2.4 Eukaryotic Cell Structure Flashcards
What are cells?
What are the two main typed of cells?
- cells are the basic unit of all living things
- 2 types: eukaryotic cells (all plant and animal cells), prokaryotic cellls (usually unicellular cells e.g. bacteria)
Define organelles
Different membrane bound compartments within the cell that form through compartmentalisation. They provide distinct environments and conditions for different cellular reactions.
Describe the function and contents of the NUCLEUS
Description: the nucleus is a large organelle that contains genetic information in the form of DNA molecules. It is surrounded by a nuclear envelope (double membrane) to protect DNA from damage. The nuclear envelope contains nuclear pores that RNA molecules move out of the nucleus through.
DNA associates with proteins called his tones to form a complex called chromatin (could and condenses to form chromosomes)
Functions: Nucleus controls cell’s activities and directs synthesis of all proteins required by the cell and therefore controls the metabolic activities of the cell (as many of these require proteins like enzymes to work)
Description and function of nucleolus
- The nucleolus is an area within the nucleus and is responsible for producing ribosomes.
- composed of proteins and RNA. RNA is used to produced rRNA which is then combined with proteins to form ribosomes necessary for protein synthesis
Description and function of mitochondria
- Mitochondria have a double membrane. The inner meme range is highly folded to form structures called cristae and the fluid interior is called the matrix (inside the cristae). The matrix contains enzyme s involved in aerobic respiration
- mitochondria contain a small amount of DNA called mitochondrial (mt)DNA - mitochondria produce their own enzymes and reproduce themselves
Function:
- the site of aerobic respiration, where ATP is produced
- mitochondria are found in large numbers in cells that are very active and require a lot of energy
Description and function of vesicles
- vesicles are small fluid-filled sacs in the cytoplasm, surrounded by a single membrane
Function:
Transport substances in and out of the cell (via the plasm membrane) and between organelles
Some are formed by the Golgi apparatus or the ER while others are formed at the cell surfaces
Function and description of lysosomes
- lysosomes are specialised forms of vesicles that contain hydrolytic/ digestive enzymes that that are responsible for breaking down waste material in cells (e.g. old organelles)
- they play an important role in the immune system as they are responsible for breaking down pathogens ingested by phagocytic cells
- play an important role in programmed cell death (apoptosis)
Description and function of the three components of cytoskeleton
- the cytoskeleton is present throughout the cytoplasm of all eukaryotic cells. It is a network of fibres necessary for the shape and stability of a cell
- organelles are held in place by the cytoskeleton and it controls cell movement and the movement of organelles wishing cells
3 components of the cytoskeleton:
- Microfilaments: contractile fibres made from the protein actin. Responsible for cell movement and cell contraction during cytokinesis
- Microtubules: made from polymerised globular tubulin proteins. Determines shape of a cell. Act as tracks for movement of organelles like vesicles around the cell
- intermediate fibres: these fibres give mechanical strength to cell to help maintain their integrity
Description and function of centrioles
- they are composed off microtubules
- component of the cytoskeleton
- two centrioles form the centrosomes which is involved in the assemble of the spindle fibres during cell division.
Description and function of flagellum
- consist of two microtubules in the centres and nine pairs around thee edge
- microtubules contract to make the flagellum move
In come cells they are used as a sensory organelle detecting chemical changes in the cells environment
Function and description of cilia
- small, hair like structures found on the surface membrane of some cells
- can be either mobile or stationary
Mobile cilia are present on sensory cells and stationary cilia beat in a rhythmic manner causing fluids to move - they have an outer membrane and a ring of nine pairs Of microtubules inside with a pair of microtubules in the middle
Description and function of the endoplasmic reticulum
The two types
The ER is a network of membranes enclosing flattened sacs called cisternae. It is connected to the outer membrane of the nucleus
Two types:
- smooth ER is responsible for lipid and carbohydrate synthesis and storage
- the rough ER has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins
Description and function of ribosomes
- either free-floating in the cytoplasm or attached to ER forming the rough ER
- not surrounded by a membrane
- they are constructed of RNA molecules made in the nucleolus
- ribosomes are the site of protein synthesis
Description and function of the Golgi apparatus
- formed of cisternae and does not contain ribosomes
- it has a role in modifying proteins and ‘packaging’ them into vesicles
These may be secretory vesicles if the proteins will leave the cell or lysosomes which stay in the cell
