Biology Paper 1 (Edexcel Checklist) Flashcards
Describe Mitosis as part of the cell cycle, including the stages interphase, prophase, metaphase, anaphase, telophase and cytokinesis
Mitosis involves splitting a cell into two genetically identical or, asexual reproduction. In the interphase the cell duplicates its DNA (in a human leading to 46 PAIRS of chromosomes rather than 23 PAIRS) in an x shape each side representing a strand of DNA.In the prophase they condense become visible and the spindle forms (a bar that attracts to the centre).Metaphase is when they are attracted to the middle.Anaphase is when all the x’s are pulled apart each arm goes to the opposite side of the cell. At Telophase another cell membrane forms and the two DNA sections become 2 nuclei (Spindle breaks). Finally at cytokinesis Two daughter cells are formed in a human they are diploids (23 pairs of chromosomes)
Describe the importance of mitosis in growth and repair and asexual reproduction
Mitosis is the way all animals and plants grow and repair as all the cells in their body are diploids. As a result to produce more means that we can grow and replace old or damaged cells. Also the only way to asexually reproduce something is through mitosis as 1 mother cell produces 2 genetically identical daughter cells.
Describe the division of a cell by mitosis in terms of cells formed and chromosome numbers
For asexual reproduction 1 mother cell become 2 daughter cells. In a human a normal cell has 23 pairs of chromosomes (46). During the interphase a copy of all these cells are made resulting in 46 pairs of chromosomes (92). Until cytokinesis occurs.
Describe Cancer as the result of changes in cells that lead to uncontrollable cell division
As a result of damage or a mutation to 3-7 of the hundreds of genes that control cell growth, the cell starts to grow or multiply uncontrollably. The cells are constantly receiving messages both form genes or other cells. Some are to grow and multiply others are to stop, rest or die. In a cancer cell the message to stop growing is missing or the messages to grow are altered. The cells mutate more can become immortal, escape destruction by the body’s defences or develop their own blood supply.
Describe growth in plants and animals including: cell division, differentiation and elongation
In a plant cell the cell grows by absorbing water into the vacuole, in a animal body it grows by increasing the number of cells. In an animal only stem cells can differentiate. In a plant cell most cells can differentiate or re-differentiate. Elongation occurs in plants when individual cells or groups of cells grow longer all cells grow different heights. Cells can elongate at different rates by using auxins to allow them to bend.
Explain the importance of cell differentiation in the development of specialised cells
Cell differentiation is the process by which a cell changes to become specialised do its job. As the cell changes it develops different organelles that allow them to perform different jobs.
Demonstrate an understanding to the use of percentile charts to monitor growth
Percentiles are measurements that show where a person is compared with others. On growth charts, the percentiles are shown as lines drawn in a curved pattern. When a doctor plots a persons weight and height they see which percentile line those measurements land on. The higher the percentile the bigger a person is compared with others. E.G if a 4 year old boy is on a 10 percentile line 10% of boys are smaller and 90% are larger.
Describe the function of embryonic stem cells in animals and meristems in plants
Embryonic stem cells are found in the early stages of a human embryo. They have the potential to turn into any kind of specialised cell. This is because all the cells in a human body came from one embryonic stem cell that changed to be 1 of every single specialised cell. Normal stem cells in adults can only turn into 1 or 2 kinds of specialised cells. The first embryonic stem cell is called a zygote. The tissue in a plant where growth occurs is called the meristem. This is full on unspecialised meristematic cells who’s job is to divide and increase the plants size. They are found in the stem end of roots and shoots. The cells specialised at these point to allow the plant to grow.
Discuss the potential benefits and risks associated with the use of stem cells in medicine
Benefits are: grow organs or complex tissue structure for transplant, produce certain cells that a person lacks so they can multiply in a persons body (Insulin), reconnect bones or nerve systems (spinal cord)
Risks are: stem cell grown tissue can be rejected, unethical as you are destroying a human embryo
Describe the structures and functions of the brain including the cerebellum, cerebral hemispheres and medulla oblongata
The left cerebral hemisphere is the part of the brain that is responsible for intelligence, language. While the right shows you ability to be aware of the environment around you (your spatial perception) . Both are found in the forebrain. The cerebellum is found your hindbrain and receives information from the sensory system, spinal cord and other parts of the brain and then regulates motor movements (responses). The medulla oblongata regulates breathing, the heart, blood vessel function, digestion, sneezing and swallowing, it is also found in the hindbrain.
Explain how the difficulties of assessing brain tissue inside the skull can be overcome by using a CT scanning and PET scanning
CT scanning allows doctors to help assess head injuries by looking at a cross sectional image of a person brain. These imagines can be put together to form a 3D image of a person Brian and assess and visible faults within someone’s brain. They work when a narrow beam of x-rays are aimed at the patient and quickly rotated around the body producing signals that the machine can use to form an image. PET scanners pick up Hama signals from tracers injected into your body. Special monoclonal antibodies are sent into your body that realise gamma rays, these then find the diseases they are checking for,they will stay stationary when they have found the pathogen or mutation allowing us to find a brain disease, blood clot or cancer cell in the brain
Explain some of the limitations in treating damage and dies ease in ten brain and other parts of the nervous system
Damaged human brain and nerve cells are made through neurogenesis and this process ceases at the age of 2. Therefore the only way to cure damaged cells is to replace them. However they are so complex that humans have not yet been able to culture such complex cells from stem cells. In addition the effects of replacing the cells or part of the system can cause other problems li,e damaging nearby tissue, not be excepted or not working with other cells correctly
Explain the structure an function of the nervous system including neurones, synapses and neurotransmitters
Neurones are specialised cells that transmit electrical signals through the body. Neurones have 2 man parts dendrites, which receive signals and conduct them towards the cell, and axons, which conduct the signals to other cells. As a impulse travels down the axon the nerve ending releases a neurotransmitter, this is a chemical that can diffuse across the synapses (a gap between nerve cells so they can only travel 1 way). The whole system works when a receptor ( sense organ) detects a stimulant and produces an electrical impulse that is sent via sensory neurones to a CNS or central nervous system (brain or spinal cord) the it’s sends a response back via a relay neurone to a motor neurone which translates the signal to a muscle as what to do
Explain the structure and function of a reflex arc including sensory, relay and motor neurones
Reflex actions are controlled by the reflex arc. When safety of an organism demands a quick response signals can be passed from a sensory neurone, via a relay neurone, straight to a motor neurone for instant unthinkable action, a reflex action. The arc is the pathway that a signal takes to make such a quick response. Therefore no matter the intelligence certain actions do not need a CNS to be made, it is built in behaviour.
Explain the structure and function of the eye as a sensory receptor including the role of the: cornea, lens, iris, rod and cone cells
The eye is a sensory receptor as it is 1 of the 5 senses that can receive a stimulus and as a result send a signal to a sensory neurone. The cornea is ten front tough, transparent outer coat of the eye and as it is convex refracts light to the centre of your eye. The iris is the coloured pigment in the eye, it contracts and relaxes to vary the size of the pupil and therefore the amount of light to enter your eye. The lens is a flexible disc behind the iris that focuses the light towards the retina. There are 2 types of photoreceptors in the retina rods and cones. Rod cells are responsible for vision at low light levels and can not see colour. Cone cells are active at high light levels are can see colour.
