Chapter 2.3 - Eukaryotic cell structure Flashcards
What are eukaryotes?
Multicellular eukaryotic(cells with a nucleus and other membrane-bound organelles) organisms
What is the ultrastructure of a cell?
The components of a cell that can be seen using an electron microscope
What is an organelle?
Membrane-bound compartments with varying functions inside eukaryotic cells
What are the main organelles of a eukaryotic cell?
- Cytoplasm
- Centrioles
- Cilia
- Endoplasmic reticulum : smooth and rough
- Golgi apparatus
- Lysosomes
- Mitochondria
- Nucleus
- Nucleolus
- Plasma membrane
- Ribosomes
- Vesicles
What is the structure and function of the nucleus?
- Contains chromosomes(linear DNA strands and associated to histone proteins) and one or more nucleoli(skeletal muscles)
- Surrounded by a double membrane structure, nuclear envelope, with a number of pores to control exchange between the nucleus and cytoplasm
- It stores DNA and coordinates the cell’s activities, which include growth, intermediary metabolism(synthesises various enzymes), protein synthesis and reproduction
What is the structure and function of the nucleolus?
- It is composed of proteins and RNA
- It is an area within the nucleus and is responsible for the synthesis of ribosomes
What is the structure and function of mitochondria?
- 1 to 10 μm long rod-shaped organelle
- Has a smooth outer membrane and inner membrane highly folded into cristae
- The matrix(fluid region inside inner membrane) contains enzymes for respiration and has their own DNA - mtDNA
- Carries out aerobic respiration in the matrix and on the cristae, producing ATP
What is the structure and function of vesicles?
- Membranous fluid-filled sacs that transport molecules to other parts of the cell or are secreted out of the cell
What is the structure and function of lysosomes?
- They are forms of vesicles that contain hydrolytic enzymes which are used for the intracellular digestion of macromolecules
- They also break down pathogens ingested by phagocytosis(lysozyme) and play a role in programmed cell death, apoptosis(if the cell gets damaged, then one of the lysosomes bursts and releases its hydrolytic enzymes which digests the cell)
What is the function of cytoplasm?
- Suspends the internal components of cells in place and protects them from damage by cushioning and guarding genetic material and organelles against harm caused by movement and collision with other cells
What is the cytoskeleton?
It is a network of fibres necessary for the shape and stability of a cell
What are the three main functions of the cytoskeleton?
- To provide mechanical strength to the cell, reducing squashing
- Aiding transport within cells including whole organisms by forming tracks along which organelles can move
- Enabling cell movement
What are the three main components of the cytoskeleton?
- Microfilaments
- Microtubules
- Intermediate fibres
What is the structure and function of microfilaments?
- Contractile fibres formed from the protein actin, 7nm in diameter
- Responsible for: whole cell movement(phagocytosis) and cell contraction during cytokinesis
What is the structure and function of microtubules?
- 18-30nm in diameter
- Made of globular tubulin proteins which polymerise to form tubes which form a scaffold-like structure, determining the shape of a cell
- Acts as tracks for organelles to move along(e.g. vesicles)
- Form spindle fibres which separate chromosomes during cell division
What is the structure and function of intermediate filaments?
- Made of a variety of proteins, 10nm in diameter
- Gives mechanical strength to cells and help maintain their integrity
- Anchors nucleus in cytoplasm
- Can attach cells to basement membranes
What is the function of centrioles?
- It is a barrel-shaped organelle that forms spindle fibres involved in mitosis and meiosis
- Organizes the microtubules within the cell
- Only visible using TEM/SEM
What is the term used for extracellular projections?
Undulipodia
What is the structure and function of cilia?
- Two central microtubules surrounded by nine pairs of microtubules ( 9+2 arrangement)
- They are short hair-like structures involved in moving substances past the cell, mobile cilia beat in a rhythmic manner, creating a current which causes fluids or objects adjacent to the cell to move
-> Have an important function in sensory organs
What is the structure and function of flagella?
- Whip-like extensions used to enable cell motility
- In some cells they are used as a sensory organelle, detecting chemical changes in the cell’s environment, such as pH and temperature
What is the endoplasmic reticulum?
It is a network of membranes enclosing flattened sacs, cisternae, and is connected to the outer membrane of the nucleus
- Smooth and rough
What is the function of the smooth endoplasmic reticulum?
- Synthesises lipids, steroids, and some hormones like testosterone and oestrogen
- Synthesises, stores, and transports carbohydrates
What is the structure and function of the rough endoplasmic reticulum?
- Has ribosomes bound to the surface
- Responsible for the synthesis and transport of proteins
What is the structure and function of ribosomes?
- They are non-membrane bound organelles free-floating in the cytoplasm or attached to the RER
- They are made up of rRNA and proteins and are composed of a smaller and larger sub unit
- 80S
- Site of protein synthesis
What is the structure and function of the Golgi apparatus?
- Free-floating network of flattened membrane sacs, cisternae
- Collects, processes, and sorts molecules that are then transported in Golgi vesicles to other parts of the cell or are secreted out
- Modify proteins
- Make lysosomes
