2.1.1 H& k EUKARYOTIC CELL STRUCTURE Flashcards
Nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction
- DNA is contained within a double membrane called a nuclear envelope to protect it from damage in the cytoplasm
- Nuclear pores allow molecules to move into and out of the nucleus.
- DNA associates with proteins called histones to form a complex called chromatin (coils and condenses to form chromosomes)
Nucleolus
Found inside the nucleus and produces ribosomes
- composed of proteins and RNA. RNA is used to produce ribosomal RNA (rRMA) which is then combined with proteins to form ribosomes necessary for protein synthesis
Mitochondria
Powerhouse of the cell, organelle that is the site of ATP (energy) production
- double membrane with a highly folded structure called cristae and a fluid interior called the matrix
- mitochondrial (mt)DNA in small amounts
Ribosomes
complexes that make proteins; free in cytosol or bound to rough ER or nuclear envelope
- 80S eukaryotic cells
- 70S prokaryotic cells
Vesicles
membranous sacs, store or transport substances
- transport materials inside the cell
Lysosomes
An organelle containing digestive enzymes
- specialised forms of vesicles that contain hydrolytic enzymes
- they break down waste material in cells in old organelles and play important role in the immune system
- play an important role in programmed cell death (apoptosis)
Cytoskeleton
A network of fibers that holds the cell together, helps the cell to keep its shape, and aids in movement
3 components: microfilaments, microtubules, intermediate fibres
Microfilaments
Long, thin fibres that function in the movement and support of the cell
- responsible for cell movement & cell contraction during cytokinesis
-made of actin
Microtubules
globular tubilun proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of a cell
- acts as tracks for the movement of organelles
- spindle fibres, which have a role in the physical segregation of chromosomes in cell division are composed of microtubules
Intermediate fibres
Give mechanical strength to cells and help maintain their integrity
Centrioles
a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibres in cell division.
- composed of microtubules where two associated centrioles form a centrosome
- centrosome is involved in the assembly and organisation of the spindle fibres
Flagella
extension that protrude from certain cell types
- enables cell mobility and can be used as a sensory organelle detecting chemical changes
Cilia
Hairlike projections that extend from the plasma membrane and are used for locomotion
- stationary: present on surface of cells and have important sensory functions
- mobile: beat in a rhythmic manner creating a current and helps move substances away
Cell membrane (plasma membrane)
phospholipid bilayer that surrounds all cells and regulates what enters and leaves the cell
- proteins also totally penetrate and appear on the inner and outer surfaces
- main function: act as a boundary between the cell and its environment (controls entry and exit= selectively permeable)
Endoplasmic Reticulum
network of membranes enclosing flattened sacs called cisternae
- Smooth/ Rough endoplasmic reticulum
Smooth Endoplasmic Reticulum
An endomembrane system where lipids are synthesised, calcium levels are regulated, and toxic substances are broken down.
- contain enzymes important in the synthesis of steroid hormones and detoxifying drugs
- stores calcium ions important in muscle contractions and secretion of vesicles
Rough Endoplasmic Reticulum
An endomembrane system covered with ribosomes where many proteins for transport are assembled.
-Transport vesicles bud from the ER keeping secretory proteins separate when in transit from one part o the cell to another
Golgi apparatus
A system of membranes that modifies and packages proteins for export by the cell
- products of endoplasmic reticulum are modified and stored
-cis face receiving department and trans face shipping department
protein production
- Nucleus- Transcription- DNA is converted to mRNA and is sent out of the nucleus into cytoplasm via the nuclear pores
- Ribosomes on RER- mRNA attaches to the ribosomes and proteins are made (translation)
- RER- proteins are folded and processed in the RER. then they are transported from the RER to the cis face of the Golgi apparatus in vesicles
- Golgi apparatus- proteins may undergo further processing (e.g sugar chains are trimmed or more are added)
- Proteins leave the Golgi apparatus from the transface in the secretory vesicles
- Secretory take the finished proteins to the plasma membrane where they undergo exocytosis and leave the cell
