Week 1: 1.3-1.5: Cells, Membranes, Membrane Proteins Flashcards
(79 cards)
What are the components of the Cell Theory?
- Cells are the basic unit of life
- all living things are made of cells
- cells arise only from other cells
What are the three main forms of life on earth?
- Eubacteria
- Archaebacteria
- Eukaryotes
What two types of prokaryotes are there?
- Eubacteria (e.coli and bacillus)
- archaebacteria
What distinguishes a prokaryotic cell from a eukaryotic cell?
Internal organization: organelles and cytoskeleton.
- Eu: more complex, has a true nucleus, and is compartmentalized. Has membrane bound organelles and has a cytoskeleton
- Prokaryotic: no nucleus, 2 compartments sometime, simple in structure, lack of internal membrane bound organelles, lack of major internal structural systems aka cytoskeleton
- prokaryotes lack membrane bound organelles
What are some of the ways that prokaryotes and eukaryotes are the same?
Structural organization
-surrounded by lipid membrane
-use of nucleic acid to transfer DNA/heritable info
Similar biochemical processes
-metabolic process: all living cells generate ATP to drive metabolism
-Genetic process: all living things use ribosomes and transfer RNA molecule during the conversion of DAN code to protein
-Signaling: use small ions like calcium for communication purposes
What are some of the ways prokaryotes are classified?
Morphology -shape: rods, spheres, spiral, flagellum Diagnostic Stains -gram (+)/(-) Comparison of the nucleotide sequence of the ribosomal rRNA gene
What is a gram-negative bacterium?
Bacteria is surrounded by lipid membrane
What are protozoa? Are they prokaryotic or Eukaryotic?
Eukaryotic simple cell or unicellular organisms that show great complexity.
-protozoa, algae, fungi (yeast)
What is the word cell derived from?
The word “cell” was
first used by Robert Hooke in the 1600’s.
- structures he saw reminded him of small rooms in monasteries where monks lived. These
small rooms were called cells after the Latin word “cellula”, or small room, and so that is why
we call cells “cells”
What are commonalities of all living cells?
- structural features
- biochemical process
- A cell is surrounded by plasma membrane
- A cell has genetic information
What is gram staining?
used to identify bacteria. uses purple or red stains that bind to proteins and peptides creating a stain.
If bacterium is surrounded by an outer membrane will it test gram negative or gram positive?
will test gram-negative b/c lipid membrane does not bind to the stain. Stain only binds to peptide bonds and proteins
If bacteria are enclosed in a coat of peptides & polymeric sugars, aka petidoglycan layer, will it test gram negative or positive?
will test gram-positive
why do some prokaryotes have a second compartment? What is this second compartment called?
- 2nd compartment is called periplasmic space
- sometimes the cytoplasm is surrounded by one double layered lipid membrane aka plasma membrane and sometimes they have two membranes aka the second comparment aka periplasmic space between them.
What are the two compartments that prokaryotes can have?
- cytoplasm or cystolic: contains water-soluble proteins and DNA
- periplasmic space: when a prokaryote has two outer membranes this is the space between them
what is a plasma membrane?
one double-layered lipid membrane that surrounds the cytoplasm
what is meant by a fluid mosaic biomembrane?
- the fluid part are the lipids (which move sideways freely but not across membrane)
- mosaic is the protein floating around (can be bound by other proteins or lipids)
What components make a biomembrane?
lipids, proteins, and carbohydrates
Why are lipids known as amphipathic molecules?
They have a polar head (water-soluble/hydrophilic) and 2 non-polar tails (excluded from water/hydrophobic) = dual solubility
What is the effect of adding cis bonds to a lipid?
One tail typically has one or more cis-double bonds (that is, it is unsaturated), while the other tail does not (that is, it is saturated). Each cis-double bond creates a kink in the tail. Differences in the length and saturation of the fatty acid tails influence how phospholipid molecules pack against one another, thereby affecting the fluidity of the membrane,
Alberts, Bruce. Molecular Biology of the Cell (p. 566). W. W. Norton & Company. Kindle Edition.
What are the three main classes of lipids in biological membranes?
- Phosphoglycerides (phospholipids)
- Sphingolipids
- Sterols
What are some of the effects of adding cholesterol to a biological membrane?
- cholesterol can change membrane fluidity and permeability
- cholesterols saturates membrane meaning the membrane is LESS permeable and LESS fluid
- cholesterol fills the spaces created by unsaturated lipids
- stops gel formation
- shifts the phase transition temp lower.
How can the fluidity of a membrane be altered?
-Temperature
(low temp: gel-like…butter)
(high temp: fluid-like…melted butter)
- adding cholesterol
- Phase transition temperature (Tm)
What is the phase transition temperature?
temp at which half of the membrane is in the gel
phase or half of the membrane is in the fluid phase