BIOL1020 Week 2 : Cell Organelles and DNA

Bacterial Cells

Simple cells that are extremely metabolically adaptable to their environments. They are supreme inhabitants of other organisms and come in a variety of shapes and sizes.

Bacterial cells are a single chamber where ALL metabolic processes occur in the same place. The chamber is surrounded by a cell membrane, cell wall, and contains cytoplasm that house the nucleoid, ribosomes and plasmids. Pill/fimbriae are cilia structures that allow the cell to attach to surfaces, while flagella provide motion and stability

Gram-positive bacteria have a thick peptidoglycan cell wall surrounding the cell membrane and gram-negative bacteria have a thin peptidoglycan in between two cell membranes

Eukaryotic Cell Composition

Contains a nucleus (which houses DNA) endoplasmic reticulum, ribosomes (protein synthesis), mitochondria (powerhouse), Golgi apparatus (postal service) and lysosomes (digestive compartments)

Plant Cells

Additionally has a cell wall (strength and structure), chlorophyll (absorb sunlight), and vacuole (storage and disposal)

Animal Cells

Additionally has a cytoskeleton essential for structure of the cell and transport molecules within the cell.

Comprised of microtubules and microfilaments important for movement and cell division and can polymerise/depolymerise according to the cell’s needs.

Intermediate filaments provide structural rigidity to the cell

Endosymbiont Hypothesis/Theory

Primitive cells that swallowed ‘smart energy-producing’ cells that eventually incorporated these cells into its structure to produce energy for it

Mitochondria appears to have derived from aerobic respiring alpha proteobacteria. Chloroplasts appear to have been derived from oxygen evolving photosynthetic cyanobacteria.

Lipids

Macromolecules that are insoluble in water. Fats are the simplest lipids, consisting of carboxylic acid (COOH) connected to a hydrocarbon chain. A triglyceride is made up of three fatty acids linked to glycerol via an ester bond

Saturated Fats

Have the maximum number of hydrogens in the hydrocarbon chain and only have single bonds. This makes it a linear shape which can pack together tightly, giving it a viscous and thick look

SOLID at room temperature

Unsaturated Fats

Have one or more double bonds in the fatty acid chains. This causes the chains to look bend/link, making it harder to pack, giving it a fluid, water look

LIQUID at room temperature

Unsaturated fats are split into monounsaturated and polyunsaturated fats depending on the number of double bonds

Double bonds can be in the CIS (same side) or TRANS (different sides) configuration

Proteins

Amino acid monomers. Contains a carboxyl end (C-terminus), amino end (N-terminus) and side chain (R-group).

Multiple amino acids are joined together via peptide bonds (C-N)

Primary Structure (Proteins)

Linear amino acid sequence in a polypeptide chain

Secondary Structure (Proteins)

Regions stabilised by hydrogen bonds which form spirals (alpha helices) or flat planes (beta sheets) in the polypeptide backbone

Tertiary Structure (Proteins)

The 3D folding shape of the protein caused by different types of bonds.

Quaternary Structure (Proteins)

Two or more tertiary subunits polypeptides assembled together to form a multi-unit complex.

Enzymes

Type of protein used in metabolism to catalyse a reaction. The Lock and Key Model is an outdated model theorising how enzymes interact with substrates; however, it has been superseded by the Induced Fit Model

Nucleic Acids

Contain nucleotide monomers. Deoxyribonucleic Acid (DNA) contains the genetic blueprint of all cells. A nucleotide contains a nitrogenous base, pentose sugar, and phosphate group. They are linked together by a phosphodiester bond

Adenine (A) always binds to Thymine (T) (or Uracil (U) in RNA)

Guanine (G) always binds to Cytosine (C)

DNA Replication

Always occurs from the 5’ to 3’ direction and occurs in the nucleus.

The leading strand of DNA goes from 5’ to 3’

Lagging strand goes in the opposite 3’ to 5’ as DNA is antiparallel

The synthesis of the leading strand is smooth and continuous, while the synthesis of the lagging strand is complicated (Synthesis only runs 5’ - 3’, opposite of the lagging strand)

Helicase

Enzyme used for DNA replication

Unzips the double helix by breaking the hydrogen bonds between the complimentary bases

Single-stranded binding proteins

Protein used for DNA replication

Protects DNA from degradation and prevent secondary structure formation (prevents the separate strands from linking back together)

Topoisomerase

Protein used for DNA replication

Unwinds the chromosomes and DNA-double helix by creating small, reversible cuts in the DNA

Prevents coiling

Primase

Protein used for DNA replication

Synthesizes short RNA sequences called primers

These primers serve as a starting point for DNA synthesis

DNA Polymerase

Protein used for DNA replication

Continues the RNA strand from the primer and duplicates the DNA content of a cell during cell division

DNA Ligase

Protein used for DNA replication

Glues the DNA fragments together to form 2 new daughter DNA strands

Facilitates the formation of phosphodiester bonds between the two DNA monomers at a time