Microscope & Cells F4 Flashcards
Function of the eyepiece lens
to look through
Objective lens magnification
total magnification is: eyepiece x objective lens
Function of the stage
holds slide and specimen
Function of the focusing knob
moves position of lens or stage to focus
Function of the light source
provides light to form an image
Why do you use the lowest power of objective lens when using a light microscope?
The field of view is wider, allowing to see more of the cells on the slide and making it easier to find the specimen
How do electron microscopes work?
They pass beams of electrons through a specimen
What does resolution mean?
The ability of a microscope to see in great detail
How do you find the true size of a biological specimen?
size observed / magnification
How do you find the magnification of an image of a biological specimen?
size observed / actual size
How do you find the magnification of an image?
measured length of scale line / given length of scale line
How do you prepare a slide of plant cells?
- take a clean slide
- lift small piece of tissue
- add drops of iodine solution
- view slide at low power
Why is iodine solution added?
To stain the cells and make them show clearly
Why does the piece of tissue need to be thin?
To allow light from the source to pass through the cells
How do you prepare a slide of animal cells?
- rub clean cotton bud on inside of cheek
- smear cotton bud on microscope slide
- add drop of methylene blue stain
- lower coverslip
- view on lowest power
What is the function of the vacuole?
contains cell sap and helps cell keep its shape
What is the function of the cell wall?
provides support to the cell
What is the function of the chloroplast?
contains chlorophyll to trap light during photosynthesis
What is the function of the nucleus?
control centre of cell containing genetic information of cell
What is the function of the chromosomes?
carry genetic material in genes
What is the function of the nuclear membrane?
boundary of the nucleus
What is the function of the cytoplasm?
where all chemical reactions take place
What is the function of the cell membrane?
selectively permeable, controls what enters and leaves the cell
What is the function of the mitochondria?
site of cell respiration
What are stem cells?
Undifferentiated cells that divide by mitosis to become a specialised cell
What are the properties of stem cells?
- can differentiate into any specialised cell types
- continue dividing by mitosis to produce more stem cells
Where can you find stem cells?
- embryos
- placenta
- umbilical cords
- bone marrow
Why are embryos favoured over adult stem cells?
- easy to grow
- easy to extract
- able to develop into many different cell types
What are the ethical issues in using embryos for stem cells?
- against some peoples religions
- some believe its against the human rights of the embryo
What is peer review?
when different scientists work together in teams to share ideas and results
Where do stem cells originate in plants?
from meristems at the apical bud of the shoot
Describe the procedure of using stem cells for Leukaemia
- chemo destroys cancerous white blood cells
- patient is given transplant of bone marrow from healthy matching donor
- donor cells multiply to produce healthy blood cells
How else can stem cells be used in medicine?
making retina cells - blindness
making brain cells - parkinson’s
What are the potential risks of using stem cells to cure Leukaemia?
- chemo leaves patient with no immune system
- viruses / diseases may be transferred
- tumours may develop of unwanted cells
What are 3 examples of organ systems in humans?
- digestive
- nervous
- reproductive
What are the functions of the digestive system?
breaks down large insoluble foods molecules into small soluble molecules (stomach)
What are the functions of the nervous system?
makes responses and responds to stimuli (brain)
What are the functions of the reproductive system?
production of young (uterus)
What are the benefits of having organ systems?
- helps transport substances through the body better
- helps communication between cells
- improves gas exchange
What is surface area to volume ratio?
As the size of the organism increases, its surface area to volume ratio decreases
What are the adaptions of exchange surfaces?
- large exchange surface area by having a folded surface
- thin exchange surface for short diffusion distance
How is the efficiency of exchanged maximised?
- good blood supply do to the capillary networks
- distribute exchanged materials to all cells
What is diffusion?
The movement of molecules from a high to low concentration
What is the process of diffusion in the lungs?
Blood continues to take in oxygen from alveolar air spaces provided by concentration of oxygen there is greater than in the blood
What factors affect the rate of diffusion?
- temperature (high temp. speeds up movement by increasing kinetic energy)
- surface area (greater area for molecules to move through)
