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.
What is the function of the golgi apparatus?
- add carbohydrate to proteins to make glycoproteins
- produce secretory enzymes
- secrete carbs
- transport, modify, store lipids
- form lysosomes
How are lysosomes formed?
when the vesicles of the golgi apparatus contain enzymes such as proteases and lipases
- they are particularly abundant in secretory cells
What is the role of lysosomes?
- hydrolyse material ingested by phagocytic cells
- release enzymes to the outside of the cell in order to destroy material
- digest worn out organelles so that the useful chemicals they are made of can be reused
- completely break down cells after they have died
What are ribosomes?
- cytoplasmic granules found in all cells
- occur in cytoplasm or RER
- a large and small subunit which each contain rRNA and protein
- occur in vast numbers
What are the 2 types of ribosome?
80S- found in eukaryotic cells
70S- found in prokaryotic cells, slightly smaller.
What are the features of a cell wall?
- consist of lots of polysaccharides, EG:cellulose
- thin layer (middle lamellae) which cements adjacent walls together
- microfibrils of cellulose strengthen the cell wall
what are the functions of the cell wall?
- provide mechanical strength to prevent cell bursting under pressure from osmosis
- give mechanical strength to the whole plant
- to allow water to pass along it a contribute to movement of water through the plant
what are algae cell walls made of?
cellulose or glycoprotein
what are fungi cell walls made of?
chitin
Describe the vacuole.
- fluid-filled
- ## bound by a single membrane- tonoplast
What are the functions of a vacuole?
- support herbaceous plants by making cells turgid
- sugars and amino acids in cell sap act as a temporary food store
- pigments colour petals making them attractive to pollinating insects
