Biology AOS 3 SAC 1

Nucleic Acid

Function: Carry genetic material of all organisms.

• etc. DNA and RNA which carry info to build proteins,

Nucleotide: Building blocks of nucleic acid

• Monomer = Base unit of a molecule (singular)

• Polymer = Multiple base units together to form a molecule

DNA (deoxyribonucleic acid)

DNA: Thin, double stranded molecule (double helix), that encodes/ contains the genetic instructions for making proteins, and is found within nucleus. 

Single Nucleotide of DNA: Contains a phosphate group, deoxyribose sugar, and nitrogenous base with pairs Adenine + Thymine, and Cytosine + Guanine.

• Thymine + Cytosine = Pyrimidine (1 Ring)

• Adenine + Guanine = Purine (2 Rings)

Bonds within nucleotides/ Direction of DNA

Covalent Bonds (phosphodiester bonds) : Occur between the phosphate and sugar “backbone”

Hydrogen Bonds : Hold bases together, e.g Two hydrogen bonds between Adenine and Thymine, and Three hydrogen bonds between Guanine and Cytosine.

• DNA direction: Occurs in 5’, 3’ direction that run antiparallel, therefore 3’ end of one strand will pair with the 5’ end of another strand.

RNA (ribonucleic acid) and types of RNA

Single Nucleotide of RNA: Contains a phosphate, ribose sugar, and nitrogenous base with pairs Adenine + Uracil, and Guanine + Cytosine.

• Messenger RNA (mRNA) = Carries a copy of genetic info from the nucleus to ribosomes 

• Transfer RNA (tRNA) = Brings a specific amino acid to the ribosome

• Ribosomal RNA (rRNA) = Together with proteins, makes up ribosomes.

Genome / Gene

Genome: Total set of genes found within a cell.

• Chromosomes > Genes > DNA > Nucleotides

Genes: Short section of DNA, which contains instructions for building  specific proteins.

Different types of Genes

Structural Genes: Code for proteins involved in cellular structure and function.

• etc. Types of proteins = Keratin, Enzymes and Hormones.

Regulatory Genes: Code for specific proteins involved in controlling the expression of structural genes.

• Transcription factors = protein that can turn structural genes “on” and “off”

Gene Structure 

Promotor: Effectively shows the starting position of a gene.

Operator: Section of a gene that can prevent the gene from being read (in specific situations)

Introns: Regions of non-coding DNA 

Exons: Regions of coding DNA

Termination sequence: Sequence of DNA that signals for the end of transcription.

Prokaryotic cells vs Eukaryotic cells 

Prokaryotic: Single cellular organism containing no membrane-bound organelles, including a nucleus.

• etc. Bacteria 

Eukaryotic: Multi cellular organism containing membrane bound organelles, including the nucleus.

• etc. Animals, Plants, Fungi 

Plasma Membrane/ Ribosomes

Plasma Membrane: Boundary of the cell that is selectively permeable, and made up of fatty acids.

• Found in eukaryotes and Prokaryotes

Ribosomes: Building site of proteins, and made up of ribosomal RNA. Translation of mRNA achieved at the ribosome.

• Found in eukaryotes and Prokaryotes

Nucleus / Rough Endoplasmic Reticulum (RER)

Nucleus: Double layered membrane which contains DNA, providing instructions to the cell. Outer membrane has small pores to let RNA out of the membrane. 

• Only in Eukaryotes 

Rough Endoplasmic Reticulum: Network of membranous sacs (cisternae) that is studded with ribosomes and links to other membranes. Involved in making proteins. 

• Only in Eukaryotes 

Golgi Apparatus / Vesicle

Golgi Apparatus: Stacks of cisternae that do not attach to other membranes. Modifies proteins and prepares them for export. 

• Only in Eukaryotes 

Vesicle: Small “container” made of phospholipids, transporting various materials in and around the cell.

• Found in eukaryotes and Prokaryotes

Mitochondria / Chloroplast

Mitochondria: Site of cellular respiration, generating ATP energy (adenosine triphosphate)

• Eukaryotes only

Chloroplast: Site of photosynthesis, generating sugar from water and carbon dioxide.

• Only found in plant cells (eukaryotes)

Steps of Exporting Proteins

1. Ribosomes: make proteins

2. Rough Endoplasmic Reticulum: folds proteins, sending them to next location

3. Transport Vesicle: Transports protein from rough ER to golgi apparatus

4. Golgi apparatus: Modifies and packages protein (etc. other chemical groups)

5. Secretory Vesicle: Transports protein to plasma membrane of cell.

Endocytosis / Exocytosis

• Both are forms of “Bulk Transport”, that requires energy, going against concentration gradient (low -high)

Endocytosis: Plasma membrane engulfs external materials, forming a vesicle around the materials in the cell.

Exocytosis: Vesicle travels and fuses with cell membrane, to release its