Biochemistry for Optometrists

Biochemistry is the study of...

A. How chemicals interact to make life

B. How cells can make/use energy

C. How substances are broken down for energy

D. How new substances are formed by the cells

E. All of the above

E

What is the basic goal of biochemistry?

explain how collections of inanimate molecules that constitute living organisms interact with each other to maintain and perpetuate life

How does biochemistry relate to energy?

living organisms extract, transform, and use energy from their environment via metabolism

degradative process that liberates free energy through the breakdown of larger molecules into smaller ones

catabolism

synthetic process that requires energy to produce new substances

Ex. Making fatty acids for the lipid layer of the tears

anabolism

energy substance that links all the different pathways in biochemistry, which is useful due to its high energy phosphate bonds

ATP

biological (usually protein) catalysts used by cells to carry out many reactions

enzymes

strings of amino acids linked via peptide bonds during translation

proteins

What makes up proteins?

amino acids

How many different amino acids are there?

20

The sequence of amino acids in a protein is determined by the sequence of what other substances? (found in RNA)

ribonucleotides

What are the 4 major ribonucleotides?

adenylate, guanylate, uridylate, cytidylate

The sequence of ribonucleotides in a ribonucleic acid (RNA) is determined by the sequence of what other substances? (found in DNA)

deoxyribonucleotides

What are the 4 major deoxyribonucleotides?

Deoxyadenylate, deoxyguanylate, deoxycytidylate, deoxythymidylate

Why do optometrists care about biochemistry? (3)

pharmacology, nutrition, pathology

What are the three main components of tears?

water, lipids, proteins

Why is it important that lipids are in the outermost layer of tears?

seal off tears so they don't evaporate off the cornea

(if tears evaporate too quickly off the cornea, that can cause damage and leave a scar)

What are three types of proteins in tears?

immunoglobulins, lysozymes, mucin

Why is it important that tears have immunoglobulins and lysozymes?

immunological defense

glycoprotein that adheres the tears (via aqueous layer) to the cornea so they don't slide right off

**some people with dry eye don't have a problem with tear production; it's more so a problem of tears staying on the eye

mucin

Why is it important that tears have mucin?

adhere tears to cornea so they don't slide off

part of the eye that controls and focuses the entry of light, consists of collagen and proteoglycans to keep it clear

cornea

What makes the cornea cloudy?

when it collects water

The cornea tends to collect water, so how does it remove water so that it stays clear and refracts light properly?

ATP driven pumps

What are the two main components of the cornea?

collagen, proteoglycans

most abundant protein in the eye that provides structural support, such as in the cornea

collagen

proteins with glycosaminoglycans linked to them, which fill in the space between collagen fibers and attract water, allowing the cornea to respond to the environment (such as your eye watering to get a foreign substance out)

proteoglycans

What is the purpose of proteoglycans in the cornea?

fill in space between collagen fibers and attract water

If you ever sleep in contacts accidentally, and you wake up and your vision is a little blurry, it's because your cornea has swollen slightly due to what?

lack of oxygen

substance in the eye that provides the cornea and lens with nutrients, such as vitamin C, antioxidants, and glucose, and also helps to maintain the pressure of the eye

aqueous (humor)

What are three important components of aqueous humor?

vitamin C, antioxidants, glucose

Why is vitamin C important in aqueous humor?

collagen synthesis

Why are antioxidants important in aqueous humor?

prevent light damage to proteins

Why is glucose important in aqueous humor?

energy production

part of the eye that focuses light rays onto the retina and contains specialized proteins, including crystallins

lens

specialized proteins in the lens that are normally highly ordered and function to increase the refractive index of the lens media

crystallins

If crystallins in the lens of the eye become disordered or aggregated, what may result?

cataracts

gel-like substance in the eye that provides the lens and retina with support, contains collagen and proteoglycans (similar to the cornea), absorbs shocks to the eye, and keeps the retina properly placed

vitreous (humor)

Similar to the cornea, what are two main components of vitreous humor?

collagen, proteoglycans

part of the eye that converts light stimuli into a biological response and contains photopigments

retina

photopigment found in rod membranes that detects low light levels

rhodopsin

Is rhodopsin found in membranes of rods or cones?

rods

photopigments found in cone membranes that detect colors and sharpness of images

photopsins

Are photopsins found in membranes of rods or cones?

cones

What are the three photopsins?

erythrolabe, cyanolabe, chlorolabe

photopigment found in the photosensitive ganglion cells of the retina, which controls the pupillary light reflex, circadian rhythms, and other non-visual functions

melanopsin

derivative of vitamin A (obtained from the diet) that is used by photopigments to absorb light; triggers a conformational change in the protein, which then triggers a cellular response involved various proteins

**if you don't have enough vitamin A, you can struggle with night blindness

retinal

Retinal is a derivative of what mineral?

vitamin A