are used to coat the forming endosome before it buds off

Question 26

Give an example of an extracellular ligand/molecule that uses caveolin-mediated endocytosis?

Answer 26

Vitamins

Question 27

What is exocytosis?

Answer 27

Export of large molecules through fusion of the vacuole membrane with the cell membrane

Question 28

What occurs in transcytosis?

Answer 28

Large molecule endocytosed at one area of plasma membrane, exocytosed at another area of membrane

Question 29

What are 2 surfaces in the plasma membrane, and where are they located relative to organ lumen?

Answer 29

Apical membrane faces towards organ lumen Basolateral membrane faces away from organ lumen

Question 30

Give an example of a molecule transported by transcytosis?

Answer 30

Antibodies passing breastmilk through intestinal cells

Question 31

In cystic fibrosis, which channel protein is defective?

Answer 31

Transmembrane chloride channel protein

Question 32

How does cystic fibrosis lead to infections?

Answer 32

Defective transmembrane chloride channel causes airways to be coated by thick mucus, which traps bacteria in lungs and causes infection

Question 33

What structure in the cell allows cell movement?

Answer 33

Cytoskeleton

Question 34

What is the main component of the cytoskeleton that controls cell shape and movement?

Answer 34

Actin filaments

Question 35

Which 2 proteins form cilia and flagella?

Answer 35

Microtubules, motor proteins

Question 36

What is cilia and flagella used for in mitosis?

Answer 36

Chromatin movement

Question 37

What structure provides strength to cells?

Answer 37

Intermediate filaments

Question 38

What intermediate filament is present in epithelial cells?

Answer 38

Cytokeratin

Question 39

How can the origin of a cancer be determined by studying the cytokeratin in a cell?

Answer 39

Epithelial cells from different tissues have different cytokeratins present

Question 40

What controls nucleus structure?

Answer 40

Nuclear membrane lamins

Question 41

What is progeria?

Answer 41

Condition characterised by premature aging in children, due to irregular collapsing nuclear membrane

Question 42

What proteins do desmosomes contain that allow cell-cell adhesion?

Answer 42

Cadherin

Question 43

What part of each cell do desmosomes attach to adjacent cells?

Answer 43

Intracellular cytoskeletons

Question 44

What attaches cells to the extracellular matrix?

Answer 44

Hemidesmosomes

Question 45

What is the pathology of pemphigus vulgaris?

Answer 45

Condition where antibodies target Desmoglein-3 (desmosome component), causes keratinocytes to fall apart

Question 46

What are 2 physical signs of pemphigus vulgaris?

Answer 46

Blisters, erosions

Question 47

What is autophagy?

Answer 47

Process by which cell disposes of unnecessary/dysfunctional organelles and denatured proteins by ingesting it

Question 48

What vesicles are formed by autophagy?

Answer 48

autophagosomes

Question 49

What is heterophagy?

Answer 49

Cells ingest extracellular foreign materials

Question 50

How is cellular waste destroyed in the cell?

Answer 50

Autophagosomes, phagosomes, endosomes fuse with lysosomes which contain digestive enzymes

Question 51

How is waste removed from the cell?

Answer 51

Exocytosis

Question 52

What process produces ATP, and where in the mitochondria does it occur?

Answer 52

Oxidative phosphorylation in intermembrane space

Question 53

Why do rapidly growing cells produce intermediates?

Answer 53

Lipids, proteins, nucleic acid are produced instead of ATP

Question 54

When rapidly growing cells produce lipids, proteins, nucleic acids instead of ATP, what is the by-product?

Answer 54

Oxygen species

Question 55

What is thermogenin, and where is it found?

Answer 55

Mitochondrial carrier protein in inner membrane that generates heat, abundant in brown fat

Question 56

What cellular process does the mitochondria regulate?

Answer 56

Apoptosis

Question 57

What 3 factors can damage the mitochondria?

Answer 57

Trauma, low blood supply, toxins

Question 58

How does mitochondrial damage affect ATP production?

Answer 58

Transition pore opens which causes ATP production to stop

Question 59

Which parent is mitochondrial DNA inherited from?

Answer 59

Maternally inherited

Question 60

What 3 conditions can cause mitochondrial diseases?

Answer 60

X-linked condition, autosomal disorder, random mutation

Question 61

What is the process of communication at neuromuscular junctions?

Answer 61

Synaptic transmission

Question 62

During synaptic transmission, what area does acetylcholine diffuse across, and what does it bind to on the post-synaptic membrane?

Answer 62

Diffuses across synaptic cleft and binds to acetylcholine receptor on the muscle cell

Question 63

What is the function of autocrine signaling?

Answer 63

To amplify a response

Question 64

What is the function of paracrine signaling?

Answer 64

To signal to adjacent cells, or cells in the immediate vicinity

Question 65

What is the function of endocrine signaling?

Answer 65

To release mediators into bloodstream so that they can signal to distant target

Question 66

What is a cell surface receptor?

Answer 66

Transmembrane protein with extracellular domains that binds to water-soluble ligand

Question 67

What type of channel is opened when the ligand binds to a cell surface receptor?

Answer 67

Ion channel

Question 68

What type of receptor are the 7 transmembrane receptors?

Answer 68

G-protein coupled receptor

Question 69

When receptor tyrosine kinase is activated, what does it phosphorylate?

Answer 69

Phosphorylates tyrosine residue of specific intracellular proteins

Question 70

How is the signaling of the receptor tyrosine kinase stopped?

Answer 70

Phosphatase removes phosphate group from the receptor

Question 71

What 3 types of receptors does non-receptor tyrosine kinase activate?

Answer 71

Immune, cytokine, insulin receptors

Question 72

What cells do pathogens signal to?

Answer 72

Innate immune cells

Question 73

What does damage to neighbouring cells signal?

Answer 73

Wound healing

Question 73

SIgnals produced by contact with neighbouring cells is mediated by which 2 factors?

Answer 73

Adhesion molecules, gap signaling junctions

Question 73

What are 4 cellular responses to signals produced by growth factors?

Answer 73

Entry of cells into cell cycle Removal of block on cell cycle progression Prevent apoptosis Enhance cell organelle synthesis

Question 74

What is an intracellular receptor?

Answer 74

Transcription factor that causes DNA to be transcribed into RNA, upon binding to a lipid-soluble ligand

Question 75

Why do intracellular receptors only bind to lipid-soluble ligands?

Answer 75

Ligands are fat-soluble so can cross the phospholipid bilayer, water-soluble ligands can't cross so must enter with cell surface receptors

Question 76

Do hormones and cytokines produce signals that trigger cellular response?

Answer 76

Yes

Question 77

What transcription factor is activated by cell surface receptors?

Answer 77

Latent transcription factor

Question 78

Give 3 reasons for why cell renewal is needed?

Answer 78

Cell growth, replacement, maintains homeostasis

Question 79

What 2 proteins regulate cell cycle progression?

Answer 79

Cyclins, Cyclin-dependent Kinases

Question 80

Why does the cell cycle have quality control checkpoints?

Answer 80

To ensure that any cells with genetic imperfections don't complete replication

Question 81

If a DNA abnormality is detected at a quality control checkpoint, what happens?

Answer 81

DNA repair mechanism

Question 82

What happens to cells with severe abnormalities?

Answer 82

Apoptosis or enter state of senescence

Question 83

Which active gene stops the cell cycle?

Answer 83

p53

Question 84

What proteins enforce quality control checkpoints?

Answer 84

CDK inhibitors (CDKIs)

Question 85

How do CDKIs interact with CDKs if a cell abnormality is detected?

Answer 85

CDKI have p16 gene which inhibits CDKs 4 and 6, so that cell cycle won't progress

Question 86

What condition can defective CDKIs increase the risk of?

Answer 86

Cancer, as more abnormal cells will mature

Question 87

What do some cancer drugs target in order to stop abnormal cell cycle progression?

Answer 87

CDK 4 and 6

Question 88

Why does the extracellular matrix anchor cells?

Answer 88

Cells are kept upright, so maintain the cell polarity

Question 89

What factor and signal does the extracellular matrix use to control cell growth?

Answer 89

Integrin cell signals, growth factors

Question 90

How is the extracellular matrix used in healing?

Answer 90

Provides scaffold for tissue renewal

Question 91

What is the tissue microenvironment, that is produced by extracellular matrix?

Answer 91

Dynamic network of cellular and non-cellular component that collectively maintain homeostasis of an organ

Question 92

Where is the extracellular matrix located, and how is it produced?

Answer 92

Secreted by cells to surround them in tissues

Question 93

What is the major structural protein of the extracellular matrix?

Answer 93

Collagen

Question 94

What vitamin is needed for collagen to maintain its strength?

Answer 94

Vitamin C

Question 95

What is osteogenesis imperfecta?

Answer 95

Condition where patient presents with brittle bones, caused by genetic collagen defect in extracellular matrix

Question 96

What is Ehlers-Danlos syndrome?

Answer 96

Condition where patient presents with fragile skin and unstable joints, caused by genetic collagen defect in extracellular matrix

Question 97

What gives extracellular matrix the ability to stretch and recoil?

Answer 97

Elastin

Question 98

What protein makes up elastin?

Answer 98

Fibrillin

Question 99

Give 2 examples of where elastin is located in body?

Answer 99

Heart valves, skin

Question 100

What is Marfan's syndrome?

Answer 100

Condition where patient presents with heart valve problems producing a murmur, due to mutation of fibrillin-1 gene

Question 101

What are integrins?

Answer 101

Transmembrane glycoproteins that bind cell to extracellular matrix

Question 102

Give 2 examples of water-hydrated gels in the extracellular matrix?

Answer 102

Proteoglycans, hylaronans

Question 103

What properties do water-hydrated gels give extracellular matrix?

Answer 103

Resistance to compression Lubrication

Question 104

Where is the presence of water-hydrated gel important?

Answer 104

Joint cartilage

Question 105

What 2 properties give stem cells the ability to mediate the cycle of replacing dead cells to maintain homeostasis?

Answer 105

Self-renewal They undergo asymmetric division to produce one daughter cell and one stem cell

Question 106

What do totipotent/embryonic stem cells give rise to?

Answer 106

All cell types in differentiated tissue (embryonic, placental, adult)

Question 107

What do adult/tissue stem cells give rise to?

Answer 107

Cell types in the tissue within within they reside

Question 108

Give 2 examples of where multipotent stem cells are derived from?

Answer 108

Bone marrow, adipose tissue

Question 109

Give 4 examples of cell types that multipotent stem cells give rise to?

Answer 109

Chondrocytes (cartilage) Osteocytes (bone) Adipocytes (fat) Myocytes (muscle)

Question 110

What is a stem cell niche?

Answer 110

Microenvironment in anatomical area where stem cells reside and receive stimuli to promote their differentiation

Question 111

Where is the stem cell niche near bone marrow?

Answer 111

In areas surrounding blood vessels in bone marrow

Question 112

Where is the stem cell niche in a hair follicle, and what happens if this niche is destroyed?

Answer 112

Bulge region, destruction causes permanent hair loss

Question 113

Where is the stem cell niche in the cornea?

Answer 113

Limbus

Question 114

Where is the stem cell niche in the GI tract?

Answer 114

Crypts

Question 115

What are the Canals of Herring in the liver, where stem cell niches are found?

Answer 115

Small ducts that transport bile

Question 116

Which region of the brain contains a neural stem cell niche, and which aggressive cancer can these cause?

Answer 116

Subventricular region, cause Glioblastoma

Question 117

Which cells can be generated in a laboratory setting?

Answer 117

Pluripotent cells

Question 118

Which genes are identified to mimic 'stem' ability of embryonic stem cells?

Answer 118

Genes who's products reprogram somatic cells

Question 119

How are induced Pluripotent Stem cells generated after reprogramming genes have been identified?

Answer 119

Genes introduced into fully differentiated cells

Question 120

Why is regenerative medicine important?

Answer 120

Generated cells can be implanted without triggering immune response