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Edexcel - Biology > Chapter 2 - Cells and Control > Flashcards

Chapter 2 - Cells and Control Flashcards

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1
Q

Chromosomes

A
  • Within the nucleus of cells
  • Contains genetic material
  • Coiled up lengths of DNA molecules
  • Have two copies of each chromosome making them diploids. One comes from the mother, the other comes from the father
  • It is reproduced through mitosis
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2
Q

Cell Cycle

A
  • Body cells divide and replicate during a process called the cell cycle
  • Multicelluar organisms use mitosis to grow or reproduce cells that have been damaged
  • Mitosis can be used as asexual organism in which only one organism is used to reproduce
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3
Q

Stages of mitosis

A
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokenesis
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4
Q

Interphase of mitosis

A
  • The cell begins to expand and increase in subcelluar structures such as ribosomes
  • The DNA duplicates so there is one copy for each cell
  • The DNA forms an X shape
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5
Q

Prophase of mitosis

A
  • The chromosomes condense

- The membrane around the nucleus break down and the chromosomes lie free in the cytoplasm

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6
Q

Metaphase of mitosis

A
  • The chromosomes line up at the centre of the cell
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7
Q

Anaphase of mitosis

A
  • Cell fibres pull the chromosome apart

- The ends of each chromosome go to opposite ends of the cell

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8
Q

Telophase of mitosis

A
  • Membranes form around each sets of chromosomes

- These form nuclei and begin to divide

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9
Q

Cytokensis of mitosis

A
  • The cell membrane and cytoplasm divide
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10
Q

Results of mitosis

A
  • Two daughter cells are produced with exactly the same set of DNA
  • They are genetically identical diploids
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11
Q

Growth

A

The increase in size or mass

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12
Q

Cell Differentiation

A
  • The process in which a cell changes to become specialised for its role
  • Allows multicellular organisms to work more efficently
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13
Q

Cell Division

A

Mitosis

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14
Q

Cell Elongation

A

This is where a plant cell expands making it grow and bigger

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15
Q

Growth in animals

A
  • Occurs by mitosis
  • Happens whilst young
  • Reach full growth
  • Cell division in adults is for repair
  • Cell differentiation is lost at an early age
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16
Q

Growth in plants

A
  • Growth in height is due to cell elongation
  • Cell division only occurs in meristems
  • Plants continuously grow with them developing new branches
  • Plants continue to differentiate
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17
Q

Cancer

A
  • Caused by uncontrollable cell division
  • The rate at which mitosis occurs is controlled by genes
  • If there is a change in one of the genes that control mitosis, then there will be an uncontrollable division
  • This creates a mass of abnormal cells called a tumour
  • This destroys tissue
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18
Q

Percentile charts

A
  • Used to monitor growth
  • Assess the development of a child so that a pattern can be shown that outlines any issues such as obesity and dwarfism
  • A baby is regularly monitored to see if it is growing normally
  • Measurements are taken from the height, weight and head circumference
  • This is represented in percentiles. The 50th percentile means 50% of babies have reached that measurement at a certain age
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19
Q

Stem Cells

A
  • Differntaite to become different types of specialised cells
  • Stem cells are originally undifferentiated
  • Depending on their role, they divide to become new cells and then differentiate
  • These can be found in human embryos. They have the potential to divide into any cell
  • These cells are important for growth and development
  • Adults also have stem cells but they are only found in select places such as bone marrow
  • These are not as versatile and can not produce all types of cell
  • In adults, they are used to replace damaged cells
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20
Q

Meristems

A
  • These are the only parts in the plant that divide through mitosis
  • Meristem tissue is found in the areas of the plant that are growing such as as roots and leaves
  • The meristems produce unspecialised cells and form any cell type in the plant. Unlike humans, they can differentiate to any cell through out the plants life
  • These cells can form xylem and phloem
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21
Q

Stem cell uses

A
  • Doctors already use some adult stem cells to treat diseases such as blood diseases like sickle cell anaemia with a bone marrow transplant
  • Scientests have experimented with embryonic stem cells and growing them. Under certain conditions they can specialise
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22
Q

Uses of embryonic stem cells

A
  • Replace cells damaged by injury or disease
  • An example is that new cardiac muscles can be implanted into someone with heart disease
  • This leads to the potential of new curwa
  • However further research and development is needed
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23
Q

First stage of embryonic stem cell development: Tumour Development

A
  • Stem cells divide quickly
  • If scientests can not control the division of stem cells within a patient then a tumour may develop
  • This needs to be 100% eradicated before stem cells are used as common medicine
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24
Q

Second stage of embryonic stem cell development: Disease transmission

A
  • Viruses can be located in cells
  • If the stem cells used contain a virus, it can pass it on to the patient
  • This can further decline their health
  • A method needs to be developed to always detect a virus before the commercial development of stem cells
25
Q

Third stage of embryonic stem cell development: Rejection

A
  • If the transplanted cells are not grown within the body, the body may trigger an immune response in which the body tries to remove the foreign cells
  • Drugs can supress this, but the immune system becomes weaker
  • This issue needs to be overcome
26
Q

Ethical issues with stem cells

A
  • People may disagree the use of stem cells because they believe that the medical researchers may be playing God
  • Also the embryonic stem cells used may have the potential for human life which may anger some people
27
Q

The CNS

A
  • Central Nervous System made up of the brain and spinal cord
  • The spinal cord is a long column of neurones that runs from the base of the brain down through the spine
  • It branches off at some point to connect with other parts of the body
  • This relays information
  • The brain is connected by billions of interconnected neurones
28
Q

Cerebrum

A
  • Largest part of the brain
  • Divided into two parts called cerbral hemispheres
  • The left hemisphere controls the muscles on the right side of the body and vice versa
  • The cerebrum is important for movement, intelligence, memory anf vision
29
Q

Cerebellum

A

Responsible for muscle coordination and balance

30
Q

Medulla Oblongata

A

Controls unconscious activitis such as breathing and heart rate

31
Q

CT scanning

A
  • Uses x-rays to produce an image of the brain
  • Shows main structures of the brain but not their functions
  • If a CT scan shows disease or damage in the brain structure and if the patient has lost wome function, the function of that part of the brain can be worked out
32
Q

PET scanning

A
  • Use radioactive chemicals to show which parts of the brain are active when the person is inside a scanner
  • Investigate both the stucture and the functions of the brain in real time
  • Useful for studying disorders such as Alzheimers as it shiws areas of the brain that sre usually active or inactive
33
Q

Issues with treating the CNS

A
  • There are many things that can go wrong with the CNS such as tumors or injuries
  • Its hard to repair damage as the neurones in the CNS do not readily repair and scientest have not developed a way to repair nervous tissue
  • It is not easy to access the CNS. e.g it is hard to remove tumors in the CNS
  • If the treatment goes wrong, then it could lead to permanent damage
34
Q

The Nervous System

A
  • The CNS coordinates responses to stimulants
  • This is done through neurones through all parts of the body
  • The body has many sensory receptors that dectect a stimulus
  • Different stimuli are detected by different receptors e.g light is detected by the eyes
  • When a stimulus is deteced, then it is converted into nervous impulses whcih are sent along to the CNS
35
Q

CNS respones

A
  • Coordiantes a response in relation to a stimulus
  • Impulses travel through the CNS along relay neurones
  • The CNS sends impulses to an effector (a muscle or a gland) along a motor neurone. The effector then responds accordingly such as by contracting or relaxing
  • The time it takes for this to occur is called the reaction time
36
Q

Neurones

A
  • All neurones have a cell body
  • This cell body has extensions to other neurones
  • Dendrites and Dendrons carry nerve impulses to the cell body and
  • Axons carry nerve impulses away from the cell body
  • Some axons are surrounded by a myelin sheath which acts as an electrical insulator and speeds up impulses
37
Q

Myelin Sheath

A
  • Joins between nerves slow down the speed of the impulses, the myelin sheath reduces this delay
38
Q

Sensory Neurone

A
  • One long dendron carries impulses from receptors tothe cell body which is located in the centre of the neurone
  • One short axon carries the impulse to the CNS
39
Q

Motor Neurone

A
  • Many short dendrites, surrounded by the myelin sheaths that carry impulses from the CNS to the cell body
  • One long axon carries the impulse from the cell body to the effector cells
40
Q

Relay Neurone

A
  • Many short dendrites carry nerve impulses from sensory neurones to the cell body
  • An axon carries nerve impulses from the cell body to motor neurones
41
Q

Synapses

A
  • Connect neurones
  • Nerve signals are transferred by chemicals calld neurotransmitters which diffuse
  • These transfer electrical signals
  • Ths transmission of s nervosu impulse is very fast but it is slowed down a bit at the synapse because of the diffusion of neurotransmitters across the gap
42
Q

Reflexes

A
  • Prevent injury due to quick action
  • Automatic and rapid
  • The passage from recpetor to effector is called the reflex arc
  • These go through the spinal cord and the medulla
  • When a stimuli is detected impulses are sent along the CNS
43
Q

Process of a reflex

A
  1. Stimulant occurs
  2. Stimulation of pain receptor
  3. Impulses moves along sensory neurone
  4. Impulses are passed along a relay neurone through a synapse
  5. Impulses travel along a motor neurone
  6. The muscles contracts or relaxes
    This does not involve thinking time so it is quicker than normal action
44
Q

Relfexes in the eye

A
  • Very bright light can damage the eye so a relfex protects it
  • Light receptors detect light and send an impulse through a sensory neurone to the brain
  • The message moves along a relay neurone to a motor neurone which causes muscles in the iris to relax or contract
45
Q

Parts of the eye

A
  • Cornea
  • Iris
  • Lens
  • Retina
  • Rods
  • Cones
  • Optic Nerve
46
Q

Role of the cornea

A

Refracts light into the eye

47
Q

Role of the iris

A

Controls how much light enters the pupil

48
Q

Lens

A

Refracts light, focuses on the retina

49
Q

Retina

A

The light sensitive part with receptor cells called rods and cones

50
Q

Rods

A

Dims light but do not detect colour

51
Q

Cones

A

Detect colour but not good in dim light

52
Q

Optic Nerve

A

Carries impulses from the recptors to the brain

53
Q

Looking at distant objects

A
  • The ciliary muscle relaxes which allows suspensory ligaments to pull tight
  • This pulls the lens into a less rounded shape so light is refracted less
54
Q

Looking at close objects

A
  • Ciliary muscle contracts which causes slackens suspensory ligaments
  • Lens becomes more rounded which refracts the light more
55
Q

Longsightedness

A
  • People are unable to focus on near objects
  • The lens does not bend light enough or the eyeball is too short
  • Light from near objects is brought into focus behind the retina
  • Glasses with convex lenses can fix this
56
Q

Shortsightedness

A
  • People who are unable to focus on distant objects
  • The lens bends the light too much or the eyeball is too long
  • Light from distant objects is brought into focus from the retina
  • Glasses with concave lenses can fix this
57
Q

Colourblindness

A
  • The most common form of colourblindness is red-green
  • Caused by the red-green cones in the retina do not work properly
  • There is no cure as cone cells can not be replaced
58
Q

Cataracts

A
  • Cloudy patch on the eyes
  • Stops light from being able to enter the eye causing blurred vision
  • Colours may not be seen as vividly
  • Treated by replacing the lens with an artificial one
  • Caused by a faulty lens

Edexcel - Biology (9 decks)

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