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What are lipids?

Ernest Z.
Ernest Z.
Featured 2 months ago

Answer:

Lipids are naturally-occurring organic compounds that are readily soluble in nonpolar solvents but insoluble in polar solvents.

Explanation:

The main biological functions of lipids include storing energy, signalling, and acting as structural components of cell membranes.

Since lipids are defined by their solubilities, they have varying structures, but they all have one thing in common: a polar, hydrophilic "head" and a nonpolar, hydrophobic, hydrocarbon "tail".

Lipids include the following classes.

Fats

Fats are esters of glycerol with long-chain fatty acids.

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The ester groups form the polar head of the molecule.

Phospholipids

In phospholipids, one of the fatty acids has been replaced by a phosphate group and a simple molecule such as choline.

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Sphingolipids

Sphingolipids are based on sphingosine rather than glycerol. Sphingomyelin is a typical example.

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Sterols

Sterols have a tetracyclic hydrocarbon ring system with an attached hydrocarbon chain. Cholesterol is a typical example.

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Fat-Soluble Vitamins

Vitamin A (retinol) is a typical example.

static.newworldencyclopedia.org

The OH group is the polar head of the molecule.

Answer:

Organisms which are from different evolutionary lines, often show similar adaptive tendencies to occupy similar habitats. Such a phenomenon is called convergent evolution.

Explanation:

Convergent evolution allows unrelated organisms to live in a habitat in similar manner. For example, ducks and frogs both show webbed feet, as they both spend time in aquatic habitat. It is also true for development of flippers in penguin, a bird and dolphin, a mammal.

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There are examples from fossil evidence as well, like reptilian organism pterodactyl, which developed wings to fly like bird and bat, a mammal.

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Convergent evolution leads to appearance of analogous organs , which means there could be morphological similarity in structure but the underlying infrastructures differ.

  • For example thorns and spines in plants may develop from axial buds, but in cacti, thorns are modified leaves.
  • Likewise wing of bat is a patagium, i.e. folds of skin supported by highly elongated fingers while in birds fingers are vestigial and wing is feathery. Then there are insects with wings but those are without any bony support: insect wings are actually made of polysaccharide chitin.

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Answer:

Chromatin is chromosome in uncoiled and hydrated state.

Explanation:

From the following illustration you will be able to understand that chromatin undergoes packaging to appear as chromosome.

https://qph.ec.quoracdn.net/main-qimg-0bd9b33ba48b487f45325b1563b7773a?convert_to_webp=true

Chromatin is chemically an integration of DNA and histone. In interphase nucleus it remains in hydrated and uncoiled condition. It undergoes dehydration and coiling when the cell enters in divisional stage, hence appear as distict chromosomes.

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Answer:

Safe for once-off consumption, but open to debate as a policy.
A country has to abide by certain international protocols before allowing marketing of GM foods for consumption.

Explanation:

Genetically modified foods are usually the product of much research and are carefully monitored by the producers who cannot afford to get a bad reputation.

On the other hand there are many critics, most of them scientific experts, who question the long-term effects and commercial motives of the producers. Their concern is mainly possible harmful effect of such organisms on biodiversity.

World community has signed a protocol to safeguard efforts for conservation and sustainable use of biological diversity, taking into account risks to human health, and focusing on transboundary movements (Article 1 of the Cartagena Protocol , SCBD 2000).

Answer:

Because it messes up the whole nucleotide sequence.

Explanation:

The addition or loss of DNA bases changes a gene's reading frame. A reading frame consists of groups of 3 bases that each code for one amino acid.

A frameshift mutation shifts the grouping of these bases, changing the code for an amino acids.

The resulting protein is usually not functional. Premature chain termination mostly takes place.

Insertions, deletions, and duplications can all be frameshift mutations.

Example:
Imagine each letter as a nucleotide, and groups of three letters as a codons.

Normal sequence, no mutations:
THE FAT CAT ATE THE FAT RAT

Frame-shift mutation, Insertion of an extra A at the A in CAT:
THE FAT CAA TAT ETH EFA TRA T

Frame-shift mutation, Deletion of an A at the A in CAT:
THE FAT CTA TET HEF ATR AT

Frame-shift mutation, Duplication of an A at the A in CAT:

THE FAT CAA TAT ETH EFA TRA T

The result of frame-shift mutations is that the wrong codons will be synthesized.

Another more scientific example:
Nucleotide sequence is on the top grouped into 3's (the codons), the amino acid it codes for is abbreviated underneath.

Original Sequence:
CAT--TCA--CAC--GTA--CTC--ATG
[his]--[ser]--[his]--[val--[leu]--[met]

Frameshift one base to the right:
C--ATT--CAC--ACG--TAC--TCA--TGC
[x]--[ile]--[his]--[thr]--[tyr]--[ser]--[cys]

Answer:

Through active diffusion.

Explanation:

Active diffusion is when molecules move through a selectively permeable membrane from an area of low to high concentration.

Active diffusion requires carrier proteins and cellular energy.
Normally small non-polar and hydrophobic molecules are able to enter and pass through the cells bi-lipid membrane, however the permeability to ions is very low, due to their charge.

Therefore, the passage of ions is aided by the presence of specific membrane transport proteins, in which the 'sodium-potassium pump' being one for potassium.

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Three sodium ions attach to the proteins, as well as the ATP, which splits to provides energy to change the shape of the protein. Sodium ions are pushed out the membrane to the outside of the cell, when the protein changes shape.

Two potassium ions bind to the protein and are then transported through the membrane to the inside of the cell, when the protein changes shape. The phosphate detaches from the protein, to resynthesises into ATP.

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