Prokaryotes and Eukaryotes Flashcards
Describe eukaryotic cells
- has a true nucleus
- multi-cellular organisms
- membrane-bound organelles
- cells are usually larger
Describe prokaryotic cells
- do not contain a nucleus
- no membrane-bound organelles
- circular DNA and plasmids
- unicellular (e.g. bacteria)
Describe the differences between prokaryotic and eukaryotic DNA
Eukaryotic: • very long • linear • associated eith histones • no introns • contain DNA in chloroplasts/mitochondria which is single-stranded and much shorter
Prokaryotic: • short • circular DNA and plasmids • not associated with protein molecules • contain introns
Why do mitochondria and chloroplasts need their own DNA that resembles that of prokaryotes?
They need a constant supply of proteins
Describe the similarities between eukaryotics and prokaryotes
- both nucleotides joined by the phosphodiester bonds
* nucleotide structures are identical
Describe compartmentalisation
- each cell has organelles which all have different specialised functions
- important for different reactions and processes to take place
- divides long tasks into smaller ones to be completed in sections
- AKA: ‘division of labour’
List the organelles bound by a single membrane
1) smooth endoplasmic reticulum
2) rough endoplasmic reticulum
3) Golgi apparatus
4) vesicles
5) vacuole
6) lysosomes
List the organelles bound by an envelope
- nucleus
- mitochondria
- chloroplast
What is an envelope
A double membrane
List the non-membrane bound organelles:
- ribosomes (70s, 80s)
- centrioles
- microtubules
- microfilaments
- cilia and flagella
Describe the nucleus:
- largest organelle
- enclosed in a nuclear envelope perforated by nuclear pores
- contains chromatin
- contains one or more nucleoli
- continuous with endoplasmic reticulum
- usually only one, but there can be multiple in very large cells (e.g. striated); multinucleated cells are called coenocytes
Describe chromatin
- DNA wound around fibrous histone proteins
* coils and condenses to form chromosomes (which control protein synthesis)
Describe nucleoli
- darkly stained
* where ribosome subunits, ribosomal RNA and tRNA are manufactured
Define DNA
inherited material which controls the various activities within the cell
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What is the function of the nuclear pores?
Control the exchange of materials between the nucleus and the cytoplasm
Describe euchromatin
- stains lightly
* thought to contain active DNA
Describe heterochromatin
- stains deeply
* thought to contain inactive DNA
Describe the smooth endoplasmic reticulum
- made up of cisternae forming tubes and sheets
- essential lipids, steroids, carbohydrates and other non-protein products are synthesised and secreted here
- SER of liver cells contain enzymes which down many chemicals
What are cisternae?
Flattened membrane bound sacks filled with fluid
Describe the rough endoplasmic reticulum
- made up of cisternae
- membrane on cytoplasmic side is lined with ribosomes which attach to the surface and are the site of protein synthesis and manufacture extracellular enzymes; NOTE: not all ribsomes are here- some are not membrane-bound and float in the cytoplasm, manufacturing intraceullar enzymes as there is no way of performing exocytosis to remove them
- forms a system of channels for transporting materials through the cytoplasm
- the intracellular membrane system aids cell compartmentalisation; stores and prepares proteins for secretion and packages the RER vesicles synthesised on the ribosomes with some of its own membrane, then transports them to the Golgi apparatus
Describe the Golgi apparatus
- made up of cisternae
- new membrane is continually added to one end and buds off as vesicles at the other end
- modified RER vesicles and other cell products delivered to it, often adding carbohydrates to form glycoproteins
- prepares modified RER vesicles for secretion by enclosing them in vesicles
- involved in formation of lysosomes
Describe the differences of the Golgi apparatus between animal and plant cells
animal -> forms an extensive network. Involved in lipid modification in ileum cells
plant -> better defined, called dicytosome. Synthesises polysaccharides and packages them in vesicles which migrate to the cell membrane for eventual incorporation into the cell wall
Describe vesicles
- carry substances around cells
- carries synthetic products of cells or products of degradation by lysosomes
- abundant in cells with high synthetic activity
Describe secretory vesicles
- undergo exocytosis
- e.g. proteins packaged at the Golgi apparatus
- e.g. cells of the Islets of Langerhans
Describe endocytic vesicles
May contain molecules to large to cross the membrane by active transport or diffusion
Describe the peroxisome
- one of the groups of vesicles known as microbodies
- each of them contains oxidative enzymes (e.g. catalase)
- particularly important in delaying cell ageing
Describe the vacuole
- a sac bounded by the tonoplast
- contains cell sap, water and waste products, enzymes (involved in recycling on cell components [e.g. chloroplasts])
- changes in volume affect the turgidity of the cell; maintains turgour pressure
What is the tonoplast
The single membrane surrounding the vacuole
What is cell sap
A solution of pigments, organic acids, salts, sugars and other solutes