Unit 1: Cell Biology Flashcards
Cell Theory
- Most basic form of life
- Make up all living things
- Cells must come from preexisting cells
Macromolecules
- Polysaccharides (sugars) (polymers)
- Lipids (not true polymers but can be large molecules)
- Nucleic acids (DNA, RNA) - polymers
- Proteins - polymers
Polymer
A long molecule consisting of many similar or identical building blocks known as monomers
How do polymers grow and disassemble
- Grow by dehydration synthesis
- Disassemble by hydrolysis
Polysaccharides
- Macromolecules, consisting of a few hundred or thousand monosaccharides joined by glycosidic linkages
- Serve as fuel and as building material, based on the monomer of glucose
Disaccharide
Consists of two monosaccharides joined by a glycosidic linkage (by losing water)
Storage polysaccharides
- Animals store sugars in the form of glycogen, most in the muscles, gets assembled from glucose monomers in the liver
- Plants store sugars in the form of starch
Types of starch
- amylopectin (somewhat branched)
- amylose (unbranched)
Structural polysaccharides
- Cellulose in plants
- Chitin in exoskeletons of arthropods
Lipids
- A diverse group of hydrophobic molecule
- Components of cell membranes
- Lipids are fats , phospholipids and steroids
Fatty acid
- Has a long carbon skeleton, usually 16 or 18 carbon atoms in length
- Carbon at one end in part of a carboxyl group (acid), the rest of the skeleton consists of a hydrocarbon chain
Triglycerides
Three fatty acid molecules joined to a glycerol with an ester linkage
Phospholipids
- Two fatty acids attached to a glycerol
- The third hydroxyl group of the glycerol is joined to a phosphate groups
- Some are kinked some are not, based on the double bond
- Heads are hydrophilic, tails are hydrophobic
- Extra molecules in the phospholipid head, length and saturation of fatty acid tails can change
Steroids
Lipids characterized by a carbon skeleton consisting of four fused rings
Proteins
- Polymers of amino acids
- A wide range of structures, resulting in a wide range of functions
- Everything in a cell is mediated by proteins
- Account for more than 50% of the cell’s dry mass
Purposes of Proteins (8)
- Enzymatic proteins accelerate specific chemical reactions
- Antibodies are proteins that protect against disease
- Storage proteins serve as a source of amino acids (ex. Casein, milk protein)
- Proteins mediate the selective transport of substances (ex. Hemoglobin transports oxygen from lungs to other body parts)
- Hormonal proteins coordinate an organisms’ activities (ex. insulin)
- Receptor proteins are responsible for the response of the cell to chemical stimuli
- Contractile and motor proteins are responsible for movement
- Structural proteins offer support (keratin)
Amino acid
- An organic molecule with both an amino group and a carboxyl group
- 20 amino acids, all with different physical and chemical properties
- The covalent bond between two amino acids in called a peptide bonds
Protein Structure
- Primary structure: The sequence of amino acids
- Secondary structure: The regions stabilized by hydrogen bonds between atoms of a polypeptide backbone (alpha helix or beta pleated sheets)
- Tertiary structure: The overall shape of a polypeptide resulting from interactions between the various amino acids
- Quaternary structure: Refers to protein complexes, where two or more polypeptides chains (subunits) aggregate into one functional macromolecule. It describes the way in which these polypeptide chains aggregate.
Heme
An iron containing molecule bound to hemoglobin and some other biological molecules
Nucleic acids
- Store, transmit and help express hereditary information
- DNA and RNA
- Polymers are called polynucleotides, monomers are called nucleotides
Nucleotide
- Monomer of a polynucleotides
- Composed of 3 parts: nitrogenous base, a five carbon sugar, and one phosphate group
DNA vs RNA
- DNA: Deoxyribose sugar (lacks an oxygen on the second carbon), Thymine
- RNA: Ribose sugar, Uracil replaces Thymine
Nitrogenous bases
- Pyrimidines: (Cytosine, Thymine, Uracil)
- Purines: (Guanine, Adenine)
- Guanine binds with Cytosine, Adenine binds with Thymine)
DNA molecule structure
- DNA molecules have two polynucleotides, or “strands” that wind around an imaginary axis, forming a double helix.
- The two phosphate backbones run in opposite 5’-3’ directions from each other (antiparallel)
RNA molecule structure
- RNA molecules exist as single strands
- Complementary base pairing occurs between two stretches of nucleotides in the same RNA molecule
What contains DNA? (eukaryotes)
The nucleus, the mitochondria, and the chloroplast
Prokaryote vs Eukaryote
- Eukaryotic cells have internal membranes that compartmentalize their functions, have a nucleus that contains DNA
- A prokaryotic cell lacks a true nucleus and the other membrane-enclosed organelles
Parts of a prokaryotic cell (7)
- Fimbriae: Attachment structures on the surface of some prokaryotes
- Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane)
- Ribosomes: Complexes that synthesize proteins
- Plasma membrane: membrane enclosing cytoplasm
- Cell wall: Rigid structure outside the plasma membrane
- Glycocalyx: Outer coating of many prokaryotes, consisting of a capsule or a slime layer
- Flagella: Locomotion organelles of some prokaryotes
Fluid Mosaic Model
The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids
Nuclear pores
Nuclear pores made by the nuclear pore complex regulate the entry and exit of proteins and RNAs, as well as large complexes of macromolecules
Nucleolus
- The nucleolus is where a type of RNA called ribosomal RNA (rRNA) is synthesized
Ribosomes
Complexes made of ribosomal RNAs and proteins that carry out protein synthesis
Free Ribosomes vs Bound Ribosomes
Ribosomes build proteins in two cytoplasmic locales:
1. Free ribosomes are suspended in the cytosol (most proteins made by free ribosomes function within the cytosol)
2. Bound ribosomes are attached to the outside of the endoplasmic reticulum or nuclear envelope (most proteins made by bound ribosomes are membrane proteins and secreted proteins)