P1- Cell biology Flashcards
Topic 1 of GCSE Biology
Define specialised cell
Cells that differentiate to form different types of cells as an organism develops
Define eukaryotic cells
A cell which has a nucleas and membrane bound organelles (e.g plant and animal cells)
Define prokaryotic cells
Cells that don’t have a nucleus or membrane bound organelles. They just have a single loop of DNA and small rings on DNA called plasmids (e.g bacteria cells)
Are eukaryotes or prokaryotes bigger?
Eukaryotes are much bigger than prokaryotes
Define plasmids
Small rings of DNA
Define DNA loop
Main genetic component not stored in the nucleas
What organelles are only in the plant cell?
Cell wall, vacuole, chloroplast
3 examples of specialised animal cells
-Sperm cell
-Nerve cell
-Muscle cell
How are sperm cells specialised?
-Long tail to swim to egg
-Streamlined
-Lots of mitochondria for energy
-Enzymes to digest cell wall
How are nerve cells specialised?
-Send electrical impulses to the body
-Have a long axon to carry impulses
-Synapse junctions for impulses to pass to other nerve cells
-Dendrites increase surface area
How are muscle cells specialised?
-They can contract
-Contain protein fibres to change their length
-Lots of mitochondria for energy
3 examples of specialised plant cells
-Root hair cell
-Xylem cell
-Phloem cell
How are root hair cells specialised?
-Increases the surface area of the root
How are xylem cells specialised?
-Carry water and dissolved minerals from roots to leaves
-Thick walls containing lignin to support the plant
-End walls are broken down so water can easily flow through
-No internal structures
How are phloem cells specialised?
-Carry dissolved sugars up and down the plant
-Contain phloem vessel cells and sieve plates to allow dissolved sugars to move through the interior
-Phloem vessel cells have companion cells for mitochondria
Elements of a light microscope
Samples can be alive but generally dead, very thin samples needed, 2D image, sample may have to be stained
Elements of an electron microscope
Samples are dead, sometimes thinly sliced, 3D image, much higher magnification and resolution
Define magnification
How much bigger a sample appears to be under microscope than it is in real life
Define resolution
The ability to distinguish between two points in a specimen
Conversion of millimetres to micrometers/ micrometres to nanometres
x1000
Equation for magnification
Magnification=Image /Actual
(I=AM)
What is binary fission?
When bacteria multiplies by simple cell division
How often does simple bacteria cell division take place?
Every 20 minutes
2 ways bacteria can be grown
-Nutrient broth solution
-Colonies on an agar gel plate
Define stem cells
An undifferentiated cell that can divide to produce many specialised cells of the same type
2 conditions treatments of stem cells may able to help?
-Diabetes
-Paralysis
What can embryonic stem cells differentiate into?
Any type of cell
What can adult stem cells (bone marrow) differentiate into?
Only blood cells (RBCS, WBCs or platelets)
Where are plant stem cells found and what do they differentiate into?
Plant meristems, differentiate into plant cells the plant may need (e.g palisade, root hair, phloem or xylem)
Define therapeutic cloning
An embryo is produced with same gene as the patient. Stem cells from embryo aren’t rejected by patients body so they can be used for medical treatment
Risks of using stem cells
-Viral infections
-Ethical or religious objections
Define mitosis
Cell division which produces two identical daughter cells for growth and repair
What are the steps of mitosis?
1) Cell grows and increases the amount of sub cellular structures
2) DNA is duplicated to form 2 copies of each chromosome
3) Chromosomes line up at the centre of the cell
4) 1 set is pulled to the poles of the cell and the nucleus divides
5) Cytoplasm and cell membrane divides to form 2 genetically identical daughter cells
Define diffusion
The movement of particles from an area of high to low concentration. The process is passive and requires no energy
What factors affect the rate of diffusion?
Concentration gradient
Temperature
Surface area of the membrane
How does the concentration gradient affect the rate of diffusion?
Greater the difference in concentration gradient, faster the rate of diffusion
How does the temperature affect the rate of diffusion?
Adding heat, adds kinetic energy. Particles collide more readily and rate of diffusion increases
How does the surface area of the membrane affect the rate of diffusion?
Larger the surface area, more space for exchange so a faster rate of diffusion
What is surface area to volume ratio?
When an organism has a huge surface area for its volume
How do you work out the surface area of a 1cm by 1cm cube
-Find area of 1 side (1 x 1)
-Multiply by 6 as there are 6 sides
What is the effectiveness of an exchange surface increased by?
-A large surface area
-A thin membrane (to provide a short diffusion path)
-Having an efficient blood supply (in animals)
-Being ventilated for gaseous exchange (in animals)
Define single cellular organisms
Have a very large surface are to volume ratio to maximise diffusion
Define multicellular organisms
Have a very small surface area to volume ratio, so needs specialised exchange surfaces to ensure all cells get the substances they need
Define osmosis
The movement of water particles from a dilute solution to a concentrated solution through a partially permeable membrane
What is the name of plant cells in a concentrated solution?
Plasmolysed cell (cell membrane shrinks, vacuole loses water)
What is the name of plant cells in pure water/ very dilute solution?
Turgid cells (cells take in water, gets bigger)
What is the name of animal cells in pure water concentration?
Lysis
What is the name of animal cells in concentrated solution?
Crenation
Define active transport
The movement of particles from an area of low to high concentration against the concentration gradient. From a more dilute solution to a more concentrated solution requiring energy from respiration
What do plants require for healthy growth?
Ions
How is active transport used in root hair cells?
To absorb mineral ions from the soil
How is active transport used in the small intestine?
When the concentration of glucose in the small intestine is lower than the concentration of glucose in the blood
How is the root hair cell adapted to increase absorption of substances from the soil
Large surface area
Name one food molecule absorbed into epithelial cells by active transport
Glucose
Why is it necessary to absorb some food molecules by active transport
Going from low to high concentration against concentration gradient requiring energy from respiration
Name one substance that plants absorb by active transport
Mineral ions
How do the highly folded cell surface help the epithelial cell to absorb soluble food
Increase the surface area
If a cell containing 8 chromosomes divides by mitosis, how many chromosomes will each new cell contain
8
What is the name of a section of a chromosome that controls a characteristic
Gene
Why is mitosis important in living organisms
To repair tissues
