The Cell Flashcards
Definition of cell
The cell is the smallest structural and functional unit that can perform life functions. It’s the most basic unit of life.
All living things are composed of one or more cells.
All cells arise from pre existing cells.
List the Eukaryotic cells
- plant cells
- red blood cells
- fibroblasts
- neurons
List the prokaryotic cells
- bacterias
Describe the composition and functions of the Plasma membrane
Composition
- 2 layers of phospholipids
- membrane proteins
- cholesterol
Functions
- outer limit of the cell
- anchor cytoskeleton
- controls what enters and exits
- communication
Explain why the plasma membrane is semi permeable
It is composed of a double layer of phospholipids. This non-polar layer makes the membrane permeable to hydrophobic substances while charged or polar molecules do not pass easily.
However, phospholipids can move to allow small molecules to pass (ex: water, dioxygen, CO2).
What are the different types of membrane proteins ?
- channels or transporters
- receptors
- structural proteins
- enzymes
What is the composition of cytoplasm
- cytosol
- organelles
Define cytosol
Gel-like mixture composed of water, dissolved molecules, soluble proteins and small structures like ribosomes.
Define organelles
Membrane bound structure that have a very specific function like the mitochondria.
What are the components of the nucleus ?
- nuclear membrane : double layer of phospholipids
- nuclear pores : allowing the passage of molecules in and out of the nucleus
- nucleolus : area of the nucleus where ribosomes are assembled
- chromatin : DNA + proteins
What are the functions of the nucleus ?
- store the genetic material under the form of multiple linear chromosomes
- mediate DNA replication during cell division
- controls gene expression
Definition of Ribosome
Small non membrane bound organelle
Each cell has thousands of ribosomes
Two sub units made of ribosomal RNA and proteins
Found within the cytosol or attached to the endoplasmic reticulum
Its function is protein synthesis
Definition of Endoplasmic reticulum
Series of tightly packed membranes that form a network of interconnected compartments within the cell.
Smooth ER lacks ribosomes while Rough ER has ribosomes attached to the cytosolic surface. The internal space is called lumen. RER and SER are interconnected and their lumen are continuous.
What are the functions of the Smooth endoplasmic reticulum ?
- synthesis of lipids (phospholipids and cholesterol)
- carbohydrate metabolism
- storage of calcium ions
- detoxification site (liver cells)
What are the functions of the Rough endoplasmic reticulum ?
- Synthesis of protein destined to the export or to other organelles
- protein folding : protein chaperones assist and facilitate the correct assembling of newly synthesized proteins.
- initial protein modification (addition of sugars)
Définition of Golgi Apparatus
Series of flattened sacks called cisternae having an internal space, the lumen.
The Cis face or entry surface receives vesicles from the endoplasmic reticulum.
The Trans face or exit surface packages molecules and transports them out of the golgi complex.
Definition and function of the lysosome
- contains a variety of digestive enzymes
- pH is 5
Functions :
- Recycling center
- Breaking down macromolecules
- Destroys cells or foreign matter that the cell has ingested by phagocytosis
- Transports un digested material to cell membrane for removal
They act as the digestive system inside a cell. They help to break down old or unneeded pa
Definition and function of peroxisome
Single membrane bounded organelle
Functions :
- metabolism of fatty acids
- reduction of reactive oxygen species (ex: catalase breaks down H2O2 which is toxic)
- implicated into the aerobic respiration
Definition and functions of Mitochondria
Composed of 2 membranes.
The outer membrane is separated by an inter membrane space
The inner membrane has inward protrusions called cristae and contains the matrix.
Functions:
- production of energy under the form of ATP
- essential for the metabolism of glucose and fatty acids
- role in programmed cell death (apoptosis)
Cytoskeleton definition and function
Made out of 3 fibers type :
- actin filament : cellular contraction
- intermediate filament : structural stability
- microtubules : structural stability and movement of materials within the cell
Functions :
- mechanical support, maintain cell’s shape
- anchor organelles
- help move substances and organelles
- involved in cell’s movement
Microfilmants definition and functions
Also called actin filaments.
Flexible and solid fiber about 7nm diameter.
Consists in 2 intertwined polymer chains of actin molecules.
It is a polarized structure where the positive end is fast growing and the negative end is slowly growing.
Functions :
- mechanical support
- shape and movement of the cell
- cell division into 2 daughter cells
- muscle contraction in association with myosin
Explain actin polymerization
Actin polymerization is a dynamic process requiring ATP. Regulation of this process depends on the concentration of G-actin and the interaction with Actin Binding Protein.
- acting bundling protein : cross links actin filaments into parallel arrays
- acting caping protein : blocks further addition of actin molecules by binding to the free end of an actin filament.
Description of microfilment
Thickest filament about 25nm in diameter and several pico in length
Hollow in the center
Composed of dimers of alpha and beta tubulin
Anchored to the Microtubules Organizing Centers via gamma tubulin rings
Polymerization of tubulin dimers requires the presence of GTP and Mg2+
Polarized structure
Microtubules functions
- structural role
- movement of chromosomes during cell division
- movement of organelles or transport of vesicles : Dyneins move toward the minus end, while Kinesins move toward the plus end
- component of cilia, flagella and centrioles
