ib biology enzymes, metabolism , digestion

levels of biological organization (5)

cells - tissues - organs - organ systems - organism

importance of enzymes to human digestion (5)

• chemically break down food to make small enough (monomers) to enter bloodstream

• increase digestion rate

• biological catalyst that can be used

• operate optimally at body temperature

• highly specific conditions for each reaction

*endonuclease is the enzyme for nucleic acids to nucleotides

exocytosis

The process by which large substances (or bulk amounts of small substances) exit the cell without crossing the membrane (requires ATP)

• Vesicles (typically derived from the Golgi) fuse with the plasma membrane, expelling their contents into the extracellular environment

• The process of exocytosis adds vesicular phospholipids to the cell membrane, replacing those lost when vesicles are formed via endocytosis

endocytosis (2)

The process by which large substances (or bulk amounts of smaller substances) enter the cell without crossing the membrane

• An invagination of the membrane envelopes the extracellular material which is then sealed off to form an intracellular vesicle containing the material

  There are two main types of endocytosis:

• Phagocytosis – The process by which solid substances are ingested

• Pinocytosis – The process by which liquids / dissolved substances are ingested (allows faster entry than via protein channels) 

denaturation

• unfolding or breaking up of a protein which alters its 3d structure and inhibits its function

metabolism

sum of all biochemical reactions inside a cell (CATABOLISM + ANABOLISM)

catabolic and anabolic pathways intersect at certain points so energy released in cata can assist in ana pathways (ENERGY COUPLING via cleaving a phosphate from ATP so it turns into ADP, cycle repeat)

advantages of having several small metabolic pathways over one large pathway

1. energy can be harvested quick and in small amounts

2. one pathway can lead to many others so many simultaneous reactions can occur

   *metabolic rxns not 100% efficient, stuff is lost to heat (needed in warmbl animals)

2 types of metabolic pathways

1. catabolic: polymers broken into monomers (simpler) via hydrolysis

   • reactions are downhill (exothermic)

   • energy RELEASEd (exo) eg. starch to glucose molecules

2. anabolic: simple molecules built into complex molecules via synthesis or condensation reactions

   • synthetic/uphill reactions (endothermic, stuff is made from small stuff)

   • energy is REQUIRED (ENDO) eg. aa’s to proteins

catabolic/anabolic rxns ib wants u to know

CATABOLIC:

• polymers (hydrolysis, water is consumed) turn to monomers

• glucose to ATP and H2O

ANABOLIC:

• monomers (condensation - produce water) turn into poly

• glucose to glycogen

• photosynthesis

ENZYME (4)

• globular proteins that serve as biological catalysts to speed up chemical reactions

• reusable, so needed in low amounts

• found in all living cells and also secreted outside cells

• have active site that substrate binds to (bring substrates of a reaction together to make into products)

active site

The region on the surface of the enzyme to which a substrate molecule binds. composed of a few aa’s to ensure shape and chem. properties of the active site complement the substrate

how do enzymes spd up rate of biochemical rxn

by lowering the activation energy (by ensuring optimal orientation rate for collision), meaning less energy is needed to convert the substrate into a product and the reaction proceeds at a faster rate

activation energy

energy required to reach transition state (where bonds are broken and weakened in the substrate)

process of enzyme catalyzing reaction

• S binds to active site which lowers activation energy and allows it to easily reach trans state

• then converted into product

• binding of S to enzyme LOWERS the energy required to reach energy reaction THEREFORE RATE OF REACTION (via collisons) INCREASES

key properties allowing enzymes to work effectively

• 1 enzyme for 1 substrate (exception of induced fit model)

• lower activation energy

• reusable

• function under specific conditions like pH and temp. can denature if outside range

Metabolism in ATP (2)

• atp converted to adp as 3rd phosphate is broken to release energy

• when adp needs to be converted back to atp, enzume places the adp and phosphate together to make conversion more likely

induced fit model (koshland) (3)

• binding of S to AS causes conformational change in both which weakens bonds in S to lower activation energy and catalyze rxn

• shape of AS and S are complimentary, not exact fit so AS returns to original shape after rxn (reverse conformational change)

• this explains why some enzymes can catalyze many diff reactions

lock and key model - fischer (3)

each enzyme works for only 1 substrate

• 3d shape and chemical properties of AS fit exactly with S

• should work with reverse rxn in that the same enzyme should break down a molecule into parts

3 possible scenarios for enzyme/substrate collisions

1. stationary Substrate, enz moves (eg. dna replication)

2. enzyme is stationary and Substrate moves (eg. ATP synthase which is embedded in cell membrane)

3. Enzyme and substrate can both move (most cellular reactions, often dissolved)

two shapes of proteins

1. fibrous - insoluble in water, eg. keratin and collagen

2. globular (enzymes!)- water soluble which are rounded and compact

function/charactistics of life: MR SHENG

1. metabolism - sum of all essential biochm rxns

2. reproduction - offspring via asexual or sexual

3. sensitivity/stimuli - Living things are responsive to internal and external stimuli

4. homeostasis - constant internal environment (negative feedback)

5. excretion - remove waste product of metabolism

6. nutrition - required for energy, growth, repair

7. growth - increase in size and number of cells

homeostasis (4)

• internal environment stays consstant such as body temp

• all systems aim to maintain homeostasis

• controlled by hormones (endocrine) but ultimately nervous system

• centers in the brain regulate temperature and sends message to glands to cancel the stimulus and retrun to homeostasis if a stimulus is bringing it out - negative feedback!!!

peristalsis

• principal mechanism of movement in the esophagus, also occurs in both the stomach and gut

• Continuous segments of longitudinal smooth muscle rhythmically contract and relax

• Food is moved unidirectionally along the alimentary canal (mouth to anus)

pancreatic juice contains: (2) (3)

1. sodium bicarbonate - basic to neutralize acid chyme excreted by stomach

2. hydrolytic enzymes to break down things to simpler molecules

   • pancreatic amylase: starch to maltose/dextrin then glucose

   • trypsin: protein to peptides

   • lipase: fat droplets to glycerol and fatty acids

what happens to the maltosse/dextrin after being broken down by pancreas (3)

• small intestine converts it to glucose.

• After glucose is formed, it is absorbed through the walls of the small intestine and enters the bloodstream. Glucose in the bloodstream travels to the liver

• In the liver, glucose can be stored as glycogen for later use, or it can be released into the bloodstream to provide energy to other tissues depending on bodily needs

glandular cell types of epithelial tissue (2)

1. exocrine - secretes product into ducts

2. endocrine - secretes product into bloodstreams

*the pancreas is both exo/endo; secrete insulin to blood and juice to small intestine via ducts

vomiting

reverse peristaltic wave causes sphincter to relax and stomach contents to barf out

cardiac sphincter

prevents food from moving out stomach into the esophagus

cells

contain various organelles responsible for various functions

tissue types (4)

layers or groups of similar cells performing common function

• epithelial

• connective

• muscular

• nervous

organ

2 or more tissue types performing a specific function

system

contains various organs having similar or related functions (one organ can function in multiple systems)

what responds to internal/external stimuli (3)

• internal: endocrine (hormones) or nervous

• external response to environment: behaviour

development/growth

all changes from conception to death

reproduction (3)

• unicellular organisms usually reproduce asexually by binary fission

• humans reproduce sexually via mitosis

• human cells reproduce asexually by mitosis

villus

fingerlike projections that increase SA in small intestine, covered in microvilli to further increase SA

microvilli on villus

increases SA of membrane, embedded (stationary enzyme!!!) with digestive enzymes like peptidase (break down peptides) and channel proteins/protein pumps to help mineral uptake

liver + responsibilities (3)

accessory organ that produces bile and contains emulsifying agents (break apart fat droplets to increase SA so lipases can digest it)

• store glycogen + convert glucose to glycogen

• metabolism of carbs, fats, proteins

enteric nervous system

• Function of the ENS:

  • The ENS monitors conditions in the GI tract, such as pH levels, chemical composition of food, and stretch of the gut wall.

  • It integrates sensory information from the gut and sends signals to control muscle contraction, secretion of digestive enzymes, and blood flow to the digestive organs.

  3. Peristalsis and How the ENS Controls It:

  • Sensory Neurons: The ENS contains sensory neurons that detect the presence of food or chyme (partially digested food) in the digestive tract.

  • Motor Neurons: smooth muscle cells in the walls of the intestines, causing two main actions:

    • Contraction Behind the Food:

    • Relaxation in Front of the Food:

  • Coordination of Contractions: This alternating contraction and relaxation of muscles create the characteristic wave-like motion of peristalsis, propelling food through the digestive tract.

features of epithelial villi lining (4)

Tight Junctions
Microvilli

• allowing for more absorption to occur

• The membrane will be embedded with immobilised digestive enzymes and channel proteins to assist in material uptake 

Mitochondria

• Epithelial cells of intestinal villi will possess large numbers of mitochondria to provide ATP for active transport mechanisms

Pinocytotic Vesicles

• Pinocytosis (‘cell-drinking’) is the non-specific uptake of fluids and dissolved solutes