Download Molecules of Life

Molecules of Life
Part 1
Learning Objectives
• Explain that the mitochondria is the
site of respiration.
• Describe how Watson & Crick built a
model of DNA.
• Explain how genes and ribosomes are
involved in making proteins.
Success Criteria
• You can label a diagram of an animal
cell with its main components.
• You can create a leaflet on the
discovery of DNA.
• You can answer some questions on
protein synthesis.
Starter
Use a whiteboard and marker to write
down ideas you already have about:
• DNA
• Genes
• Chromosomes
• Inheritance
You have 5 minutes until you feedback to
the rest of the class.
What’s in a Cell?
• An animal cell contains the following parts:
Cell membrane –
controls the
movement of
substances in and
out of the cell.
Cytoplasm – where
many chemical
reactions happen.
• Copy this diagram into your book.
Nucleus – carries
genetic information.
Chromosomes –
genetic information
is carried on these
structures (DNA).
Mitochondria
• Along with everything present on the previous slide,
there are also structures called mitochondria.
• Add a couple to your diagram.
Mitochondria
– the site of
aerobic
respiration.
• Remember back to year 10: You were taught that
aerobic respiration released energy from glucose.
• The mitochondria are the site of this reaction.
Task
1. Match up each part of the cell with the job it does.
Copy the completed table into your book.
Part of Cell
Job
Nucleus
Makes up most of the cell and is where
dissolved chemicals can react.
Cytoplasm
Structures in which respiration takes place.
More active cells will have a larger amount.
Cell membrane
Large structure which contains the
chromosomes and therefore, the genetic
material of the cell.
Mitochondria
The barrier around the cell that controls the
entry and exit of substances.
2. Suggest a reason why sperm cells have many
mitochondria.
3. Why might a cell need to make proteins?
From DNA to Chromosomes
• DNA is a molecule that is twisted into a double helix
shape – like this.
• The molecule is very long and is split into genes
which are codes for making proteins.
• A chromosome is simply a very long DNA molecule
that has been folded into a shape like this:
There’s a lot more
DNA packed into
the chromosomes
than shown here!
hair colour gene
• It’s easy to forget DNA, genes and chromosomes
mixed up.
Task
1. Complete Worksheet 1 and then stick it in your book.
Answers:
A. Top to bottom:
membrane, nucleus, cytoplasm, chromosome, DNA,
gene.
B. Because liver cells need more energy from respiration.
Watson & Crick
• Watson & Crick contributed a lot to discovering the
structure of DNA.
• However, there were others involved in the discovery
too – namely Rosalind Franklin.
• She was instrumental, as it was her X-ray
crystallography technique that indicated DNA had a
double helix shape.
• Another scientist, Erwin Chargaff was responsible for
discovering that DNA contained 4 bases (next lesson).
HIGHER
Higher
• The code stored within a DNA molecule is essential for
making proteins.
• Proteins are made of chains of amino acids and the
DNA controls the order of amino acids in a protein.
• Eg:
Code =
Amino
Acids:
Gene 1:
ATC GCT TGA CGT ACT
Code =
Gene 2:
GCT GCT ATC CGT TAC
Amino
Acids:
• This protein synthesis is carried out by ribosomes.
Task
ALL:
Create a leaflet on the discovery of DNA using
information from this lesson and the student textbook.
Include ideas about:
•
•
•
•
•
the structure of DNA
the names of the two scientists who first built a model of DNA
the X-ray data they used to help them and the scientists that produced
the X-rays
the name of the scientist who found that there were pairs of bases
the scientists that gained the Nobel prize for their work
HIGHER:
Your leaflet should also include
•
•
•
reasons why some people may not have believed the scientists who
made the discovery
reasons why we are now more certain about the structure of DNA
how DNA is linked to the role of ribosomes in the cell
HIGHER EXTENSION TASK
Higher Extension Task
Read page 11 of the new student textbook and answer
the following questions:
1. Which evidence was used to show DNA was a double
helix?
2. Suggest why ribosomes can’t be seen using a light
microscope.
3. Why was Rosalind Franklin’s work so important in the
discovery of DNA?
4. Why is it important that scientists repeat the work of
other scientists.
5. As DNA is made of two strands, can you think of a
possible copying mechanism it may have?
Answers
1. The X-ray crystallography evidence obtained by
Rosalind Franklin and Maurice Wilkins.
2. Light microscopes aren’t powerful enough.
3. It showed that DNA wasn’t a triple-stranded molecule,
but a double-stranded molecule.
4. To validate the results of others.
5. The strands separate and form a template for new
strands to form.
PLENARY
Answer the questions 1-10 in
the student textbook.
Answers
Q1 Nucleus • Q2 Gene • Q3 Watson and
Crick • Q4 Muscle cells need a lot of
energy and mitochondria release energy
during respiration Q5 Bases • Q6 X-ray
crystallography • Q7 Erwin Chargaff •
Q8 Too small • Q9 Confirmed DNA was a
double helix not a triple helix • Q10 To
make the results more valid
Learning Objectives
• Explain that the mitochondria is the
site of respiration.
• Describe how Watson & Crick built a
model of DNA.
• Explain how genes and ribosomes are
involved in making proteins.
Success Criteria