2.4 Eukaryotic cell structure Flashcards
What is the cytoskeleton?
Network of fibres throughout the cytoplasm of all eukaryotic cells
Necessary for shape and stability, controls cell movement and organelle movement within the cell
Made up of microfilaments, microtubules and intermediate fibres
What are microfilaments?
8nm
Contractile fibres from protein actin, strands in a double helix
Responsible for cell movement by muscle contraction or crawling
Responsible for cell contraction in cytokinesis (cytoplasm division)
Maintain cell shape by resisting tension
What are microtubules?
25nm
Globular tubulin proteins which polymerise to form hollow tubes which determine the shape of the cell
Act as a track for organelle movement
Maintain cell shape by resisting compression
Move chromosomes during cell division
Assist formation of cell plate during plant cell division
What are intermediate fibres?
10nm
Lamin/vimentin/teratin fibres wound into thicker cables
Gives mechanical strength to cells and maintains shape
Anchors nucleus and some other organelles
Nucleus
Contains coded genetic information in the form of DNA molecules
DNA - directs the synthesis of all proteins required by the cell (means the nucleus controls metabolic activity of the cell because lots of these proteins are needed for metabolism), associates itself with histone proteins to form chromatin, which coils and condenses to form chromosomes
What are vesicles?
Sacs filled with fluid with a single membrane
Used to transport materials inside the cell
What are lysosomes?
Specialised vesicles that contain hydrolytic enzymes
Break down waste materials in cells including old organelles and pathogens that have been ingested by phagocytes
Important role in programmed cell death or apoptosis
What are mitochondria?
The site of the final stage of cellular respiration where the energy stored in the bonds of complex organic molecules is made available to the cell to use by the production of ATP molecules
Has a double membrane - inner membrane called cristae which is highly folded and fluid interior called matrix
Can produce their own enzymes and replicate themselves
What is the nucleolus?
Area within the nucleus responsible for producing ribosomes
Composed of proteins and RNA - used to produce ribosomal RNA and combined with proteins form ribosomes
What are centrioles?
Component in cytoskeleton made of microtubules
2 associated centioles form the centrosome which is involved in assembly and organisation of spindle fibres during cell division
What are flagellum and cilia?
Flagella
- enable cell motility
- in some cells they are used as sensory organelles to detect chemical changes in the cell’s environment
Cilia
- mobile cilia - beat in a rhythmic manner, create currents causing fluids or objects to move, present in trachea to move mucus away from lungs and in fallopian tubes to move egg cells from ovary to uterus
- stationary - sensory
- each cilium contains two central microtubules surrounded by nine pairs of microtubules, pairs of parallel microtubules slide over each other causing the cilia to move in a beating motion
What is the endoplasmic reticulum?
Network of membranes enclosing flattened sacs called cisternae
Connected to outer membrane of nucleus
Rough ER
- ribosomes bound to surface - responsible for protein synthesis and storage
Smooth ER
- responsible for lipid and carbohydrate synthesis and storage
What are ribosomes?
Site of protein synthesis
Constructed of RNA molecules made in the nucleolus
Not surrounded by a membrane
Free floating in cytoplasm or attached to RER
What is the golgi apparatus/body?
Compact structure formed of cisternae
Has a role in modifying proteins and packaging them into vesicles
What is the plasma membrane?
Based on a frame work of fat-based molecules called phospholipids which physically prevent hydrophobic substances entering or exiting the cell
Studded with proteins: gatekeepers, markers, fasteners, communicators
