B1 Cell Structure And Transport Flashcards
Diffusion
Diffusion takes place when particles can move from a higher concentration to a lower concentration.
Factors that increase the rate of diffusion include:
- Concentration gradient: The bigger the difference in concentration, the faster diffusion will be.
- Temperature: The warmer the fluid, the faster diffusion will be.
- The surface area of the exchange surface: When the surface area is larger, diffusion will be faster.
- The distance the molecules must diffuse: If the molecules have to travel a shorter distance, diffusion will be faster.
Osmosis
It is the movement of water from a dilute to a more concentrated solute solution through a partially permeable membrane that allows water to pass through. Transport of water from high to low concentration, down a concentration gradient.
Key points:
A partially permeable membrane is just one with very small holes in it.
Tiny molecules like water can pass through it, but bigger molecules like sucrose can’t.
Differences in the concentrations of solutions inside and outside a
cell cause water to move into or out of the cell by osmosis.
Animal cells can be damaged if the concentration gradient outside the cell changes dramatically.
Eukaryotes and Prokaryotes
Eukaryotic cells all have a cell membrane, cytoplasm, and genetic material enclosed in a nucleus.
Prokaryotic cells consist of cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not in a distinct nucleus. It forms a single DNA loop. Prokaryotes may contain one or more extra small rings of DNA called plasmids.
Bacteria are all prokaryotes.
Plant and animal cells
Plant cells may be specialised to carry out a particular function.
Examples of specialised plant cells are root hair cells, photosynthetic cells, xylem cells, and phloem cells.
Plant cells may be specialised to function within tissues, organs, organ systems, or whole organisms.
Animal cells:
As an organism develops, cells differentiate to form different types of cells.
As an animal cell differentiates to form a specialised cell it acquires different sub-cellular structures to enable it to carry out a certain function.
Examples of specialised animal cells are nerve cells, muscle cells, and sperm cells.
Animal cells may be specialised to function within a tissue, an organ, organ systems, or whole organisms.
Magnification calculations
A student observed a sperm cell using a microscope.
The sperm cell image measured 22 mm long.
The real length of the sperm cell is 0.055 mm.
Use the equation to calculate the magnification the student used to see the sperm cell.
Magnification= size of image
—————–
size of real object
Ans: you do 22 mm÷0.055 mm which gives the answer: x400
Surface Area to Volume Ratio
Side length (cm)= 2 cm
Volume (cm3)= 2x2x2=8cm3
Surface area (cm2)= 6x(2x2)
=6x4
=24cm2
SA:V
24:8
24:8
-----
8 8
3:1
Active transport
Key points:
Particles are pumped by special “carrier proteins” from an area of LOW concentration to an area of HIGH concentration.
Movement is against the concentration gradient (this is the opposite of diffusion).
This process requires energy.
Sperm cell
Contain lots of mitochondria for energy
They contain the genetic information from the male
They have to break the egg
Have long tails to swim to the female reproductive system
Contains enzymes to break down layers of the egg
Large nucleus containing the genetic information
Nerve cell
Nerve cells carry electrical signals around the body.
1) Nerve cells are long to cover more distance in the body.
2) They have branches at the end to connect to other nerve cells.
Root hair cell
Root hair cells absorb water and minerals.
1) Root hair cells grow into long “hairs” that stick out soil.
2) This gives the plant a big surface area for absorbing water and mineral ions from the soil.
