Molec Cell Ch. 1

An Overview of Cells and Cell Research

What is the critical characteristic of the macromolecule from which life evolved?

The ability to replicate itself

What are two major macromolecules?

Nucleic acids and proteins

Which macromolecule is capable of self-replication?

Nucleic acids

What did Altman and Cech first discover?

RNA is capable of catalyzing chemical reactions, including the polymerization of nucleotides

What is RNA able to do for its replication?

RNA is able to both serve as a template for, and to catalyze its own replication.

What may be the initial genetic system?

RNA

What is RNA world?

A period of evolution

All present-day cells…

use DNA as the genetic mateiral and have the same mechanisms for replication and gene expression.

Genes

segments of DNA that encode proteins or DNA

Transcription

Nucleotide gene sequence is copies into RNA

Translation

Nucleotide sequence of RNA is used to specify the order of amino acids in a protein

What was part of the first cell?

Self-replicating RNA and phospholipid membrane

Phospholipids

Basic components of all present-day biological membranes

Amphipathic

a chemical compound containing both polar (water-soluble) and nonpolar (not water-soluble) portions in its structure

Are phospholipids amphipathic?

* Water-insoluble (hydrophobic) **hydrocarbons chains**
* water-soluble (hydrophilic) **head groups** that contain phosphate

What happens when phospholipids are placed in water?

Phospholipids spontaneously aggregate into a bilayer

What do all cells use as their source of metabolic energy?

Adenosine 5’-triphosphate (ATP)

What are the mechanism that generate ATP?

Glycolysis, photosynthesis, oxidative metabolism

Glycolysis

Glucose → lactic acid (generates 2 ATP)

Photosynthesis

CO2 + H2O + sunlight → Glucose + O2

Oxidative Metabolism

Glucose + O2 → CO2 + H2O (Generates 36-38 ATP)

How did glycolysis evolve?

* Glycolysis evolved when the Earth’s atmosphere was anaerobic.
* Glucose broke down to lactic acid, with 2 ATP gained.
* All present-day cells carry out glycolysis

Photosynthesis allowed…

Some cells to harness energy from sunlight

Use of H2O in photosynthesis…

changes Earth’s atmosphere by making free O2 available

Complete oxidative breakdown of glucose yields how many ATP molecules?

36-38 ATP

What are the two types of cells?

Prokaryotic (bacteria) and Eukaryotic

Prokaryotic

lack a nuclear envelope

Eukaryotic

Have a nucleus that separates genetic material from cytoplasm?Wha

What is the difference of the 2 cell types?

What is a typical prokaryotic cell?

E. Coli

What are some key features in prokaryotes, especially in E. coli?

1. **Cell wall:** polysaccharides + peptides
2. **Plasma membrane:** phospholipid bilayer + associated proteins
3. DNA: **single circular molecule in the nucleoid** - **not surrounded by a membrane**
4. Cytoplasm: 30,000 **ribosomes**

Present-day prokaryotes are:

* Archaea
* Bacteria
* Prokaryotes
* Cyanobacteria

Archaea habitat?

extreme environments (ex: hot sulfur springs)

Bacteria…

* include the common forms of present-day prokaryotes
* in a wide range of environments

Prokaryotes… (size and DNA)

* Most are small, diameters: 1 to 10 um
* DNA ranges from 0.6 million to 5 million base pairs, encodes about 5000 different proteins

Cyanobacteria

Photosynthesis evolved, largest and most complex prokaryotes

Eukaryotic cells are…

much larger and more complex, with a nucleus, other organelles, and cytoskeleton

What are the key organelles in euks?

1. Nucleus
2. Mitochondria
3. Chloroplasts
4. Lysosomes and Peroxisomes
5. Vacuoles: in plant cells
6. Endoplasmic Reticulum
7. Golgi apparatus
8. Cytoskeleton

What is the largest organelle in euks? What does it do?

* Nucleus is the largest organelle
* contains the linear DNA molecules
* site of DNA replication and RNA synthesis

What do mitochondria do in euks?

site of oxidative metabolism

What do chloroplasts do in euks?

site of photosynthesis

what do Lysosomes and peroxisomes do in euks?

specialized metabolic compartments for the digestion and macromolecules and for various oxidative reactions

What do vacuoles do in euks?

in plant cells

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Do a variety of functions: digestion of macromolecules and storage of waste products and nutrients

What does the endoplasmic reticulum do in euks?

* Network of intracellular membranes, extending from the nuclear membrane throughout the cytoplasm
* Functions in processing and transport of proteins and lipid synthesis

What does the golgi apparatus do in euks?

* Proteins are further processed and sorted for transport to their final destinations


* site of lipid synthesis; and (in plant cells) synthesis of some polysaccharides that compose the cell wall

What does the cytoskeleton do in euks?

a network of protein filaments extending throughout the cytoplasm

* provides structural framework
* determines cell shape and organization
* involved in movement of whole cells, organelles, and chromosomes during cell division

How are eukaryote organelles thought to have arisen?

Endosymbiosis → prokaryotic cells living inside the ancestors of eukaryotes

What organelles support endosymbiosis? Why?

Mitochondria and chloroplasts:

* similar to bacteria in size
* like bacteria: reproduce by dividing in two
* both contain their own DNA
* DNA is replicated when the organelle divides. Genes are transcribed within the organelle and translated on organelle ribosomes
* Ribosomes and ribosomal RNAs are more closely related to those of bactiera than to those encoded by the eukaryote nuclear genome

Are there any unicellular euks?

Yes

What are the simplest eukaryotes?

Yeasts

Approx how many germ cells and somatic cells do multicellular organisms have?

16 germ cells and 2000 somatic cells

What is another example of the transition to multicellularity?

amoeba *Dictyostelium discoideum* is able to **alternate between unicellular and multicellular forms** depending on the availability of food

What led to the complexity and diversity of present-day plants and animals?

Increasing specialization and division of labor among the cells of multicell organisms

What are the main tissue systems in plants?

1. Ground Tissue
2. Dermal Tissue
3. Vascular Tissue

Ground Tissue

* Has parenchyma cells - site of metabolic reactions, including photosynthesis
* Collenchyma and sclerenchyma - have thick cell walls and provide structural support

Dermal Tissue

covers the surface of the plant; forms a protective coat and allows absorption of nutrients

Vascular Tissue

Xylem and Phloem - elongated cells which transport water and nutrients throughout the plant

What are the 5 main tissue types in animals?

1. Epithelial cells
2. Connective tissues
3. Blood
4. Nervous Tissue
5. Muscle Cells

Epithelial Cells

Can form sheets that cover the surface of the body and line internal organsCo

Connective Tissue

Includes bone, cartilage, and adipose tissue.

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Loose connective tissue is formed by fibroblasts.

What types of cells does blood have?

* Red blood cells (erthrocytes) function in oxygen transport
* White blood cells (granulocytes, monocytes, macrophages, and lymphocytes) function in inflammatory

Nervous Tissue

Composed of supporting cells and nerve cells, or neurons, and various types of sensory cells

Muscle Cells

Rresponsible for the production of force and movement