Cells

Features of prokaryotes

• no membrane bound organelles

• found in bacteria

• 1 circular chromosome in cytoplasm

• DNA in nucleotide region

• unicellular

• binary fusion

Features of eukaryotes

• has membrane bound organelles

• linear chromosome inside the nucleus

• mitosis/meiosis occurs

• multi or unicellular

• plant cell: contains cell wall

Cell theory

• All living things are composed of cells and cell products

• New cells are formed only by the division of pre-existing cells

• The cell contains inherited information (genes) that are used as instructions for growth, function and development

• The cell is the functioning unit of life; all chemical reactions of life take place within cells

Elongated cells

A way of increasing a cell’s surface area whilst retaining the same volume (also known as an ellipsoid or rod-shaped cell)

Cell membrane

• Found in all cells

• Separates the interior of the cell from the outside environment

• Consists of a lipid bilayer that is selectively permeable

• Regulates the transport of materials entering and exiting the cell

Cytoplasm

• Watery solution

• Gel-like in consistency

• Contains dissolved substances, enzymes, organelles and structures

• Function is to transport, maintain cell shape and structure, protect, store macromolecules

• Acts as the host to metabolic processes

Vacuole

• Filled with fluid

• Found in the cytoplasm

• Store nutrients, water, ions and waste products

• Break down waste materials

• Bigger in plant cells

Ribosome

• Small, dark circular bodies

• Found in either the cytoplasm or attached to the endoplasmic reticulum

• Site of protein production

• Translates RNA codons into amino acid sequences to produce polypeptides

• The proteins made in the cytoplasm are for local use within the cell and. those made from the endoplasmic reticulum are for transport

Smooth endoplasmic reticulum

• Tubular, network-like organelle

• Site for lipid synthesis

• Works in detoxification

• Transports lipids and proteins to the Golgi Apparatus

Rough endoplasmic reticulum

• Curved channels of membrane with surface-attached ribosomes

• Function is protein synthesis

• Proteins produces are usually destined for secretion, insertion in the cell membrane or to lysosomes

Lysosome

• Tiny membrane bound sacs found in the cytoplasm

• Contains transport enzymes that break down food and foreign matter

• Destroys unwanted/damaged cell parts or molecules

Golgi apparatus/body/complex

• Layers of curved membrane found towards the outside edges of a cell

• Modifies, sorts and packages proteins and lipids into vesicles

• Produces enzymes for lysosomes

• ‘Tags’ proteins to be expelled from the cell by exocytosis

Mitochondria

• Double-membrane structure and has their own circular DNA (mtDNA), found in cytoplasm

• Converts nutrients (glucose, fatty acids) and oxygen into ATP via oxidative phosphorylation

• Regulates cell growth, division, signalling and apoptosis

Nucleus

• Double membraned central organelle and contains most of the genetic material (DNA)

• Contains a nuclear envelope, nucleolus and chromatin which forms chromosomes

• Regulates gene expression and protein synthesis

• Control centre for growth metabolism and reproduction

Chloroplast

• Contains the green pigment chlorophyll

• Dense stacks of membranes within a fluid

• Sites for photosynthesis and generate metabolic energy

• Found only in plant and some protist cells

Cell wall

• Can be rigid or flexible

• Structural layer surrounding the cell membrane in plants, fungi, algae and most bacteria

• Provides rigidity and acts as a protective barrier

• Generally permeable, allows water, oxygen and nutrients to pass through unlike the selectively permeable cell membrane

Centrosome

• Composed of two centrioles

• Organizes microtubules

• Provide structure for the cell

• Work to pull chromatids apart during cell division

Macromolecules

Gigantic molecules which populate a cell and provide it with important functions for life

• Structural support

• Source of stored fuel

• Ability to store and retrieve genetic info

• Ability to speed biochemical reactions

(Carbohydrates, proteins, lipids, nucleic acids)

Nucleic Acids

• Also known as DNA and RNA

• Long chains of nucleotides consisting of phosphate, sugar and a base

• Carries and transfers the ‘recipes’ for making proteins out of amino acids

• Carries basic instructions for proteins (DNA) and transfers instructions from the chromosomes to the ribosomes (RNA)

Proteins

• Also known as polypeptides

• Complex molecules of sub-units called amino acids joined by peptide bonds

• Is the structural component of cells and tissues

• Hormones: regulate and control many functions

• Enzymes: Control the rate of chemical reactions

Carbohydrates

• Also known as sugars, starches and saccharides

• Sources of chemical energy or energy storage

• Form structural components

• E.g. glucose, sucrose, starch, cellulose, glycogen, fructose, lactose

Lipids

• Also known as fats and oils

• Act as energy storing molecules in plants and animals

• Steroids act as hormones and vitamins

• Primarily produced in the endoplasmic reticulum (ER), especially the smooth ER, which synthesises phospholipids, steroids, and other lipids for cell membranes

• Phospholipids act as a main component of cell membranes

• E.g. cholesterol, bile, cortisone, fat

Nucleotide

Formed of a sugar, phosphate group and nitrogenous base made up of adenine, thymine, guanine, cytosine and uracil

• Found in DNA

• Antiparallel (5 prime, 3 prime)

Genes

A sequence of DNA that carries instructions of building functional RNA or proteins

• controls the inheritance of physical, biochemical and behavioural traits

Primary transcript

Length of RNA that results from the process of transcription

RNA polymerase

A type of enzyme which moves along the template strand to create the mRNA

mRNA

Type of RNA that encodes the information for the proteins and carries it to a ribosome from the nucleus

Codon

Coding triplet of mRNA bases

Polypeptide

String of amino acids, assembled on a ribosome (protein)

Transcription

Process by which genetic information encoded in DNA is copied onto mRNA

• occurs in the nucleus

• DNA to mRNA

Translation

Process by which information encoded in mRNA is used to assemble a protein at a ribosome

• occurs at the ribosome

• mRNA to protein

Template strand

The actual gene strand which carries the ‘recipe’ for making a protein

Non-template strand

A complimentary strand/copy of the gene. It is copied (transcribed) to form mRNA. This means that mRNA is a direct copy of the template strand but with uracil rather than thymine.

tRNA

Reads the genetic code by matching its anticodon to the corresponding mRNA codon, delivering the appropriate amino acid to the ribosome.

rRNA

Provides the scaffold for ribosomal proteins and forms the catalytic peptidyl transferase centre. Is essential for decoding mRNA and is transcribed in the nucleolus.