Additional Science Flashcards
Name the 4 cell features shared by both plant and animal
Cell membrane, cytoplasm, nucleus, mitochondria
Name the 3 cell features of only a plant cell
Cell wall, vacuole, chloroplasts
Describe the function of the cell membrane
Separates the content of the cell and its surroundings and controls the movement of substances in and out of the cell
Describe the function of cytoplasm
It is where many of the chemical reactions needed to carry out life processes take place and it also contains organelles
What is the nucleus?
An organelle that contains DNA, it also controls all the activities of the cell
What is mitochondria?
The organelle in which respiration occurs
What is the function of the cell wall
It is made of cellulose to support the cell and allow it to keep its shape
What is the vacuole?
A space in the cytoplasm that is filled with cell sap to help support the plant by keeping the cells rigid
What do chloroplasts do?
They contain chlorophyll that absorbs the light energy used in photosynthesis
When was the electron microscope invented?
1930s
What does the electron microscope do?
It uses beams of electrons to magnify specimens up to about 2000000 times
How did electron microscopes change our understanding of bacteria cells?
Because they showed that bacteria have two kinds of DNA
What is chromosomal DNA?
It is a giant loop of DNA that contains the majority the genetic material
What is plasmid DNA?
It’s smaller loops of DNA that carries extra information
What is the difference between a plant cell wall and a bacteria cell wall?
A bacteria cell wall isn’t made from cellulose and is more flexible
What is the function of flagella?
They are a long, whip-like structure that bacteria can use to move themselves
What do chromosomes contain?
Genetic information
What are chromosomes made from?
A chemical called DNA
What are genes?
Sections of DNA molecules that contain instructions for specific proteins used in the body
What is the double helix?
It is the two strands in the molecule of DNA that are coiled together
What are the two strands in the double helix linked together by?
Bases
Name the 4 bases
Adenine-Thymine
Cytosine-Guanine
What are the matching bases known as?
Complementary base pairs
What are the base pairs joined together by?
A weak hydrogen bond
The ‘back bone’ of DNA is made from what?
Sugar (deoxyribose) and phosphate
On which molecule do the bases join to?
The sugar
Describe the role of Wilkins and Franklin in the discovery of DNA
They were directing beams of X-Ray’s onto purified DNA and used photos to record how the molecule scattered the X-ray and then from this they could work out how the atoms were arranged
Describe the role of Watson and Crick in the discovery of DNA
They used the X-Ray photographs (given to them by Wilkins without Franklins permission) from Franklin and Wilkins to create a 3D model of DNA
Describe the human genome project
It was an international effort that involved scientists in 18 different countries and sharing the data they collected about the human genome
What did the scientists working on the HGP work out?
The sequence of the 3 billion base pairs that make up the human genome which then showed that everyone has 99.9% of DNA in common
Name 5 ways in which the knowledge of the human genome can help medical technologies
Improved testing for genetic disorders
Ways of finding genes that increase risk of certain diseases
New treatments and cures for disorders
Showing evolution as the genome changes over time
Personalised medicines
What is genetic engineering?
The process of removing a gene from one organism and inserting it into the DNA of another
Give an example of a way in which genetic engineering has been used
Scientists have inserted the gene for human insulin into plasmid DNA into bacteria so that the bacteria can produce insulin
What is the name given to organisms that have been genetically engineered?
Genetically modified organisms
Describe how the genetic modification from wild rice to golden rice is beneficial for humans
Golden rice make beta-carotene which is needed by humans to make vitamin A. A lack of Vitamin A can cause death and blindness
Why’re some people worried about the GM rice?
They worry that it will crossbreed with wild rice and contaminate its DNA and others worry that GM food may harm them
What are the advantages and disadvantages of herbicide resistant crops?
Advantages:
Reduces the amount of crop spraying needed by farmers
One large dose of herbicide than lots of small ones
Disadvantages:
Herbicide resistant plants
Loss of biodiversity
Name the advantages and disadvantages of insulin producing bacteria
It can be used by vegans
Supply doesn’t rely on animals anymore
Can be made in vast quantities
Can be made cheaply
Doesn’t suit everyone as there are slight differences
What are the two enzymes used in the genetic modification of bacteria to produce insulin
Cutting enzymes and sticking enzymes
What is a diploid cell?
A cell that contains 2 sets of the 23 chromosomes
What form of cell division occurs for growth or the repairing of damaged cells?
Mitosis
Describe the stages of mitosis
DNA replication occurs so that there are now 4 sets of the chromosomes rather than just 2, the cell then divides and each daughter cell gets one copy of each chromosome, making them identical to each other and the parent cell
What kind of reproduction is mitosis?
Asexual reproduction
Give two examples of asexual reproduction
Bacteria cells often just split in half
Some plants do this by making new plantlets which are initially attached to the, but then split off and grow on their own
What is the name of the other kind of reproduction (not asexual)?
Sexual reproductions
Describe the process of sexual reproduction
This requires two haploid (one set of chromosomes) gametes which fuse during fertilisation to form a diploid zygote which then develops into an embryo
What kind of cell division is needed to produce haploid gametes?
Meiosis
Name the differences between meiosis and mitosis
Meiosis has two cell divisions and thus produces four haploid daughter cells which aren’t genetically identical
Describe the stages of meiosis
DNA replication occurs in the diploid cell so that there are 4 copies of the chromosomes, the diploid divides in two and then in two again to form four haploid cells which aren’t genetically identical as each has different sections of the DNA
What is a clone?
Individuals that are genetically identical
Describe how plants can be cloned
You start with a cutting from the plant which can then be planted and will continue or grow (this is an example of asexual reproduction)
Describes the benefits of cloning
It is useful to make an organism with desirable characteristics
E.g. bulls who produce high quality calves, good sniffer dogs
Can produce individuals with GM traits such as cows who produce insulin in their milk
Describe the drawbacks of cloning
Very low success rate
Can grow orders more quickly and die younger
What are the stages of cloning a mammal?
Removal of diploid nucleus from body cell
Enucleation of egg cell
Insertion of diploid nucleus into enucleated cell
Stimulation to start mitotic division
Implantation into surrogate mother
What is a stem cell?
A cell that can differentiate into different types of cells
Why are embryonic stem cells more useful than adult stem cells?
Because embryonic can differentiate into any cell whereas an adult stem cell is limited to certain types
Why is the use of embryonic stem cells controversial?
Because in the process of extracting the stem cells, the embryo is killed
Describe how a bone marrow transplant works
The patients white blood cells are destroyed and adult stem cells from someone else are put into the patient to produce healthy white blood cells
Why do bone marrow transplants not always work?
Because the body may reject the new cells and destroy them
How could the problem of rejection be solved in bone marrow transplants?
Because they could take a skin cell from the person to create an embryo, the stem cells could then be used to produce cells that make white blood cells and the body would recognise these cells as their own
What is a drawback of embryonic stem cell use?
They could be used to create human clones
What does the base order on the DNA strand form?
The genetic code
What is the process of amino acid chains forming proteins?
Protein synthesis
Where does transcription occur? (In protein synthesis)
In the nucleus
Describe what happens in transcription during the process of protein synthesis
The DNA unzips and the complementary bases to the strand will link together forming a molecule of mRNA
What does mRNA stand for?
Messenger RNA
What are the differences between DNA and RNA?
RNA uses the base Uracil instead of thymine and only has one strand so is therefore small enough to move out of the nucleus into the cytoplasm
After the mRNA leaves the nucleus, where does it attach?
It attaches to a small structure called the ribosome
What is the role of the ribosome?
It moves from one end of the mRNA to the other and decodes the bases in groups of 3 (codons)
What is an amino acid connected to?
transfer RNA
What happens once the ribosome has decoded the mRNA?
The complementary tRNA will line up with the mRNA and releases the amino acid to join the chain
What happens once the amino acid has joined the chain?
The tRNA is released as the ribosome moves onto the next codon