A2.2 Cell structure Flashcards
(24 cards)
What are the cell theories?
- organisms are made up of 1 or more cells
- cells are the smallest unit of life
- all cells come from pre-existing cells
What are the 2 types of microscopes?
Light & electron microscopes
What are the characteristics of a light microscope?
- magnifies up to x200
- can be used for both living and non living organisms
- black & white
What are some characteristics of an electron microscope?
- Magnifies up to x500,000
- can be viewed in 3D
- uses electron beams
- for non living organisms
- black & white
How is total magnification calculated?
ocular x objective
How is magnification calculated?
image size / actual size
What are artefacts?
Structures that are produced due to perpetration processes, inevitable
What is freeze fracture for?
study of the layers of the membrane
How is freeze fracture prepared for electron microscopy?
- specimen frozen
- physically broken apart (fracture)
What are the functions of life?
(MR SHENG)
Metabolism
Reproduction
Sensitivity
Homeostasis
Excretion
Nutrition
Growth
What are features common to all cells?
Plasma membrane
DNA
Cytoplasm
What are some characteristics of prokaryotic cells?
- 1st life forms on earth
- Uni-cellular
- “naked” - not associated with histone proteins, mostly found in nucleoid
What is the flagella for?
Movement
What is the pili for?
Attachment & communication, can also exchange genetic material
What is the naked DNA (Nucleoid) for?
DNA and chromosomes, genetic code
- no nuclear envelope
- not associated with histones
What is the 70S ribosome for?
Protein production
What is the plasmid for?
Extra DNA, replicates independently
What is the plasma membrane for?
allowing and restricting movement of substances in & out of the cell (also used for binary fission)
What is the cell wall for?
Helps maintain the cell structure, prevent bursting
What is the capsule for?
Survival of the cell, adherence, extra layer (only some have this)
What are the steps in binary fission and which cell does it occur in?
Prokaryotic cells
1. chromosome is semi replicated semi conversely
2. 2 copies of DNA move to opposite ends of the cell
3. Cell elongates
4. Plasma membrane grows inward & pinches off
5. Creates 2 separate genetically identical cells
What is binary fission for?
reproduction of prokaryotic cells
What are the advantages of compartmentalisation?
- Create higher concentrations of certain substances within organelles
- Separate toxins & potentially damaging substances from the rest of the cell
- Control conditions inside organelles to maintain optimal conditions (for enzymes)