Molecular Composition of Cells Flashcards
What are carbohydrates? What do they do?
Carbohydrates include simple sugars as well as polysaccharides.
They are the major source of nutrients in the cell and are a major structural molecule that plays a role in signalling and cell recognition.
What are monosaccharides?
Simple sugars with the basic formula (CH2O)n
What are triose sugars?
Breakdown products of glucose from glycolysis and a precursor of pyruvate
What is ribose?
A pentose sugar important for forming the backbone of RNA molecules
What is glucose?
A hexose sugar which functions as the principle source of the cell’s energy
What is a disaccharide?
2 monosaccharides linked together by glycosidic bonds (lactose or sucrose)
What is an oligosaccharide?
3 or more monosaccharides linked together by glycosidic bonds
What is a polysaccharide?
100s to 1000s of monosaccharides linked together by glycosidic bonds (glycogen or starch)
What is glycogen? What is its function?
Branched alpha glucose polymer.
Major storage polysaccharide in animal cells
What is starch? What is its function?
Branched or unbranched alpha glucose polymer.
Major storage polysaccharide in plants.
What is cellulose? What is its function?
Unbranched polymer of beta glucose molecules.
Structural component component of plant cell walls.
What is chitin? What is its function?
Unbranched polymer of beta glucose molecules.
Structural component of fungal cell walls and the exoskeletons of crabs and insects.
What is the function of lipids? What are they a major component of?
Lipids provide energy storage and play a role in cell signalling and cell recognition.
Major component of cell membranes.
What is the structure of fatty acids?
Fatty acids consist of long hydrocarbon chains. The bonds between carbon and hydrogen are non-polar, resulting in fatty acids being hydrophobic.
What is the structure of triacyglycerols? What is their purpose?
Consist of three fatty acids linked to a glycerol molecule. Not soluble in water.
Store fatty acids.
What are phospholipids? What do they do?
Consist of two fatty acids joined to a polar head group, and a hydrophobic tail.
Amphipathic. Principal components of cell membranes.
What is the function of glycolipids?
Help facilitate cell stability and cellular recognition.
What are steroid hormones? What do they do?
Steroid hormones are derivatives of cholesterol and act as signalling molecules both with and between cells.
What is deoxyribonucleic acid? Where is it located?
DNA is the genetic molecule of the cell and is located in the nucleus of eukaryote cells.
What does messenger RNA do?
Carries information from DNA to the ribosomes.
What are ribosomal and transfer RNA involved in?
Protein synthesis.
What is the structure of DNA and RNA?
Polymers of nucleotides, which consist of purine and pyrimidine bases linked to phosphorylated sugars.
What is the function of purine and pyrimidine bases?
Provide the identity to nucleotides of DNA and RNA that are critical for base-pairing and the genetic code.
What are nucleosides?
A nitrogenous base linked to the ribose or deoxyribose sugar.
What are nucleotides?
Contain the phosphate group and are the basic building blocks of RNA and DNA
Where do phosphodiester bonds form?
Between the 5’ phosphate of one nucleotide and the 3’ hydroxyl on the sugar of another.
What joins amino acids together?
Peptide bonds
What are polypeptides?
Linear chains of amino acids
What is the primary protein structure?
The linear sequence of amino acids in the protein’s polypeptide chain.
What is the secondary protein structure? What are 2 types of secondary structures?
The regular arrangement of amino acids within localized regions of the polypeptide.
An alpha helix and a beta sheet are two types of secondary structures/
What is the tertiary structure of proteins?
The third level which consists of the folding of the polypeptide chain as a result of interactions between the side chains of amino acids that lie in different regions of the primary sequence.
What are tertiary structures stabilized by?
- hydrophobic interactions with proteins
- hydrophilic interactions on the surface of the protein
- disulphide bonds between cysteine residues
What is the quarternary structure of proteins?
The fourth level which consists of the interactions between different polypeptide chains in proteins composed of more than one polypeptide.
What is the structural organization of the cell membrane?
Bilayer of amphipathic phospholipids with associated proteins and other specialized proteins.
How do lipid bilayers behave?
As dynamic, two-dimensional fluids in which individual molecules are free to rotate and move in lateral directions.
What characteristics of lipids determine membrane fluidity?
- membranes with short chain fatty acids are less rigid
- unsaturated fatty chains increase membrane fluidity
- cholesterol makes the membrane less fluid at the region where it is inserted
What do channel proteins do?
Form open pores through the membrane, allowing free passage of any molecule of the appropriate size and structure
What do carrier proteins do?
Selectively bind and transport specific small molecules, such as glucose
What is passive transport?
A process where molecules are transported by either channel or carrier proteins across membranes in the energetically favourable direction
What is active transport?
A process where molecules are transported in an energetically unfavourable direction (against the concentration gradient) across a membrane if their transport is coupled to ATP hydrolysis as a source of energy
