2.4- Eukaryotic Cell Structure Flashcards
nucleus and its function?
- contains coded genetic information in the form of DNA molecules.
- DNA directs the synthesis of all proteins required by the cell.
- DNA associates with proteins called histones to form chromatin which then coils and condenses to form chromosomes.
- Also controls the metabolic activities of the cell.
nucleolus and its function?
- It is an area within the nucleus.
- responsible for producing ribosomes.
- composed of proteins and RNA
- RNA is used to produce ribosomal RNA which is then combined with proteins to form the ribosomes necessary for protein synthesis.
What is the nuclear envelope?
DNA is contained within a double membrane called a nuclear envelope to protect it.
- contains nuclear pores that allow molecules to move into and out of the nucleus.
- DNA itself is too large to leave the nucleus to the site of protein synthesis so it is transcribed into smaller RNA molecules.
mitochondria and its function?
- mitochondria have a double membrane. the inner membrane is highly folded to form structures called cristae. This inner membrane contains enzymes used in aerobic respiration.
- the fluid interior is called matrix.
- they are the site of ATP(energy currency) production during aerobic respiration.
- they are self-replicating, so they can reproduce themselves if the cell requires more energy.
- they are abundant in cells where lots of metabolic activity takes place.
Lysosomes and their function?
- Small bags formed from the golgi apparatus. Each is surrounded by a single membrane.
- contain hydrolytic(digestive) enzymes. they are responsible for breaking down waste material in cells, including old organelles.
- important role in the immune system = responsible for breaking down pathogens ingested by phagocytic cells.
- important role in apoptosis(programmed cell death)
endoplasmic reticulum (ER) the 2 types and its function?
- the ER is a network of membranes enclosing flattened fluid-filled sacs called cristernae. it is connected to the outer membrane of the nucleus.
- smooth ER is responsible for lipid and carbohydrate synthesis, and storage.
- rough ER has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins.
Golgi apparatus and its function?
- a compact structure formed of cristernae and does not contain ribosomes.
- Secretory vesicles bring material to and from the organelle.
- it has a role of modifying proteins and packaging them into vesicles
ribosomes and their function?
- can be free floating in the cytoplasm or attached to endoplasmic reticulum (RER).
- not surrounded by a membrane.
- constructed of RNA molecules made in the nucleolus of the cell.
- Ribosomes are the site of protein synthesis.
- mitochondria and chloroplasts contain ribosomes.
centrioles and its function?
- component of the cytoskeleton composed of of two bundles of microtubules at right angles to eachother.
- involved in cell division.
- involved in the positioning of flagella and cilia.
- look like a flower/sun shape.
- two associated centrioles form the centrosome (involved in the assembly and organisation of spindle fibres during cell division)
Vesicles and their function?
Membranous sacs used for storage and transport of materials inside the cell.
Consist of a single membrane with fluid inside.
Cytoskeleton and its function?
- Network of fibres necessary for the shape and stability of a cell.
- Holds organelles in place and controls cell movement and movement of organelles inside a cell.
- Found in cytoplasm or eukaryotic cells.
Has 3 main components:
-microfilaments: contractile fibres formed from actin. Responsible for cell movement and cell contraction during cytokinesis.
- microtubules: globular tubulin proteins polymerise to form tubes that determine the shape of a cell. They act as tracks for the movement of organelles around the cell. They make up the spindle fibres used in cell division.
- intermediate fibres: give mechanical strength to cells and help maintain their integrity.
Flagella and cilia and their function?
Both are extensions that protrude from some cells.
Flagella are longer but cilia are often present in larger numbers.
Flagella enable cells motility, they are sometimes used as a sensory organelle detecting chemical changes in the cell’s environment.
Stationary cilia is important in sensory organs (nose)
Mobile cilia create a current to move fluids and objects (present in the trachea to move mucus away from lungs + in fallopian tube to move egg cells)
Each cilium has a 9+2 formation (two microtubules with 9 pairs of microtubules around it)
Explain the steps of protein production.
- Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum.
- They pass into its cisternae and are packaged into transport vesicles.
- Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton.
- Proteins are further processed and modified at the Golgi apparatus.
- Secretory vesicles carry the proteins to be released from the cell. The vesicles fuse with the cell-surface membrane, releasing their contents by exocytosis.
