Tutte le cellule sono rivestite da una membrana cellulare, formata da un doppio strato fosfolipidico; le cellule vegetali hanno anche una parete rigida costituita da cellulosa.

I batteri sono cellule procariote; queste cellule sono prive di membrana cellulare e possono vivere anche negli ambienti più estremi.

La parte fluida del citoplasma, il citosol, è una soluzione di ioni, piccole molecole e grosse proteine; nelle cellule eucariote metà del citoplasma è costituito da piccole strutture chiamate organuli.

Le cellule Eucariote: hanno dimensioni limitate per favorire il rapporto superficie/volume e rendere le cellule metabolicamente attive.

Il nucleo, avvolto da una doppia membrana dotata di pori per poter comunicare col citoplasma, contiene il DNA sotto forma di cromatina e un nucleolo che assembla i ribosomi.

Il citoscheletro mantiene la forma della cellula, fissa gli organuli, dirige il traffico interno e le consente di muoversi; è formato da filamenti di actina, microtubuli e filamenti intermedi.

Ciglia e flagelli sono formati da filamenti proteici; servono per il movimento.

Il vacuolo è una cavità citoplasmatica contenente acqua e soluti, delimitata da una membrana; le vescicole con funzione di trasporto, sono piccole e hanno una struttura uguale al vacuolo

Il reticolo endoplasmatico è costituito da un sistema di membrane; il reticolo rugoso ricoperto di ribosomi da ribosomi sintetizza le proteine e il reticolo liscio sintetizza soppratutto lipidi.

I lisosomi sono vescicole che racchiudono gli enzimi coinvolti nelle reazioni di idrolisi, i proteasomi sono specializzati nel demolire proteine per riciclare amminoacidi, i perossisomi contengono diversi enzimi ossidativi.

I cloroplasti svolgono la fotosintesi clorofialiana ; nei mitocondri, invece, avviene la respirazione cellullare.

I ribosomi sono sono siti presso cui vengono assemblati gli amminoacidi per la sintesi delle proteine.

L'apparato di golgi è un centro di elaborazione di molecole complesse che vengono poi avvolte in vescicole e trattenute nella cellula stessa o esportate.

I have always been bullish about India's potential. I still am, and I feel India is a country that really has an enormous amount of potential and has the human capital to succeed.

Legislation to create a new 10 percent tax bracket, reduce the marriage penalty, cut the tax rate on dividends and capital gains, and increase the child tax credit have been essential elements in this economic expansion.

Morality in its noblest forms remains inexplicable unless one takes into account that power of growth in the human soul which has led generation after generation from lower religious and ethical standards to higher ones which often clash with worldly advantages.

I use self-tanners at least once a week, and I get darker than I do then when I am in the sun.

My house has always been like everyone's house. You walk in, you're a part of the family, no matter who you are, what celebrity status you are, everyone is treated the same - with love from my mom.

Unity is a beast in itself. If a wolf sees two little boys playing in the woods on one side, and a big strong man on the other, he will go to the one who stands alone.

In time of war steamships and improved arms are the most important things.

Perhaps if we all subscribed to the African concept of Ubuntu - that we all become people through other people, and that we cannot be fully human alone, we could learn a lot. There'd be less hatred and more harmony.

Ideas are cheap. The difficult part is finding the team to execute them.

Mountains aren't eternal: even the most imposing massifs are smoothed away by weathering in a few hundred million years or less. Plate tectonics makes new ones, and without it, our future would be flat.

Simply put, I believe we should not seek the lowest common denominator when it comes to wilderness and saddle a wilderness designation with exceptions, exclusions, and exemptions.

I love listening to old school stuff. I listen to some new cats out here, but I'm really into, like, Tech N9ne and his clique; I really like Eminem and those guys - cats that got real flow: I really connect with that. But I do love rock. I love a lot of electronica because I love programming synthesizers.

The first person a customer speaks with has the greatest impact on that customer's impression of Safeway.

We can't continue to tax, borrow, and spend at the rates that we are, and it's just got to be stopped.

Harmonies come really naturally to me. I don't have to labor too hard over them. I'll sing a lead vocal, and then I will immediately have all of these other ideas for vocal harmonies. I think that some of the most fun parts of recording, for me, are the vocal harmonies.

Demons dont play by the rules. They lie and they cheat and they stab in the back.

When I was growing up, there was no such thing as a touring ukulele player.

Using a service such as Chegg.com, students can save on average more than $600 a year when they rent textbooks over purchasing them.

Sharks are as tough as those football fans who take their shirts off during games in Chicago in January, only more intelligent.

Any superhero, regardless of how different they are from Superman, recalls Superman in some way. They're either pushing against Superman or reflecting Superman; there's something about them that comes from Superman.

I played Othello, but I didn't sit around thinking how Laurence Olivier did it when he played it. That wouldn't do me any good.

I don't love football the way I once loved the game. I don't look at it as fun anymore, and it definitely used to be fun. A lot of the fun has been taken away from it, I guess, because you go through so much on the field and off the field.

Because of her interest and demands, I amplified an average baritone voice into one that is loud and clear.

I have been working for Africans since I was 18, when I got involved with the Nelson Mandela concerts. I got involved with debt cancellation because Desmond Tutu demanded that the world respond to that situation.