[Unit 2.1] Cell Structure Flashcards
Cells (40 cards)
define magnification
How enlarged an images is compared to its actual size
define Resolution
Refers to how much detail can be seen as is measured as the smallest distance between two separate points
How do electron microscopes work, and what are the two types.
Use beams of electrons to create microscope images
Scanning electron microscope(SEM) - focused beam
Transmission electron microscope(TEM) - broader beam
How do light microscopes work
visible light passes through a specimen and then through glass lenses, which magnify the image
(Dis)advantages of light microscope
Dis - low magnification and low resolution
Ad - specimen can be alive and in colour
(Dis)advantages of TEM
Dis - monochrome; specimen has to be (dead) in vacuum chamber; specimen must be very thin
Ad - 200,000x magnification and 1nm resolution
(Dis)advantages of SEM
Dis - monochrome and specimen has to be (dead) in vacuum chamber
Ad - 100,000x magnification and 10nm resolution.
define cell fractionation
method of investigating the insides (organelles) of a cell
-homogenisation
-ultracentrifugation
stage 1 of cell fractionation
place cells in cold (slows enzymes activity to prevent digestion of organelles), buffered(prevent denaturing), isotonic(prevent bursting or shrivelling of organelles) solution.
stage 2 of cell fractionation
Homogenisation, cells broken apart by homogeniser (blender) to break open cells release organelles (breaks down cell membrane)
stage 3 of cell fractionation
blended tissue is filtered through sieve to remove insoluble material / unbroken cells / larger cellular material such as cell walls etc.
stage 4 of cell fractionation
ultracentrifugation, spin fast to separate solution by mass (centrifugal force) into pellet and supernatant (faster you spin, the LIGHTER the organelle that makes up pellet)
list from largest to smallest the organelles
nucleus, mitochondria, lysosomes, ribosomes
Name differences between prokaryotic cells and eukaryotic cells (9)
Prokaryotic cells:
-No nucleus, circular loop of DNA “free floating” instead
-DNA doesn’t have histones (can’t block transcription)
-Have extra DNA that can be exchanged between prokaryotes
-Don’t have membrane-bound organelles (no mitochondria)
-Chloroplasts too big, have chlorophyll to make glucose
-Ribosomes are smaller
-Cell walls made of murein (a glycoprotein) (not cellulose)
-Has slime capsule
-Some have flagellum
What is the purpose of the slime capsule?
Prevent drying out, and helps evade phagocytosis (engulfed by white blood cells).
What is the use of exchanging plasmids between prokaryotes?
Allows the prokaryotes to share mutations
Often plasmids code for antibiotic resistance.
What is the flagellum?
hair like structure that rotates to propel cell.
It allows for directional movement.
What is the role of attachment proteins?
attaches onto host cell and allows it inside.
What is the role of the envelope in viruses?
What is the role of the envelope?
What is the role of the capsid in viruses?
Stores and protects genetic information
What is the role of the viral genome in viruses?
It is the code (DNA/RNA) that allows for the virus to reproduce.
How big is a virus
100nm (1000x smaller than bacteria)
What are the (5) stages of a life cycle of a virus?
1-enter your body and attach to a cell
2-Enter host and burst open releasing viral genomes
3-Viral genome enters nucleus and tricks into being copied and gets proteins coded for in ribosomes
4-virus is replicated millions of times ultimately bursting the cell making you fell unwell
5-Immune system is provoked and starts attacking viruses and your own cells (the hosts)
structure of Nucleus
largest organelle
dark patches - chromatin
surrounded by nuclear envelope
nuclear pores allow large molecules through
nucleolus is small darkly stained body
