Lecture 6 Flashcards
Basic information of cells/Cell theory
- All living organisms are composed of one or more - cells
- The cells is the basic unit of structure and organisation
- All cells arise only from pre-existing cells
- Cells are small due to the balance between surface area and size
Universal similarities between cells:
- DNA as the heritable material, RNA as a messenger and proteins as the workers (the central dogma = DNA makes RNA which makes proteins)
- Major cellular organelles - functions and arrangements within the cell
- ATP as an energy source
Prokaryote
Structure:
Smaller cells
Lack a membrane-bound nucleus/organelles
Both have:
Plasma membrane, cytosol, DNA, RNA, protein and ribosomes
Eukaryote
Structure:
Larger cells, have a membrane-bound nucleus
(we are eukaryotes)
Both have:
Plasma membrane, cytosol, DNA, RNA, protein and ribosomes
Is there a limit to cell size
Yes, most cells tend to be 10-20 microns in diameter, due to optimal balance between size and surface area
Humans have roughly 37 trillion cells
Cytoplasm
Structure/components:
Everything inside the cell/plasma membrane including organelles but NOT the nucleus
Cytosol
Is the fluid portion of the cytoplasm
Sturcture:
Water plus dissolved and suspended substances (ions, ATP, proteins, lipids)
Major organelles
Nucleus (nuclear outer membrane - for
transport)
Endoplasmic Reticulum (smooth and rough)
Golgi apparatus
Lysosomes
Mitochondria
Ribosomes
Other (non-major) organelles
Centrosome
Peroxisome
What is included in the endomembrane system
Plasma membrane
Nucleus - more so the outer membrane
Endoplasmic Reticulum
Golgi apparatus
Lysosomes
They work together to package, label and ship molecules. Endomembrane system refers to how the membranes of the rough ER, Golgi and PM share membranes (through vesicles leaving and attaching)
Microvilli
Smallest membrane extensions
Cilia
Mid-sized membrane extensions
Flagellum
Largest membrane extensions
Plasma membrane
Structure:
Made of a bilayer of phospholipids - each phospholipid has a hydrophilic polar head (phosphate) and 2 hydrophobic lipid tails (fatty acids), and they are arranged so tails meet - with embedded proteins
Membranes are not static - they are dynamic and cell specific. The proteins which are represented in the present on a membrane change all the time.
Fluid mosaic model - membranes made of of the bilayer of phospholipids and it is constantly moving. It will have different proteins/molecules based on what is happening at the present time
Membranes of organelles have the same membrane bilayer
Functions:
Physical barrier separating inside and outside of cell
A selectively permeable barrier controlling the passage of substances in and out of cell and separating inside/outside of cell - fats in cell membrane are hydrophobic and therefore provide the barrier to water. Much of our body is hydrophilic
What is the fluid in the cytoplasmic and extracellular areas cell made out of
Water along with other things
What are the two types of membrane proteins?
Integral
Peripheral
Integral proteins:
Structure:
Membrane proteins that are embedded (partially or fully) into the membrane eg. transmembrane proteins are integral membrane proteins that fully span entire membrane, contacting both extracellular and cytoplasmic areas
Often amphipathic - partially polar and partially non-polar
NOT ALL ARE TRANSMEMBRANE
Function:
Plasma Membrane proteins allow for cell-cell identification and facilitate intercellular communication