TOPIC 6 : CELL DIVISION AND CELLULAR ORGANISATION Flashcards
2.6.1 The Cell Cycle and Mitosis
What is the cell cycle?
The process that all body cells in multicellular organisms use to grow and divide
It starts when a cell has been produced by cell divisionand ends with the cell dividing to produce two identical cells
2.6.1 The Cell Cycle and Mitosis
Explain the overview of the cell cycle
Stage of cycle:
INTERPHASE:
G1 (gap phase 1) - Cells grow + proteins are made (end of this the first checkpoint)
G1 checkpoint - The cell check that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase
S (synthesis) - DNA replicates
G2 (gap phase 2) - Checks for damage in the replication of DNA
G2 checkpoint - The cell checks whether all the DNA has been replicated without any damage. If it has the cell can enter mitosis
(before M phase and just after gap phase 2)
MITOSIS:
P - Nuclear envelope breaks down + cytoplasm lies free
M - Chromosomes line up along the middle of the cell
A - Divide, seperating each pair
T - Two nucleis form
CYTOKINESIS:
Two daughter cells that are genetically identical to the orginal cell and to each other forms
2.6.1 The Cell Cycle and Mitosis
What is a checkpoint?
A checkpoint is defined as a period in which information from many cellular processes (DNA synthesis, protein synthesis, growth signals etc.)
is intergrated to determine whether or not to continue with the cell cycle
2.6.1 The Cell Cycle and Mitosis
What occurs in interphase?
Synthesis of organelles, prominent nucleoli and actively synthesising ribosomal material
Just before celll division the DNA and histone of each chromosome replicates
Each chromosomes now exists as a pair of CHROMATIDS joined by the CENTROMERE
The chromasomal material will now stain and is called Chromatin
2.6.1 The Cell Cycle and Mitosis
What occurs in prophase?
Chromatids shorten and thicken by coiling and condensation of the DNA
In animals cells the centrioles move to opposite poles of the cell
Short microtubules may be seen radiating from the centrioles
At the end of prophase the nuclear envelope fragments and a spindle is formed
2.6.1 The Cell Cycle and Mitosis
What occurs in metaphase?
The pairs of chromatids become attached to the spindle at their centromeres
The chromatids move along the spindle until their centromeres line up along the equator of the spindle
2.6.1 The Cell Cycle and Mitosis
What occurs in anaphase?
A rapid stage
The centromeres split into two and the spindle fibres pull the daughter centromeres to opposite poles
The seperated chromatids now called chromosomes are pulled along behind the centromeres
2.6.1 The Cell Cycle and Mitosis
What occurs in telophase?
The chromosomes reach the poles of the cells, uncoil and lengthen
The spindle fibres disintegrates and the centrioles replicate
A nuclear envelope re-forms around the chromosomes at each pole and nucleoli reappear
Telophase may lead straight to cytokinesis
2.6.1 The Cell Cycle and Mitosis
What occurs in cytokinesis?
The cytoplasm divides
In animals cells, a cleavage furrow forms to divide the cell membrane
There are now two daughter cells that are genetically identical to the orginal cell and to each other
Cytokinesis occurs usually at the beginning of anaphase and at the end of telophase
Separate process to mitosis
2.6.1 The Cell Cycle and Mitosis
What is the role of mitosis?
Used for growth of organisms
Repair of damaged tissues
Replacement of cells
Asexual reproduction
2.6.1 The Cell Cycle and Mitosis
What does mitosis produce?
Produces 2 diploid genetically identical daughter cells
2.6.1 The Cell Cycle and Mitosis
Where does mitosis occur in plants and animals?
PLANTS: Meristem
ANIMALS: Many PARTS of the BODY
2.6.1 The Cell Cycle and Mitosis
What is the structure of chromosomes in mitosis?
The chromosomes are made two strands joined in the middle by a centromere
The seperate strands are called chromatids
Two strands on the same chromosome are called sister chromatids
There are two strands because each chromosome has already made an identical copy of itself during interphase
When mitosis is over, the chromatids end up as one-strand chromosomes in the new daughter cells
2.6.1 The Cell Cycle and Mitosis
How can cancer cells form?
When cells continue to replicate rapidly without the control systems that normal cells have
Cancer cells will form lumps or tumors, that damage the surrounding tissues
Sometimes cancer cells break off from the orginal tumor and spread in the blood to other parts of the body
When a tumor spreads to another part of the body it is said to ahve metastasized
They continue to replicate and make more tumours = called secondary tumours
2.6.1 The Cell Cycle and Mitosis
What can be used to treat cancer cells?
Medicine is used to treat cancer and are sometimes aimed at killing cells that are rapidly dividing by mitosis
They inhibt they synthesis or function of DNA - called chemotherapy
More modern medicine target specifi cancer in different ways
Many inhibit the growth signals for that type of cell
2.6.2 Sexual Reproduction and Meiosis
What are gamete in males and females?
Gametes are the sperm cell in males and egg cells in females
2.6.2 Sexual Reproduction and Meiosis
What do two gametes form?
Two gametes join together at fertilisation to form a zygote, which divides and develops into a new organisation
2.6.2 Sexual Reproduction and Meiosis
What is homologous chromosomes
This carries the same genes
2.6.2 Sexual Reproduction and Meiosis
What are diploid number (2n) of chromosomes in a normal body cell?
It means each cell contains tow of each chromosomes, one pair from the mum and one from the dad - in a normal body cell
2.6.2 Sexual Reproduction and Meiosis
What are haploid number (n) of chromosomes in gametes?
This is where there is only one copy of each chromosome
At fertilisation, a haploid sperm fuses with a haploid egg, making a cell with the normal diploid number of chromosomes
Half these chromosomes are from the father (the sperm) and half are from the mother (the egg)
The diploid cell produced by fertilisation is called a zygote
2.6.1 The Cell Cycle and Mitosis
What is the difference between cancer cells and normal body cells?
NORMAL:
Larger cytoplasm
Single nucleus
Single nucleolus
Fine chromatin
CANCER:
Small cytoplasm
Multiple nuclei
Multiple and large nucleoli
Coarse chromatin
2.6.1 The Cell Cycle and Mitosis
What is p53?
2.6.2 Sexual Reproduction and Meiosis
What is meiosis?
A type of cell division where a parent cell divides to create four genetically different haploid cells
2.6.2 Sexual Reproduction and Meiosis
What is interphase in meiosis?
The whole of meiosis begins with interphase
During interphase, the cell’s DNA unravels and replicates to produce double-armed chromosomes called sister chromatids
2.6.2 Sexual Reproduction and Meiosis
What occurs in prophase 1?
- Chromosomes are visible
- Nucleolus disappears as nuclear envelop disintegrates
- Bivalents form (non-chromatids attach at points called chiasmata)
- Crossing over occurs
- Cell membrane intact
- Centrioles at the poles
- Microtubule spindles are synthesised
2.6.2 Sexual Reproduction and Meiosis
What occurs in metaphase 1?
- Bivalents line up along Equator in a random order (random assortment)
- Spindle attaches to centromeres
2.6.2 Sexual Reproduction and Meiosis
What occurs in anaphase 1?
- Spindles pull apart chromosomes in each bivalent to opposite poles
- Centromeres don’t divide
- Chiasmata seperate so lengths of chromosomes have swapped
2.6.2 Sexual Reproduction and Meiosis
What occurs in telophase 1?
- 2 nuclear envelopes forms around each set of chromosomes
- Cytokinesis occurs
- In animals cells : Very short interphase in which chromosomes uncoil
- In plant cells: straight into meiosis II
2.6.2 Sexual Reproduction and Meiosis
What occurs in prophase 2?
- Chromosomes are visible
- Nucleolus disappears as nuclear envelop disintegrates
- Cell membrane intact
- Centrioles at the poles which are 90’C to the previous position in meisosis 1
- Microtubule spindles are synthesised
2.6.2 Sexual Reproduction and Meiosis
What occurs in metaphase 2?
- Chromosomes line up along equator
- Spindle attaches to centromeres
- Chromatids are randomly arranged (random assortment)
2.6.2 Sexual Reproduction and Meiosis
What occurs in anaphase 2?
- Centromere divide, seperating the chromatids
- Spindles pull apart chromatids of each chromosomes to opposite poles
2.6.2 Sexual Reproduction and Meiosis
What occurs in telophase 2?
- Nuclear envelopes form around gentic information in haploid, gentically unique daughter cells
- In animals cells = cytokinesis
- In plant cells = cells form a cell plate where the equator was
2.6.2 Sexual Reproduction and Meiosis
What occurs in cytokinesis in mitosis?
- The cytoplasm divides
- Four haploid daughter cells are produced that are gentically different to parent cell
2.6.2 Sexual Reproduction and Meiosis
What are the differences in meiosis and mitosis?
Mitosis:
2 daughter cells produced
Identical to parent cell
Diploid
Occurs in all body cells
Used for growth and repair
Meiosis:
4 daughter cells produced
Different to parent cells
Haploid
Only occurs in sex organs
Used for gametes
2.6.2 Sexual Reproduction and Meiosis
What do non sister chromatids do?
They join, swap parts and rejoin
2.6.2 Sexual Reproduction and Meiosis
What is genetic variation?
This is the difference that exist between individuals’ genetic material
And meiosis is important because it creates genetic variation and makes gametes genetically different
2.6.2 Sexual Reproduction and Meiosis
How does crossing over during prophase 1 create genetic variation?
- Homologous chromosomes line up together in synapsis
- Non-sister chromatids join at random points called chiasmata
- The chromatids break apart and apart and re-join forming recombinant chromatids
- This cause a recombination of alleles
2.6.2 Sexual Reproduction and Meiosis
How does independent assortment of chromosomes during metaphase 1 and anaphase 1 lead to genetic variation?
- During metaphase 1 it is random as to which homolog lines up on which side of the equstorial plate of the cell and thus which homolog ends up in each cell at the end of the first division
2.6.2 Sexual Reproduction and Meiosis
How do independent assortment of chromatids into the daughter cells lead to genetic variation?
Gives haploid daughter cells that are genetically different from each other and from the parent cell
2.6.3 Stem cells and Differentiation
What are stem cells?
Stem cells are undifferentiated cells which are genetically identical and have the ability to develop into any of the various kinds of cells.
2.6.3 Stem cells and Differentiation
What is the use of stem cells?
- Repair of damaged tissues
- Treatment of neurological disorders such as Parkinson’s and Alzheimer’s
- Studying development
2.6.3 Stem cells and Differentiation
What is differentiation?
- A cell specialised to carry out a particular function
2.6.3 Stem cells and Differentiation
How are erthrocytes (red blood cell) specialied for a particular function?
Describe how the cell structure is different to the typical cell:
- Lacking a nucleus
- Having a biconcave disc shape
- Flexible cell membrane
Outline the cell’s function:
Transports oxygen in the blood
Explain how thr different structure aids its function:
Optimises the surface area to volume ratio, facilitating gas exchange
2.6.3 Stem cells and Differentiation
How are neutrophil (white blood cell) specialied for a particular function?
Describe how the cell structure is different to the typical cell:
- Multi- globed nucleus
- Short lifespan
Outline the cell’s function:
Body’s primary defense against infection by rapidly migrating to sites of infection
Explain how the different structure aids its function:
The neutrophils which contains antimicrobial are involved in attacking and destroying foreign microorganisms in the process of phagocytosis
2.6.3 Stem cells and Differentiation
How are squamous epithelial cell specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- Flatten Nucleus
- Cell shape is more rounded
- Very thin (allows for efficient diffusion of gases)
Outline the cell’s function:
Protects the body from injury and infection, and allows for the diffusion of materials
Explain how the different structure aids its function:
Promoted diffusion/gas exchange of waste & nutrients
2.6.3 Stem cells and Differentiation
How are ciliated epithelial cell specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- Hair like projections
Outline the cell’s function:
Move substances and fluid across the surface
Explain how the different structure aids its function:
Moves back and forth to help move the particles out of your body
2.6.3 Stem cells and Differentiation
How are sperm cells specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- has a flagellum
- sperm head cell
Outline the cell’s function:
To fertilize a female egg by delivering the male genetic material to it
Explain how the different structure aids its function:
- The acrosome contains digestive enzymes to enables the sperm to penetrate the surface of the egg
- Lots of mitochondria to provide the energy to swim
2.6.3 Stem cells and Differentiation
How are palisade cell specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- High number of chloroplasts
- Elongated & column shape
Outline the cell’s function:
Perform photosynthesis the process that converts light energy into chemical energy
Explain how the different structure aids its function:
- Maximises the absorption of light
- the walls are thin, so carbon dioxide can easily diffuse into the cell
2.6.3 Stem cells and Differentiation
How are root hair cells specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- Large surface area due to its long-thin hair like projections
- Thin cell wall ( for entry of water and ions )
- Lack of chloroplast
Outline the cell’s function:
Absorb water and nutrients from the soil and transport them throughout the plant
Explain how the different structure aids its function:
- Long projection that increases the SA that the plant can use to absorb water & minerals
2.6.3 Stem cells and Differentiation
How are guard cells specialised for a particular function?
Describe how the cell structure is different to the typical cell:
- unevenly thickened cell wall
- Thicker inner wall facing the stomatal pore
Outline the cell’s function:
Regulating the opening and closing of tiny pores called stomata on plant leaves
Explain how the different structure aids its function:
- Regulates the rate of transpiration by opening and closing the stomata
2.6.3 Stem cells and Differentiation
How do cells differ?
they differ in shape
they differ in structure
they differ in the production of each organelle
2.6.4 Tisues, Organs and Systems
What are tissues?
A collection of similar cells( not necessarily identical ones) that works together to perform a specific funtion
e.g epithelial tissues , xylem tissues
2.6.4 Tisues, Organs and Systems
What are organs?
Organ is a collection of tissues that are coordinated to perform a variety of functions
e.g in stomach
muscle tissue, connective, nerve tissue
e.g in a leaf
epithelial tissue, phloem (sucrose), xylem (water)
2.6.4 Tisues, Organs and Systems
What is an organ system
Where organs work together as a single unit
e.g digestive system
stomach, small intestine, liver, pancrease
e.g respiratory system
lungs, tranchea
e.g. circulatory system
heart, arteries, veins
2.6.3 Stem cells and Differentiation
Explain the production of RBCs and WBCs
Blood cells develop from hematopoietic stem cells and are formed in the bone marrow through the highly regulated process of hematopoiesis
Hematopoietic stem cells are capable of transforming into red blood cell, white blood cells and platelets
These stem cells can be found circulating in the blood and bone marrow in people of all ages, as well as in the umbilical cords of new born babies
Stem cells from all three sources may be used to treat a variety of diseases
2.6.4 Tisues, Organs and Systems
What are the apical meristems and how do they link to meristems?
a type of meristem
Causes primary growth
Occurs at tips of shoots and roots
Produces new leaves and flowers
influences the shapes of the mature plants since the patternt for subsequent growth are laid down in the meristems
2.6.4 Tisues, Organs and Systems
How do squamous epithelium group to make up a tissue for a particular function?
- single layer of fat cells lining a surface
- Found in many places in the body, including alveoli in the lungs
- provides a thin exchnage surface for substances to diffuse across quickly (function)
2.6.4 Tisues, Organs and Systems
How do cilliated epithelium group to make up a tissue for a particular function?
is a layer of cells covered in cillia
found on surfaces where things need to be moved
cillia waft mucas along
2.6.4 Tisues, Organs and Systems
How do muscle tissue group to make up a tissue for a particular function?
made up of bundles of elongated cells muscle fibres
contraction, enabling movement, maintaining posture, stabilizing joints, and generating heat to maintain body temperature. (function)
2.6.4 Tisues, Organs and Systems
How do cartilage group to make up a tissue for a particular function?
a type of connective tissue found in the joints
shapes and supports the ears, nose and windpipe
protects bones and joints, provides structure for the body (function)
2.6.4 Tisues, Organs and Systems
How do xylem group to make up a tissue for a particular function?
a plant tissue
transports water around the plant
supports the plant
contains hollow xylem vessel cells (which are dead) and living parenchyma cells
The specialised cells that make up xylem and phloem are located in a meristem known as cambium
Cambium cells are found between regions of xylem and phloem tissue in plant stems and roots
changes that occur when cambium cells differentiate into xylem cells include:
the deposition of lignin in cell walls
loss of cytoplasm
loss of end walls
2.6.4 Tisues, Organs and Systems
How do phloem group to make up a tissue for a particular function?
transports sugars around the plant
arranged in tubes and is made up of sieve cells
each sieve cell has end walls with holes in them, so that sap can move easily through thwm
These end walls are called sieve plates
changes that allow cambium cells to differentiate into phloem sieve tubes include:
a reduction in cytoplasm volume
loss of some organelles
end walls develop into sieve plates
2.6.4 Tisues, Organs and Systems
Where are stem cells found in plants?
meristems
2.6.4 Tisues, Organs and Systems
What is the vascular cambium and what does it do?
a ring of meristematic tissue located between the primary xylem and primary phloem
this extends throughout the length of the plant from the tips of the shoots to the tips of the roots
2.6.4 Tisues, Organs and Systems
What does primary meristems do?
Produced by divisions in the apical meristem region are soon identifiable as three zones of distinct tissues that differentiate below the apical meristems
2.6.4 Tisues, Organs and Systems
Totipoten meaning
A cell whcih can become any other cell, including trophoblast
2.6.4 Tisues, Organs and Systems
Pluripotent meaning
A cell which can become any body cell
2.6.4 Tisues, Organs and Systems
Where are there stem cells in the body?
Skin and bone marrow
2.6.4 Tisues, Organs and Systems
What are the two properties of stem cells?
Ability to provide and differentiate
2.6.4 Tisues, Organs and Systems
Unipotent meaning
A cell which can only become one type of differentiated cell
2.6.4 Tisues, Organs and Systems
Multipotent meaning
A cell which can become a few different types of cells
2.6.4 Tisues, Organs and Systems
What is cell therapy?
replacing damaged cells with functional cells
2.6.4 Tisues, Organs and Systems
Where can stem cells be found?
In the umbilical cord and an early embryo
2.6.4 Tisues, Organs and Systems
Three possible uses of stem cells
drug testing, the study of disease, replace animal test
2.6.4 Tisues, Organs and Systems
What are included in pluripotent stem cells?
Cells which are the result of a new type of reprogramming using molecules to convert a differentiated somatic cell in a pluripotent cell
2.6.4 Tisues, Organs and Systems
How can stem cells help with alzheimers?
Stem cells could regrow healthy nerve cells in people with alzheimers
2.6.4 Tisues, Organs and Systems
How can stem cells help with Parkinson’s?
Transplanted stem cells may help to regenerate the dopeamine - producing cells
2.6.4 Tisues, Organs and Systems
Embryonic stem cells in medicine
Factors to consider when evaluating the use of embryonic stem cells in medicine include:
ethical concerns around the use of embryonic stem cells which have the potential to develop into an adult human
any adult stem cells used in medical treatment could cause an immune response unless they are a close tissue match
stem cells have the ability to divide indefinitely; if this division becomes uncontrolled then it can lead to cancers
2.6.4 Tisues, Organs and Systems
Tissue & stem cells
Tissue damage can occur due to:
accidental damage
degenerative disease
autoimmune condition
Stem cells could be encouraged to differentiate into a damaged cell type and used to repair damaged tissue, e.g.
skin cells to treat burn patients
neurones to repair a damaged spinal cord
pancreas cells to treat type 1 diabetes
retina cells for the treatment of macular degeneration in the eye
2.6.4 Tisues, Organs and Systems
Treating neurological conditions
Brain cells and neurones can be affected by some diseases, affecting the body’s ability to coordinate responses to stimuli
Stem cells could be used to generate new neurones in order to treat the symptoms of these conditions,
e.g. replacing damaged brain cells in Alzheimer’s and Parkinson’s disease
2.6.4 Tisues, Organs and Systems
Developmental biology
Embryonic stem cells have the ability to differentiate into embryos, allowing scientists to study the developmental stages of the early embryo
Research on developmental biology can provide important information about:
developmental problems
the effects of medicines on embryos
