barricadefairytales:

loveprideanddeepfriedchicken:

I think I’ll try defining gravity

THIS IS THE PUN OF ALL PUNS EVERYBODY CAN GO HOME NOW

barricadefairytales:

loveprideanddeepfriedchicken:

I think I’ll try defining gravity

THIS IS THE PUN OF ALL PUNS EVERYBODY CAN GO HOME NOW

sciencesoup:

Photosynthesis: Properties of Light and Chlorophyll

A while back, we talked about how organisms fall into different categories based on what food they eat and how they get it. Humans, for example, are heterotrophs because they get their energy from organic compounds that they didn’t make themselves—another organism did. Autotrophs, however, have special mechanisms to transform energy from the environment into a kind of energy that they can consume. Heterotrophs rely on autotrophs to make their food for them; they’re like the base of the foodchain, supporting everything else.

You’ve probably guessed what kind of autotrophs I’m talking about: plants.

Photosynthesis is the process plants use to convert light energy from the sun into chemical energy that we use in cellular respiration—glucose! Think of a plant’s leaves as solar collector, letting in light, water, and carbon dioxide: the three key ingredients for the photosynthetic process. These are allowed in through little passageways or holes called stomata. Oxygen is produced as a byproduct and is shuttled out via the same route. When the stomata are open, they can also allow the leaf to lose water vapor to the atmosphere—so to prevent plants drying out, the stomata are flanked by guard cells, which control when they open or close.

The leaves of a plant are filled with photosynthetic cells that contain chloroplast, the organelle where photosynthesis takes place. Chloroplasts are filled with stacked-up thylakoid membranes, which contain chlorophyll—pigments used in photosynthesis.

image

These chlorophyll pigments are actually contained within two light-harvesting protein complexes embedded in the membrane, called photosystem I and photosystem II. Their goal is to capture and pass on light energy. Just so you know, photosystem II is used first and photosystem I is used second; they’re only named I and II because that’s the order they were discovered.

To understand how we can get energy from light, we have to understand a bit about light itself. You know when you pass light through a prism and it’s separated into different colours? Each colour represents a different wavelength of light: red is the longest and violet is the shortest. Colours with shorter wavelengths are more energetic, so, for example, X-Rays and UV light have shorter wavelengths than visible light, which are in turn shorter than radio waves.

image

When light interacts with matter, it can be either reflected, transmitted, or absorbed. A pigment is a substance that absorbs light. Pigments are usually only good at absorbing only certain wavelengths of light. Black is good at absorbing all visible light and white isn’t—it mostly reflects colours back. There are two chlorophyll pigments (called chlorophyll a, which is the primary pigment, and chlorophyll b) and they’re are good at absorbing most wavelengths of visible light except for green—they reflect green back, which is why most plants are green. Chlorophyll a is most efficient at absorbing red light while chlorophyll b is most efficient at absorbing blue light.

image

There are also a couple of “accessory pigments” called carotenoids (like xanthophyll and carotene), which help pick up the wavelengths that chlorophyll doesn’t, and also helps protect them from damaging wavelengths.

Photosynthesis depends on chlorophyll capturing light energy, as we’ll see in the next article.

Cool background fact: photosynthesis most likely originated in the infolded regions of the membrane in ancient bacteria. In photosynthetic bacteria today, their membranes are folded in such a way as to act like the theylakoid membranes (remember that bacteria are prokaryotes and don’t have organelles).

Body images sourced from Wikimedia Commons

  1. Camera: Canon EOS 5D Mark II
  2. Exposure: 1/200th
  3. Focal Length: 50mm
rasjomanny:

July’s Sunspot!
rasjomanny:

July’s Sunspot!

rasjomanny:

July’s Sunspot!

eatsleepdraw:

"Cosmic Matter" by Alejandra Sáenz

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mucholderthen:

Directly visualizing hydrogen bonds
IMAGE: The hydrogen-bonding interaction causes the atoms on each individual N-methylacetamide molecule to vibrate in unison. Credit: L. De Marco/UChicago

Using a newly developed, ultrafast femtosecond infrared light source, chemists at the University of Chicago have been able to directly visualize the coordinated vibrations between hydrogen-bonded molecules—the first time this sort of chemical interaction, which is found in nature everywhere at the molecular level, has been directly visualized. They describe their experimental techniques and observations in The Journal of Chemical Physics.

SOURCE: Phys.org

  • SARAH: Daddy, were you in the shower?
  • DAD: Yes, I was in the shower.
  • SARAH: Why?
  • DAD: I was dirty. The shower gets me clean.
  • SARAH: Why?
  • DAD: Why does the shower get me clean?
  • SARAH: Yes.
  • DAD: Because the water washes the dirt away when I use soap.
  • SARAH: Why?
  • DAD: Why do I use soap?
  • SARAH: Yes.
  • DAD: Because the soap grabs the dirt and lets the water wash it off.
  • SARAH: Why?
  • DAD: Why does the soap grab the dirt?
  • SARAH: Yes.
  • DAD: Because soap is a surfactant.
  • SARAH: Why?
  • DAD: Why is soap a surfactant?
  • SARAH: Yes.
  • DAD: That is an EXCELLENT question. Soap is a surfactant because it forms water-soluble micelles that trap the otherwise insoluble dirt and oil particles.
  • SARAH: Why?
  • DAD: Why does soap form micelles?
  • SARAH: Yes.
  • DAD: Soap molecules are long chains with a polar, hydrophilic head and a non-polar, hydrophobic tail. Can you say ‘hydrophilic’?
  • SARAH: Aidrofawwic
  • DAD: And can you say ‘hydrophobic’?
  • SARAH: Aidrofawwic
  • DAD: Excellent! The word ‘hydrophobic’ means that it avoids water.
  • SARAH: Why?
  • DAD: Why does it mean that?
  • SARAH: Yes.
  • DAD: It’s Greek! ‘Hydro’ means water and ‘phobic’ means ‘fear of’. ‘Phobos’ is fear. So ‘hydrophobic’ means ‘afraid of water’.
  • SARAH: Like a monster?
  • DAD: You mean, like being afraid of a monster?
  • SARAH: Yes.
  • DAD: A scary monster, sure. If you were afraid of a monster, a Greek person would say you were gorgophobic.
  • (pause)
  • SARAH: (rolls her eyes) I thought we were talking about soap.
  • DAD: We are talking about soap.
  • (longish pause)
  • SARAH: Why?
  • DAD: Why do the molecules have a hydrophilic head and a hydrophobic tail?
  • SARAH: Yes.
  • DAD: Because the C-O bonds in the head are highly polar, and the C-H bonds in the tail are effectively non-polar.
  • SARAH: Why?
  • DAD: Because while carbon and hydrogen have almost the same electronegativity, oxygen is far more electronegative, thereby polarizing the C-O bonds.
  • SARAH: Why?
  • DAD: Why is oxygen more electronegative than carbon and hydrogen?
  • SARAH: Yes.
  • DAD: That’s complicated. There are different answers to that question, depending on whether you’re talking about the Pauling or Mulliken electronegativity scales. The Pauling scale is based on homo- versus heteronuclear bond strength differences, while the Mulliken scale is based on the atomic properties of electron affinity and ionization energy. But it really all comes down to effective nuclear charge. The valence electrons in an oxygen atom have a lower energy than those of a carbon atom, and electrons shared between them are held more tightly to the oxygen, because electrons in an oxygen atom experience a greater nuclear charge and therefore a stronger attraction to the atomic nucleus! Cool, huh?
  • (pause)
  • SARAH: I don’t get it.
  • DAD: That’s OK. Neither do most of my students.
  • (The Dad is Stephen McNeil, "an Assistant Professor of Chemistry at the University of British Columbia Okanagan in Kelowna, British Columbia.")

divineirony:

Science “journalism” is why we can’t have nice things.