B1.2 Flashcards
What does DNA stand for?
Deoxyribonucleic acid.
What is the structure of a DNA molecule?
DNA is a double helix made from two strands twisted around each other.
Is DNA a monomer or a polymer? Explain.
DNA is a polymer — it is made of many repeating units called nucleotides.
What are the three components of a DNA nucleotide?
1) One sugar molecule
2) One phosphate group
3) One organic base (A, C, G, or T)
What forms the ‘backbone’ of a DNA molecule?
The sugar and phosphate group of each nucleotide.
What are the four organic bases in DNA?
Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
What is complementary base pairing in DNA?
A always pairs with T, and C always pairs with G.
How many bases code for a single amino acid?
A group of three bases codes for one amino acid.
What happens when many amino acids join together?
They form a protein.
What are chromosomes made of?
Chromosomes are structures made from long molecules of DNA.
Why can’t DNA leave the nucleus to make proteins?
DNA is too large to leave the nucleus.
What is the purpose of protein synthesis?
To copy and transport genetic information from the DNA to the ribosomes to make proteins.
What happens first in protein synthesis?
The DNA helix is untwisted and unzipped.
What matches to the unzipped DNA bases?
Messenger RNA (mRNA) nucleotides match to their complementary DNA bases
What is the result of the mRNA nucleotides joining together?
They form a new strand called the template strand.
What is the name of the process that forms the mRNA template strand?
Transcription
What happens to the template strand after transcription?
It moves out of the nucleus into the cytoplasm.
Where does the mRNA strand go in the cytoplasm?
To structures called ribosomes.
How is the mRNA read at the ribosome?
In groups of three bases (codons), each coding for one amino acid.
What is the name of the process where the mRNA is read to build a protein?
Translation
What brings amino acids to the ribosome?
Carrier molecules called tRNA
What happens to the amino acids at the ribosome?
They are joined together to form a protein.
What determines which protein is produced?
The sequence of triplet base codes (codons) on the mRNA.
What happens after the protein chain is complete?
The protein folds to form a unique 3D structure.
What are enzymes?
Enzymes are biological catalysts — substances that speed up chemical reactions without being used up.
What are enzymes made of?
Enzymes are protein molecules.
Why is the shape of an enzyme important?
Each enzyme has a uniquely shaped active site that fits a specific substrate.
What is the lock and key hypothesis?
The substrate fits into the enzyme’s active site because their shapes are complementary, forming an enzyme-substrate complex.
What happens after the enzyme-substrate complex forms?
The reaction occurs and the products are released from the enzyme’s surface.
What is the formula to calculate the rate of a reaction?
Rate = change in concentration ÷ time
What is the optimum temperature for most enzymes?
Around 37°C (body temperature).
How does temperature affect enzyme activity up to the optimum?
Reaction rate increases with temperature up to the optimum.
What happens to enzymes at high temperatures above the optimum?
The enzyme’s structure breaks down — the active site changes shape.
What is it called when the enzyme’s shape changes and it stops working?
The enzyme is denatured.
What is the optimum pH for most enzymes?
pH 7, but some enzymes (like in the stomach) have a lower optimum pH
What happens if the pH is too high or too low?
The forces holding the amino acid chains are affected, changing the active site’s shape.
What is the result of an enzyme’s active site changing shape due to pH?
The enzyme becomes denatured and can no longer function.
What happens to the rate of reaction as substrate concentration increases?
It increases because there are more substrate molecules to collide with enzymes.
Why does increasing substrate concentration eventually stop affecting the rate?
All enzyme active sites become full, so adding more substrate has no further effect.
How does enzyme concentration affect the reaction rate at first?
Increasing enzyme concentration increases the reaction rate.
Why does the rate stop increasing after a certain point?
There are not enough substrate molecules to react with all the enzyme molecules.
