Questions

[MM1]

Hi, I've decided to create a general Biology questions thread so we can all ask/discuss about concepts rather than creating separate threads thereby congesting the forum. Hopefully this will be of some benefit to all

So, here's my question: I'm having troubles trying to properly understand the concept of monomers/polymers for lipids. What exactly is the monomer and polymer of a lipid as an organic molecule?

Cheers!

[psyxwar]

Lipids don't form polymers, they just form aggregates of small molecules (the phospholipid bilayer is an aggregate of many phospholipid molecules). Thus they don't really have monomers either.

[Tyleralp1]

Lipids are the only bio-macromolecule which aren't a polymer. A polymer is defined as chain of repeating monomers. The monomers of fatty acid are said to be fatty acid chains. However, due to it's pair with it's counterpart, glycerol, it can either form a triglyceride or phospholipid. Due to the nature of the condensation reaction, it limits the amount of times the lipid monomers can repeat to either 2 or 3.

Hope that helps

[Yacoubb]

Hi, I've decided to create a general Biology questions thread so we can all ask/discuss about concepts rather than creating separate threads thereby congesting the forum. Hopefully this will be of some benefit to all

So, here's my question: I'm having troubles trying to properly understand the concept of monomers/polymers for lipids. What exactly is the monomer and polymer of a lipid as an organic molecule?

Cheers!

Something to keep in mind is that if VCAA asks you to state the monomers of lipids, say glycerol + fatty acid molecules. As mentioned, lipids don't form polymers. Aggregations are formed, and depending upon the hydrophilic/hydrophobic nature of the lipid, the aggregation is created in an orientation where hydrophobic ends attract, and hydrophilic ends attract.

[MM1]

Thanks all^.

Btw what are structures such as cilia and flagella classified as?

AND, since plant cells lack centrioles, how do they divide during mitosis since they don't have centrioles to produce a spindle to act as the anchor etc etc?


Thanks in advance

[Yacoubb]

Thanks all^.

Btw what are structures such as cilia and flagella classified as?

Thanks in advance

Cilia and flagella could just be considered as cellular structures. Just know that cilia and flagella provide a means of motility to unicellular organisms; this becomes especially important when you start to look at pathogens and how they have flagella as a means of motility, which actually provides a structural adaption for them. Also, the respiratory tract epithelial cells are lined with cilia; this is important because when these like hair-like appendages beat in unison, they can guide non-self matter clogged up in mucus to the mouth or the nose, where the mucus is expelled. Hope this helped.

AND, since plant cells lack centrioles, how do they divide during mitosis since they don't have centrioles to produce a spindle to act as the anchor etc etc?


Thanks in advance

Plant cells have centrosomes that replicate during interphase. Thus, microtubule-like filaments that act like spindle fibres are produced that enable the chromosomes (coiled genetic material) to be anchored, and nuclear division can thus take place.

[MM1]

Cilia and flagella could just be considered as cellular structures. Just know that cilia and flagella provide a means of motility to unicellular organisms; this becomes especially important when you start to look at pathogens and how they have flagella as a means of motility, which actually provides a structural adaption for them. Also, the respiratory tract epithelial cells are lined with cilia; this is important because when these like hair-like appendages beat in unison, they can guide non-self matter clogged up in mucus to the mouth or the nose, where the mucus is expelled. Hope this helped.

Plant cells have centrosomes that replicate during interphase. Thus, microtubule-like filaments that act like spindle fibres are produced that enable the chromosomes (coiled genetic material) to be anchored, and nuclear division can thus take place.

Thanks so much! Great explanation.

Btw what are the constituents of hormones? I know they're chemical messengers; I feel as if that's a vague understanding though.

[Yacoubb]

Thanks so much! Great explanation.

Btw what are the constituents of hormones? I know they're chemical messengers; I feel as if that's a vague understanding though.

Hormones are chemical signalling molecules produced by one type of cell, that diffuse through extracellular fluid to act on the cell they were synthesised by (autocrine signalling), neighbouring target cells in the intermediate vicinity (paracrine signalling) or travel through the bloodstream and act on target cells situated far away (endocrine signalling). Hormones act in minute quantities and produce profound responses by specific target cells. Target cells are specific cells that have specific receptors for specific signalling molecules.

Hormones fall into one of three categories:
(a) Lipid-soluble hormones; these are hormones that are hydrophobic in nature, and so are able to readily diffuse throught the phospholipid bi-layer of target cell membranes, and bind to specific hormone receptors within the cytosol of these target cells, activating several molecules in a transduction pathway, and eventually leading to a specific cellular response.
(B) Water-soluble hormones; protein hormones (made up of more than 200 amino acids) and peptide hormones (made up of less than 200 amino acids) are water-soluble. As a result, they are unable to readily cross the phospholipid bi-layer of target cell membranes. As a result, these hormones have protein receptors located on the outside of these cells. Once the specific water-soluble hormone binds to this protein receptor, a secondary messenger molecule (like a G protein) is activated, and carries the message through the cell. During this transduction phase, many molecules in the pathway are activated, and the last molecule in the pathway brings about the specific cellular response. This process by which the cell receives a signal, and the cascade of events following this leading up to the response by the cell, is called signal transduction.

These cellular responses can include:
(a) The synthesis of a protein (through gene expression)
(b) Increased permeability of the cell membrane to a substance (e.g. insulin increases the permeability of target cell membranes to glucose, for cells to increase glucose uptake and thereby reduce blood glucose levels).