cellular energy

Our ancestor’s ‘leaky’ membrane answers big questions in biology

All life on Earth came from one common ancestor – a single-celled organism – but what it looked like, how it lived and how it evolved into today’s modern cells is a four billion year old mystery being solved by researchers at UCL using mathematical modelling.

Findings published today in PLOS Biology suggest for the first time that life’s Last Universal Common Ancestor (LUCA) had a ‘leaky’ membrane, which helps scientists answer two of biology’s biggest questions:

1. Why all cells use the same complex mechanism to harvest energy

2. Why two types of single-celled organism that form the deepest branch on the tree of life – bacteria and archaea – have completely different cell membranes

The leakiness of the membrane allowed LUCA to be powered by energy in its surroundings, most likely vents deep on the ocean floor, whilst holding in all the other components necessary for life.

The team modeled how the membrane changed, enabling LUCA’s descendants to move to new, more challenging environments and evolve into two distinct types of single-celled organism, bacteria and archaea, creating the deepest branch of the tree of life.

Caption: Pumping and phospholipid membranes arose independently in archaea and bacteria. Credit: Victor Sojo et al.

clones-not-as-clones high school au where cosima and tony date and are the coolest/hottest/cheekiest couple in school 

Photosynthesis Dry Lab (Bromothymol/BTB)

QUESTIONS

This lab aimed to teach us about photosynthesis and respiration, and how they work together. We wondered things like “What causes BTB to change?” “Since oxygen doesn’t create acid for BTB to react with, would a plant photosynthesizing create anything?” “How would an animal’s presence and carbon dioxide affect BTB?” and “What color would BTB become in these situations?”

PROCEDURE

Materials needed: 250 mL (per experiment), a beaker, and about two squirts of BTB (per experiment).

  1. BTB is mixed into the water and let to sit in light for about an hour, to observe if anything changes. *
  2. BTB is mixed into the water and the snail is set in the beaker and left for about an hour in light. *
  3. BTB is mixed into water and the plant is submerged into it, then let to sit for an hour in light. *
  4. The same procedure for #3 is followed, but the snail is also added to the beaker. Then the beaker is left for three hours in light conditions and three hours in dark conditions. *

*The beaker is washed out between each experiment.

EVIDENCE

  1. In the first experiment, we observed no apparent change in the mixture. The BTB remained blue-green in the water.
  2. The second experiment showed significant change- the liquids became yellow.
  3. The plant didn’t change the BTB in any observable way- the mixture stayed blue-green.
  4. With both the snail and the plant, the beaker didn’t change at all in light, but in a dark environment the liquids turned yellow.

RESEARCH

  1. On the paper we received to do this write-up, the “FACTS” section showed that in a neutral pH, BTB doesn’t change. Water has a neutral pH.
  2. In the “FACTS” section, I found that carbon dioxide in water creates carbonic acid, and bromothymol reacts with acid. The snail, an animal that respires, breathes out carbon dioxide.
  3. In the “FACTS” portion of the paper, Oxygen isn’t described as something that creates acid.
  4. Carbon dioxide creates acid that BTB would react with- but it also creates sugar and oxygen when there’s chlorophyll and sunlight present.

REFLECTION/CONCLUSION

  1. Because water has a neutral pH, the BTB didn’t change, and remained a blue-green. I believe this very much makes sense, since water is such a good neutral substance to mix with things.
  2. In this beaker, the snail respired and creates carbon dioxide, which creates carbonic acid that BTB reacts with, which is why it turned yellow. This conclusion makes sense with the evidence and research I have gathered and written about.
  3. Taking into consideration the fact that plants output Oxygen and only carbon dioxide creates acid that BTB will react with, the plant obviously didn’t create any acid that would change the BTB as long as they were in a light environment.
  4. In a light environment, the plant can photosynthesize and get its nutrients from the snail’s carbon dioxide and the water and the sun combined. This way, the water doesn’t create carbonic acid because the plant will be using it. Because of this, the BTB didn’t react with anything and the beaker remained blue-green. However, in a dark environment the plant can’t photosynthesize, so it doesn’t take the carbon dioxide away. This makes the BTB change into a yellow color.

Based on what I’d read, I could draw my own conclusions on what did or didn’t make the BTB change, and when I wrote a little more in-depth, I could say why. I learned from this lab about how small-scale respiration and photosynthesis work together.

Phenylketonuria (PKU) Webquest

1. What enzyme is most commonly defective in people with phenylketonuria?

An enzyme that breaks down amino acids in protein; phenylalanine hydroxylase (PAH). Phenylalanine is an amino acid that PAH should break down, but in people with PKU, the enzyme won’t digest it.

2. What reaction does this enzyme catalyze? (What is the substrate and what product is produced?)

PAH is supposed to take phenylalanine (the substrate) and turn it into another amino acid called tyrosine (the product).

3. Describe the symptoms of phenylketonuria.

  • irritability
  • musky odor (mouse-like)
  • paleness in hair and skin
  • seizures/epilepsy
  • delays in development

4. What causes the symptoms of PKU, the lack of a substance or the buildup of one? Explain.

The buildup of a substance. The enzyme PAH cannot break down a protein in PKU and the amount of phenylalanine that builds up in the brain can become very harmful.

5. How common is phenylketonuria? How is it treated?

I would say that PKU is relatively common. It doesn’t affect a large number of the population, but there are still a lot of people who have it. PKU is treatable through a diet that is low in protein or enzymes or neurotransmitters being replaced.

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