B2: Cell Division Flashcards
What are 3 specialised cells in animals?
Sperm cells
Nerve cells
Muscle cells
What is differentiation?
When a cell changes (adapts?) to carry out a specific function, so it becomes specialised.
What is a specialised cell?
A cell which has adaptations which help it to carry out a particular function.
What is the job of the sperm cell?
To join with an ovum (fertilisation) and combine its genetic information with the ovum
How is a sperm cell specialised for its job?
Contains genetic information in the nucleus - contains half of the normal adult cell.
Long tail, allowing them to swim to the ovum.
Streamlined head to make it easier to swim.
Packed with mitochondria, providing energy for swimming.
Contain enzymes which allow them to digest their way through the outer layer of the ovum.
What is the job of a nerve cell?
Send electrical impulses around the body.
How is a nerve cell specialised for its job?
Long axon - carries the impulse from one part of the body to another.
Axon covered with myelin - insulates the axon and speeds up the transmission of nerve impulses.
Synapses at the end of axon - junctions which allow the impulse to pass from one nerve cell to the other.
Dendrites - increase surface area, so that other nerve cells can connect more easily.
What is the job of a muscle cell?
Contraction
How is a muscle cell specialised for its job?
Contain protein fibres which can change their length - when the cell contracts, they shorten and decrease the length of the cell.
Packed with mitochondria - provide energy for muscle contraction.
Work together to form muscle tissue.
What are some examples of specialised plant cells?
Xylem cells
Phloem cells
Root hair cells
What is the job of a root hair cell?
Increase the surface area of the root - so it can absorb water and dissolved minerals more efficiently.
How is a root hair cell specialised for its job?
Hair - increases SA of the root.
No chloroplasts - as they are underground and do not photosynthesise due to the absence of light.
What is the job of a xylem cell?
Found in plant stem.
Long tubes which carry water and dissolved minerals from the roots to the leaves
How are xylem cells specialised for their job?
Form long tubes.
Thick wall containing lignin - provides support to the plant.
Because cell walls are sealed with lignin, it causes the xylem cells to die.
End walls between cells have broken down - cells now form a long tube so water and dissolved minerals can flow easily.
No nucleus, cytoplasm, vacuole or chloroplasts (no internal structures), makes it easier for water and minerals to flow.
What is the job of phloem cells?
Carry dissolved sugars up and down the plant.
How is a phloem cells specialised for its job.
Consists of 2 different types of cells:
Phloem vessel cells - contain no nucleus and only limited cytoplasm. End walls have pores (sieve plates). Both features allow dissolved sugars to move through the cell interior.
Each phloem vessel cell has a companion cell connected by pores. Mitochondria in a companion cell provides energy to the phloem vessel cell.
How do bacteria multiply?
Through simple cell division - one bacterial cell splits into two bacterial cells (binary fission).
How often do bacteria multiply?
Once every 20 mins, as long as they have enough nutrients and the temperature is suitable.
How do you calculate the number of bacteria after a certain period of time?
Number of bacteria = 2^n
where n = number of rounds of division.
What is the cell cycle?
The process through which a cell divides.
What is the first stage of the cell cycle?
DNA replicates to form 2 copies of each chromosome.
Cell grows and copies its internal structures, such as mitochondria and ribosomes.
What is the second stage of the cell cycle?
Mitosis takes place -
one set of chromosomes is pulled to each end of the cell. Nucleus divides.
What is the final stage of the cell cycle?
Cytoplasm and cell membrane divide to form identical cells.
What are the functions of mitosis?
Essential for growth and development of multicellular organisms (like plants and animals).
Mitosis takes place when an organism repairs itself e.g. when a broken bone heals.
Happens during asexual reproduction.
