Knes 323 Midterm

What is homeostasis?

- condition of equilibrium in the body's internal environment

- maintained by the body's regulatory processes

what must the control system do to maintain homeostasis?

- detect deviations from normal in the internal environment that need to be held within narrow limits

- integrate this information with other relevant information

- make appropriate adjustments to restore a factor to its desired value

what is the set point in homeostasis?

- normal range for a given system

- monitored by the control centre for that particular system

What is a circadian rhythm?

- the biological clock; regular bodily rhythms that occur on a 24-hour cycle

- allows organisms to adapt to a fluctuating environment

what are intrinsic controls?

local controls that are inherent in an organ

what are extrinsic controls?

- regulatory mechanisms initiated outside an organ

- accomplished by nervous and endocrine systems

What are feedback loops?

responses made after a change, can be negative or positive

what are feedforward loops?

responses made in anticipation of a change

ex: saliva production prior to eating prepares for the breakdown of carbohydrates

occurs through central command

What are components of a feedback loop?

1. stimulus

2. controlled condition

3. receptors

4. control center

5. effectors

6. response

7. return to homeostasis

what is a negative feedback loop?

- primary type of homeostasis control

- main goal is to keep the internal environment stable

what are examples of negative feedback loops?

- calcium levels in the blood

- body temperature

- glucagon and insulin in the blood

what are positive feedback loops?

- amplifies an initial change and therefore does not truly contribute to homeostasis, instead it disrupts it

- does not occur as often as negative

- response reinforces the stimulus like a snowball effect

what are examples of positive feedback loops?

childbirth and blood clotting

what is a disorder?

any abnormality of structure or function

what is a disease?

illness characterized by a recognizable set of signs and symptoms

What are macromolecules?

- large molecules necessary for life that are built from smaller organic molecules

- made up from polymers

what are polymers?

- long molecules made up of similar building blocks of smaller molecules

- most can be broken down through hydrolysis

- lipids are broken down through lipolysis

what are carbohydrates?

- 2:1 hydrogen, oxygen ratio

- enables configurations that are useful for digestion and fuel sources

what are the three main types of carbohydrates?

monosaccharides, disaccharides, polysaccharides

What are monosaccharides?

- simplest sugars (1)

- cannot be broken down by hydrolysis into smaller molecules

- readily used as fuel sources

what are dietary monosaccharides?

- glucose, fructose, galactose

- are readily absorbed by the small intestine

what is glucose?

- important energy source

- used to make ATP

What is fructose?

- naturally occurring

- used to aid in glycolysis

- helps replenish liver glycogen stores

What are disaccharides?

- sucrose, lactose, maltose

- two monosaccharides are joined together

- one is always glucose

what is sucrose?

- most common dietary disaccharide and makes up to 25% of calories consumed

- occurs naturally

- in most foods containing carbs

what is lactose?

- only natural source is from milk and milk sugar products

- not found in plants

- is the least sweet of the main three

what is maltose?

- made form two glucose molecules

- found in beer, breakfast cereals, germinating seeds etc.

- small portion of total carb intake

What are polysaccharides?

- large macromolecules formed from monosaccharides

- branched or unbranched

what are the two forms of starch ?

amylose: long, straight chains that are twisted to form helical coils, so tightly packed it's slow to breakdown

amylopectin: highly branched glucose, fast to breakdown because of its accessibility for hydrolysis

what is glycogen?

- storage form of carbohydrates within animals

- highly branched, fast to breakdown

- converted to glucose via glycogenesis

what is cellulose?

- most abundant naturally occurring polysaccharide

- found in plant walls and provides structural support to the cell

- made of long-straight chains which provide plant cells with their rigidity

- very hard to breakdown

what is chitin?

- found in the exoskeleton of arthropods

- provides structural support to the cell

- made of long-straight chains

- can be made into flexible surgical thread that decomposes over time

what are the essential functions of proteins?

- catalyzing chemical reactions

- synthesizing and repairing DNA

- transporting materials across the cell

- receiving and sending chemical signals

- responding to stimuli

- providing structural support

What are proteins?

- polymers of specific amino acid sequences that form peptide chains

- function depends on shape

- any small change will result in a dysfunctional cell

What are enzymes?

- proteins that catalyze biochemical reactions, that would not take place otherwise

- essential for chemical processes

what are the two types of enzymes?

anabolic: build more complex molecules from their substrates

catabolic: breakdown their substrate

what are the enzymes essential for digestion?

- amylase: digestion carbohydrates in the mouth and small intestine

- pepsin: digestion of proteins in the stomach

- lipase: emulsify fats in the small intestine

- trypsin: further digestion of proteins in the small intestine

what are hormones?

- proteins that are secreted by endocrine cells and act to control or regulate specific physiological processes

- others act as receptors to detect concentrations of chemicals and send signals to respond

- some are lipid steroids (helps with communication)

what is insulin?

regulates blood glucose levels

what are lipids?

- fats, oils, waxes etc found in our bodies

- made from carbon, hydrogen and oxygen

- majority are non-polar (do not dissolve in water), instead transported via lipoproteins

- mainly used for energy storage and structure

what are saturated fatty acids?

- maximal number of hydrogen atoms possible for the structure

- no double bonds

- tend to be a solid at room temp

ex. butter

What are unsaturated fatty acids?

- have one or more double bonds

- usually of plant origin and contain cis fatty acids

- form liquids at room temp

ex. oil

What are phospholipids?

- components of the plasma membrane

- composed of fatty acid chains attached to a glycerol backbone

- two fatty acids: uncharged, tail is non-polar and hydrophobic (between phospholipid bilayer)

- phosphate group: negative, head is polar and hydrophilic (water loving) (toward inside of cell or outside of cell)

what is the phospholipid bilayer?

- acts as a semipermeable membrane

- only lipophilic solutes can easily pass the bilayer

what are steroids?

- play roles in reproduction, absorption, metabolism regulation and brain activity

- all have four linked carbon rings

- grouped with lipids because they are hydrophobic and insoluble in water

what is cholesterol?

- most common steroid

- synthesized in the liver

- precursor to vitamin D, steroid hormones like estrogen, testosterone and progesterone, plays a role in synthesizing aldosterone, which is used for osmoregulation

- contributes to the formation of cortisol, which plays a role in metabolism

How is energy intake calculated?

internal heat produced+external work+internal work+energy storage

what is the law of thermodynamics?

- energy cannot be created or destroyed, it can only be shifted from one form to another

- there is a balance between energy input and energy output

what is energy input?

- energy in ingested food

- cells capture portion in high-energy bonds of ATP

What is energy output?

- external work

- energy expended when skeletal muscles are contracted to move external objects or to move body in relation to the environment

- energy from nutrients that is not used to perform work, transformed into thermal energy or heat

What is internal work?

- all other forms of biological energy expenditure that do not accomplish mechanical work outside the body

- skeletal muscle activity used for purposes other than external work (postural maintenance contractions, shivering)

- all the energy-expending activities that go on continuously just to sustain life

what are the three states of energy balance?

- neutral energy balance: energy input = energy output, body weight remains constant

- positive energy balance: energy input is greater than energy output, energy not used is stored primarily as adipose, body weight increases

- negative energy balance: energy input is less than energy output, body must use stored energy to supply energy needs, body weight decreases

how to calculate metabolic rate?

energy expenditure/unit of time

What is basal metabolic rate?

minimal internal energy expenditure we need to maintain in order to meet the basic physiological functions in our body

what influences metabolic rate?

- thyroid stimulating hormone

- sympathetic stimulation: epinephrine/norepinephrine

- exercise

- daily activities

- sex/gender

- age

What is metabolism?

- set of life-sustaining chemical processes that enables organisms to transform the chemical energy stored in molecules into energy that can be used for cellular processes

- breaks down carbs, lipids, proteins and nucleic acids

what is exothermic?

energy is released from a reaction

what is endothermic?

energy is needed to continue a reaction

what is a competitive inhibitor?

- similar enough to a substrate that it can bind to the enzymes active site to stop it from binding with the substrate

- "competes" with the substrate

- less substrate concentration but same speed as a normal reaction

What is non-competitive inhibition?

- binds to an enzyme in a site that is not the active site (called allosteric site)

- substrate may still bind, but the inhibitor changes the shape of the enzyme so no reaction occurs

- less of a reaction rate

what are allosteric activators?

- increase reaction rate

- bind to allosteric site and induces a conformational change that increases the affinity of the enzyme's active site for its substrate

What are cofactors and coenzymes?

- promotes optimal conformation and function

- most common are dietary vitamins

What is feedback inhibition?

reaction product is used to regulate its own further production

what is the most common fuel source for the body?

carbohydrates

what is sugar catabolism?

breaks polysaccharides down to their individual monosaccharides

what is the most common fuel for ATP production?

- glucose via cellular respiration

- hence why there are so many endocrine control functions to regulate glucose in the bloodstream

what is the fuel source used in beta-oxidation?

- triglycerides

- about half of the excess fat is stored under the skin

- other half is stored in other tissues and organs

What are oxidation-reduction reactions?

- important in energy transfer

- some of the energy released during oxidation reactions is captured when ATP is formed

- a phosphate group is added to ADP along with energy to form ATP

What are the steps for energy transfer?

1. catabolic reactions transfer energy from complex molecules to ATP

2. heat is released

3. simple molecules

4. anabolic reactions transfer energy from ATP to complex molecules

5. heat is released

6. complex molecules

What is glycolysis?

breakdown of glucose to pyruvate after it is absorbed across the walls of the small intestine and makes its way to the liver

What is glycogenolysis?

breakdown of glycogen to glucose when it's ready to be transported back into the blood stream after being stored in the liver

What is glycolysis?

- occurs in the cytoplasm

- 2 ATP and 2 NAD+ are used to convert 1 glucose molecule into 2 pyruvate molecules, 4 ATP and 2 NADH

which step is the all or nothing step of glycolysis?

- step three

- catalyzed by phosphofructokinase

- first committed step, PFK is a central target for allosteric regulation of the entire glycolysis pathway

- you have to put ATP back in during this step. if no ATP is available, the reaction can no longer continue

What is AMP?

- UP REGULATION

- when a cell is low on ATP, it squeezes more ATP out of ADP by converting them to ATP and AMP

- high levels of AMP means that the cell is low on energy and that glycolysis must engage quickly to replenish

What is the down regulation of glycolysis?

- ATP is a negative regulator of PFK (if there's lots of ATP in the cell, glycolysis doesn't need to make more)

- Citrate (first product of the citric acid cycle) building up is a sign that glycolysis can slow down. The citric acid cycle is backed up and doesn't need anymore fuel

how many ATP molecules are gained in the anaerobic pathway?

2

what happens to RBCs if glycolysis is interrupted?

- RBCs are not capable of aerobic processes

- glycolysis is the only way for them to produce ATP

- lose their ability to maintain their sodium potassium pumps and eventually they die

what is the Krebs cycle?

- second stage of cellular respiration

- pyruvate molecules from the end of glycolysis are transported into the mitochondria (site of oxidative cellular respiration)

- pyruvate is transformed into acetyl CoA (mainly used to deliver the acetyl group derived from pyruvate to the next stage of the pathway)

- take place in the matrix of the mitochondria

- closed loop series

- CO2 is produced as the cycle progresses

what is produced in the Krebs cycle (1 glucose molecule)?

2 ATP, 8 NADH, 2 FADH2, CO2

what is the electron transport chain?

- where the bulk of ATP is produced in cellular respiration

- only section of glucose metabolism that uses atmospheric oxygen

- four redox reactions that enable electrons to be rapidly passed from one component to the next

- protons expelled into the intermembrane space from the ETC are used to form ATP through chemiosmosis

What is chemiosmosis?

- pumping of protons through special channels in the membranes of mitochondria from the inner to the outer compartment

- protons diffuse down the established gradient through a transport protein called ATP synthase

- flow of protons catalyze the pairing of a phosphate with ADP, forming ATP

what is the net yield from all three cycles of glucose metabolism?

4 ATP

30 ATP (from 10 NADH)

4 ATP (from 2 FADH2)

=38 ATP from one glucose molecule

what is the actual net yield of ATP in a real world?

30-32 ATP/1 glucose

What is fermentation?

- deoxidizing NADH to NAD+ for reuse as an electron carrier in the glycolytic pathway so it can continue

- occurs when oxygen is not present

- lactic acid fermentation

- occurs in muscles used to the point of fatigue

- lactate accumulation is removed via circulatory system and metabolized in the liver

what is lipolysis?

- triglycerides are broken down by hydrolysis into fatty acids and glycerol

- occurs in the cytoplasm

- fatty acids are oxidized by beta-oxidation into acetyl-CoA, which is used by the Krebs cycle (skipping glycolysis)

Can protein be used as a fuel source?

- yes, under extreme circumstances like starvation

- last choice possible

- AA enter cellular respiration at the pyruvate/acetyl CoA or TCA cycle stages

- proteins are better used to build muscle in the body

what are examples of exocrine glands?

mucous, sweat, oil, and salivary glands

What is the endocrine system?

releases slower acting hormones into the blood stream or interstitial fluid

what are hormones called that act on neighbouring cells?

paracrine

what are hormones that act on the same cell that secreted them?

autocrine

What are lipid soluble hormones?

- steroid hormones, thyroid hormones, nitric oxide

- circulate bound to transport proteins

- diffuse across plasma membrane

- bind to receptors within target cells

- activate genes to allow ribosomes to synthesize specific proteins

What are water soluble hormones?

- amine hormones, peptide and protein hormones, eicosanoid hormones

- circulate freely in the plasma

- bind to receptors on the exterior of the cell

- activates a secondary messenger to phosphorylate cellular proteins

What does phosphorylation do?

- either activates (excitatory) or inactivates (inhibitory)

- when activated, results in the production of proteins through a chain reaction

what is up regulated?

become more sensitive in low concentrations of hormone

what is down regulated?

become less sensitive in high concentrations of hormone

What is a synergistic effect?

hormones work together to produce greater effect

what is an antagonistic effect?

hormones act in opposition of one another

how is hormone secretion regulated?

- chemical changes in the body

- signals from the nervous system

- other hormones that signal

- rely on feedback systems

what hormones does the hypothalamus release?

-thyrotropin-releasing hormone

-growth hormone-releasing hormone

-gonadotropin-releasing hormone

-corticotropin-releasing hormone

-prolactin-releasing factor

- growth hormone inhibiting hormone

- prolactin inhibiting hormone (dopamine)

what is secreted by somatotrophs in the anterior pituitary?

human growth hormone