B3a: Molecules for Life

The fundamental processes of life occur inside cells. This item examines the role of DNA in the production of proteins, the building blocks of living things. This item provides the opportunity to explain phenomena using scientific theories, models and ideas. Using the discovery of the structure of DNA it also illustrates the collaborative nature of science and the need for new discoveries to be validated. 

Where does respiration take place? What does it provide?
In the mitochondria and provides energy for life processes.
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Where are chromosomes found?
In the nucleus.
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What do chromosomes carry?
Coded information in the form of genes.
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What are chromosomes made of?
A molecule called DNA
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What is information in genes in the form of? What is this called?
Coded instructions called the genetic code.
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What does the genetic code control?(2)
Cell activity and consequently some characteristics of the organism.
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What does DNA control the production of?
Different proteins.
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What two things are proteins needed for?
The growth and repair of cells.
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Who first worked out the structure of DNA?
Watson and Crick.
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Why do liver cells have large numbers on mitochondria?
Because they carry out lots of energy-demanding metabolic reactions
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Why do muscle cells have large numbers on mitochondria?
Because they need energy to contract and cause movement
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What are small structures in cells too small to do? Give an Example.
Be seen with the light microscope - e.g ribosomes
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Where are ribosomes found? What are they the site of?
In they cytoplasm - and are the site of protein synthesis.
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What is the structure of DNA?
Two strands coiled to form a double helix, each strand containing chemicals called bases, of which there are four different types, with cross links between the strands formed by pairs of bases.
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What are chromosomes?
Long, coiled molecules of DNA, divided up into regions called genes.
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What does each gene contain?
A different sequence of bases
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What does each gene code for?
A particular protein.
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Where are proteins made?
In the cytoplasm
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Why is a copy of the gene needed for protein synthesis?
Genes cannot leave the nucleus - they are too large.
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What are the four bases?
A, T, C and G
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What are the two complementary base pairings?
A and T, C and G
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How is the protein structure determined by DNA base code?
The base sequence determines the amino acid sequence, and each amino acid is coded for by a sequence of 3 bases.
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Explain the use of (messenger) mRNA carrying DNA from the nucleus.
Ribosomes are the site of protein synthesis. They are found in the cytoplasm but DNA is found in the nucleus. The genetic code needed to make a particular protein is carried from the DNA to the ribosomes by a molecule called mRNA.
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What is transcription?
mRNA from DNA
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What is translation?
Proteins from mRNA
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Talk about the functions of cells and proteins.
The proteins produced in a cell affect how if functions. Some determine structure, others control cell reactions. Different types of cell have different functions because they make different proteins.
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Name a protein that controls cell reactions.
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Why do cells only make certain proteins?
Because only some of the full set of genes is used in any one cell. Some genes are "switched off" which means the proteins they code for aren't produced. The genes that are switched on determine the function of a cell.
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Describe how Watson and Crick used data from other scientists to build a model of DNA. (2)
The data they used showed that bases occurred in pairs. Further x-ray data showed that there were two chains wound into a double helix.
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Why aren't new discoveries, like Watson's and Crick's, accepted or rewarded immediately?
Because it is very important that other scientists repeat or test the work.
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Other cards in this set

Card 2


Where are chromosomes found?


In the nucleus.

Card 3


What do chromosomes carry?


Preview of the front of card 3

Card 4


What are chromosomes made of?


Preview of the front of card 4

Card 5


What is information in genes in the form of? What is this called?


Preview of the front of card 5
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