Structure and function of organelles Flashcards
Where are eukaryotic cells found?
Plant and animal cells
What are the functions of the nucleus?
- produces mRNA for protein synthesis
- retains genetic information in the form of DNA or chromosomes
What do the nuclear pores do?
They allow the passage of large molecules, such as mRNA, and ribosomes.
What does the nucleolus do?
It is the site for the formation of rRNA to make ribosomes.
What is the function of the mitochondria?
Site of ATP synthesis
What does the small circle of DNA do?
It enables mitochondria to make some of their own proteins and self-replicate
What is the function of the Cristae?
They provide a large surface area for the attatchment of enzymes involved in respiration
What is the relevance of the shape of a mitochondria?
Being cylindrical gives a larger surface area than a sphere of the same volume
This also reduces the distance of diffusion between the edge and the centre (respiration is more efficient)
What is the function of the stroma?
It is fluid filled and contains some of the products of photosynthesis, including lipid droplets and starch grains.
What are the functions of the 70s ribosomes and circular DNA?
They enable them to make some of their own proteins and self-replicate
How is stacking thylakoids into a Granum good?
Produces a large surface area, efficient for trapping light energy
What are the two types of ER?
Smooth ER and Rough ER
What is the structure of the ER?
1) Flattened sacs
2) Fluid- filled spaces between them, called cisternae.
3) Continuous with nuclear membrane
What is the function of the rough ER?
Has ribosomes on the outer surface - synthesis and transport of proteins.
Found in cells making amylase in salivary glands
What is the function of the smooth ER?
It is associates with the synthesis and transport of lipids.
Found in cells with large quantities of fat, carbs and proteins e.g liver
What is the structure of the Golgi body?
Vesicles containing polypeptides pinch off from the RER and fuse with the stack of flattened stacks which constitute the Golgi body.
What are the functions of the Golgi body?
*Packaging proteins
*Secreting carbohydrates
*Transporting and storing lipids
*Forming lysosomes containing digestive enzymes for exocytosis
*Building more complex molecules
What is the structure of a lysosomes?
Temporary vacuoles surrounded by a single membrane.
What is the function of the lysosomes?
They isolate potentially harmful digestive enzymes from the remainder of the cell - release these when the cell needs to recycle worn out organelles
Their enzymes can digest bacteria engulfed by phagocytosis
What is the structure of a vacuole?
A fluid- filled sac bounded by a single membrane, the tonoplast.
What is the function of the vacuole?
- Support soft plant tissues
- Contains cell sap which stores chemicals such as glucose, amino acids and minerals
How is the cell wall involved in transport?
Gaps between cellulose fibres make the wall permeable
Space outside the cell where solution moves is the apoplast
The apoplast pathway is the main way that water crosses plant roots
How is the cell wall involved in mechanical strength?
The structure of cellulose microfibrils and their arrangement makes the cell wall strong
When the vacuole is full of solution the contents of the cell is pushed against the cell wall - turgid
How is the cell wall involved in communication between cells?
Cell walls have pits where plasmodemata (strands of cytoplasm) pass, these run between cells.
The network of cytoplasm is called the symplast - the symplast pathway is important in water transport
What structures are found in an animal cell?
Cell Wall, Chloroplasts, Plasmodemata, Vacuole, Centrioles, Energy store
Animal Cell:
Cell Wall - Absent
Chloroplasts - Absent
Plasmodemata - Absent
Vacuole - Present (small, temporary)
Centrioles - Present
Energy store - Glycogen
What structures are found in a plant cell?
Cell Wall, Chloroplasts, Plasmodemata, Vacuole, Centrioles, Energy store
Cell Wall - Present
Chloroplasts - Present in cells above ground
Plasmodemata - Present
Vacuole - Present (large, permenant, central)
Centrioles - Absent
Energy Store - Starch
What is the function of a chloroplast?
To trap light used for photosynthesis
What is the function of a ribosome?
They are important in protein synthesis and the site of translation where mRNA is used to assemble a polypeptide chain.
What is the function of chromatin?
During cell division it condensed into chromosomes
