3.4 Eukaryotic cell structure Flashcards
what are eukaryotic cells?
cells which contain a distinct nucleus and membrane-bound organelles.
What is the role of the nucleus?
- control centre of the cell through production of mRNA and tRNA, and therefore protein synthesis.
- Retains genetic material in form of DNA and chromosomes.
- Makes rRNA and ribosomes
What are the main parts of the nucleus?
- nuclear envelope
- nuclear pores
- nucleoplasm
- chromosomes
- nucleolus
Describe the nuclear envelope.
A double membrane that surrounds the nucleus.
- outer membrane is continuous with the endoplasmic reticulum and has ribosomes on the surface.
- controls the entry and exit of materials and contains their reaction.
Describe the role of the nuclear pores.
Allow the passage of large molecules, such as mRNA out of the nucleus.
Describe the nucleoplasm
granular jelly making up most of the nucleus.
Describe the chromosomes.
protein-bound, linear DNA
Describe the nucleolus
Small spherical region in the nucleoplasm. makes rRNA and assembles ribosomes.
What is the role of the mitochondria?
- site of the aerobic stage of respiration.
- Responsible for the production of ATP from respiratory substrates
Very common in metabolically active cells such as epithelial cells from the intestines which require energy for active transport.
What are the main feature of the mitochondria?
- a double membrane
- cristae
- matrix
What is the role of the double membrane in a mitochondrion?
- controls entry and exit of material
- inner membrane is folded into extensions (cristae)
What is the role of the cristae in a mitochondrion?
Extensions of the inner membrane, provide a large SA for the attachment of enzymes and proteins involved in respiration.
What us the role of the matrix in the mitochondria?
- contains proteins, lipids, ribosomes and DNA which allows it to make its own proteins
- enzymes are also found there.
What is the role of chloroplasts?
the harvest sunlight to carry out photosynthesis.
What are the main parts of a chloroplast?
- the chloroplast envelope
- the grana
- the tylakoids
- the stroma
describe the chloroplast envelope.
- double plasma membrane surrounding the organelle
- highly selective of what enters and exits
Describe the grana and the thylakoids.
- the grana are stacks of discs (thylakoids)
- the grana is where the first stage of photosynthesis happens
- the thylakoids contain chlorophyll
Describe the stroma.
- fluid-filled matrix where the synthesis of sugars takes place.
How are chloroplasts adapted to their function/
- the granal membranes provide a large SA for the attachment of chlorophyll, electron carriers and enzymes.
- fluid in the stroma has all the enzymes needed to make up sugars in part 2
- chloroplasts contain DNA and ribosomes so they can manufacture proteins needed for photosynthesis.
What is the endoplasmic reticulum?
- a 3D system of sheet-like membranes which spread through the cytoplasm and is continuous with the outer nuclear membrane.
- membranes enclose a network of flattened sacks called cisternae
- cells which manufacture and store lots of proteins, carbohydrates and lipids have an extensive ER, EG: epithelium of intestines.
Describe the rough endoplasmic reticulum.
- has ribosomes on its surface
- provides large SA for synthesis of proteins and glycoproteins
- provides a pathway for transport of materials, especially proteins
Describe the smooth endoplasmic reticulum.
- no ribosomes on surface
- synthesises and transports lipids
- synthesises, stores and transports carbohydrates
describe the structure of the golgi apparatus.
- similar to the SER, but more compact
- consists of a stack of membranes that make up flattened sacs (cisternae) with small, rounded hollow structures (vesicles)
how is the golgi apparatus related to the ER
- proteins and lipids produced in the ER are passed through the GA in sequence.
- Golgi modifies proteins and adds non-protein components
- it labels them so they can be sorted.
