BIO EVENTS

Event6.pptx

Event 6

Although vitamin D is commonly called a vitamin, it is not actually an essential dietary vitamin in the strict sense, as it can be synthesized in adequate amounts by most mammals exposed to sunlight. A substance is only classified as an essential vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from its diet. In common with other compounds commonly called vitamins, vitamin D was nevertheless discovered in an effort to find the dietary substance lacking in a disease, namely rickets, the childhood form of osteomalacia.[4] Additionally, like other compounds called vitamins, in the developed world, vitamin D is added to staple foods, such as milk, to avoid disease due to deficiency.

Synthesis from exposure to sunlight, as well as intake from the diet, generally contribute to the maintenance of adequate serum concentrations. Evidence indicates the synthesis of vitamin D from sun exposure is regulated by a negative feedback loop that prevents toxicity, but, because of uncertainty about the cancer risk from sunlight, no recommendations are issued by the Institute of Medicine, USA, for the amount of sun exposure required to meet vitamin D requirements. Accordingly, the Dietary Reference Intake for vitamin D assumes no synthesis occurs and all of a person's vitamin D is from food intake, although that will rarely occur in practice. Beyond its use to prevent osteomalacia or rickets, the evidence for other health effects of vitamin D supplementation in the general population is inconsistent.[5] [6] The best evidence of benefit is for bone health.[7] The effect of vitamin D supplementation on mortality is not clear, with one meta-analysis finding a decrease in mortality in elderly people,[8] and another concluding there is no clear justification for recommending vitamin D.[9]

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Review of previous activities.

Lecture quiz

Statistical significance

On-line (and upcoming) activities

Cells: The fundamental units of life

Pigments in plants

Cancer and pigments in humans

Assignment, Event 6

Quiz

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Quiz

You hypothesize that your body weight is higher on Monday than on other days of the week and conduct a two-week experiment to investigate this.

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Given these data, what specifically would you do next? (Two sentences.)

Quiz

My answer:

I would conduct a statistical analysis of these data to determine whether my hypothesis was true. Based on the conclusions from this analysis, I may decide to collect additional data.

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Should not modify the experiment without first analyzing the data!

Final quiz

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Event 5: Statistical significance

Assignment, Event 5:

Hypotheses formulation and statement.

Mann-Whitney U tests.

Use statistics to accept or reject your hypothesis.

Explanation of your work.

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See: Rattlesnake Mann-Whitney U example.pdf

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UNIT 3 The Cell

UNIT 4 Metabolism

UNIT 5 Cell Division

UNIT 6 Classical Genetics

UNIT 7 Evolution

UNIT 2 Introduction

to Chemistry

UNIT 8 Ecology

UNIT 1 Introduction

On-line activities, Event 6

CHAPTER 3: The Cell

Module 7: Chapter Introduction*

Module 8: Eukaryotic Cells*

Module 9: Chapter Introduction: Metabolism*

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* Module with quiz.

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Animal cell

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Plant cell

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Microscopy is critical for studying cells

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Cells exist within three-dimensional space

Escherichia coli

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Cells exist within three-dimensional space

Cells have been sectioned to permit

a “two-dimensional” view

Cell walls

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Plant cells

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Plant cell

Rough + smooth

endoplasmic

reticulum

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Vacuole

Nucleus

Cell walls

(plasma membrane

inside)

Mitochondrion

Ribosome

Plant cells (sectioned) – organelles

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Cell walls are made of the carbohydrate cellulose

Plant cells (sectioned) – Leaf cells

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Chloroplast

Pigments in nature

= substances produced by living organisms that have a color resulting from selective color absorption.

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Biological pigments, also known simply as pigments or biochromes[1] are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biological structures, such as skin, eyes, fur and hair contain pigments such as melanin in specialized cells called chromatophores.

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The color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves, which also contribute to the color.

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Absorbs red and green and reflects or transmits blue

pigment

molecules

+Any visible light that strikes the object and becomes reflected or transmitted to our eyes will contribute to the color appearance of that object. So the color is not in the object itself, but in the light that strikes the object and ultimately reaches our eye. The only role that the object plays is that it might contain atoms capable of selectively absorbing one or more frequencies of the visible light that shine upon it. So if an object absorbs all of the frequencies of visible light except for the frequency associated with green light, then the object will appear green

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Chloroplasts are complex membrane- rich organelles inside cells

Pigment =

chlorophyll 

 Light energy capture in photosynthesis

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Plant cells (sectioned)

Plant cells (sectioned) – Carrot root cells

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Chromoplast

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Plant cells (sectioned)

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Plant cells (sectioned) – Petal cells

Pigments in vacuoles

are water soluble

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Eastern bluebird

(Sialia sialis)

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Granular poison frog

(Oophaga granulifera)

The Granular Poison Frog, Oophaga granulifera

The frog is an aposematic animal, and it uses poison only for self-defense from predators. Its clearly visible red color is designed as a warning signal to all possible predators.

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Lupinus sp.

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Pantone Inc. is a corporation headquartered in Carlstadt, New Jersey.[1] The company is best known for its Pantone Matching System (PMS), a proprietary color space used in a variety of industries, primarily printing, though sometimes in the manufacture of colored paint, fabric, and plastics.

Pigments and cancer

Skin cancer is the most common form of cancer in the United States.

More than 2,000,000 skin cancers are diagnosed annually.

One in five Americans will develop skin cancer in their lifetimes.

Skin cancer is closely associated with UV light exposure.

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Most of us are exposed to large amounts of UVA throughout our lifetime. UVA rays account for up to 95 percent of the UV radiation reaching the Earth's surface. Although they are less intense than UVB, UVA rays are 30 to 50 times more prevalent. They are present with relatively equal intensity during all daylight hours throughout the year, and can penetrate clouds and glass.

Studies over the past two decades, however, show that UVA damages skin cells called keratinocytes in the basal layer of the epidermis, where most skin cancers occur. (Basal and squamous cells are types of keratinocytes.) UVA contributes to and may even initiate the development of skin cancers.

UVA is the dominant tanning ray, and we now know that tanning, whether outdoors or in a salon, causes cumulative damage over time. A tan results from injury to the skin's DNA; the skin darkens in an imperfect attempt to prevent further DNA damage. These imperfections, or mutations, can lead to skin cancer.

UVB, the chief cause of skin reddening and sunburn, tends to damage the skin's more superficial epidermal layers. It plays a key role in the development of skin cancer and a contributory role in tanning and photoaging. Its intensity varies by season, location, and time of day. The most significant amount of UVB hits the U.S. between 10 AM and 4 PM from April to October. However, UVB rays can burn and damage your skin year-round, especially at high altitudes and on reflective surfaces such as snow or ice, which bounce back up to 80 percent of the rays so that they hit the skin twice. UVB rays do not significantly penetrate glass.

Pigments in nature

Skin cancer is the most common form of cancer in the United States.

More than 2,000,000 skin cancers are diagnosed annually.

One in five Americans will develop skin cancer in their lifetimes.

Skin cancer is closely associated with UV light exposure.

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Pigments and cancer

Cancer begins when some cells divide and start grow out of control.

Cells become cancerous because of damage to DNA, which would cause normal cells to die.

In most cases cancer cells form a tumor although not all tumors are cancerous.

Cancer cells may invade other tissues.

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Cancer

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Squamous cell

Basal cell

Melanocyte

Epidermis

Dermis

Epidermis

Dermis

Hypodermis

Hair follicle

Skin cell types

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Melanocytes produce melanin in response to UV exposure and resulting DNA damage

Melanocytes i / mɛˈlænɵsaɪt / are melanin-producing cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea),[1] the inner ear,[2] meninges,[3] bones,[4] and heart.[5] Melanin is the pigment primarily responsible for skin color.

Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Melanin protects the body by absorbing solar radiation. Excessive solar radiation causes direct and indirect DNA damage to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but the UV-B in sunlight can also cause sunburn. The tanning process can also be created by artificial UV radiation, which can be delivered in frequencies of UV-A, UV-B, or a combination of both.

There are two different mechanisms involved in production of a tan by UV exposure: Firstly, UV-A radiation creates oxidative stress, which in turn oxidises existing melanin and leads to rapid darkening of the melanin. UV-A may also cause melanin to be redistributed (released from melanocytes where it is already stored), but its total quantity is unchanged. Thus, the effect of UV-A leads to skin darkening, but this is only cosmetic since it does not lead to greatly increased production of melanin and therefore also to little increase in protection against UV-B, or protection against sunburn.[ 1]

In the second process, triggered primarily by UV-B, there is an increase in production of melanin (melanogenesis),[2] which is the body's reaction to direct photodamage (formation of pyrimidine dimers) from UV radiation.[3] Melanogenesis leads to delayed tanning, and first becomes visible about 72 hours after exposure.[2] The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin, and is also actually protective against UV skin damage and sunburn, rather than simply cosmetic. However, in order to cause true melanogenesis-tanning by means of UV exposure, some direct DNA photodamage must first be produced, and this requires UV-B exposure (as present in natural sunlight, or sunlamps that produce UV-B).

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Squamous cell

Basal cell

Melanocyte

Epidermis

Dermis

Epidermis

Dermis

Hypodermis

Hair follicle

Pigments and cancer

Seek the shade, especially 10:00 AM-4 PM.

Do not burn.

Avoid tanning and UV tanning booths.

Cover up with clothing, including hats.

Use a broad-spectrum (UVA/UVB) sunscreen; 2 tablespoons for entire body 30 minutes in advance.

Examine your skin head-to-toe every month.

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Skin cancer – Prevention guidelines

Pigments and cancer

https://www.cancer.gov/melanomarisktool/

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Skin cancer – Risk assessment.

You are “the patient”

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Skin pigmentation and cancer risk

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Evolution …?

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Vitamin D3 synthesis

Photo-protection against folate loss & damage to sweat glands

Darker skin: Reduced UV radiation penentration, as go poleward, selection more for vitamin D synthesis and less on photoprotection. (Females may be lighter skinned on average to permit synthesis of relatively higher amounts of vitamin D3 during pregnancy and lactation.)

UV-induced photolysis of folate and spermatogenesis in addition to sunburning, which can damage sweat glands, and skin cancer.

Cooling by evaporation of eccrine sweat is impeded by thick body hair (9); the primary selective pressure promoting the evolution of hair loss in humans was thermoregulation, more active upright walking.

Females need more calcium during pregnancy and lactation. The body synthesizes vitamin D from sunlight, which helps it absorb calcium. Females evolved to have lighter skin so their bodies absorb more calcium

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Assignment, Event 6: Cells

“Cells exhibit many of the fundamental emergent properties of life.”

In an essay of less than 100 words, use your understanding to explain in detail what this quotation means. Your audience is a professional biologist.

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Quiz

You entered the classroom today wearing a light blue shirt…

If this room is completely dark what color will you you perceive your shirt to be? That is, what color will it be?

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Body weight (pounds, at 7:00 AM each day)

Week Sunday Monday Tuesday Wednesday Thursday Friday Saturday Average 1 158 159 157 158 158 157 158 157.9 2 158 158 158 158 157 158 158 157.9

Average 158.0 158.5 157.5 158.0 157.5 157.5 158.0 157.9

Body weight (pounds, at 7:00 AM each day)

WeekSundayMondayTuesdayWednesdayThursdayFridaySaturdayAverage

1158159157158158157158157.9

2158158158158157158158157.9

Average158.0158.5157.5158.0157.5157.5158.0157.9