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HORTICULTURE Flashcards

(54 cards)

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1
Q

What colour are carotenoids?

A

Red/yellow/orange

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2
Q

Carotenoids are colourless until which point in the carotenoid pathway?

A

Carotenoids are colourless until Lycopene in the carotenoid pathway.

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3
Q

Explain the difference between α-carotine and β-carotine

A

From lycopene you can either go to α-carotine or β-carotine and the ends of the lycopene molecule get wrapped around into rings

The α arm has two β rings

The β arm has a β ring and an episilon (ε) ring

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4
Q

What addition turns a carotene to a xanthophyll?

A

Addition of a hydroxyl (OH) group

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5
Q

Which 3 carotenoids are precursors for retinal?

A

β-carotene

β-crytpoxanthin

α-carotene

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6
Q

Where are carotenoids stored in plants?

A

In chromoplasts and chloroplasts as either crystals or lipid globules

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7
Q

Which carotenoids form crystals when stored?

A

Lycopene and ß-carotene tend to form crystals, which are less bioavailable than lipid granules

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8
Q

Explain the absorption of carotenoids

A

Occurs in small intestine

Carotenoids are lipophilic so their absorption is improved when its in conjunction with oils/fats

Oils/fats help create mixed micelles (carotenoids, bile salts and lipids)

The mixed micelles release carotenoids into enterocytes by active/passive diffusion

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9
Q

How are carotenoids transported around the body?

A

Carotenoids are cleaved and then attached to transport proteins called chylomicrons. They are then secreted into lympatic system

They then travel to the liver where they are repackaged onto lipid carrier proteins (LDL or HDL)

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10
Q

How many retinals can be made from ß-carotene

A

1 ß-carotene = 2 retinals

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11
Q

What enzymes cleaves ß-carotene into retinal?

A

ß-carotene oxygenase 1

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12
Q

What are some good sources of pro-vitamin A?

A
  • Carrot
  • Sweet Potato
  • Pumpkin
  • Mango
  • Papaya
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13
Q

What is a retinoic acid deficiency called and what does it cause?

A

Xerophthalmia = loss of goblet cells in the membrane covering the eye, which can destroy the cornea and potentially cause irreversible blindness

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14
Q

Which two carotenoids can accumulate in the macula?

A

Zeaxanthins and luteins

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15
Q

What is AMD and what does it affect?

A

Age-related macular degeneration. Effects the macular which is the part of the retina which is used for reading. AMD causes central blindness (but good peripheral)

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16
Q

How do zeaxanthin and lutein prevent AMD?

A

They act as ‘sunglasses’ for the macular and are good at oxidising blue light (which is damaging)

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17
Q

What are some examples of dietary Zeaxanthin?

A
  • Corn
  • persimmon
  • spinach
  • oranges
  • mandarins
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18
Q

What are good sources of luteins?

A

Dark leafy greens

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19
Q

What are the RDIs for zeaxanthin and luteins?

A

No actual RDI has been established but there is consensus among health professionals:

  • Luteins: 10mg/day
  • Zeaxanthins: 2mg/day
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20
Q

What is supergold corn and what is the benefits?

A

Biofortified sweet corn with added zeaxanthin

normal corn has approx 25% of all caroteinoids as zeaxthain, supergold has 74%

100g of supergold corn has >2mg of zeathanin

More gold in colour than regular corn

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21
Q

What foods are good sources of lycopene?

A
  • Tomatoes
  • red papaya
  • red watermelon
  • red fleshed grapefruit
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22
Q

What two mechanisms are used in biofortification of high lycopene tomatoes

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A

1) Modifying the carotenoids pathway so that less lycopene is converted to ß-carotene
2) doubling the amount of chloroplasts (for storage)

Combined these give 300% more lycopene

23
Q

Where are flavenoids in higher concentration?

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A

Often found in higher conc. in the skin than in the flesh e.g. blueberries

24
Q

Where in the cell are flavenoids synthesised and stored?

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A

Synthesised in the endoplasmic reticulum and then transported to be stored in the vacuole

25
What determines the colour of anthocyanins?
pH
26
What are sugar molecules often attached to anthocyanins?
for stabilities and for storage purposes
27
What is an anthocyanin called before a sugar is attached?
Anthocyanidin
28
What are the two most common anythocyanins in fruit and veg?
- Petarogonidin (red) | - Cyanidin (purple)
29
How are flavenoids thought to benefit health?
- They tend to be a favourable substrate for fermentation in the gut and promote growth of healthy microbiotic population - anthocyanins appear to be the flavenoid which is best at lowering hypertension. Peonidin (in cranberries and purple sweet potato) is structuraly similar to vasoactive drug apocynin
30
What is the benefit of Queen Garnett Plums?
10x more anthocyanins than regular blood plums
31
What has recent research by Desjardins (2014) suggested about the role of polyphenols in the human body?
Polyphenols appear to have antioxidant capacity in vitro, however appear to have low bioavailability and negligible contribution to the body's antioxidant network However research suggests polyphenols could provide cues about the quality of diet which triggers metabolic adaptations through gene expression May also have a prebiotic effect in the gut
32
Which family are glucosinolates exclusive to?
The brassicales family (cabbages, broccoli, radishes etc) | Also known as cruciferous
33
What is the active form of glucosinolates and how are they converted to this?
Glucosinolates = stable form Isothiocyanates = active form Myrosinase = converting enzyme
34
How are glucosinolates thought to be of benefit to humans?
They are thought to work by their ability to induce the release of detoxification enzymes (phase 2 enzymes) in cells e.g. glutathione-transferase Inhibit phase 1 enzymes
35
Where are glucosinolates stored in cells and where is myrosinase stored? How do they meet?
Both are stored in vacuoles but of different cells Can only interact when the cells are physically damaged and allow them to mix and produce isothiocyanate
36
Give an example of an anti-nutrition glucosinolate
Progoitrin gets converted to goitrin This can induce goitre by interfering with iodine uptake and inhibiting thyroid function by blocking the incorporation of iodine and thyroxine precursors
37
What is a source of progoitrin?
Kale
38
Where are glucosinolates found in plants?
- Leaves - Stems - Roots - Flowers - Fruit Even in the same plants different tissues can have different glucosinolates
39
What is ESP and what does it do?
ESP (epithiospecifier protein) is a co-enzyme which modifies myrosinase and redirects glucosinolate hydrolysis to nitrile compounds
40
Which brassicas have ESP and which don't?
Do contain ESP: - cabbage - kale - broccoli Do NOT contain ESP: - watercress - red raddish - white mustard - papaya
41
Explain how glucosinolates detoxify carcinogens
1) Glucoraphanin (a glucosinolate) → sulforaphane (an isothiocyanate) 2) Sulforaphane is uptaken to enterocytes 3) The isothiocyanate splits Nrf2 from Keap1 4) Nrf2 goes into the nucleus to act on Antioxidant Response Element (a gene promotor) 5) Antioxidant Response Element turns on GST gene 6) GST produces and enzyme called glutathione transferase 7) Glutathione transferase catalyses the binding of glutathione and the carcinogen so they can be excreted from the cell
42
What is folate found in?
Dark leafy greens
43
What is the link between folate and neural tube defects?
Increased folate intake in pregnancy is linked to decreased risk of spina bifida
44
What is caused as a result of a folate deficiency?
Megaloblastic anaemia
45
What is the difference between folate and folic acid?
Folate is deprotonated | Folic acid is neutral
46
What is folic acid converted to in the body?
Converted to tetrahydrofolate (THF) which is the natural form of folate in plants
47
What is the RDI for folate?
RDI is expressed as folic acid equivalents RDI = 400µg/day RDI during pregnancy = 600µg/day UL = 1000µg/day
48
What is the role of zinc in human health?
- Interacts with testosterone - Skin health - Lower levels of depression - Enables folate absorption
49
What is the role of selenium in human health?
- Broad spectrum anti cancer agent - Thyroid metabolism - Increased immune response - Can alter mood
50
Where is zinc located in the nut?
In protein bodies. The protein body cells tend to be interspersed with oil globules
51
How is zinc stored and how is bioavailable to the human body?
Zinc ions can be chelated by phytate, however humans do not have phytase so cannot digest the minerals stored in phytate
52
What is the best source of selenium?
Brazil nuts are by far the best source of selenium, containing ~2000µg/100g
53
What is the RDI for selenium?
- Women: 70µg | - Men: 90µg
54
What is the RDI for Zinc?
- Women: 8mg | - Men: 15mg

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