Cell Structure Flashcards
What is Cell Fractionation?
the process where
- cells are broken up
- different organelles they contain are separated out based on size/mass using gravity
The 3 Steps of Cell Fractionation.
1) homogenisation
2) filtration
3) ultracentrifugation
Define what is meant by magnification.
Magnification - how many times bigger the image is compared to the actual size of a speciman
Define what is meant by resolution.
Resolution - how clearly you are able to distinguish between two points close together on an object
What is homogenisation?
When cells are broken up by homogeniser (blender), releasing organelles from the cell.
- makes a homogenate.
What is filtration?
When the homogenate is filtered to get rid of any large pieces of debris.
What is ultracentrifugation?
The process where fragments in filtered homogenate are separated in a centrifuge - which spins the tube at very high speeds.
- the heaviest organelles are forced to the bottom, forming pellets.
- leaving supernatant (fluid) at the top
What type of microscope produces a 3D image?
SEM - scanning electron microscope
List key features of TEM
- shoots beams of electrons at a thin sample and detects electrons that make it through to the other side
- very high resolution, so good for learning structure of inner components of a cell
List key features of SEM
- uses focused beams of high-energy electrons which reflect off the surfaces of structures
- produces a 3D image
- samples do not have to be as thin
Describe the key features of a cell surface membrane
1) it is a partially permeable membrane
- controls the exchange of materials between the internal and external cell environment
2) formed from a phospholipid bilayer
Describe the key features of the cell wall
1) offer structural support - provided by cellulose
2) freely permeable
Describe the key functions of chloroplasts
- surrounded by double membrane
- thylakoids - membrane bound flattened discs
- grana joined by flattened membranes - lamellae
Explain the consequence of water loss from vacuoles
1) water moves out of the vacuole and cytoplasm
2) the vacuole shrinks
3) the cell wall is unsupported
4) the plant wilts
What is the main component of fungal cell walls?
- Chitin
List the structures in the nucleus
1) nuclear envelope
2) nuclear pores
3) nucleoplasm
4) chromosomes
5) nucleolus
What is the nuclear envelope?
- double membrane surrounding the nucleus
What is the nucleoplasm?
- granular, jelly-like material in the nucleus
What is the nucleolus?
- small sphere inside the nucleus
- the site of rRNA production and makes ribosomes
What is the function of the nucleus?
- site of DNA replication and transcription (making mRNA)
- contains genetic code for each cell
What is the structure of the endoplasmic reticulum (ER)
- they have folded membranes called cisternae
What is the difference between RER and SER?
RER - has ribosomes on the cisternae
SER - no ribosomes
What is the function of RER?
- protein synthesis
What is the function of SER?
- synthesises and stores lipids and carbohydrates
List the structures in mitochondria
1) double membrane
2) inner membrane -cristae-
3) mitochondrial matrix
4) loop of mitochondria DNA
What is the function of mitochondria?
- site of aerobic respiration
- ATP production
- DNA to code for enzymes needed in respiration
What are the two types of ribosomes?
- 80s ribosomes
- 70s ribosomes
What are 80s ribosomes?
- large ribosomes
- found in eukaryotic cells
What are 70s ribosomes?
- smaller ribosomes
- found in mitochondria, chloroplasts and prokaryotic cells
What is the function of ribosomes?
- site of protein synthesis
What are ribosomes made of?
- protein
- mRNA
State the structure of a vacuole
- fluid filled sac
- surrounded by a single membrane called a tonoplast
What is the function of a vacuole?
- temporary store of sugars and amino acids
- provide support, make cells turgid
What is the structure of chloroplasts?
- surrounded by double membrane
- contains thylakoids
- has fluid filled stroma containing enzymes for photosynthesis
Which cells have cell walls?
1) plant cells
2) fungi cells
Structure of cell wall in plants
- made of microfibrils of cellulose
Structure of cell wall in fungi
- made of chitin
Function of the cell wall
- provide structural strength to the cell
Function of the plasma membrane
- controls what molecules enter and exit the cell
What is the structure of the plasma membrane?
- phospholipid bilayer
molecules embedded within and attached on the outside - proteins, carbohydrates, cholesterol
Features of a eukaryotic cell
- DNA is contained in a membrane bound nucleus
- DNA is coiled into linear chromosomes
