Cells Flashcards
Nucleus
Information centre of eukaryotic cell
- DNA is stored, replicated and copied into mRNA
Nuclear pores
Gaps in the nuclear envelope that allow substances to move in and out of the nucleus
Nuclear envelope
Double membrane that separates the contents of the nucleus form the cytoplasm
Nucleolus
Part of the nucleus that produces ribosomes
Cell surface membrane
Phospholipid bilayer that contains cholesterol and proteins
• it is a fluid layer that surrounds the cell and enables it to communicate with other cells (cell signalling)
• detect and respond to changes in the environment
• physical barrier - controls what enters and exits the cell
Extracellular matrix
The material in between cells that holds tissues together
- usually made of scaffolding proteins such as collagen
- important for cell signalling
Rough endoplasmic reticulum (RER)
Site where proteins are made, folded and moved to Golgi body
Smooth Endoplasmic reticulum
- lipid and steroid synthesis
- drug detoxification
Ribosomes
Make new proteins from mRNA through translation (protein synthesis)
- found as free ribosomes in cytoplasm and attached to rough ER
Golgi body
Modifies, packages and directs newly made proteins to where they are needed
Cytoplasm
Site of chemical reactions
- viscous aqueous fluid containing water, proteins and other inorganic molecules and organelles
Mitochondria
Supply chemical energy to the rest of the cell
- they are surrounded by a double membrane
Microfilaments
Made from repeating actin subunits
- responsible for cell movement and changes in shape, making muscle contractions possible
- thinnest component of the cytoskeleton
Vacuole
Internal, surrounded by a membrane, which cells use for storing food and waste
Microtubules
Small, tubular assemblies of protein
- Help maintain cell’s internal structure and move organelles and cytoplasm using molecular motors
- part of cytoskeleton
Centrioles
A pair of organelles that organise microtubules into spindles on which chromosomes are separated when cells divide
Lysosomes
Membrane bound organelles that digest other organelles (e.g. Bacteria)
- contain hydrolysis enzymes (lysozymes)
Light microscope
- illuminates the specimen with light
- beam is focused using the eyepiece and objective lense
- specimen can be live
- section view of specimen
- relatively cheap
- coloured dyes required
Transmission electron microscope (TEM)
- uses electron beam
- max magnification: x1,000,000
- max resolution: 0.1nm
- specimen must be dead
- expensive
- heavy metal stains required
- 2D
Scanning electron microscope (SEM)
- uses electron gun and electromagnetic lenses
- max magnification: x500,000
- max resolution: 1nm
- 3D
Prokaryotes
Capsule- slippery layer outside cell wall of some bacteria
• protects the cell and prevents desiccation
Cell wall- made of peptidoglycan
• protects and supports each cell
Ribosomes 70s- protein synthesis occurs here
Nucleoid- irregularly shaped region that holds nuclear material without a nuclear membrane
• genetic information found
Plasmid- small loops of DNA
• carry genes beneficial for the survival of the organism
Protein trafficking
- Transcription- mRNA is made in the nucleus. DNA can’t fit through the nuclear pore so mRNA is made (smaller, length of one gene)
- mRNA leaves the nucleus through a nuclear pore
- Translation- mRNA is made into a polypeptide on the ribosomes on the rough ER then enters the RER
- Polypeptide moves through the RER. As it moves, it if folded and gains it’s 3D shape
- The end of the RER buds off with the folded polypeptide inside (becomes vesicle)
- The vesicle travels to the Golgi body and the membrane fuses with it. The folded polypeptide is now inside the Golgi body
- Modification- the polypeptide is modified as it moves through the Golgi body
8a. If protein is an intracellular protein then it buds off the Golgi and remains in the cell e.g. RNA polymerase
8b. If the protein is an extracellular protein then it binds off the Golgi body and leaves the cell in exocytosis
e.g. secretory enzymes like amylase or hormones
