Review Biology and DNA

BIT 120

General Animal Cell1. MitochondrionAn important cell organelle in respiration2. CytoplasmThe fluid that fills the surroundings of the cell and forms a vacuole3. Golgi ApparatusThe processing area in the creation of proteinsendoplasmic reticulum (ER).4. Endoplasmic ReticulumAn important organelle in protein synthesis that bears ribosomesThe finished off and 'packaged' protein product6. NucleusThe 'brain' of the cell, containing the genetic information for the coding of biological processes7. Ribosomes: Ribosomes are responsible for assembling the proteins of the cell.

Cell Membrane

• The cell membrane, (otherwise known as the plasma membrane) is a semi-permeable structure consisting mainly of phospholipid (fat) molecules and proteins. They are structured in a fluid mosaic type model, where a double layer of phospholipid molecules provide a barrier accompanied by proteins. IT is like a sandwich:

___________ fat ___________ fat

• The plasma membrane allows only selected materials to pass in and out of a cell. The protein in the membrane can transport selected materials, as stated below.

Cell Transport• Active Transport - Active transport is the transport of molecules

with the active assistance of a carrier, in most cases being a protein. AREA OF LOW CONCENTRATION TO AREA OF HIGH CONCENTRATION requires energy

• Passive Transport (Diffusion) - The movement of molecules from areas of high concentration (i.e. outside a cell) to areas of low concentration (i.e. within a cell) via a carrier, though does not require energy : AREA OF HIGH CONCENETRATION TO LOW CONCENTRATION -SEE FIGURE

• Simple Diffusion - The movement of molecules from areas of high concentration to areas of low concentration in a free state. Osmosis of water involves this type of diffusion through a selectively permeable membrane (i.e. plasma membrane) Does not require energy

Cell Energy – ATP

• ATP: Adenosine triphosphate. A compound containing the nitrogenous base adenine, the carbohydrate ribose, and three phosphates. Breakdown of ATP provides the energy needed to carry out energy-requiring processes in cells.

Glycolysis/Krebs Cycle

• OVERHEADS

Cell Nucleus

• Structure/function correlations• Store genes on chromosomes • Organize genes into chromosomes to allow cell

division.• Transport regulatory factors & gene products via

nuclear pores • Produce messages ( messenger Ribonucleic

acid or mRNA) that code for proteins • Produce ribosomes in the nucleolus • Organize the uncoiling of DNA to replicate  key

genes    

Cell Nucleus

Introduction to DNA

• DNA is made up of subunits which scientists called nucleotides.

• Each nucleotide is made up of a sugar, a phosphate and a base.

• There are 4 different bases in a DNA molecule: • adenine (a purine) • cytosine (a pyrimidine) • guanine (a purine) • thymine (a pyrimidine) • uracil (a pyrimidine) is found in RNA only

Intro. to DNA (cont’d)

• The number of purine bases equals the number of pyrimidine bases

• The number of adenine bases equals the number of thymine bases

• The number of guanine bases equals the number of cytosine bases

• The basic structure of the DNA molecule is helical, with the bases being stacked on top of each other

• a nucleoside is the combination of a sugar (ribose or 2-deoxyribose) and a nitrogen containing base

• when you add 1 or more phosphate to the sugar portion of a nucleoside, you get a nucleotide

Pics of DNA

• Pictures from Snustad• Some facts:• DNA is a double helix. • The Watson and Crick model of a double helix

structure provides an answer to the regularity of the composition in bases and its physiological properties (replication in the cell). It is confirmed by diffraction data. Models using beads are useful to handle the concept.

• The base composition is variable, but in all cases the amount of adenine is equal to the amount of thymine (A=T). In the same manner, C=G. Consequently A+C= T+G .

More Facts

• E. coli has a single circular DNA molecule of 4,600,000 base pairs. The total length is 1.4 mm.

• In man, the DNA molecule in a diploid cell, if fully extended, would have a total length of 1.7 metres. If you unwrap all the DNA you have in all your cells, you could reach the moon ...6000 times!

• In addition to functioning as building blocks of nucleic acids, nucleotides are important because they are used to store and transfer chemical energy (e.g. ATP).

Genome size/content

• Bacterium ( E.coli) 4 million b.p. 100% coding

• Fruitfly (Drosophila) 180 million b.p. 33% coding

• Human 3.5 billion b.p. 9%-27% coding

DNA Replication

• The actual DNA to act as an exact template

• A pool of relevant and freely available nucleotides

• A supply of the relevant enzymes to stimulate reaction

• ATP to provide energy for these reactions

• http://www.ncc.gmu.edu/dna/repanim.htm

DNA TranscriptionmRNA Translation

• See overheads

Proteins

• Types of Protein• Over time and diversity of organisms, a huge

amount of proteins exist and perform a unique function in the body. Primarily, their are three types of protein

• Fibrous Proteins - These fibre like proteins are used for structural purposes in organisms. This is because fibrous proteins are arranged in long strands and are insoluble in water. Examples of use include providing a barrier in the cell wall of plants and myosin in skeletal muscle

Types of Proteins• Globular Proteins - The polypeptide chains (protein chains) in

globular proteins are folded together into a knot like shape essential in the fact that are present in the following

1. Enzymes - Biological catalysts, enzymes are responsible speeding up reactions in an organism

• 2. Hormones - Hormones are chemical messengers responsible for initializing a response in organisms.

•3. Antibodies - Antibodies are used to defend the body against foreign agents e.g. bacteria, fungi and viruses.

• 4. Structural Protein - Globular proteins form part of the cell membrane, which has a structural role as well as a role in transporting ions in and out the cell.

More types of Proteins

• Conjugated Proteins - Conjugated proteins are essentially globular proteins that possess non-living substances, such as the haem found in haemoglobin, which possesses iron (a non-living substance)