2.4 Eukaryotic cells Flashcards
What are the 2 types of organisms?
Prokaryotes and eukaryotes
Define metabolism
The sum of all chemical reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material
Where do reactions take place within a cell?
The cytoplasm
What separates the cytoplasm of eukaryotic cells from the cell’s external environment?
Cell-surface membrane / plasma membrane
Define organelle.
What is their function?
Compartments with varying functions inside eukaryotic cells
Provide specific environments and therefore specific conditions for different cellular reactions.
What is the nucleus?
What is the function of the nucleus and how does it carry this out?
Large organelle surrounded by a nuclear envelope.
Contains DNA molecules
Controls the cell’s activity by controlling the transcription of DNA
What is the function of DNA?
Directs the synthesis of proteins required for the cell (but remember protein synthesis occurs in ribosomes)
What does the nuclear envelope contain?
What is the function of this?
Nuclear pores - allow substances to move into and out of the nucleus
How is DNA inside the nucleus transferred outside of the nucleus?
DNA is transcribed into smaller RNA molecules, because DNA itself is too big to leave the nucleus, and the RNA molecules are then exported via nuclear pores
How is chromatin formed?
When DNA associates with histones
Define histones
Proteins that form a complex with DNA called chromatin
How are chromosomes formed?
When chromatin coils and condenses
What is the nucleolus?
What is the function of the nucleolus?
What is the nucleolus composed of?
- An area within the nucleus
- Produce ribosomes
- RNA and proteins
Describe the structure of mitochondria
• Double membrane:
- Inner membrane highly folded, forms cristae
- Membrane forming the cristae contains enzymes used in aerobic respiration
• Fluid interior known as matrix
• Contain DNA - mtDNA (mitochondrial DNA) + ribosomes
What is the function of mitochondria?
Site of aerobic respiration, where ATP is produced
• Can produce their own enzymes and reproduce themselves
Where are mitochondria found in high numbers?
In active cells
What are cristae?
What is the function of cristae?
Fold of inner mitochondrial membranes
Increase SA where reactions of the electron transfer chain can occur
What are vesicles?
Small fluid-filled sacs in the cytoplasm surrounded by a membrane
What are vesicles used for?
Transporting materials inside the cell
Define lysosomes
Specialised vesicles containing hydrolytic enzymes used to digest invading cells or for the breakdown of waste material inside cells
What is the function of lysosomes?
- Break down waste material inside the cell
- Break down invading pathogens ingested by phagocytes
- Programmed cell death / apoptosis
What is the function of the membrane surrounding a lysosome?
To keep the digestive enzymes in the lysosome separate from the cytoplasm
What is the cytoskeleton?
A network of fibres in the cytoplasm of eukaryotic cells
What are the 4 functions of the cytoskeleton?
- Maintains the shape and stability of the cell
- Holds organelles in place
- Controls cell movement
- Controls movement of organelles within the cell
What are the three components of the cytoskeleton?
- Microfilaments
- Microtubules
- Intermediate fibres
What is the function of microfilaments?
- Control cell movement
* Control cell contraction during cytokinesis (process when a single eukaryotic cell divides into two daughter cells)
What is the function of microtubules?
- Determine cell shape
* Control movement of organelles + vesicles around the cell
What is the function of intermediate fibres?
- Provide the cell with mechanical strength
* Help maintain the cell’s integrity
What are centrioles?
In what organisms are centrioles found?
- A component of the cytoskeleton - Small, hollow cylinders made up of microtubules
- Eukarotic cells except flowering plants and most fungi
How is the centrosome formed?
When 2 centrioles associate
What is the function of the centriole?
Involved in the organisation of spindle fibres during cell division
What are flagella?
What is the structure of flagella?
What is the function of flagella?
- Protrusions that extend from some Euk cells. They stick out from the cell surface and are surrounded by the plasma membrane. Longer than cilia, whip-like
- Contains 2 central microtubules surrounded by a ring of 9 pairs of microtubules. ‘9+2 arrangement’
- Enable cell motility
- Can act as sensory organelles detecting chemical changes in the cell’s environment
- Enable cell motility
What are cilia?
What is the structure of cilia?
What are the 2 types of cilia and what is their function?
- Protrusions that extend from the plasma membrane of some Euk cells. Shorter than flagella, but found in greater numbers. Hair-like
- Contains 2 central microtubules surrounded by a ring of 9 pairs of microtubules. ‘9+2 arrangement’
- Mobile - Beat in a rhythmic manner which creates a current and causes substances next to the cell to move
Stationary - Role in sensory organs
What is the endoplasmic reticulum?
A network of membranes enclosing flattened sacs called cisternae.
Attached to the outer membrane of the nucleus.
What is the difference in structure between the Smooth ER and the Rough ER?
RER - ribosomes bound to surface
SER - no ribosomes
What is the function of the smooth endoplasmic reticulum?
Synthesises + stores lipids and carbohydrates
What is the function of the rough endoplasmic reticulum?
Synthesises + transports proteins
Where are ribosomes found?
What is the structure of ribosomes?
What is the function of ribosomes?
- Free floating in the cytoplasm or attached to the RER
- No membrane, made up of RNA
- Site of protein synthesis
What is the golgi apparatus?
What is the function of the golgi apparatus?
A group of fluid-filled, membrane bound flattened sacs. Vesicles are often found next to the sacs. No ribosomes.
Modifies and packages proteins into vesicles;
Secretory vesicles if the protein leaves the cell,
Lysosomes if the protein stays in the cell
What are the 5 steps of protein production?
- Proteins are synthesised in ribosomes bound to the ER
- Synthesised proteins pass into the cisternae of the ER and are packaged into transport vesicles
- Transport vesicles move towards Golgi apparatus via cytoskeleton
- Transport vesicles fuse with the cis face of the Golgi app. and release the proteins.
The proteins are structurally modified before leaving the Golgi app. in vesicles through the trans face - If the proteins should leave the cell, they’re carried in secretory vesicles. The vesicles move to + fuse with the plasma membrane and release the proteins via exocytosis
