Eukaryotic Cell Structure (Tutorial #6) Flashcards
What are the four general functions of cell membranes?
- semi-permeable barrier for the cell
- semi-permeable barrier for organelles
- regulate the transport of molecules
- receives signals
Explain the fluid-mosaic model of membrane structure.
membranes are organized as a lipid bilayer with embedded proteins
What is the most common type of lipid in cell membrane?
phospholipid
Define amphipathic.
has both hydrophilic and hydrophobic characteristics
What components of a cell membrane are amphipathic?
- phospholipids (hydrophobic tails at the interior of the membrane and hydrophilic heads that face outward towards the inter and extracellular environments)
- trans-membrane proteins
Define selective permeability.
Some substances can readily pass through the phospholipid bilayer (non-polar molecules, small molecules, and lipids) while others cannot readily pass through the bilayer and must cross through a transport protein (polar, large, and charged molecules)
What do aquaporins do?
Facilitate the transport of water molecules across the cell membrane.
Define active transport.
A type of transport that requires some type of input of metabolic energy.
Define passive transport.
A type of transport that does not require any energy.
What are the different types of passive transport?
Simple diffusion, ion channel, and facilitated diffusion.
What is the general function of the nucleus?
- store the main genetic material within the cell
- site of all gene expression
Describe the general structure of the nucleus.
- surrounded by a double membrane called the nuclear envelope
- has nuclear pores for mRNA to exit the nucleus
- houses the nucleolus, which contains a very active group of genes that encode and transcribe rRNA
What are ribosomes?
Structures made of rRNA molecules and proteins that are the sites of protein synthesis in cells.
Are ribosomes considered an organelle?
No because they are not enclosed by a membrane.
What is the function of a free ribosome?
To make proteins that are used within the cell.
What is the function of a bound ribosome?
To make proteins that are either excreted from the cell, used in the cell membrane, or used in a membrane-bound organelle.
Where does protein production take place?
In a netwoek of membrane-bound chambers called the endomembrane system.
What are the components of the endomembrane system?
- Smooth ER
- Rough ER
- Golgi apparatus
What does the smooth ER do?
Plays a major role in:
- synthesizing lipids
- storing calcium ions
- degrading toxins
What does the rough ER do?
- synthesizes proteins that are targeted for export outside the cell
What structurally distinguishes the rough ER from the smooth ER?
The rough ER has ribosomes bound to its surface while the smooth ER is smooth.
What does the Golgi apparatus do?
- processes proteins
- glycosylation (carbohydrates are added to proteins)
What do lysosomes do?
They break down materials in the cell using special hydrolytic enzymes. They can break down old cell parts or destroy invading bacteria.
What are the three major components of the cytoskeleton?
Microfilaments, intermediate filaments, and microtubules.
Microfilamnets
- smallest
- made of actin protein
- facilitate cell movement
Intermediate filaments
- made of fibrous proteins wrapped around one another to form a thick, cable-like structure
- they support cell structures and anchor organelles in the correct positions within a cell.
Microtubules
- largest element within the cytoskeleton
- hollow tubes consisting of rows of paired tubulin molecules
- used in cell division, for structural support, and for cell mobility (cilia and flagella)
What do mitochondria do?
They convey the energy in food into the form of ATP, which provides energy for many cellular reactions.
Describe the basic structure of mitochondria.
- double membrane consisting of a smooth outer membrane and an inner membrane that is contorted into a complex of inter-foldings called cristae.
- the space within the cristae is called the mitochondrial matrix
- the space outside of the cristae but still inside of the outer membrane is the intermembrane space.
What form is the genetic material which mitochondria posess?
They possess genetic material in the form of circular DNA.
How is mitochondrial genetic material inherited?
Maternally in sexually reproducing organisms.
What are chloroplasts?
Double membrane-bound organelles found in plants that are the sites of photosynthesis.
What causes the green color of chloroplasts?
Chlorophyll.
What form is the genetic material which chloroplasts possess?
They possess genetic material in the form of circular DNA.
Explain the endosymbiont theory of eukaryotic evolution.
Mitochondria and chloroplasts have evolved from prokaryotes that inhabited the cells of larger prokaryotes. This was a result of the larger organism engulfing the smaller organism.
What evidence do mitochondria present for the endosymbiont theory?
- double membrane
- inner membrane resembles prokaryotic membrane
- circular DNA
- smaller size
- replication similar to binary fission
- able to produce their own protein
