🧠 Concepts Introduced

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Cell Theory

structural unit of life, carry out function cells from division from a pre-existing cell

unicellular & multicellular

Artificial cells

JCVI Mycoplasma mycoides genome JCVI sequenced mycoplasma mycoides genome (smallest

History

Hydrothermal vents

Microscope

Robert Hooke refined design of compound microscope ​He coined the term cells

Antonie Van Leeuwenhoek is the first person to see bacteria (initially termed as animalcules) + capable of magnifying 270x

light microscope

Universal Principles / Properties of Living Cells

1. Cells possess a Genetic programme

   1. 

2. Cells are highly Complex and Organized

3. Cells are capable of Reproducing Cells reproduce by division (a 'mother' cell distributes into two 'daughter' cells) Most asexual reproduction undergo 'mitosis' while sex cells undergo 'meiosis'

4. Cells Acquire and Utilize energy Every biological process requires energy

   For plants, light energy is trapped by light-absorbing pigments present in the membranes of photosynthetic cells Light energy is then converted to chemical energy that is stored in energy-rich carbohydrates (as sucrose or starch)

   For animal cells, energy arrives pre-packaged, often in the form of sugar/glucose

   In humans, glucose is released by the liver into the blood for circulation to cells Once in a cell, glucose is disassembled and stored in a readily available form of ATP for immediate use Large amount of energy is used for breaking down and rebuilding the macromolecules and organelles of which they are made

5. Cells carry out variety of Chemical reactions Cells function like miniaturized chemical plants Almost all chemical changes in cells require enzymes The sum of chemical reactions in a cell represents the cell's metabolism

   The chart represents a portion of the cellular reactions that are taking place every second in a mammalian cell -> cells are great multitaskers

6. Cells engage in Mechanical Activities

   1. In cells, materials are transported from place to place

   2. Structures are assembled and disassembled

   3. The entire cell moves itself from one site to another too

   4. The cell movement is controlled by changes in the shape of 'motor' protein to carry out mechanical activities

   5. eg. a macrophage extending a pseudopodium towards an E. coli bacterium (green)

7. Cells are able to Respond to Stimuli Ranging from simplistic to complicated or highly specific

   eg. A single-celled protist moves away from an object in its path or moves toward a sourcenutrients

   Multicellular plants or animals rely on receptors that interact with substances in the environment in more specific way

8. Cells are able of Self-Regulation Cells are robust or durable

   Achieve homeostasis for self-survival eg. failure of a cell to correct a mistake when it duplicates its DNA may result in a debilitating mutation, causing certain loss of functions in the cells, or worse cell death

   However, the repairing or self-regulating activities are usually carried out in an organized way

   This is because one event could automatically trigger the next event in a reaction sequence in a cell

9. Cells are able of Evolve eg. bacterial cells becoming resistant to antibiotics

   Mutations provide the genetic variation that allows cell populations to evolve over generations.

   Evolution is not simply an event of the past, but an ongoing process that continues to modify the properties of cells

Prokaryotic & Eukaryotic cell

Smilarities:

• Plasma membrane function similar

• Genetic information encoded in DNA using identical genetic code

• Similar mechanism for transcription and translation

• Shared metabolic pathway (glycolysis and TCA cycle)

• Similar photosynthesis mechanism (cyanobacteria and green plants)

• Similar mechanism for synthesizing and inserting membrane proteins

• Proteosome (protein digestion enzymes) of similar construction

Features of eukaryotic cell not found in prokaryotes:

1. Plasma membrane chemical composition different. eg. cellulose-containing cell walls (in plants)

2. Complex chromosomes composed of DNA and associated proteins compacting into mitotic structures

3. Complex membranous cytoplasmic organelles (ER, golgi apparatus, lysosomes, peroxisomes) :

   • Specialized cytoplasmic organelles for aerobic respiration (mitochondria) and photosynthesis (chloroplasts)

   • Complex cytoskeletal system (microfilaments, microtubules) and associated motor proteins

   • Complex flagella and cilia

4. Cell division using microtubules-containing mitotic spindle that separates chromosomes

   • Two copies of gene per cell (diploidy), one from each parent

   • Presence of 3 different RNA synthesizing enzyme (RNA polymerase)

5. Sexual reproduction requiring meiosis and fertilization