Body Flashcards
What does DNA stand for?
Deoxyribonucleic acid
How many chromosomes do humans have?
46
(23 from each parent)
Where is DNA?
DNA is in the nucleus of every one of our cells. Each long molecule of DNA is a chromosome.
What are short sections of DNA called?
(E.g that code for a characteristic, such as eye colour)
Genes
What do genes do?
The code that a gene contains causes specific proteins to be made. The particular proteins determine the cells function.
What is the structure of DNA?
DNA is made of two strands. These strands are joined together by bases. The strands are then twisted together. This forms a shape known as a double helix.
What is DNA made of?
DNA is made up of lots of small units called nucleotides, which are joined together. This means that DNA is a polymer.
About nucleotides
Each nucleotide is made of a sugar called deoxyribose, a phosphate group and a base =
Deoxyribose- phosphate- base
The two strands of DNA are held together by bonds between the bases
How many types of nucleotides are there in DNA
Four
What are the different bases of the nucleotides?
Adenine
Thymine
Cytosine
Guanine
What base in a nucleotide of DNA is characterised by the letter G?
Guanine
What base in a nucleotide of DNA is characterised by the letter A?
Adenine
What base in a nucleotide of DNA is characterised by the letter T?
Thymine
What base in a nucleotide of DNA is characterised by the letter C?
Cytosine
How do the bases in DNA bind?
To hold the strands of DNA together a base from one stand bonds with another base on the other strand. This forms a base pair. The base pairs always bond together in the same formation - this is called complementary base pairing.
What is complementary base pairing?
Two bases of nucleotides that bond together to hold the strands of DNA
What is the complementary base pair of adenine?
Adenine bonds with thymine
A-T
What is the complementary base pair of cytosine?
Cytosine always bonds with guanine
C-G
What is the complementary base pair of thymine?
Thymine always bonds with adenine
T-A
What is the complementary base pair of guanine?
Guanine always bonds with cytosine
G-C
What is mRNA?
mRNA (messenger RNA) is like a single strand of DNA
How is mRNA produced
Through transcription
What is transcription?
-The DNA around a gene unzips so both strands are separated
-one of the DNA strands act as a template
-Complementary bases attach to the strand being copied
-for example cytosine (C) joins to guanine(G)
-this forms a strand of mRNA
-there is no thymine(T) in mRNA so a base called uracil (U) bonds with adenine
-once complete the, strand of mRNA detaches from the DNA template and the DNA zips back up
-mRNA is small enough to fit outside of the nucleus. It travels to sub cellular structures called ribosomes in the cytoplasm. This is where the protein will be made
What is Uracil?
Uracil (U) is a base that bonds with adenine (A) during the creation of mRNA via transcription
What are proteins made from?
A protein is made from amino acids, different amino acids join together to form different proteins.
What determines which amino and proteins are made?
The order of nucleotides in your DNA determines the type and the order of amino acids, and this determines which proteins are produced
How are proteins made?
Proteins are made via a process called translation. The mRNA attaches to a ribosome. Here the nucleotide sequence is interpreted and the new protein is made:
How does translation work?
-the ribosome “reads” the nucleotides on the mRNA in groups of three
-these groups are called base triplets (or codons)Each triplet code for a specific amino acid. For example, CGU codes for a different amino acid to ACG
-the ribosome continues to “read” the triplet code,adding more and more amino acids
-The amino acids join together in a chain.This is a protein
What determines how the protein will fold?
The sequence of amino acids determines how the protein will fold. Each type of protein has a specific shape. This is important for protein function. Many types of proteins are produced including enzymes and hormones.
What are enzymes?
-Enzymes are made of protein
-they are biological catalysts
-this means they speed up a reaction without being used up themselves
-once a reaction is finished they can be used to speed up the same type of reaction again
What reactions in our bodies are enzymes involved in?
-Building larger molecules from small ones, such as in protein synthesis
-break down large molecules into smaller ones, such as in digestion
What do enzymes look like?
Enzymes,like all proteins are made up of long chains of amino acids.
These are folded together to form a specific shape. The shape of one part of the enzyme is particularly important
Here, molecules of other substances bind to the enzyme.
This is called the active site
What is the molecule that binds to the enzyme called?
The substrate
Do enzymes bind to all molecules?
No, enzymes are highly specific.
This means they can only bind to one type of substrate molecule
The substrate must fit exactly into the active site.
If it does not, the molecule cannot bind.
What is the term given to the process of molecules or substrate binding to an active site of an enzyme.
Lock and key hypothesis
What factors affect enzymes?
The rate of an enzyme-catalysed reaction depends on a number of factors such as:
Temperature
Ph
How does temperature affect enzymes
At higher temperatures the enzyme and substrate molecules move faster and collide more often.
What happens if the temperature is too high?
The amino acid chains in the protein start to unravel, changing the shape of the active site.
The enzyme is now denatured.
What happens when an enzyme becomes denatured?
The substrate can no longer bind and so the rate of reaction decreases.
Once all enzymes are denatured, the reaction stops. Most denatured enzymes cannot return to their original shape - the change is irreversible.