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GCSE OCR Biology What happens in cells (and what do cell need )Complete Revision Summary
What happens in cells (and what do cells need)?
What happens in cells (and what do cells need)?
- Rates of reaction
Protein synthesis – Higher
Enzymes
Factors affecting enzyme action
Practical – The effect of pH on the rate of reaction of amylase
Rates of reaction
DNA – Deoxyribonucleic acid
Deoxyribonucleic acid (DNA) is a large macromolecule made up of a large number of monomeric units of nucleotides. Each nucleotide is composed of nucleoside and a phosphate group
Chromosome – These are the structure that holds our genetic information
DNA – Double Helical Structure which contains genetic information
Gene – It is the segment of DNA that code for protein
DN
DNA : A POLYNUCLEOTIDE
HUMAN GENOME
- Genome is the complete genetic materials of the organism.
- International collaboration to sequence around three billion bases and more than 20,000 genes.
Importance of Human Genome Project
- a) Understanding of genetic Diseases and inherited disorders
- b) Better personalised medicines
- c) Understanding Evolution
- d) Indentifying new drugs target.
PROTEIN SYNTHESIS
- The DNA copies the code and form mRNA by the process of transcription.
- The mRNA leaves the nucleus and reaches the ribosome.
- The ribosomes reads the bases in the sequence of three bases. The t-RNA brings the corresponding amino acid and forms polypeptide chain .
- The polypeptide chain than forms proteins.
ENZYMES
- They are biological catalyst that increases the rate of a biological reaction without being used up.
- They increases the rate of the reaction by providing an alternative route that works by lowering the activation energy.
- They are protein in nature so they are sensitive to heat and pH.
What happens in cells_ (1)-merged
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LOCK AND KEY MODEL
Enzymes are highly specific due to the active site. As the active site has a shape complimentary to the substrate. So the specific substrate molecule can fit into the active site of the enzyme.
FACTORS AFFECTING ENZYME ACTIVITY
SUBSTRATE CONCENTRATION
ENZYME CONCENTRATION
FACTORS AFFECTING ENZYME ACTIVITY
Temperature
| Denaturation is the change in the shape of the enzyme with increase in temperature and pH beyond optimum which results in the change in shape of the active site As a result, substrate molecules can no longer fit into the active site decreasing the rate of the reaction. |
- Rate of reaction increases as particles gain kinetic energy and they collide more increasing
- The optimum temperature. It is the point where the enzyme activity is the highest.
pH
- Different enzymes has different pH optimum.
- Stomach enzymes works in acidic conditions which are maintained by hydrochloric acid Intential enzymes works in alkaline pH maintained by bile
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References:
BBC Bitesize
Wikipedia
Wikimedia Commons
Image Source:
Wikipedia
Wikimedia
Commons
Flickr
Pixabay
Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.