Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MNSR > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What are the different roles of calcium in the body?

A
  • Structural
    In bones and teeth
  • Signalling
    Constriction and relaxation of blood vessels, nerve impulse transmission, muscle contraction, secretion of hormones (e.g. insulin), mechanism of vision, taste and smell
  • Co-factor in proteins and enzymes
    Clotting/coagulation of blood in association with vitamin K dependent proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the factors affecting calcium absorption in the body?

A

Absorption enhanced by:
Vitamin D, which promotes the production of a calcium binding protein in intestinal cells. Vitamin D deficiency can lead to rickets.

Lactose, other sugars and proteins keep calcium in a soluble form

Absorption inhibited by:
Oxalic acid binds to calcium and makes it insoluble

High fat diet results in unabsorbed fats, which will form soaps with calcium preventing absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does calcium absorption primarily occur, and why?

A

In the duodenum, since it has a low pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the source of calcium for the human body?

A
  • Plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two ways that calcium can be absorbed?

A
  • Active transport

- Passive diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When does calcium’s solubility increase?

A
  • When the pH decreases

Calcium enters the body as a salt, which is not soluble in water, but it becomes more soluble with a decrease in the pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Two types of bone?

A

Cortical bone (Compact bone) and Trabecular bone (Cancellous bone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Cortical bone (Compact bone)?

A

Dense, low porosity, found in the shaft and forms outer shell around cancellous bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Trabecular bone (Cancellous bone)?

A

Low density, high porosity, forms insides of the bones. The spaces between the bone are filled with fluid bone marrow cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two type of chemical components of bone?

A

Two types:
Organic (protein) matrix and Inorganic minerals

-Bone is composed of collagen stiffened by crystals of calcium hydroxyapatite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Organic (protein) matrix?

A
  • Comprises mainly type 1 collagen (highly cross-linked triple helical protein structure)
  • Also found in cartilage
  • Osteocalcin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Inorganic minerals?

A
  • Major minerals are calcium and phosphate

- Found as calcium hydroxyapatite which has a molecular formula: Ca5(PO4)3(OH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How much of human bone is mineralised?

A

About 60%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the mineral component of human bones?

A

Calcium hydroxyapatite

Ca5(PO4)3(OH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens if you increase the mineral component of bones (calcium hydroxyapatite)?

A
  • Increases stiffness
  • Reduces flexibility

Ex: Auditory ossicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens if you increase the mineral component of bones (calcium hydroxyapatite)?

A
  • Decrease stiffness
  • Increase flexibility
    (Can absorb energy without breaking)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the 3 types of cells only found in the bone?

A
  • Osteoclasts: responsible for degrading bone (resorption), and come from bone marrow
  • Osteoblasts: cells that form new bone, and come from bone marrow
  • Osteocytes: sense bone deformation and signal then the need for adaptive remodelling of bone size/shape, and they come from osteoblasts, once they become trapped in the matrix they secrete
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Osteoid?

A
  • New bone produced by the osteoblasts, which is made of collagen and other protein
  • They control calcium and mineral deposition
19
Q

Bone modeling?

A

Produces a change in the size and shape of bone, when new bone is deposited without previous bone resorption

20
Q

Bone remodeling?

A
  • Resorption by osteoclasts precedes bone formation by osteoblasts
  • Coupling of osteoblast and osteoclast activities
  • Need to remove bone to build it up again
21
Q

Remodeling of bone (more in depth)?

A
  1. Osteocytes release local factors that attract cells from blood and marrow into the remodeling compartment
  2. Osteoclasts resorb matrix and microcrack, then successive teams of osteoblasts deposit new bone
22
Q

Production of extracellular organic matrix?

A

The first step in bone formation (osteogenesis):

Consists of type 1 collagen and osteocalcin (non-collagenous protein)
- In bone, collagen formed of tropocollagen subunits

23
Q

Tropocollagen molecule?

A
  • Each molecule contains three helices
    of protein chains wound around each other to form a helical rod 3000 Å long and 15 Å in diameter
  • The three protein chains are linked together by hydrogen bonds, which can be formed bc some amino acids in tropocollagen are oxidised
24
Q

What is the purpose of the 400 Å gaps between the tropocollagen subunits?

A

Serve as nucleation sites for the deposition of long, hard, fine crystals of the mineral component (hydroxyapatite)

25
What does a collagen fibre consist of?
A staggered array of tropocollagen molecules
26
What causes scurvy?
- A lack of vitamin C Bc since some amino acids in tropocollagen are oxidised, and that oxidation requires vitamin C, if there is a lack of that vitamin then the body will be unable to make collagen
27
Mineralisation?
- Calcium and phosphate are derived from blood plasma - Mineralisation occurs soon after deposition of extracellular organic matrix - Mineral crystals form along the collagen fibrils and osteocalcin chains
28
Osteocalcin?
It contains carboxyl groups (COO-) for binding calcium Ca2+
29
What contributes to bone strength?
- Renewal of bone - Remodeling causes increase in bone density up to 25 yrs - Bone mass and density are stable until 45 yrs - >45 yrs bone mass starts to decrease - In women bone loss starts a few years before menopause
30
Postmenopausal Osteoporosis?
Low estrogen levels in menopausal women can lead to increased bone resorption and accelerated bone loss
31
Osteoporosis?
- Bone disease in which the amount of bone reduces significantly, causing them to become weaker - Structural integrity of trabecular bone is impaired and the cortical bone becomes more porous and thinner
32
What do strong and dense bones result from?
A balance between bone resorption and bone formation
33
What happens if the balance between bone resorption and bone formation is disturbed?
- Activity of bone-degrading osteoclast cells becomes greater than activity of bone-building osteoblast cells - Bone resorption become more important than bone formation and results in weak bones that are prone to fracture
34
What are the most important risk factors for osteoporosis?
- Female gender - Increased age - Estrogen deficiency - Smoking
35
How to treat osteoporosis?
- Use a type of drug called antiresorptive agents - Prevent further bone loss but also inhibit new bone formation, as the activities of osteoblast and osteoclast are coupled
36
Classes of antiresorptive agents?
- Estrogens and selective estrogen-receptor modulators - Peptide hormone (calcitonin) - Bisphosphonates
37
Estrogen-Replacement Therapy?
- To treat osteoporosis by slowing bone resorption by blocking signaling to the osteoclasts Pros: - Relief of menopausal symptoms - Prevention of bone loss and fractures Cons: - Risk of endometrial carcinoma (cancer) - Risk of breast carcinoma (cancer)
38
Selective estrogen-receptor modulator?
- To treat osteoporosis by slowing bone resorption by blocking signaling to the osteoclasts Pros: - Reduce the rate of bone turnover - Prevention of bone loss and fractures
39
Calcitonin?
- To treat osteoporosis by rapidly inhibiting the action of osteoclasts Pros: - Therapy results in an increase in bone mineral density Cons: - Expensive, must be given by injection or nasal spray - Some patients become resistant to its action during long-term use
40
Bisphosphonates?
- Most widely prescribed antiresorptive agents - first-line therapy for the treatment of post-menopausal osteoporosis - Block bone resorption with immediate effect - Bisphosphonates reside in the bones for long period: resorption still inhibited after discontinuation of the therapy
41
Mode of action of non N-containing bisphosphonates?
- Bind to bone mineral when they are administered and are then slowly released as bone is resorbed by osteoclasts - Suppress resorption by inhibiting the attachment of osteoclasts to bone matrix - Enhance osteoclast apoptosis (cell death)
42
Mode of action of N-containing bisphosphonates?
- Inhibit modification of proteins required for signaling | - Block signals important for osteoclast activity
43
What percentage of calcium in your food is going to be absorbed?
10-40%
44
What causes rickets?
A lack of vitamin D, which causes the skeleton to be weak

MNSR (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions