Cell Division and Exchange Flashcards
What is Mitosis
Cell division that results in 2 diploid daughter cells that are genetically identical to the parent cell and to each other
What are the functions of Mitosis
Growth and development of tissues in multicellular organisms
Repair of tissues in multicellular organisms
Asexual reproduction in multicellular organisms and binary fission (a type of mitosis in bacteria) in unicellular organisms
What is a Cell Cycle
Series of stages that a cell goes through when it grows and divides.
What is the Mitosis Cell Cycle
G1 - sub-cellular structures duplicate (excluding chromosomes)
S - Each of the 46 chromosomes is duplicated to form 2 copies of each chromosome
G2 - DNA is checked for errors made during replication. Done using enzymes, and any errors can be fixed
Mitosis - the chromosomes move to opposite poles of the cell and 2 nuclei form
Cytokinesis - cytoplasm divides and cell membrane separates creating 2 new cells
G0 - Temporary cell resting. Some cells will never divide again (e.g. nerve cells)
What are the 6 Phases involved in the Cell Cycle
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
Interphase
G1, S & G2 (makes up about 90% of the cell cycle, the next phases all happen in Mitosis which is only about 10% of the cell cycle)
Prophase
Nuclear membrane disappears DNA unwinds & condenses into chromosomes (2 sister chromatids held together by a centromere which is a circle in the middle of the 2 chromatids) Spindle fibres (fibres that will pull the chromatids apart later, the spindle fibres emerge from the centriole) form & become visible
Metaphase
The chromosomes line up along the equator of the cell (vertical not horizontal)
Spindle fibres attach to chromosomes at the centromere of the chromatids
Anaphase
Sister chromatids are pulled to the edges of the cell (the poles) by the spindle fibres (now there are 2 different chromosomes on each side)
Telophase
A nuclear membrane forms around each of the sets of chromosomes separating them from one another and creating 2 nuclei.
Cytokinesis
Splitting the cytoplasm to create two separate diploid cells each with identical chromosomes.
Diffusion
movement of particles from a high concentration to a low concentration down a concentration gradient
What is a general rule of SA:V ratios
The bigger an object is the smaller it’s surface area to volume ratio will be
Why is SA:V ratio important
SA:V ratio large - lot of surface area for diffusion & not much volume to travel through - organisms can get all the substances it needs by simple diffusion
SA:V ratio small - Large multicellular organisms - several layers of cells between centre & environment - useful substances - longer to diffuse in & out, may be used up by outer layers before reaching inner cells.
Therefore, large multicellular organisms need specialised exchange surfaces.
Exchange Surfaces
Allow transport in & out of all cells for all the organism’s needs.
Features of an Exchange Surface
Large surface area (increase site of exchange)
Thin membrane (decrease diffusion pathway) (distance)
A method of transporting substances to and from the exchange site (e.g. a good blood supply) – maintains a steep concentration gradient (lot of substance in one area and not a lot in another means diffusion will be faster there)
(In animals) being well ventilated for gaseous exchange
Gas Exchange in Humans
In Alveoli
Oxygen enters lungs & diffuses into bloodstream via capillaries covering the alveoli
Higher concentration of oxygen in the alveoli than blood - oxygen moves into blood
Higher concentration of CO2 in blood than alveoli - CO2 moves out of blood
Why is the Alveoli surrounding the lungs a good exchange surface
Large SA for Gas Exchange
V. thin – short diffusion distance
Capillaries surround the alveoli - good blood supply. As oxygen is constantly moved away from the lungs - maintains a steep concentration gradient. (it is the same for CO2 leaving the blood)
Moist - gases dissolve to aid efficient diffusion
Function & Adaptions of the Villi in the Small Intestine
Function - Absorbing the products of digestion
Substances Exchanged - Glucose & Amino Acids
Adaptations - Good blood supply – assists with quick absorption
Cell wall is one layer thick – small diffusion distance
Large SA - increased site of exchange
Function & Adaptions of the root of a plant
Function - Uptake water from the soil
Substances Exchanged - Water and mineral ions
Adaptations - Roots project deep into the soil - can get to minerals & water
Projections - increase SA
Water constantly moves away from roots - steep concentration gradient
Function & Adaptions of the underside of the leaf
Function - Gas exchange in plants
Substances Exchanged - Oxygen & CO2
Adaptations - Stomata - small holes - movement of gasses
Flattened shape - Large SA
Function & Adaptions of the gills
Function - Gas exchange in fish
Substances Exchanged - Oxygen & CO2
Adaptations - Good blood supply - assists w/quick absorption
Thin walls - shorter distance for gasses to diffuse
Gill filaments - Large SA
Structure of Lungs
Trachea is the long pipe leading into the lungs
The ribs surround the lungs and heart
The intercostal muscles are in-between the rib bones
There is a right and left lung
The heart sits between them both in the middle
The trachea leads into 2 pipes called the left/right main stem bronchus
These main stems branch off into Bronchus’ which then branch of into Bronchioles and at the end of these Bronchioles are Alveoli which are spherical.
The diaphragm sits under the lungs and heart
The Pleural Membrane sits over the chest cavity
How do we inhale
Diaphragm contracts & flattens/moves down
Intercostal (internal + external) muscles contract
Ribs move up & out
Volume inside the chest increases
Pressure decreases inside the chest & the air pressure outside the chest is higher
Air rushes in
How do we exhale
Diaphragm relaxes & moves up
Intercostal (internal + external) muscles relax
Ribs down & in
Volume inside the chest decreases
Pressure increases inside the chest & the air pressure outside the chest is now lower
Air leaves the lungs
