B5 Flashcards

Question	Answer
What can be done to multicellular cells?	In organisms that are multicellular, cells are specialised to do different jobs.
What are cells of the same type? Give an example of this.	Cells of the same type can be grouped into tissues. For example, muscle cells can be categorised as muscular tissue.
What are organs? Give an example.	Organs are different tissues grouped together and work with one another. For example, the heart contains muscular tissue, blood and nervous tissue.
Explain the difference between a tissue and an organ.	A tissue is a group of specialised cells, whereas an organ is a group of tissues working together.
What are organ systems?	An organ system is a group of organs that work together to perform one or more functions. Each does a particular job in the body, and is made up of certain tissues.
What is a zygote?	A zygote is a fertilised egg which divides by mitosis to form an embryo. (2, 4, 8 etc)
Describe the cells in a human embryo up to the eight cell stage.	The cells are identical and unspecialised. These are called embryonic stem cells, meaning that they can be turned into any type of cell.
What happens to the cells after the eight eight cell stage?	The cells become specialised, so they can no longer turn into all types of cells. The cells are un-identical.
Why are adult stem cells different to embryonic stem cells?	Adult stem cells can only differentiate into a limited number of cell types, for example bone marrow cells can turn into different types of blood cell but only blood cells, whereas embryonic stem cells can turn into any type of cell. In adult stem cells, some genes are switched on or off, but in embryonic stem cells, the genes can all be switched on.
What are xylems and phloems, and what are their functions in plants?	The xylem is a tissue formed by specialised plant cells. It transports water and mineral salts. Phloem transports the products of photosynthesis, it is also a tissue formed by specialised plant cells.
What is the name given to any plant tissue that can produce new cells?	They are called meristem cells and they produce growth in height and width in a plant.
Why do plants continue to keep growing throughout their lives but animals stop at a certain point?	Unlike animal cells, some plant cells remain unspecialised, so they can keep producing new cells which increase their size. Only certain cells are capable of dividing to produce new cells.
How can plants be cloned?	Pieces of plants, such as plant stems, containing meristems- are called cuttings and are used to produce clones of plants.
What are the advantages of taking cuttings?	It can be used to produce plants with the same desirable features as the parent. The clones produced are genetically identical to the parent plant.
How is root growth in plants promoted/increased?	It can be increased by using plant hormones - hormone rooting powder.
What is a different way of cloning plants other than taking cuttings?	Tissue culture.
What is tissue culture?	A small piece of a plant tissue/or cells are placed in agar jelly, containing nutrients and plant hormones. Each will grow into an individual plant or plantlet.
What are the steps involved in tissue culture?	1) Cells are taken from a plant root 2) Enzymes are used to separate the cells 3) Individual cells are placed in agar jelly 4) Plantlets grown are transferred to compost to grow into identical plants
What are auxins?	Auxins are plant hormones that help to increase the growth of cells in plants. It increases cell division and cell enlargement, promoting cell growth. It is implemented in agar jelly, as well as rooting powder.
What is phototropism?	Phototropism is a plants response to the direction of light. They either grow towards it, or away from it.
What does it mean if a plant is positively or negatively phototropic?	If a plant is positively phototropic, it means that it grows towards the source of light, whereas if it is negatively phototropic, it grows AWAY from the source of light.
Why do plants grow towards light?	Light is essential for photosynthesis, so by growing towards light, plants increase their chance of survival.
Where are auxins found?	Auxins are found in the growing tip of plant shoots.
What happens if a plant is illuminated from one side?	•The auxin produced in the tip acts on the shaded part of the plant, producing growth in the shoot. •This pushes the plant to grow towards the light.
What is mitosis?	Mitosis is the type of cell division that takes place when an organism grows, and cells divide to repair tissues.
What is the result of mitosis?	Mitosis results in the production of two daughter cells, which are genetically identical (have the same number of chromosomes as the parent cell).
What happens before mitosis?	The DNA from each chromosome is copied. This means that each chromosome is now a double chromosome, with two DNA molecules.
What is known as the events between and leading up to cell division, and cell division itself?	It is called the cell cycle.
What are the main processes of the cell cycle?	1) Cell growth: cell increases in size, organelles increase, DNA in chromosome is copied. 2) Mitosis : two daughter cells are produced that are identical to the parent cell as the the strands of each double chromosome separates to form two separate nuclei.
What is meiosis?	Meiosis is the type of cell division that is used to produce gametes (sex cells - egg and sperm cell, in pollen grains in flowering plants as well as animals)
What is the difference between an embryo and a foetus?	The embryonic period is all about the formation of important systems of the body - such as the heart, lungs, brain etc. The foetus is still forming The foetal period, on the other hand, is more about growth and development so your baby can survive in the outside world.
How many chromosomes do each type of sex cell contain?	Overall, there are 46 chromosomes in a zygote. However, there are exactly 23 chromosomes in each sex cell - egg and sperm. Each sex cell contains 1 chromosome from each pair of a body cell.
What are chromosomes?	Chromosomes are thread-like structures that is found in the nucleus. They are made from a DNA molecule and can be grouped into pairs (e.g human cells contain 23 pairs)
What is DNA?	DNA is a double helix, containing two strands facing each other.
What are the strands of DNA made from?	Strands of DNA are made up of units linked by chemicals called bases.
What types of bases are there?	There are four different bases- A, T, C, and, G. There are specific pairs. A with T and C with G.
What is the role of the genetic code?	The genetic code gives the instructions for the assembly of a protein - the amino acids in the protein, and how they are arranged.
Where is the genetic code carrying the instructions for protein synthesis found?	It is found in the nucleus in plant and animal cells.
How can the genetic code reach the cytoplasm without the genes leaving the nucleus?	mRNA is produced in the nucleus, carrying the instructions into the cytoplasm.
Where are proteins assembled?	Proteins are assembled on organelles in the cytoplasm called ribosomes.
What does the number and sequence of an amino acid determine?	It determines the type of protein produced and its properties.
What are base triplets?	The DNA code is a triplet code. Each triplet, a group of three bases, codes for a specific amino acid: the triplet of bases on the DNA and mRNA is known as a codon.
What are mRNA's?	mRNA is a copy of the base sequence of the DNA that makes up a gene. It carries the instructions for a specific protein to the cytoplasm, attaching to a ribosome.
Where does protein synthesis occur?	Protein synthesis occurs in the cytoplasm.
What are the role of tRNA's?	They ferry/transfer amino acids to the ribosome, where they are bonded together.
Why are embryonic stem cells so different from adult stem cells?	In embryonic stem cells, any gene can be switched on or off, so they can turn into any type of cell. In adult stem cells, genes are already switched either on or off, and cannot be changed.
What are the uses of embryonic stem cells?	Embryonic stem cells, as well as adult stem cells, have the potential to replace cells that have become damaged or diseased. For example, tissue cells can be replaced by embryonic stem cells.
Why do cells only produce certain proteins?	The cell only produces the proteins it needs to carry out its function.
Where are adult stem cells found?	Adult stem cells are found in various locations in the body, such as the bone marrow, as well as skin, teeth etc.
Why is the use of embryonic stem cells controversial?	In removing cells, the embryo is destroyed. Some believe that it is only God's choice to destroy and create life, and not our choice whether the embryo lives or dies.
Where are embryonic stem cells removed?	They are removed from surplus embryos from in vitro fertilisation. (IVF)
Why does therapeutic cloning overcome some ethical issues of using embryonic stem cells?	It involves: •Replacing the nucleus of an egg by the nucleus of the body cell. •Stimulating the egg cell to produce an 'embryo'

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	Created by Czean Holgado about 7 years ago