24 Şubat 2015 Salı
23 Şubat 2015 Pazartesi
PROTEİNLER
Proteins are large molecules.
They are not really soluble, rather they form colloids
- colloids are about 500nm, which is larger than particles in solution, but smaller than particles in suspension
- colloids exist in a "sol-gel state", whereby sometimes they appear to be liquid and at other times they are jelly-like (much of the material in cytoplasm is colloid)
Proteins contain: C, H, O and N, sometimes S and P
There are an almost limitless number of proteins, which vary between species and are often species-specific (fajlagosok). They determine the characteristics of a species.
Types of Proteins
a. Structural proteins - these form the organism. eg. hair, nails, feathers, etc.
b. Physiological proteins - these carry out functions, examples include:
-enzymes (biocatalysts)
-carrier molecules (szállítómolekulák)
- pigments (eg. various colour molecules in skin and eyes, haemoglobin in red blood cells)
- hormones (chemical messengers)
- contractile material in muscles
- antibodies (disease protection)
** Proteins are rarely stored (only in seeds and eggs). Proteins are only broken down for energy if a living organism is starving.
PROTEIN STRUCTURE
- a protein is a polymer. Its monomers are called amino acids.
Image from http://api.ning.com/files/xO6ybWgUbfFlk7GUXm9d8dfR--U-fUdPOJEtDzVGgDY_/aminoacidstruc.jpg
- some amino acids are basic, others are neutral - this depends on the variable group
- some amino acids are polar and others are apolar - this depends on the variable group
-amino acids are soluble in water, where they form dipolar ions (zwitterion = ikerion), this means they have BOTH acid-base properties, so they have good buffering capacity.
Synthesis of polypeptides
- amino acids attach to each other by condensation to form covalent peptide bonds
2 amino acids condense to form a dipeptide, 3 form a tripeptide and many joined together form a polypeptide.
- if more than 100 amino acids attach together it is considered a protein
- polypeptides (and proteins) are broken down by hydrolysis
*both condensation and hydrolysis require enzymes to occur.
Structure
Primary structure: this is the number and sequence of the amino acids.
*Insulin was the first protein to have its primary structure determined by a researcher named Fred Sanger
Secondary structure: This type of structure is created by H-bonds forming between amino acid monomers
Alpha helix (eg. keratin - a major component of hair and skin)
Image from http://www.bio.miami.edu/~cmallery/150/protein/alpha-helix.jpg
Beta-pleated sheet (eg. silk protein)
Image from http://student.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/images/betasheet.jpg
-both structures can be found in a single protein.
Tertiary structure: This is the secondary structure folded in 3-dimensional space.
-usually forms globular shapes
-bonded by S-bridges (requires the amino acid cysteine), ionic bonds, H-bonds and van der Waals forces
Image from http://lectures.molgen.mpg.de/ProteinStructure/Levels/tertiary.gif
Quaternary structure: A protein has quaternary structure if it is formed of 2 or more subunits (polypeptides). They are held together by various forces including hydrophobic interactions, H-bonds and ionic bonds.
eg. Haemoglobin
Image from http://www.theironfiles.co.uk/images/Haemoglobin_Structure.jpg
Proteins can further be catagorized as simple or complex. A simple protein contains only amino acids, complex proteins often include other elements, such as the iron containing haeme molecule found in haemoglobin (above).
Protein Stability and Denaturation
A protein will be stable (maintain its shape and function) if the environment it is in is appropriate. The most common environmental factors that will cause a protein to denature (lose its shape and/or function) are temperature and pH levels. Some proteins have a wide range of tolerance (can function at 4C and at 40C), while others have a very narrow range. This is a protein-specific characteristic. An example of protein denaturation is when we cook an egg. The white of the egg is almost entirely made of the protein albumin. At room temperature it is a clear liquid. If we increase the temperature, the protein starts to denature (lose its shape and therefore function too) and it become solid and white. Denaturation occurs because the bonds between the amino acids are broken.
Sometimes denaturation is permanent (like cooking an egg), other times it can be reversible.http://bilingualbiology11a.blogspot.com.es/2010/09/lesson-4-chemistry-of-life-proteins.html
They are not really soluble, rather they form colloids
- colloids are about 500nm, which is larger than particles in solution, but smaller than particles in suspension
- colloids exist in a "sol-gel state", whereby sometimes they appear to be liquid and at other times they are jelly-like (much of the material in cytoplasm is colloid)
Proteins contain: C, H, O and N, sometimes S and P
There are an almost limitless number of proteins, which vary between species and are often species-specific (fajlagosok). They determine the characteristics of a species.
Types of Proteins
a. Structural proteins - these form the organism. eg. hair, nails, feathers, etc.
b. Physiological proteins - these carry out functions, examples include:
-enzymes (biocatalysts)
-carrier molecules (szállítómolekulák)
- pigments (eg. various colour molecules in skin and eyes, haemoglobin in red blood cells)
- hormones (chemical messengers)
- contractile material in muscles
- antibodies (disease protection)
** Proteins are rarely stored (only in seeds and eggs). Proteins are only broken down for energy if a living organism is starving.
PROTEIN STRUCTURE
- a protein is a polymer. Its monomers are called amino acids.
Image from http://api.ning.com/files/xO6ybWgUbfFlk7GUXm9d8dfR--U-fUdPOJEtDzVGgDY_/aminoacidstruc.jpg
- some amino acids are basic, others are neutral - this depends on the variable group
- some amino acids are polar and others are apolar - this depends on the variable group
-amino acids are soluble in water, where they form dipolar ions (zwitterion = ikerion), this means they have BOTH acid-base properties, so they have good buffering capacity.
Synthesis of polypeptides
- amino acids attach to each other by condensation to form covalent peptide bonds
2 amino acids condense to form a dipeptide, 3 form a tripeptide and many joined together form a polypeptide.
Formation of a dipeptide
Image from http://www.mrothery.co.uk/images/Image46.gif- if more than 100 amino acids attach together it is considered a protein
- polypeptides (and proteins) are broken down by hydrolysis
*both condensation and hydrolysis require enzymes to occur.
Structure
Primary structure: this is the number and sequence of the amino acids.
*Insulin was the first protein to have its primary structure determined by a researcher named Fred Sanger
Secondary structure: This type of structure is created by H-bonds forming between amino acid monomers
Alpha helix (eg. keratin - a major component of hair and skin)
Image from http://www.bio.miami.edu/~cmallery/150/protein/alpha-helix.jpg
Beta-pleated sheet (eg. silk protein)
Image from http://student.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/images/betasheet.jpg
-both structures can be found in a single protein.
Tertiary structure: This is the secondary structure folded in 3-dimensional space.
-usually forms globular shapes
-bonded by S-bridges (requires the amino acid cysteine), ionic bonds, H-bonds and van der Waals forces
Image from http://lectures.molgen.mpg.de/ProteinStructure/Levels/tertiary.gif
Quaternary structure: A protein has quaternary structure if it is formed of 2 or more subunits (polypeptides). They are held together by various forces including hydrophobic interactions, H-bonds and ionic bonds.
eg. Haemoglobin
Image from http://www.theironfiles.co.uk/images/Haemoglobin_Structure.jpg
Proteins can further be catagorized as simple or complex. A simple protein contains only amino acids, complex proteins often include other elements, such as the iron containing haeme molecule found in haemoglobin (above).
Protein Stability and Denaturation
A protein will be stable (maintain its shape and function) if the environment it is in is appropriate. The most common environmental factors that will cause a protein to denature (lose its shape and/or function) are temperature and pH levels. Some proteins have a wide range of tolerance (can function at 4C and at 40C), while others have a very narrow range. This is a protein-specific characteristic. An example of protein denaturation is when we cook an egg. The white of the egg is almost entirely made of the protein albumin. At room temperature it is a clear liquid. If we increase the temperature, the protein starts to denature (lose its shape and therefore function too) and it become solid and white. Denaturation occurs because the bonds between the amino acids are broken.
Sometimes denaturation is permanent (like cooking an egg), other times it can be reversible.http://bilingualbiology11a.blogspot.com.es/2010/09/lesson-4-chemistry-of-life-proteins.html
HÜCRE DÖNGÜSÜ, REPLİKASYON, MİTOZ VE MAYOZ
Topic 11: Cell cycle, DNA replication, mitosis and meiosis
DNA is found in the nucleus. It carries the genetic information in all eukaryotes.
How is DNA organized?
-its basic structure is the double helix
-this is then wound around proteins (called histones) to form chromatin. Under an electron microscope, it looks like beads on a chain. This is the form that DNA is stored in between cell divisions
-during cell division the DNA winds up more tightly and the chromatin coils on itself, looping and coiling to form thick rods called chromosomes, which are visible under the light microscope
Image from: http://themedicalbiochemistrypage.org/dna.html
What happens?
DNA is copied when it is uncondensed, then it condenses into chromosomes that have 2 halves (each a copy of the other). Each half is called a chromatid. Sister chromatids are identical. The point at which the DNA narrows and the chromatids are connected is called the centromere. Each chromosome has many genes, each gene defines a single characteristic.
The number and shape of chromosomes are species-specific. eg. Humans = 46 chromosomes, dogs = 78, pea = 14, fruit fly = 8
All sexually reproducing organisms have 2 sets of chromosomes, one from each parent (this is the diploid state). In humans a diploid cell has 46 chromosomes, half from the mother and half from the father (23). The chromosomes which carry the same kind of information are called homologous chromosomes.
Cell division
There are 2 types:
- mitosis (számtartó sejtosztodás): purpose is growth and repair, 2 identical daughter cells are produced
- meiosis (számfelező sejtosztodás): purpose is to produce gametes (sex cells) for reproduction, 4 genetically different cells are produced
The cell cycle describes the typical cycle of a somatic (body) cell that will go through mitosis:
Image from: http://www.cdli.ca/courses/biol3201/unit02/unit02_org01_ilo02/b_activity.html
During the first growth phase, the cell simply grows and carries out its normal functions. At a certain point, the cell enters the synthesis phase, where the DNA is replicated.
DNA replication refers to the creation of another DNA double helix using the first helix as a template. In order for this to occur:
Once DNA replication has occured, the nucleus then has 2 copies of all of its DNA and will continue to grow and carry out some normal functions, but it will also prepare for cell division, which is either mitosis or meiosis, depending on whether or not it is a cell that will simply copy itself, or a cell that is designed to produce gametes (eggs or sperm).
Mitosis is divided into 4 phases:
Prophase:
-chromatin condenses to chromosome
-nuclear envelope disintegrates and disappears
-spindle (magorsó) forms
Metaphase:
-chromosomes line up at the equator
Anaphase:
-chromatids are pulled to opposite poles of the cell
Telophase:
-cell plasma divides
-nuclear envelope reappears
(don't worry about the extra stages in the image below!!)
Image from: https://www.msu.edu/~robiemat/science.htm
Image from : http://imcurious.wikispaces.com/Midterm+Exam+2010+Review+P1
Meiosis occurs to produce haploid cells that will be gametes (sperm and eggs).
It is a division that reduces the chromosome number by half. It is divided into meiosis I and meiosis II
Meiosis I
Prophase I
-chromatin condenses to chromosomes
-chromosomes "find" their homologous pairs and crossing over occurs
Metaphase I
--nuclear membrane disappears
-homologous chromosomes line up at the equator and attach to spindle fibres
Anaphase I
- chromosomes pairs are split as they are pulled to opposite poles
Telophase I
- cell plasma divides
- nuclear membrane reforms
Short interphase, with no DNA replication
Meiosis II
Prophase II
-chromosomes condense
- nuclear membrane disappears
-spindle forms
Metaphase II
-chromosomes line up at the equator
Anaphase II
-chromatids are pulled to opposite poles of the cell
Telophase II
-cell plasma divides
-nuclear membrane forms
Image from: http://commons.wikimedia.org/wiki/File:Meiosis_diagram.jpg
So mitosis and meiosis share some characteristics, but are also unique in many ways. The following diagram presents a comparison of the two. Be sure to consider how they are similar and how they are different.
Image from: http://bioactive.mrkirkscience.com/09/ch9summary.html
How is DNA organized?
-its basic structure is the double helix
-this is then wound around proteins (called histones) to form chromatin. Under an electron microscope, it looks like beads on a chain. This is the form that DNA is stored in between cell divisions
-during cell division the DNA winds up more tightly and the chromatin coils on itself, looping and coiling to form thick rods called chromosomes, which are visible under the light microscope
What happens?
DNA is copied when it is uncondensed, then it condenses into chromosomes that have 2 halves (each a copy of the other). Each half is called a chromatid. Sister chromatids are identical. The point at which the DNA narrows and the chromatids are connected is called the centromere. Each chromosome has many genes, each gene defines a single characteristic.
The number and shape of chromosomes are species-specific. eg. Humans = 46 chromosomes, dogs = 78, pea = 14, fruit fly = 8
All sexually reproducing organisms have 2 sets of chromosomes, one from each parent (this is the diploid state). In humans a diploid cell has 46 chromosomes, half from the mother and half from the father (23). The chromosomes which carry the same kind of information are called homologous chromosomes.
Cell division
There are 2 types:
- mitosis (számtartó sejtosztodás): purpose is growth and repair, 2 identical daughter cells are produced
- meiosis (számfelező sejtosztodás): purpose is to produce gametes (sex cells) for reproduction, 4 genetically different cells are produced
The cell cycle describes the typical cycle of a somatic (body) cell that will go through mitosis:
During the first growth phase, the cell simply grows and carries out its normal functions. At a certain point, the cell enters the synthesis phase, where the DNA is replicated.
DNA replication refers to the creation of another DNA double helix using the first helix as a template. In order for this to occur:
1. The DNA double helix begins to unwind or unzip at one end to form a replication fork. Unwinding requires the help of an enzyme called a helicase.
2. Enzymes called DNA polymerases bind to the single strands of DNA. They then proceed to "read" the template strand (in the 5' to 3' direction) and add complementary nucleotides. Since the polymerase only travels in one direction, it will move more quickly along the leading strand, but on the lagging strand it will attach at the fork and move toward the end, until it meets up with a previously formed DNA strand fragment, then it will detach and reattach at the continuously unwinding replication fork. The fragments that are created in this way are called Okazaki fragments. They are "glued" together with the help of enzymes called ligases.
The end result is two semi-conservative daughter double helixes- meaning that each double helix contains one strand from the original and one strand that is new.
If you want to see a video: http://www.youtube.com/watch?v=teV62zrm2P0
Once DNA replication has occured, the nucleus then has 2 copies of all of its DNA and will continue to grow and carry out some normal functions, but it will also prepare for cell division, which is either mitosis or meiosis, depending on whether or not it is a cell that will simply copy itself, or a cell that is designed to produce gametes (eggs or sperm).
Mitosis is divided into 4 phases:
Prophase:
-chromatin condenses to chromosome
-nuclear envelope disintegrates and disappears
-spindle (magorsó) forms
Metaphase:
-chromosomes line up at the equator
Anaphase:
-chromatids are pulled to opposite poles of the cell
Telophase:
-cell plasma divides
-nuclear envelope reappears
(don't worry about the extra stages in the image below!!)
Image from: https://www.msu.edu/~robiemat/science.htm
Image from : http://imcurious.wikispaces.com/Midterm+Exam+2010+Review+P1
Meiosis occurs to produce haploid cells that will be gametes (sperm and eggs).
It is a division that reduces the chromosome number by half. It is divided into meiosis I and meiosis II
Meiosis I
Prophase I
-chromatin condenses to chromosomes
-chromosomes "find" their homologous pairs and crossing over occurs
Metaphase I
--nuclear membrane disappears
-homologous chromosomes line up at the equator and attach to spindle fibres
Anaphase I
- chromosomes pairs are split as they are pulled to opposite poles
Telophase I
- cell plasma divides
- nuclear membrane reforms
Short interphase, with no DNA replication
Meiosis II
Prophase II
-chromosomes condense
- nuclear membrane disappears
-spindle forms
Metaphase II
-chromosomes line up at the equator
Anaphase II
-chromatids are pulled to opposite poles of the cell
Telophase II
-cell plasma divides
-nuclear membrane forms
Image from: http://commons.wikimedia.org/wiki/File:Meiosis_diagram.jpg
So mitosis and meiosis share some characteristics, but are also unique in many ways. The following diagram presents a comparison of the two. Be sure to consider how they are similar and how they are different.
Image from: http://bioactive.mrkirkscience.com/09/ch9summary.html
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