b1.2 what happens in cells? Flashcards
what does DNA stand for?
deoxyribonucleic acid
what is DNA?
a polymer
how many strands does DNA have?
two, forming a double helix
what is DNA made up of?
nucleotides
what makes up a nucleotide?
a sugar, a phosphate group and a base
what are the 4 bases?
A: adenine
T: thymine
G: guanine
C: cytosine
what is the function of DNA?
it contains the genetic material that determines the characteristics of an organism
what are the complementary bases?
C-G
A-T
what does a group of three bases code for?
an amino acid
what are chromosomes?
structures made up of long molecules of DNA
what are the two stages of protein synthesis
transcription and translation
what is a gene?
a section of DNA that codes for a protein
describe what happens during transcription
- In the nucleus, the two DNA strand unzip around the gene to make it accessible.
- DNA is used as a template to make the mRNA. base pairing ensures mRNA nucleotides match to their complementary bases.
describe what happens during translation
- the mRNA moves out of the nucleus to the cytoplasm and joins with ribosomes
- amino acids join with matching triplet codes on the mRNA, in the correct order. this makes the protein.
- the amino acids are brought to the ribosome by tRNA.
- when the chain is complete, the protein forms a unique 3D structure
what are enzymes?
biological catalysts that speed up the rate of chemical reactions without being used up or changed
how do enzymes work?
- every enzyme has a uniquely shaped active site where the substrate binds onto it (the substrate is complementary to the shape of the active site)
- once bound, the reaction takes place
how are enzymes necessary to life regarding metabolic reactions?
enzymes allow metabolic reactions to occur at a rate that can sustain life
what are 3 factors that affect enzyme reactions?
temperature
pH
concentration
how does temperature affect enzymes?
- each enzyme has an optimum temperature when the reaction goes fastest (around 37 degrees C)
- the rate of reaction increases with an
increase in temperature - when the temperature becomes too hot, bonds in the enzymes structure begin to break and change the shape of the active site
- the enzyme denatures and no longer works
how does pH affect enzymes?
- if the pH is too high or too low it interferes with the bonds holding the enzyme together: changing the shape of the active site and can denature the enzyme
- optimum pH is usually 7
how does enzyme concentration affect the rate of reaction?
- increasing the concentration increases the rate because the more enzyme molecules there are, the more likely a substrate molecule will join
- if the concentration is too high, the enzyme will no longer work
