B2.1 Flashcards
What is Diffusion?
- What does it mean by being a passive process?
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient (until the conc gradient is 0)
2) this means energy is not transferred during diffusion- it happens due to ordinary motion of particles in air.
Where does diffusion take place?
Diffusion takes place in our body in our cells that need glucose and oxygen. Diffusion also happens out for waste products formed, such as Co2
How does SA: V ratio help diffusion and where?
1) surface area to volume ratio
- By increasing to SA:V ratio, the rate of diffusion increase (remember do this by smaller organism) this happens in small intestine wall, which is highly folded increasing the surface area touching the oxygen in the same volume, increasing the diffusion if molecules produced in digestion such as glucose and amino acids which is very useful.
How decrease distance help diffusion?
By decreasing the distance particles need to move, the rate of diffusion increase.
Such as in blood capillaries which are ONE CELL THICK, it takes less time for particles to diffuse across a shorter distance easy.
How does concentration gradient affect the rate of diffusion?
Increase the concentration gradient leads to a higher net movement of particles and more diffusion.
For example as plants use co2 for photosynthesis, the concentration of co2 decreases, which increases the concentration gradient - leading to a greater net movement of particles.
(Similarly in animals at exchange surfaces you need a good blood supply so concentration gradient is always kept low)
What are difficulties of diffusion with unicellular organisms vs complex multi cellular ones?
What osmosis?
What is osmosis?
Osmosis is the net movement of water molecules from an area of high WATER POTENTIAL to an area of low WATER POTENTIAL down a concentration gradient through a partially permeable membrane. (Such as a CELL MEMBRANE)
(Still a type of diffusion but just for water molecules)
What happens to cells in plants with osmosis
1) if surroundings are less concentrated (meaning more water potential) then cells, then water will move in to the cell, causing it to expand and increases tugor pressure. This means it becomes TUEHID/ FIRM.
(Plants take water in from high water potential soil until they have a decent tugor pressure, or else they droop. They still maintain shape thanks to inelastic cell wall though)
2) same concentration nothing happens
3) if surroundings are more concentrated ( meaning they have less water potential) then water will move out of the cell. This causes a loss of turgor pressure and causes the cell to become FLACCID. Eventually cell contents collapse away from the cell wall- this cell is now under PLASMOLYSIS.
What happens to human cells with osmosis?
1) if surroundings are less concentrated, then water moves into cells. This causes cell to expand swell and potentially burst = LYSIS
2) same then same as no net movement of water
3) if surroundings are more concentrated, then water moves out of cell. This causes the cell to become CRENATED (it crinkles).
Summary of what happens to plant and animal cell
Plant
Water in = turgid firm
Water out = flaccid. Eventually contents collapse- >plasmolysis
Animal
Water in = lysis and may burst
Water out= crenated (crinkles)
What is active transport and what does it use (2 things)
Active transport is the movement of particles from an area of low concentration to an area of high concentration against a concentration gradient , using carrier proteins to do so.
- going against the concentration gradient it requires ATP too.
Why do cells that carry out active transport need mitochondria?
- what does this tell you about the rate of active transport.
Cells that carry out active transport contain more levels of mitochondria as ATP is required for the carrier proteins to rotate. This shows that rate of active is proportional and dependent to the rate of respiration
What are carrier proteins?
- proteins that SPAN ACROSS THE WIDTH OF THE CELL MEMBRANE and are found in the cell membrane
- they transport molecules in active transport in and out of membrane. They bind to the molecule, rotate or change shape and then release. However this requires energy .
Examples in plants and human small intestine
1) plants use it to transport nitrates and minerals from the soil to them, to make proteins for example. There is always going to be or normally a lower concentration of nitrate particles in the soil, therefore active transport instead of diffusion must be used. Root hair cells use active to transport them into the cell.
2) the glucose that just digests in small intestine actively transport into vili, as it would be inefficient to wait for diffusion as we would starve.
No mitosis: what is mitosis and what is it used for (3 things). What does it produce
Mitosis is the process by which cells divide, mitosis is used for REPAIR damaged TISSUE, enable to organism to increase in size, and replace worn out cells. Also finally for asexual reproduction for other organisms
( can’t say repair cells- they would just get replaced)
- Mitosis produces two genetically identical daughter cells from 1 parent cell.
What are the 4 stages of mitosis which is known as the cell cycle?
1) DNA Replication
2) movement of chromosomes
3) cytokinesis
4) growth of daughter cells
How does DNA replication work?
) Double Helix molecule unzips to expose both strands
2) free nucleotides in the nucleus line up against the strand, based on complementary base pairing.
3) DNA base pairs are made, and when all of them are done
= two new genetically identical molecules of DNA. They zip back together.
How does movement of chromosomes work
This forms bulk of mitosis ,PMAT
1) Chromosomes all line up in the centre of the cell
2) the chromosomes are pulled apart two opposite ends f the cell by spindle fibres.
3) two new nuclei form around each set of chromosomes which now contain all the genetic information for the cell.
Then cytokinesis takes place
How does cytokinesis work?
This is last stage o
1) the cell membrane then pinches inwards on the two cells, separating them, and then they split off the parent cell to become two genetically identical daughter cells.
Finally what happens in growth of daughter cells
Here the daughter cells then independently gore . Finally the cycle repeats as when the time comes the whole process will happen again…
How often does mitosis take place in parts of the body? Why does it vary?
Approximately 300 million body cells die and are replaced every minute. However mitosis happens all the time in places like the skin, but rarely in places like nerves which don’t need to be replaced all the time…
Times of cell cycles vary in different tissues because of different replacement rates- some replace there’s Often, others don’t.
What does it mean for a cell to differentiate during development ?
It means the process by which a cell changes to become SPECIALISED for a specific job .
This involves changing structures or producing sub cellular structures to be more adapted for a job. This makes the entire organism more efficient.
Cells can be so specialised they only perform one function in the body- such as red blood cells
So what is a stem cell and what are they used for?
Stem cells are undifferentiated cells in the human body that divide by mitosis and can differentiate into many types of cells - forming types of tissues and organs.
- Split into adult stem cells and embryonic stem cells.
- they are used by the body DURING DEVELOPMENT, growth and repair.
Embryonic stem cells
Where found
What can they do
What do they do
What important for
- Found in Embryos (which is formed after zygot divides)
- All cells are totipotent= embryonic stem cells can differentiate into any type of cells.
- divide by mitosis and important in development of a human as they produce all the different cells needed
