Bio104- Chapter 4

exam 9/26

What does life depend on?

chemistry

Why do we eat?

we need energy and nutrients

Why we need energy

we require calories from food to produce ATP to power all of the biochemical functions of our cells

Energy functions

• Growing- adding new cells to our bodies

• Repairing/replacing proteins or cells

• Powering the expansion and contraction of our muscles

• Powering the electrical signals in our brains

Why we need nutrients

we require raw materials to make/repair our cells

Nutrient functions

• Building new cells

  • Membrane

  • DNA

  • Proteins/enzymes

  • Organelles

• Repairing/replacing proteins or parts of cells

The molecules that make up our food can provide either:

• energy: by being broken down and metabolized

• building blocks: being used to synthesize new structures

Apple

• collection of plant cells

• each cell contains a nucleus full of DNA, organelles, sugars, proteins, etc

• By eating, we break down THEIR structures and molecules for energy and their component parts

• then we use each to build and power OUR cells

What does an organic molecule contain?

• carbon and hydrogen

• also contain nitrogen, oxygen, phosphorus, and sulfur

Functional groups of organic molecules

• hydroxyl

• carboxyl

• amino

• phosphate

4 groups of organic molecules

• carbohydrates

• proteins

• lipids

• nucleic acids

Which organic molecules are in our food?

carbohydrates, proteins, and lipids (fats)

What important resources does food contain?

1. potential energy stored in the chemical bonds of our food molecules such as carbohydrates, proteins, and lipids are used in respiration to generate ATP

2. chemical building blocks are used to build the animal’s body - including simple sugars, fatty acids, amino acids, nucleotides, water, vitamins, and minerals

Monomers

a single unit of a carbohydrate, protein, or nucleic acid

Polymers

formed by repeating units of monomers

Dehydration synthesis (carbohydrates)

• a type of chemical reaction where a water molecule is lost

• to synthesize a polymer, enzymes form bonds between 2 monomers

• as part of the reaction, a water molecule is released

Hydrolysis (carbohydrates)

• a type of chemical reaction that breaks polymers apart

• to “digest” or break down a polymer, enzymes break bonds between the monomers

• a water molecule is required for the reaction to occur

Carbohydrates

• include simple sugars

• simple sugars are contained in plant cells and dissolve in water

Monosaccharides

• simple sugars

• they are the monomers that make up larger carbohydrates

• by connection sugar monomers together- larger polysaccharides can be made

Enzyme mediated chemical reactions

the process of linking monosaccharides together and breaking them apart

Polysaccharides

• long chains of carbohydrates

• larger chains of carbohydrates create branched and cross-linked structures

• these structures can be used to store energy- or as physical structures of the living body

Cellulose

plant cell wall structure

starch

stored energy in a potato

glycogen

stored energy in the liver

chitin

crustacean and insect exoskeletons

Where are carbohydrates in our diet?

• bread

• pasta

• fruit

• nuts

• sugar

Proteins

• the “molecular toolkit” for the cell

• chemical reactions that take place in the cell are most often mediated by proteins we call enzymes

• variety is endless

Proteins have many different structures and functions

• “workers” of cells

• create cellular structures

• produce muscle contractions

• make up enzymes and membrane transport sytems

Amino acids

• monomers of proteins

• 20 different amino acids

• have the same general structure

• soluble in water

Dehydration synthesis (proteins)

binds 2 amino acids together, forming a dipeptide

Polypeptide

long chain of amino acids

Hydrolysis (proteins)

separates dipeptides and polypeptides into individual amino acids

R groups in amino acids

• amino acids have 3 main groups, carboxyl groups, the amino group, and a radical which can change

• R groups are the radical, meaning it is the variable part of amino acids

• they determine protein structure and function

Each amino acid has its own chemical and physical properties

• the 20 different amino acids have 20 different R groups

  • some are polar, some are non-polar, some are charged

  • some are small, some are medium, some are bulky

  • these properties in turn determine the properties of the protein

Building blocks of proteins

amino acids

How are proteins linked together?

with C-N bonds forming a linear chain

What do amino acids need?

nitrogen

primary structure

amino acid sequence of polypeptide

secondary structure

localized areas of cells, sheets, and loops with a polypeptide

tertiary structure

overall shape of one polypeptide

quaternary structure

overall protein shape, arising from interaction between the multiple polypeptides that make up the functional protein

Protein function

can be altered or destroyed if cellular conditions change

Denatured

• proteins lose their shape as the interactions and bonds formed between R groups are broken

• denatured proteins do not function

Where are proteins in our diet?

found in high abundance in animal muscle tissue and in plant seeds

Essential proteins

1. histidine

2. isoleucine

3. leucine

4. lysine

5. methionine

6. phenylalanine

7. threonine

8. tryptophan

9. valine

Conditionally essential proteins

1. arginine

2. cysteine

3. glutamine

4. glycine

5. proline

6. tyrosine

Non- essential proteins

1. alanine

2. aspartic acid

3. asparagine

4. glutamic acid

5. serine

6. selenocysteine

7. pyrrolysine

Complete protein sources

• meat

• eggs

• dairy

• soy

Incomplete protein sources

• nuts

• seeds

• legumes

• vegetables

Nucleic acids

• carry genetic information

• include DNA and RNA

primary structure

determined by the linear order of nucleic acids

nucleotides

monomers of nucleic acids

3 parts of a nucleotide

phosphate group, five-carbon sugar, and a nitrogenous base

DNA and RNA both incorporate…

adenine, cytosine, and guanine

Only DNA uses…

thymine

Only RNA uses…

uracil

Dehydration synthesis (nucleic acid)

• binds 2 nucleotides together

• DNA and RNA are long chains of nucleotides

• the sugar-phosphate backbone forms each strand of DNA and RNA

Hydrolysis (nucleic acid)

separates nucleic acids into individual nucleotides

Where are nucleic acids in our diet?

DNA and RNA are living cells inside the nucleus and in the cytoplasm

Lipids

• all lipids are hydrophobic

• they have various functions in energy storage, membrane structure and fluidity, and hormones

Hydrophobic

does not dissolve in water

Unlike carbohydrates, proteins, and nucleic acids…

lipids are NOT built from chains of monomers

Triglycerides

• (fats and oils) are energy-rich

• we need them for long-term energy

• formed by covalently attaching 3 fatty acid molecules to a glycerol molecule

Steroids

• important lipid molecules

• have a 4-ring structure

Dehydration synthesis (lipids)

links the fatty acids to the glycerol, forming a triglyceride

Hydrolysis (lipids)

separates fatty acids from glycerol

Saturated fatty acid

• bonded to 4 other atoms

• contain all of the hydrogens they can

• makes the fatty acid have a straight shape

Unsaturated fatty acid

• contains at least one double bond between carbon atoms, which gives the fatty acid a bent shape (prevents from packing close together)

phospholipids

• made of a molecule of glycerol, a phosphate group, and 2 fatty acids

• compose cell membranes

The phosphate head is…

hydrophilic

Fatty acid tails are…

hydrophobic

Phospholipid bilayers

• because of their chemical structure, phospholipids spontaneously form a bilayer when they are surrounded by water

Cholesterol

regulates the fluidity of animal cell membranes; it is also used to synthesize many sex hormones

Where are lipids in our diet?

• fats act as storage molecules, and lipids make up cell membranes

• fatty tissues of animals and many plant seeds