Cell Cycle Flashcards
Describe chromosome
Chromatids attached to a centromere
What must happen for a cell to divide?
Organelles must replicate
DNA must replicate
cells must grow
Stages of cell cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Describe stage 1 of cell cycle
Interphase:no actual division during this phase , cell preparing for division
Describe interphase G1
Protein synthesis of those from which cell organelles are produced(transcription/ translation)
Organelles replicate
Size of cell increases
Describe interphase S phase
Semi conservative DNA replication
Describe interphase G2
Energy stores are increased
Organelles grow and divide
Size of cell continues to increase
Replicated chromosomes are checked for error and repaired
Describe stage 2 of the cell cycle
Mitosis : one set of chromosomes pulled to each end of cell
Describe stage 3 of cell cycle
Cytokinesis
Cytoplasm /cell membrane divides to form two genetically identical cells
Both cells also receive sub cellular structures eg mitochondria and ribosomes from parent cellsv
Why is mitosis important?
Growth of new cells
repair of damaged tissue
asexual reproduction
Stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Describe prophase
Chromosomes condensed, getting shorter and fatter
Centrioles moved opposite end of cell
two chromatids attached by centometre
nuclear envelope disappears
Describe metaphase
Spindle apparatus forms in cytoplasm
Chromosomes arrange themselves at the equator of cell
Describe anaphase
Spindle fibres attached to the chromatids contract and shorten
sister chromatids are separated to opposite poles of cells
Describe telophase
Chromosomes reach poles and become indistinct
nuclear envelope and nucleolus reform
spindle disintegrate
cell division – division of cytoplasm
Why are the chromosomes v shaped ?
Separation of chromosomes so they’re v shaped
Describe the steps in phagocytosis
The phagocyte is attracted to the pathogens by chemoattractants and move towards the pathogen along the concentration gradient.
The phagocyte binds to the pathogen
the lysosomes within the phagocyte towards the phagosome formed by engulfing the bacterium.
The lysosomes released the lytic enzymes into the zoom where they break down the bacterium
the breakdown products of the bacterium absorbed by the phagocyte
Define endocytosis
Movement of large molecules into cells using vesicles e.g. phagocytosis
Define exocytosis
Movement of lodge molecules out of cells using vesicles. The phagolysosome fuses with the cell membrane and releases the debris from the broken down pathogen.
How did T cells respond to foreign antigen?
A phagocyte has engulfed the pathogen and displays the antigen on its surface
The antigen is displayed to many different T cells in the lymph node
Clonal selection – stimulated t cell divides many times
Helper t cell – these secrete chemicals which stimulate phagocyte cells, stimulate the cell to produce antibodies and killer t cells
Killer T cells – these bind to cells presenting the complementary antigen
Describe performing
Causes perforation in the cell membrane making the cell fully permanently perforated
Describe t lymphocytes
Matures in the thyroid gland
involved in some mediated immunity
Responds to foreign material inspired body cells
Responds to own cells altered by viruses or cancer to transplanted tissue
Describe b lymphocytes
Matures in bone marrow
Involved in humoural immunity
Produces antibodies
Responds to foreign material outside body cells
Responds to bacteria and viruses
What does the time taken for each stage of mitosis vary depending on ?
Type of cell
Environmental conditions
How do you calculate the length of stages ?
Number of cells in a stage / total number of cells counted in all stages of
Define mitotic index
The proportion of cells in a tissue sample that are undergoing mitosis
What does high mitotic index for an animal tissue indicate ?
The tissue repair is taking place or that there’s cancerous growth in the tissue
It’s calculated incorrectly it’s not between 0 and 1 or 0% and 100%