Intro Chapter 13 Essay

Submitted By christinetadros
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Cell and Molecular Biology

What is a cell?
- An autonomous biological unit
- Smallest living unit
Individual cells can:
- Grow, reproduce process information, respond to stimuli, communicate, and carry out chemical reactions
- Carry hereditary material
- Surrounded by a plasma membrane

Naked Mole Rat
- Can live up to 35 years in the wild when wild rats average lifespan <1 and a pet rat is <3
- They are healthy and cancer free and can live so long because-
- Cells have proteasomes that degrade proteins
- As we age proteasomes lose function and miss-formed proteins accumulate
- Naked mole-rat cells have something that protects and increases proteasome function therefore live longer

All Organisms Are Bacteria, Achaea, or Eukaryotes
- Biologists recognized two types of cells 1) prokaryotes 2) eukaryotes
- The simpler type is characteristic of bacteria (Prokaryotes) and the more complex type characteristic of plants, animals, fungi, algae, and protozoa (eukaryotes)
- The main distinction between prokaryotes vs. eukaryotes is the membrane-bound nucleus that eukaryotic cells have

- Recently there has been a changing view of prokaryotes. The term prokaryote is unsatisfactory in describing non-nucleated cells
- Sharing of a large structural feature is not necessarily evidence of being related
- Based on rRna sequence analysis, prokaryotic cells can be divided into the wide categories of bacteria and archaea

-Bacteria and Archaea are as divergent from one another as humans and bacteria are
- Biologists now recognize three domains  Archaea, bacteria and eukarya (eukaryotes)

- These include most of the commonly encountered single-celled, non-nucleated organisms traditionally called bacteria
Examples: - Escherichia coli, - Pseudomonas, - streptococcus

- Archaea were originally called archebacteria before they were discovered to be very different from bacteria
- They include many species that live in extreme habitats and have diverse metabolic strategies
- Types of archaea include: methanogens- obtain energy from hydrogen and convert CO2 into methane halophiles – occupy extremely salty environments thermacidoophiles- thrive in acidic hot springs
- they are considered to have descended from a common ancestor that also gave rise to eukaryotes long after diverging from bacteria

Limitations on Cell Size
Cells come in various sizes and shapes
Some of the smallest bacteria are about 0.2-0..3 um in diameter
Some highly elongated nerve cells may extend a meter or more
Despite the extremes, cells in general fall into predictable size ranges
Bacteria cells normally range from 1 to 5 um in diameter
Animal cells have dimensions In the range of 10 – 100um

Eukaryotic Cells Use organelles to Compartmentalize Cellular Function
A solution to the concentration problem is the compartmentalization of activities within specific regions of the cell
Most eukaryotic cells have a variety of organelles, membrane-bounded compartments that are specialized for specific functions
e.g cells in a plant leaf have the most of the materials needed for photosynthesis compartmentalized into structures called chloroplasts

Presence of a membrane-bound nucleus
A eukaryotic cell has a true, membrane bound nucleus
The nuclear envelope consists of two membranes
The nucleus also includes the nucleolus, the side of ribosomal RNA synthesis and ribosome assembly

Eukaryote Organelles
Nearly all eukaryotes make extensive use of internal membranes to compartmentalize specific functions and have numerous organelles
E.g endoplasmic reticulum, Golgi complex, mitochondria, chloroplasts, lysosomes, peroxisomes and various types of vacuoles and vesicles
Each organelle contains the materials and molecular machinery needed to carry out functions for which the structure is specialized

Chapter 13 Transduction Mechanisms: 1. Electrical and Synaptic signaling in neurons

Signal Transduction Mechanisms: 1. Electrical and Synaptic Signaling in Neurons