2.6 - Cell Division, Diversity And Organisation Flashcards
What makes up a chromatin?
DNA and Histones
What is a chromatin called when it is visible?
A chromosome
What are the 2 main parts of the cell cycle?
Interphase and the mitotic phase
What are the 3 main points in interphase?
G1, S and G2
What happens in G1?
The cell contents duplicate and the cell gets bigger
What does the G1 checkpoint do?
It ensures that there is nothing wrong so the cell can go into S phase
What happens in the S phase?
The 46 chromosomes are duplicated
What happens in the G2 phase?
The cell caries on growing
What happens at the G2 checkpoint?
It checks the DNA for damage
What can happen to a cell before it enters the S phase?
It can go into the G0 phase
What happens in the G0 phase?
The cell leaves the cycle due to:
- Cell differentiation
- DNA damage
- Senescence (the cell is to old)
Is the G0 phase permanent?
It can be or it can be temporary
What does a chromosome look like?
It is one chromatid with a centromere
What is it called when there are 2 chromatids joined together?
Sister chromatids
What is mitosis?
It is the part of the cell cycle where nuclear division takes place
What are the products of mitosis?
2 genetically identical daughter cells
What are the 4 phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens in prophase?
- The DNA condenses (supercoiling)
- Chromosomes become visible
- The nuclear envelope breaks down
- The centrioles move to the poles of the cell
What happens in metaphase?
- The chromosomes line up at the equator
- The centrioles spindle and attach to the centromeres
What happens in anaphase?
- The centromeres divide
- The spindle fibres contract and shorten because of motor proteins
What happens in telophase?
- The chromosomes condense
- A nuclear membrane forms around the chromosomes
What is cytokinesis?
This is when the cell splits into 2
When does cytokinesis happen?
It happens after telophase in both mitosis and meiosis
How do you work out the mitotic index?
The number of condensed chromosomes
————————————— X100
The total number of cells
What is a haploid cell
A cell containing 23 chromosomes
What are examples of a haploid cells?
An egg cell and sperm cell
What is a haploid cell called in meiosis?
A gamete
What is a diploid cell?
A cell containing 48 chromosomes
What are examples of diploid cells?
Body cells
What is the male chromosome?
XY
What is the female chromosome?
XX
What are the 2 main parts of meiosis?
Meiosis 1 and meiosis 2
Do cells go straight into meiosis 2?
Only some plant cells, animal cells have a break
What is the difference between prophase and prophase 1?
In prophase 1 the chromatids do something called ‘crossing over’
What is crossing over?
The chromatids from different homologous pairs twist around each other and parts swap
What is the deference between metaphase and metaphase 1?
In metaphase 1 the cells undergo independent assortment when lining up at the equator
What is independent assortment?
When they line up on the equator randomly so the spindles pull back different homologous pairs, so there are multiple options of combinations
What is the difference between anaphase 1 and anaphase 2?
In anaphase 1 it pulls the chromosome pairs to opposite side not the chromatids
What is the product of meiosis?
4 genetically different daughter cells
What is mitosis and example of?
Asexual reproduction
What is meiosis an example of?
Sexual reproduction
What is an homologous pair?
Two chromosomes that join together, 1 from the egg and 1 from the sperm
What is a stem cell?
An undifferentiated cell that has the ability to turn into different types of cells
What does pluripotent mean?
The ability to differentiate into any type of cell (eg. Embryonic stem cells)
What can stem cells do before they differentiate?
They can divide by mitosis to make more cells
What are the different types of stem cells?
Human:
- Embryonic stem cells
- Adult stem cells
Plants:
- Meristem tissue
Where are embryonic stem cells found?
In a blastocyst (when the zygote begins to divide)
Where are adult stem cells found?
They are found in:
- Blood
- Brain
- Muscle
- Bone
- Adipose tissue (fat storage)
- Skin
Where else can stem cells be found?
- Umbilical-cord blood
- iPS cells
What are iPS cells?
Differentiated cells that are reprogrammed in a lab to turn on a certain gene to become undifferentiated again
What are stem cells used for?
- Bone marrow transplant
- Drug research
- Developmental biology
Why are stem cells used in bone marrow transplants?
To treat diseases of the blood and immune system (eg. Leukaemia and SCID
Why are stem cells used in drug research?
To test new drugs so they don’t have to test on animals
How are stem cells used in developmental biology?
- To study how the cells develop
- To learn how cells function and what happens when they are diseased
- To find out if they can extend the capacity that embryos have for growth and repair in later life
What are stem cells going to be able to treat in the future?
- Type 1 diabetes
- Liver disease
- Alzheimer’s
- Parkinson’s
- Spinal injuries
- Used a bioscaffolding for growing organs
- Strokes
- Burns
Heart disease
What does totipotent mean?
The ability of a single cell to divide and produce all the differentiated cells in an organism
What does multipoint mean?
The capacity of stem cells to differentiate into particular cell types
Why do multicellular organisms need cell differentiation and specialisation?
They have a small SA:Volume ratio so most of the cell is not in direct contact with the environment
What does differentiation in animal cells cause?
- Different proportion of organelles
- The shape of the cell changes
- Some contents of the cell change
What are types of specialised animal cells?
- Erythrocytes (blood cells)
- Neutrophils(white blood cells that ingest pathogens
- Spermatozoa
- Epithelial cells
What does an erythrocyte do?
It carries oxygen from the lungs to respiring cells
How are erythrocytes specialised?
- It has a biconcave shape to increase surface area
- It has no nucleus so there is more space for heamoglobin
- It has an elastic membrane so that it can change shape easily to fit through the capillaries
- The cytoplasm contains lots of haemoglobin for oxygen to bind to
What does a neutrophil do?
It injest pathogens
How is a neutrophil specialised?
- They have a flexible shape to fit through junctions
- The flexibility allows them to engulf pathogens
- Contains lots of lysosomes to help digest pathogens
What does a spermatozoa do?
It fuses with the egg cell in reproduction to share their genes
How is the spermatozoa specialised?
- It has a nucleus containing 23 chromosomes
- It has acrososome in its head that contains digestive enzymes to help break down the outer layer of the egg cell
- It has lots of mitochondria to release energy so that it can move
- The flagellum rotates so it can move to the egg cell
What are the the 3 specialised plant cells?
- Root hair cells
- Guard cells
- Palisade cells
What does a root hair cell do?
It absorbs water and mineral ions from the soil
How is a root hair cell specialised?
- They have hairs to increase the surface area
- Thin walls for a short diffusion pathway
- A permanent vacuole with cell sap to maintain the water potential gradient
- Mitochondria for active transport of mineral ions
- Special carrier proteins in the plasma membrane to actively transport mineral ions
What does a guard cell do?
They control the opening of the stomata
How is the guard cell specialised?
- Inner cell walls are thicker and the outer cell walls are thinner for when the cell goes turgid
- Chloroplasts for ATP production
What do palisade cells do?
They carry out photosynthesis to produce glucose and oxygen
How is a palisade cell specialised?
- Lots of chloroplasts to maximise the absorption of light
- Tall and thin shape to allow light to penetrate deeper
- Cells are densely packed for a short diffusion pathway
- A large vacuole near the chloroplasts to create a short diffusion pathway
- Motor proteins and cytoskeleton threads to move the chloroplasts closer to the light
What are the 4 specialised animal tissues?
- Cartilage
- Muscle tissue
- Ciliated epithelium
- Squamous epithelium
What does cartilage do?
It provides support
How is cartilage specialised?
- It is flexible and found all over the body
- It separates living cells
- It allows other tissues to withstand force
- Forms rings along the trachea to support it and keep it open
Where is hyaline cartilage found?
It makes up the skeleton in the embryo
What does muscle tissue do?
They contract for movements
How is muscle tissue specialised?
- They have layers of protein filaments so that they can slide over each other
- High density of mitochondria
- Skeletal muscles fuse together so that they can contract in unison
What does ciliated epithelium do?
They move substances across the surface of the tissue
How is ciliated epithelium specialised?
- They have cilia that move in coordination
- Goblet cells that secrete mucus to trap things so that they cant enter any vital organs
What does squamous epithelial tissue do?
It provides an outer layer on a variety of organisms (eg. Blood vessels)
How is squamous epithelium specialised?
- They have a single layer of flattened cells along the basement membrane
- They have a thin cross-section to increase diffusion
- It is permeable so gasses can easily diffuse through
What are the 2 types of specialised plant tissue?
- Xylem vessel cell
- Phloem vessel cell
What does the xylem vessel cell do?
They transport water and dissolved ions
How it the xylem vessel tissue specialised?
- No top or bottom walls so water can move via transpiration
- The cells are dead to allow the free movement of water
- Has lignin to thicken the walls for support
What do phloem vessel cells do?
They transport dissolved sugars and amino acids
How are phloem vessel cells specialised?
- Made of living cells that are supported by companion cells
- Cells are joined end to end so that things can easily flow
- Very few sub cellular structures to aid in the flow of materials
