cellular metabolism - chapter 4

metabolism

sum of all chemical reactions in the body

cellular metabolism

sum of all chemical reactions occurring in a cell

anabolism

small molecules are built into large ones; requires energy

catabolism

larger molecules are broken down into smaller ones; releases energy

dehydration synthesis

smaller molecules are bound together to for larger ones; h2O produced in the process; used to produce poly saccharides, proteins, and triglycerides; example of anabolism

hydrolysis

used to decompose carbohydrates, proteins, and lipids; uses h2O to split the substances; reverse dehydration synthesis; example of catabolism

enzymes

control rates of both catholic and anabolic reactions; greatly increase reaction rates

enzymes (protein catalysts)

• Increase rates of chemical reactions
  • Lower the activation energy necessary to start reactions
  Not consumed in the reaction, so are used repeatedly
  • Each enzyme is specific to a particular substrate
  • Ability to recognize substrate depends on shape of active
  site of enzyme

cofactor

non-protein substance that combines with the enzymes to activate it

• help bind enzyme to substrate

• can be ion, element, or small organic molecule

coenzyme

organic molecule that acts as cofactor

• most are vitamins, which are essential organic molecules that humans must get from their diet

cellular respiration

process that transfers energy from molecules, and makes it available for cellular use

atp (adenosine triphosphate)

molecule that carries energy in a form the cell can use; main energy carrying molecule in a cell; energy from atp breakdown is used for cellular work

atp 3 portions

adenine, ribose, 3 phosphates

2nd and 3rd phosphate are attached by

high energy bonds

when atp loses last phosphate it becomes

adenosine dephosphate (adp)

when adp can be converted back into atp by attaching a 3rd phosphate

phosphorylation (requires energy from cellular respiration)

cellular respiration of glucose occurs in 3 interconnected
reaction sequences

glycolysis , citric acid cycle , electron transport chain

occurs in a metabolic cycle in which the final product reacts to replenish original substrate

citric acid cycles

anaerobic reaction

do not require O2, makes little atp

aerobic reaction

requires O2; make most of ATP

glycolysis

break down of glucose into 2 smaller molecules; anaerobic, occurs in cytosol

glycogen

the stored form of glucose

glycogenolysis

glycogen is broken down into glucose to provide immediate energy

glycogenesis

the process of synthesizing glycogen from glucose

dna

the genetic material; molecule that stores information on its sequence of nucleotides, that instructs a cell to how synthesize certain protein

genetic information

instructions to tell cells how to construct proteins; stored in dan sequence

gene

sequence of DNA that contains information for making 1 protein

genome

complete set of genetic information in a cell

exome

small portion of the genome that codes of proteins

gene expression

control of which proteins are produced in each cell type

nucleotides consist of

5-carbon sugar, deoxyribose; a phosphate group; a nitrogenous base (adenine, cytosine, guanine, or thymine)

dna structure

bases from the 2 complementary strands are linked together by hydrogen bonds; double stranded; 

adenine pairs with (dna)

thymine

cytosine pairs with (dna)

guanine

dna replication

process that produces an exact copy of a DNA
molecule; occurs during interphase

rna differs from dna in following ways:

• single strand of nucleotides
• contains the sugar, ribose,
instead of deoxyribose
• contains uracil
• much shorter than dna

transcription

dna → mrna

mrna

carries genetic code from DNA to ribosome in cytoplasm

rna polymerase

enzyme that catalyzes the formation of mRNA from the proper strand of DNA

codon

a sequence of three bases on an mRNA molecule.

start codon

AUG codes for methionine, and begins
the amino acid sequence of the protein

stop codons

UAG, UGA, and UAA: signal “end of
message,”

translation

mrna → protein

steps of translation

1. mRNA leaves nucleus and binds to ribosome, to act as template for protein synthesis

2. tRNA brings amino acids

3. The ribosome helps the codon (on mRNA) and anticodon (on tRNA) pair up correctly

4. Each time a new tRNA brings an amino acid, the ribosome links it to the growing chain

5. When the ribosome reaches a stop codon (UAA, UAG, or UGA), translation ends

translation occurs in the 

cytoplasm (ribosome)

transcription occurs in the

nucleus