Senin, 23 Februari 2009

Molekul Penyusun Sel

Sel : unit terkecil (struktural & fungsional) penyusun mahluk hidup

Sel membentuk sejumlah molekul besar dari sekelompok molekul-molekul yang lebih kecil

Molekul organik yang kecil :
tersusun dari senyawa karbon (BM antara 100 – 1000) dan mengandung lebih dari 30 atom karbon
Beberapa digunakan sebagai monomer untuk menyusun makromolekul
Beberapa juga berfungsi sebagai sumber energi


Empat macam molekul organik kecil yang ada dalam sel

Cells make most of their large molecules
By joining smaller organic molecules into chains called polymers
Cells link monomers to form polymers
By a dehydration reaction (synthesis) or condensation

Polymers are broken down to monomers
By the reverse process, hydrolysis
CARBOHYDRATES
Monosaccharides are the simplest carbohydrates
The carbohydrate monomers Are monosaccharides


The monosaccharides glucose and fructose are isomers
That contain the same atoms but in different arrangements
Fungsi monosakarida
Sumber energi dalam proses respirasi

Rangka peyusun molekul-molekul yang lebih besar
Pati, glikogen, selulosa
Ribosa (gula pentosa) ; digunakan untuk membentuk RNA dan ATP
Deoksiribosa : digunakan untuk membentuk DNA

Didalam sel Monosakarida dapat bergabung membentuk
disakarida atau polisakarida
Contoh disakarida misalnya : sukrosa dan maltosa

How sweet is sweet?
Beberapa molekul, termasuk yang bukan gula
dapat terasa manis karena molekul tersebut terikat pada reseptor perasa “manis” yang ada di lidah.

Contoh polisakarida (merupakan cadangan energi):
Pati (pada sel tumbuhan)
Glikogen (pada sel hewan/manusia)

Cellulose is a polysaccharide found in plant cell walls
oligosakarida
Dapat membentuk ikatan kovalen dengan
Protein : glikoprotein
Lemak : glikolipid

Glikoprotein dan glikolipid merupakan komponen membran sel


Lipids are grouped together because they are hydrophobic

Asam lemak tersimpan didalam sitoplasma sel dalam bentuk molekul trigliserida (tiga rantai asam lemak yang bergabung dengan gliserol)
Lemak hewan : daging, butter, cream
Lemak tumbuhan : minyak jagung, minyak zaitun

Asam lemak (trigliserida)tidak larut dalam air (hidrofobik, non-polar) tetapi larut dalam pelarut organik
Misal : benzene, ethanol, chloroform, eter

Fats, also called triglycerides
Are lipids whose main function is energy storage
Consist of glycerol linked to three fatty acids

Phospholipids, waxes, and steroids are lipids with a variety of
functions
Phospholipids are a major component of cell membranes
Waxes form waterproof coatings
Steroids are often hormones
Saturated and unsaturated fats and fatty acids
Asam lemak tak jenuh (unsaturated) : memiliki ikatan ganda -C-C=C-C-C, mudah meleleh (minyak tumbuh-tumbuhan)
Jika terdapat lebih dari dua ikatan ganda : poliunsaturated

Asam lemak jenuh : umumnya berasal dari hewan
Saturated and unsaturated fats and fatty acids

Peran trigliserida : sebagai sumber energi

Lemak disimpan disejumlah tempat pada tubuh manusia : dibawah lapisan dermis pada kulit dan disekitar ginjal
CONNECTION
Anabolic steroids pose health risks
Anabolic steroids
Are synthetic variants of testosterone
Can cause serious health problems
PROTEINS

Each amino acid contains
An amino group
A carboxyl group
An R (variable) group, which distinguishes each of the 20 different amino acids

Each amino acid has specific properties
Based on its structure

Cells link amino acids together
By dehydration synthesis
The bonds between amino acid monomers
Are called peptide bonds

A protein’s specific shape determines its function
A protein consists of one or more polypeptide chains
Folded into a unique shape that determines the protein’s function

Primary Structure
A protein’s primary structure
Is the sequence of amino acids forming its polypeptide chains

Tertiary Structure
A protein’s tertiary structure
Is the overall three-dimensional shape of a polypeptide

Quaternary Structure
A protein’s quaternary structure
Results from the association of two or more polypeptide chains (subunits)
TALKING ABOUT SCIENCE
Linus Pauling contributed to our understanding of the
chemistry of life
Linus Pauling made important contributions
To our understanding of protein structure and function
NUCLEIC ACIDS
Nucleic acids are information-rich polymers of nucleotides
Nucleic acids such as DNA and RNA
Serve as the blueprints for proteins and thus control the life of a cell

The sugar and phosphate
Form the backbone for the nucleic acid or polynucleotide

DNA consists of two polynucleotides
Twisted around each other in a double helix
RNA, by contrast, is a single-stranded polynucleotide Three types of RNA


1 accatttgtt ggcagagaca gatggtcagt ctggaggatg acgtggcgtg aacatctgcc
61 tggagtcccg cccctgccca gaacccttcc tgagacctcg ccggccttgt tttattcaaa
121 gacagagaag accaaagcat tgcctgccag agctttgttt tatatattta ttcatctggg
181 aggcagaaca ggcttcggac agtgcccatg caatggcttg ggttgggatt ttggtttctt
241 cctttcctgt gaaggataag agaaacaggc ccggggggac caggatgaca cctccatttc
301 tctccaggaa gttttgagtt tctctccacc gtgacacaat cctcaaacat ggaagatgaa
361 agggcagggg atgtcaggcc cagagaagca agtggctttc aacacacaac agcagatggc
421 accaacggga ccccctggcc ctgcctcatc caccaatctc taagccaaac ccctaaactc
481 aggagtcaac gtgtttacct cttctatgca agccttgcta gacagccagg ttagcctttg
541 ccctgtcacc cccgaatcat gacccaccca gtgtctttcg aggtgggttt gtaccttcct
601 taagccagga aagggattca tggcgtcgga aatgatctgg ctgaatccgt ggtggcaccg
661 agaccaaact cattcaccaa atgatgccac ttcccagagg cagagcctga gtcaccggtc
721 acccttaata tttattaagt gcctgagaca cccggttacc ttggccgtga ggacacgtgg
781 cctgcaccca ggtgtggctg tcaggacacc agcctggtgc ccatcctccc gacccctacc
841 cacttccatt cccgtggtct ccttgcactt tctcagttca gagttgtaca ctgtgtacat
901 ttggcatttg tgttattatt ttgcactgtt ttctgtcgtg tgtgttggga tgggatccca
961 ggccagggaa agcccgtgtc aatgaatgcc ggggacagag aggggcaggt tgaccgggac
1021 ttcaaagccg tgatcgtgaa tatcgagaac tgccattgtc gtctttatgt ccgcccacct
1081 agtgcttcca cttctatgca aatgcctcca agccattcac ttccccaatc ttgtcgttga
1141 tgggtatgtg tttaaaacat gcacggtgag gccgggcgca gtggcctcac gcctgtaatc

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