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help please 1

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help please 1

Postby Stephen1993 » Thu Feb 16, 2012 2:30 pm

hi

what does each bullet points mean?

- Cells themselves are composed of lifeless molecules.
- Life is an emergent property that is only manifested at the level of an intact cell.
- We have now entered the post-genomic era- What is the post-genomic era?
- The rate at which biological knowledge and biotechnology is advancing probably supercedes the rate at which information technology has advanced over the last decades and will certainly have profound implications for us in the future.
- In biology a hypothesis can only be supported or rejected, it is not proven.
- The naked eye cannot resolve objects less than 200 micrometres so to observe most cells we have to use a microscope- So does this mean that a naked eye can see a cell but cannot clearly see it?
- For an electron microscope what is the electron source?
- Because we get are looking at a 3-dimensional structure with shadows, we get a greater depth of field than with the TEM, but less magnification.
- The cell theory is one of the great unifying theories of biology- What does the unifying bit mean?
- Only at the level of the cell do the properties of life emerge.
- Important properties of weak interactions: They are reversible. They are transient.
- Ionic bonds are weakened in water. When this happens they are called ionic attractions.
- This type of weak interaction is usually a stabilising force; Van der Waals interactions form after other weak interactions do.
- A hydrophobic interaction is the tendency of non-polar molecules to associate with one another- Isn’t this something to do with the water molecules as well?
- Polar or ionic molecules are hydrophilic (water-loving)- they have an affinity for water and can form hydrogen bonds with water molecules- Firstly ionic substance are not molecules? And secondly aren’t certain polar molecules can form hydrogen bonds with water molecules? And lastly how can ionic substances form hydrogen bonds with water molecules?
- The effect of this is that any hydrophobic molecules are ‘excluded’ from all of this hydrogen bonding- So away from just water molecules? Or away from polar molecules as well?
- The non-polar molecules do not experience an actual attractive force. Instead, attractive forces between the hydrophilic molecules drive their associations.
- The joining of monomers is a process that requires an input of energy. This is accomplished by activating the monomers with energy before joining them together- What does the last bit/ sentence mean?

ty

p.s how do you add an attachment because it doesn't seem to work?
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Postby JackBean » Fri Feb 17, 2012 11:44 am

They mainly mean basically what's written in there.
http://www.biolib.cz/en/main/

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Re: help please 1

Postby Stephen1993 » Wed Feb 22, 2012 10:57 pm

hi

i don't get what you mean
can anyone help me please?

cheers
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Postby JackBean » Wed Feb 22, 2012 11:04 pm

e.g. Cells themselves are composed of lifeless molecules. simply means, that cells themselves are composed of lifeless molecules. There is hardly something to explain. At least not almost 20 statements :roll:
http://www.biolib.cz/en/main/

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Re: help please 1

Postby Stephen1993 » Wed Feb 22, 2012 11:19 pm

how about these?

Lecture 4
- All organisms except Bacteria and Archaea (including plants, animals, fungi and protists) are in the domain Eukarya- they are eukaryotes and have eukaryotic cells- In brackets are they Bacteria and Archaea or are not Bacteria and Archaea?
- The term ‘karyote’ means ‘nucleus’, and the prefix ‘eu’ means ‘genuine’, so a eukaryote has a ‘genuine nucleus’- What does genuine mean in this case?
- The prefix ‘pro’ means ‘before’, so prokaryotes are thought to be primitive organisms (‘before nucleus’)- What does the whole thing mean and what does before mean in this case?
- If a eukaryotic cell has internal compartments whereas they are not found in the prokaryotic cells then why do bacteria have ribosomes then?
- All cells require genetic information, and store it in one or more DNA molecules- What does it say require? Why not use that all cells have genetic information?
- The bacterial chromosome is circular and is organised into an amorphous structure called a nucleoid that is not enclosed in a membrane- What do they mean by amorphous in this case?
- The cross-linking is so extensive that a bacterial cell can be viewed as being surrounded by a single gigantic molecule.
- Instead the chromosomes exist in a loosely packaged complex of DNA and protein called chromatin- What do they mean by loosely packaged- it sounds like an oxymoron? And what does the protein do and what is the point of chromatin?
- Chromatin is seen as granular material inside the nucleus- What do they mean by granular in this case?
- The protein lattice called the nuclear lamina- What do they mean by lattice in this case?
- The nuclear pore complexes that perforate the nuclear envelope- What do they mean by perforate in this case?
- Peroxisomes- They carry out a wide range of reactions including detoxification of oxygen radicals- What do they mean by oxygen radicals?
- The internal compartments of chloroplasts are formed from membranes and the whole structure is surrounded by two more membranes.

ty
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Re: help please 1

Postby AstraSequi » Thu Feb 23, 2012 7:20 am

I've commented on a few of them. You really need to look things up yourself though (Google, Wikipedia, textbooks, biology teachers, etc).

Stephen1993 wrote:- Cells themselves are composed of lifeless molecules.
- Life is an emergent property that is only manifested at the level of an intact cell.
- Only at the level of the cell do the properties of life emerge.

Life is defined by certain characteristics, like the ability to reproduce, the ability to adapt to changes in the environment, etc. Only complete cells can fulfill all the criteria.

That being said, "life" is a definition that humans have decided on. There is nothing fundamentally different about the molecules - it's just that when the molecules are in a particular kind of chemical system, we call that system a living organism.

- We have now entered the post-genomic era- What is the post-genomic era?

This is the time after the sequencing of the human genome.

- In biology a hypothesis can only be supported or rejected, it is not proven.

This is true in all of science; it is a characteristic of the scientific method. "Proof" is a rigorous philosophical term which is only correctly used when referring to mathematics and logic. For example, you cannot "prove" that gravity exists, in the sense that there's always a tiny possibility that all of reality actually doesn't exist, or aliens are tricking us every time we see something fall, or similar things like that. Of course, if there is no evidence for these claims, it isn't logical to claim that they are true. :)

Another way to say this: you can pick up and drop a pencil a million times, but that doesn't mean you know that it will happen again the next time (which would be "proof") - it's just extremely likely. In fact, it's so likely that there's no reason to think that it will do anything else, so it's as close to proof as anyone could want, but is not strictly the same thing.

- The naked eye cannot resolve objects less than 200 micrometres so to observe most cells we have to use a microscope- So does this mean that a naked eye can see a cell but cannot clearly see it?

It means that we can see some very large cells, like human oocytes, but we cannot see the vast majority of them. You can also look up the precise definition of "resolution" for more specific information - it's the same thing as the resolution on your camera.

- The cell theory is one of the great unifying theories of biology- What does the unifying bit mean?

It means that it explains many, many things that are not able to be explained without cell theory - that it applies to almost all of biology as far as we know it (within certain limits, because some parts of biology don't involve cells). In other words, it is one of a few basic principles that tell us how biology works - just like atomic theory is one of the basic principles that tell us how physics works.

- The term ‘karyote’ means ‘nucleus’, and the prefix ‘eu’ means ‘genuine’, so a eukaryote has a ‘genuine nucleus’- What does genuine mean in this case?
- The prefix ‘pro’ means ‘before’, so prokaryotes are thought to be primitive organisms (‘before nucleus’)- What does the whole thing mean and what does before mean in this case?

These are just terms that people thought would be convenient. Prokaryotes have no nucleus (they first arose on Earth before the evolution of the nucleus), and eukaryotes do have a nucleus. I think that 'eu' is the opposite of 'pro' in Greek, so someone added the 'eu' to make the names sound better.

- If a eukaryotic cell has internal compartments whereas they are not found in the prokaryotic cells then why do bacteria have ribosomes then?

Ribosomes are not internal compartments - they are extremely large enzymes. (Ribozymes, to be precise.)
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Postby JackBean » Thu Feb 23, 2012 8:27 am

Sure, brong some more. Maybe someone will comment on them :roll:

This one is good one
All organisms except Bacteria and Archaea (including plants, animals, fungi and protists) are in the domain Eukarya- they are eukaryotes and have eukaryotic cells- In brackets are they Bacteria and Archaea or are not Bacteria and Archaea?
It's like saying - OK, all people except Americans and Australians live in Europe, Asia or Africa.
http://www.biolib.cz/en/main/

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Re: help please 1

Postby Stephen1993 » Thu Feb 23, 2012 9:15 am

thank you for that guys

also i wonder how you study well for biology
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Re: help please 1

Postby Stephen1993 » Sun Feb 26, 2012 7:06 am

also is there crossing over between the sex chromosomes (between XX and between XY) during meiosis?

ty
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Postby JackBean » Mon Feb 27, 2012 5:17 pm

yes
http://www.biolib.cz/en/main/

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