Revision 1

Molecules of life

Comparing cell structure

The mitochondria

• Usually sausage-shaped structures found in the cytoplasm of cells. They are often called the “powerhouses” of a cell because they are where most energy is released during respiration.

What’s in a cell?

• Nucleus – contains genetic information, this is carried on chromosomes

• Cell membrane – controls movement of substances in and out of the cell

• Cytoplasm – where many chemical reactions happen

• Mitochondria – cell respiration is carried out here. Energy is released from glucose in the presence of oxygen.

ENZYMES

DIGESTS EGG MEMBRANE / PENETRATE / GET INSIDE THE EGG

RESPIRATION

Chromosomes and their genes are made of a molecule called DNA.

DNA molecules carry the code that controls what cells are made of and what they do.

DNA stands for deoxyribonucleic

acid.

Each chromosome is a very long molecule of tightly coiled DNA.

Which part of a DNA molecule holds this information?

What is DNA?

How do you think the four bases are paired?

DNA and base pairs

There are four types of bases, and they are usually identified by their initials.

A

T

C

G

adenine

cytosine

guanine

thymine

The double helix ‘ladder’ of a DNA molecule is held together by ‘rungs’ made from pairs of chemicals called bases.

Base pairs hold the two strands of the DNA helix together.The rules for base pairing are…

There are millions of base pairs in a DNA molecule, and they always follow these rules.

‘A’ always pairs with ‘T’ ‘C’ always pairs with ‘G’

It is the sequence of these bases along a DNA molecule that forms the genetic code – it’s that simple!

How do bases pair together?

A T C G

DNA code• Found in the nucleus. Forms structures called chromosomes. A

section of a chromosome is called a gene. Each gene is a code for making proteins. Our bodies need proteins to grow and make proteins. Everyone has his or her unique DNA code.

• DNA – double helix; complimentary base pairs (adenine – thymine; cytosine – guanine)

• Each time a cell divides the DNA copies itself. This is called DNA REPLICATION. The base pairs separate and the strand unzips to form two single strands. New bases pair up by complimentary base pairing to form two new double strands.

• The order of bases found in a section of DNA is called the base code. Each THREE bases code for an amino acid.

• E.g. AAA TAT CTC CCC TCA ACC GGG CGG TAA ATG (10 amino acids are coded for here)

• The complimentary base pairs would be:• TTT ATA GAG GGG AGT TGG CCC GCC ATT TAC

DNA fingerprinting• Isolate blood of cell sample• Extract DNA• Use restriction enzymes to fragment the DNA• Place DNA fragments on gel• Apply and separate fragments using an

electric current (electrophoresis)• Banding of DNA fingerprint can be matched.

DNA is cut into fragments

DNA FRAGMENTS SEPARATED / ELECTRIC CURRENT APPLIED / ELECTROPHORESIS

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CAT GAG ACT