Cells Flashcards
How is an electron microscope better than a light microscope?
Allow us to see greater detail in the cells e.g. mitochondria and internal detail of the nucleus and chloroplasts
What are some disadvantages of electron microscopes?
Are large and very expensive and require specialised rooms in a lab
What is the calculation for magnification?
Magnification = size of image ÷ size of real object
Convert 1 mm into micrometer
1mm = 1000µm
What organelles are in a plant cell only?
Chloroplast, cellulose cell wall and permanent vacuole
What is the function of the nucleus?
Contains genetic information in the form of chromosomes
What is the function of the nuclear membrane?
Controls what enters and leaves the nucleus.
What is the function of the cytoplasm?
Site of chemical reactions
What is the function of the cell wall?
Made of cellulose, helps support the plant and make it tough
What is the function of chloroplast?
Contains the green pigment chlorophyll, which traps light energy for photosynthesis
What is the function of the permanent vacuole?
Contains cell sap and gives the cell support.
What is the function of the mitochondria?
Site of cell respiration
What features are found in a bacterial cell?
Plasmid, DNA is free in the cytoplasm
What is a plasmid?
A ring of DNA found in bacteria
Define stem cell
A stem cell is a simple unspecialised cell in animals and plants that has the ability to differentiate to form specialised cells.
Where are stem cells found?
Embyos, bone marrow (adult)
What is the difference between embryonic stem cells and adult stem cells?
Embryonic can differentiate into a greater range of cell types
Adult stem cells have a limited range of cell types e.g. blood cells
Where are stem cells found in plants?
Meristems (at apices) of roots and stems
What are the benefits of using plant stem cells?
Retain ability to divide so can be used for cloning techniques which can produce large numbers of genetically identical plants
How is stem cell research validated?
Validated using peer review (other scientists repeat and compare results of experiment)
What are the benefits of stem cell?
*bone marrow transplants for treating leukaemia (cancer of white blood cells);
*healing burns;
*treating paralysis
What are some risks and ethical implications of stem cells?
*pre-treatment using radio- or chemotherapy lowers the immune system (killing healthy cells too);
*transfer of diseases or viruses from other animals;
*formation of tumours due to uncontrollable stem cell division;
*development of unwanted cell types.
*Kills/destroys embryo
How can stem cells be used for treatment of leukaemia?
1.Chemotherapy and radiotherapy are used to kill the cancerous white blood cells
2.This stops the patient’s bone marrow producing new blood cells
3.Patient is given a transplant of bone marrow producing new blood cells from a matching healthy donor
4.If successful, the donor stem cells will multiply and produce healthy blood cells
Define tissue
A group of cells that work together to carry out a particular function e.g. blood, skin
Define organ
A group of tissues types that work together to carry out a particular function e.g. heart contains muscle, nerve and blood tissues
Define organ system
A group of organs that work together to carry out a particular function e.g nervous system contains brain, spinal cord, eyes, muscles
How do multi-celled organisms form specialised tissues, organs and organs systems?
Multi-celled organisms can differentiate their cells to form specialised tissues, organs and organs systems.
How will an increase in temperature effect diffusion?
Increased temperature, increases the kinetic energy of molecules and increases the rate of diffusion
How will an increase in surface area affect diffusion?
Increased surface area, increases the rate of diffusion e.g. villi in ileum; alveoli in lungs
How does an increase in concentartion gradient affect diffusion?
A steeper concentration gradient, increases the rate of diffusion e.g. the circulation of blood and the movement of gases away from exchange surfaces maintains the steep concentration gradient
What three factors affect diffusion?
Temperature, surface area, concentration gradient
Define diffusion
The movement of particles from an area of high concentration to an area of lower concentration. This does not require energy (it is a passive process.)
Why cant multicelled organisms use diffusion to obtain oxygen?
Diffusion across the body surface is no longer viable as organisms grow bigger (increase in volume) and contain more cells.
How do multicelled organisms obtain oxygen and nutrients?
Multi-celled organisms with a small surface area to volume ratio need exchange surfaces (e.g. alveoli, villi, mesophyll cells) and transport systems (circulatory system, respiratory system, vascular system).
How do single-celled organisms obtain oxygen and nutrients?
Have a large surface area to volume ratio. They can obtain their oxygen and nutrients from the surrounding environment by diffusion.
