The Diversity of Cells Flashcards
Where did monomers come from?
- Monomers came from space
- Monomers came from atmospheric reactions
- Monomers came from hydrothermal vents
What did Stanley Miller and Harold Urey show in 1953?
Stanley Miller and Harold Urey showed in 1953 that the gases in the atmosphere could react to form small organic molecules (amino acids; fatty acids; organic acids). Rainfall would have washed those into the ocean forming an “organic soup” and leading to self-assembly into polymers and additional chemical reactions.
How did the first cells form?
- Cells first formed in water
Lipids are amphiphilic. When they are mixed with water, they form micelles and vesicles with bilayers, trapping other organic molecules inside. Those that assembled to self-replicating units would constitute the first “proto-cells”. They came into existence in aquatic environments.
Describe the basic cell structure.
All cells have certain structures in common:
- Genetic material – in a Nucleoid or Nucleus
- Cytoplasm – a semifluid matrix
- Plasma membrane – a phospholipid bilayer
The membrane lipid bilayer contains
phosphoglycerides, glycolipids and can also
contain cholesterol (in animals) and sphingolipids.
The surface of the membrane is polar and contains
charged groups.
What are the simplest cells?
The simplest cells are prokaryotes.
When were cells first discovered?
Cells were discovered in 1665 by Robert Hooke.
Describe Schwann’s Cell Theory
Schleiden and Schwann proposed the Cell Theory (1839):
- All organisms are made of cells
- Cells are the fundamental unit of life
- Cells come from other cells
What are some characteristics of bacteria?
Bacteria
•Cell membrane contains ester bonds
•Cell wall made of peptidoglycan
•React to antibiotics differently than Archaea
•May be Gram-positive or Gram-negative
What are some characteristics of archaea?
Archaea
•Cell membrane contains ether linkages
•Cell wall lacks peptidoglycan
•Extremophiles-thrive in extreme conditions (high salt/temp)
•Genes and some metabolic pathways closely related to Eukaryotes (enzymes involved in transcription/translation)
•Most Archaea stain Gram-negative
How did the first eukaryotic cells come into existence?
Eukaryotes evolved from prokaryotes
Describe the endomembrane system
The endomembrane consists of a series of interconnected membranes in the cytoplasm:
- The endoplasmic reticulum
- The Golgi apparatus
- Lysosomes
Describe the rough endoplasmic reticulum
The rough ER is responsible for the synthesis of proteins with a signal
sequence. These proteins either remain in the ER, are sent to Golgi, lysosomes, vacuole, or plasma membrane, or are secreted. When misfolded/ unfolded proteins accumulate in the ER lumen due to stress, a mechanism known as the unfolded protein response (UPR) is activated. This triggers a reduction of protein synthesis and an increase in protein degradation. Failure in the response leads to apoptosis (programmed cell death).
Describe the smooth endoplasmic reticulum
The smooth ER plays a role in the synthesis of lipids and steroid hormones, and in calcium storage.
What is the Golgi apparatus?
The Golgi apparatus modifies, transports, and packages proteins and lipids for transport to their destination in the plasma membrane, lysosome, vacuole, or for secretion. In plants, it also produces cell wall polysaccharides.
Describe lysosomes
Lysosomes are membrane-bound vesicles that break down macromolecules and foreign matter.
Describe the evolution of the nucleus and the
endomembrane system
Why would it be beneficial for an ancient eukaryote to engulf but not degrade an aerobic prokaryote?
The acquisition of aerobic bacteria would have provided a cell with the ability to carry out oxidative metabolism, and aerobic metabolism produces the most energy.
Describe some details about mitochondria
Mitochondria occur in virtually all cells of animals, plants, and fungi
• They are surrounded by 2 membranes:
- smooth outer membrane
- folded inner membrane with layers called cristae
- They contain some of their own DNA; part of their genetic information is located in the nucleus
- Mitochondria are the location of ATP production through the citric acid cycle and oxidative phosphorylation.
Describe the function of mitochondria-associated ER membranes (MAMs)
The MAM plays a role in lipid trafficking
and, possibly, Ca-signaling and the secretory pathway.
They are held together by protein-tethering complexes along with the mitochondria.
What is the purpose of mitochondrial cristae?
Increase surface area of the mitochondrial inner membrane, thereby increasing the efficiency of energy production.
How do cells modify mitochondria to lead to thermogenesis?
Uncoupling of proton transport from ATP production can lead to thermogenesis.
Describe the Endosymbiosis Theory
The Endosymbiosis theory proposes that mitochondria and chloroplasts evolved from a symbiotic relationship. One prokaryote engulfed a second prokaryote and benefitted from its ability to, for example, photosynthesize. Over time, it lost its autonomy – some genes from the endosymbiont were transferred to the nucleus of the host.
What is the evidence supporting the Endosymbiosis Theory?
- Chloroplasts and mitochondria have 2 membranes: the outer membrane
resembles the eukaryotic membrane; the inner membrane resembles the
prokaryotic membrane - Possess DNA and ribosomes; the ribosome resemble prokaryotic ribosomes
- About the size of a prokaryotic cell
- Divide by a process similar to bacteria (binary fission)
Why do we think mitochondria were first endocytosed?
Cells with chloroplasts also contain mitochondria, but not all cells with mitochondria contain chloroplasts.
