BIOG 1440 Prelim 2

What is nutrition?

it is the set of processes by which organisms obtain and use the nutrients required for maintaining life

How do autotrophs acquire their nutrients?

They do not require an organic source of carbon; they are primary producers but they also depend on other organisms for nutrients that are NOT carbon

How to heterotrophs acquire their nutrients?

They require organic compounds from other things which is mainly used for their energy; they also need to obtain vitamins 

What are photoheterotrophs and what are some examples?

They do not require carbon from other sources but they require light energy; some examples include cyanobacteria, algae, and plants

What are chemoautotrophs and what are some examples?

They do not require carbon from other sources and they do not require light energy but they obtain energy from inorganic oxidation. Some examples are extremophiles, achaea, and bacteria

What are photoheterotrophs and what are some examples?

They require carbon from other sources and also light energy. Some examples include rhodospirillum.

What are chemoheterotrophs and what are some examples?

They require carbon from other sources, no light, but get energy from inorganic oxidation; some examples include E. coli and S. aureus

What are organotrophs and what are some examples?

They require carbon from external sources and do not obtain energy from light or inorganic oxidation; some examples include bacteria, fungi, and animals 

What are the components of a plant’s diet?

energy source (light), water, carbon dioxide, and minerals

What are the components of an animal’s diet?

They need water, carbohydrates, proteins, lipids, vitamins, and minerals

How do plant roots extract ions from the soil?

The root hairs take up dissolved oxygen, ions, and water form the film of soil water that surrounds them. Anions like nitrate (NO3-) are available to plants because they are not bound to soil particles. Cations like Ca2+ AND Mg2+ adhere to soil particles and they are released by cation exchange 

How do plants increase their surface area in order to increase absorption?

Plants have fractal structures (branching to multiple levels). The root system consists in an arborization (4-5 levels) and root hairs increase a root’s absorptive surface. 

What is mycorrhizae?

It is a symbiotic relationship between fungal threads and plants which increases a plant’s absorption.

Why do organisms digest?

Food is not ingested in a suitable state so digestion includes nutrient breakdown and absorption.

What is the gastrovascular cavity and how does it digest?

Animals with simple body plants have a gastrovascular cavity, which is a two way digestive tract. This functions as both digestion and distributions of nutrients. Extracellular digestion is the breakdown of food particles outside of cells (the gut lumen is continuous with the outside of the animal’s body)

Describe the animal digestive tract

Most animals have a flow-through digestive tract with two openings (mouth, anus). Their digestive tract is regionalized (stepwise). 

What is the simple flow of food processing?

Ingestion, digestion, absorption, elimination

What does the alimentary canal consist of in the mammalian digestive tract?

Mouth, esophagus, stomach, small intestine, large intestine, and rectum

What are the accessory glands of the mammalian digestive tract?

Salivary glands, pancreas, liver, and gallbladder

How does gut length vary in animals?

Gut length varies with diet. Herbivores have longer posterior digestive tract reflecting the longer time to digest vegetation. The cecum aids in the fermentation of plant material in non-ruminants (hindgut fermenters) 

What is a monogastric digestive system and what are some examples?

It is a simple chambered stomach and some examples are humans, pigs, cats, and dogs.

What is a ruminant digestive system and what are some examples?

It is a multi-compartmented stomach and some examples are cows and deer. This system is adapted to herbivory

What is a hindgut fermentor digestive tract and what are some examples?

It has a simple, but very complex intestine. Some examples are horses and ostritches. This is also adapted to herbivory. 

What is phase 1 of human digestion? 

It is the breakdown and digestion in the oral cavity first by mechanical breakdown. Salivary glands lubricate food and secrete salivary amylase which begins the breakdown of carbohydrates. Saliva also has mucus and ends with deglutition (swallowing)

What is phase 2 of human digestion? 

The stomach stores food and secretes gastric juice which converts food bolus into chyme. Protein degradation begins and proceeds through chemical (denaturation by acidic pH) and enzymatic (pepsin). The stomach is protected by a mucus layer and bicarbonate secretion (buffer) 

Explain the production of gastric juice in the stomach

This is part of phase 2 of digestion. Pepsinogen and H+ Cl- are secreted into the lumen. HCl denatures proteins and converts proenzyme (zymogen) pepsinogen to active enzyme pepsin. Pepsin then activates more pepsinogen, starting a positive feedback loop (chain reaction)

What are zymogens?

Zymogens are inactive forms of enzymes.

What is the lineage of the small intestine?

Duodenum —> jejum —> ileum. The duodenum performs most of digestion.

What is phase 3 of mammalian digestion?

It occurs in the small intestine (duodenal digestion). Chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself

What does the pancreas contribute to digestion?

Buffer (HCO3), amylases, trypsin, chymotrypsin, nucleases, lipases

What does the duodenum contribute to digestion?

Disaccharidases, dipeptidases, and nucleosidases.

What do the liver (production) gallbladder (storage) contribute to digestion?

Bile emulsifies lipids (detergent effect)

Describe absorption in the small intestine in the jejunum and ileum? 

Enormous villar and microvillar surface greatly increases nutrient absorption and transport across the epithelium can be active or passive. 

Describe absorption in the small and large intestine

Absorbed lipids enter the lymphatic system and absorbed amino acids and suars enter the hepatic portal vein which goes to the liver.

What is symbiosis?

It is living together between organisms: the interaction and possibly co-evolution with associated microbes

What is mutualism?

Where both species benefits

What is commensalism?

One species benefits and the other one is neutral

What is parasitism? 

Where one species benefits and the other one is harmed

What are endosymbionts and what are some examples?

They are microbes that actually live inside cells of an organism. Examples are rhizobium (nodules of plants), wolbachia, humans do not have endosymbionts. 

What are microbiota?

It is the ecological community of microorganisms associated with a host. The plant microbiota include communities of leaf surfaces and in the rhizosphere (region surrounding plant roots). Human microbiota refers to microbes living in or on the human body (gut microbiota lives in the lumen of the gut) 

Describe two types of mutalisic relationships in the rhizosphere

PGPR (plant growth-promoting rhizobactera): produce antibiotics that protects plants form disease, and can help increase nutrient availability.

AMF (arbuscular mycorrhizal fungi): a mutualistic symbiosis between plants and fungi, increase nutrient availability 

How is soil bacteria important for nitrogen fixation?

Plants can only absorb nitrogen as NO3- or NH4+ (NOT N2). Most nitrogen available to plants come from actions of soil bacteria. The nitrogen cycle transforms nitrogen and nitrogen-containing compounds in NH4+ and NO3-. Nitrogen fixing bacteria generate NH4+ from N2.

Ammonifying bacteria also generate NH4+.

Nitrifying bacteria generate NO3- from NH4+

What are rhizobia and what do they do? 

Rhizobia are endosymbionts of legumes. Along legume’s roots there are nodules (swellings) which are colonized by Rhizobium. The rhizobium obtain sugar and an anerobic environment. Flavanoids (root cells) trigger nod factors production which alters root cell activity 

What is the community like of bacteria in the rhizosphere?

Rhizobacteria depend on nutrients secreted by plant cells and in return help to enhance plant growht by producing chemicals that stimulate plant growth, producing antibiotics that protect roots, absorbing toxins, and increasing nutrient availability 

How many microbes are on the human body?

About 100 trillion

What are the 3 sectors that make up the human microbiota?

Bacteria, archaea, and eukarya

How has science tried to overcome sequencing our genome?

Most microbiota are non-culturable. However, next-genertion sequencing has allowed us to sequence genomes without culturing.

What are microbial communities?

Microbiota consist of communities that vary at different body sites. There are thousands of different species on the skin alone.

How does the gut microbiota vary along the GI tract?

The large instesine is the preferred site, with over 70% of all bacteria in the colon. It is not as diverse as other microbiota since it is only dominated by 2 phyla: firmicutes and bacteriodetes. Bacteria abundance and diversity increase from the proximal to the distal GI tract. 

How is the gut microbiota linked to health?

Alterations in the gut microbiota is linked with multiple diseases. We are currently trying to link the gut microbiota from correlation to causation

What are the key functions of the gut microbiota?

The gut microbiota is central to intestinal homeostasis and physiology.

1. immunity: prevent pathogen colonization, educates the immune system, stabilized gut barrier function 

2. metabolic role: caloric salvage, produce short chain fatty acids, produced vitamin K and folate

3. chemical modulator: drug metabolism and deconjugates bile acids 

What else does the gut microbiota influence

Alongside digestion, it is seen that the gut microbiota also impacts behavior (gut-brain axis). Our microbiota is impacted by our experiences and in turn, microbes send chemical signals which impact memory, emotions, and behavior. 

How different are gut microbiomes? 

Each person has their own unique microbiome. The fecal microbiota remains stable over a person’s lifetime but host genetics and diet can impact the gut. 

Where does our gut microbiota come from?

Initial exposure through the birth canal which is influenced by mother

How does our gut microbiota change?

Up to 3 years: bacterial abundance and diversity increases but mostly the first year. During this time, we “shape” our own community

After that: final bacterial abundance is reached at around 1 year old and maintained. Composition continues to vary.

What is dysbiosis in a body?

Dysbiosis is a microbial imbalance in the body, which can be caused by a changein diet and community 

What is diffusion in the body? 

diffusion is the movement of molecules in the environment. This type of movement is only along concentration gradients and can only be effective across short distances. The rate of diffusion is inversely proportional to distance. 

What is bulk flow circulation and how does this solve the size problem?

Multicellular organisms use bulk flow to move materials long distances. Circulation of a liquid solution carrying molecules. The movement in the pipe along pressure gradients is much faster than diffusion over long distances. It includes a plumbing system and a source of pressure. 

What is the pipe system in plants?

There are two separate vascular systems:

1. xylem: movement of water and minerals that is from root to leaves (unidirectional)

2. phloem: transport of organic materials that is bidirectional (from source [often leaf] to sink [often fruit, flower, etc])

Where do xylem and phloem occur in herbaceous plants?

Xylem and phloem occur in vascular bundles

Where do xylem occur in woody plants? 

Xylem occurs in the heartwood

What is the structure of xylem?

The xylem is made up of dead cells. Tracheids (elongated) and vessel elements (short) are two cell types composing xylem. Vessel elements have perforation plates linking cells in a common tubular structure. Tracheids have primary wall (cellulose) and secondary wall (lignin). Non-uniform lignin are pits. 

Describe the vessel system of xylem

Vessels are columns of water that require constant tension to maintain water cohesion. 

Describe tracheids in the xylem system

They have high surface to volume ratio and can hold water against gravity by adhesion when transpiration is not occuring 

What is the xylem sap>

The xylem sap is normally under negative pressure (tension). The cohesion-tension theory states that transpriation and water cohesion pull water from shoots to roots. Transpriation in the lead pulls wate rin the xylem 

What is the structure of the phloem?

The phloem translocates the products of photosynthesis from source tissues to sinks.

What are sieve elements?

Sieve elements are the cells composing the tubes (living cells with no nucleus at maturity = partial programmed cell death) 

What are companion cells?

Cells that are closely associated and transport sugars

What is the phloem sap?

It is an aqueous solution that is high in sucrose. It travels from a sugar source (organ that is a net producer of sugar, such as mature leaves) to a sugar sink (an organ that is a net consumer of sugar). this can be reversed 

What are the steps of phloem movement (aka translocation)? 

1. active (H+ cotransporter) or passive loading of carbon molecules by sources

2. water follows by osmosis, increasing hydrostatic pressure

3. at the sink, sugar is unloaded 

4. water is recycled 

What are the components of the circulatory system?

Circulatory fluid, a set of interconnecting vessels, a muscular pump (heart)

Describe what the circulatory system connects

It connects fluid that surrounds the cells with organs that exchange gases, absorb nutrients, and dispose of wastes. Circulatory systems can be open or closed and vary in the number of circuits in the body. 

Talk a little about open circulatory systems

Less energy is used, less efficient delivery. ex. arthropods and mollusks

Talk a little about closed circulatory systems

Large vessels branch into smaller vessels. ex. annelids and vertebrates

What are the 3 types of vessels in closed circulatory systems?

1. arteries (heart to periphery)

2. veins (periphery to heart)

3. capillaries (connect arteries and veins and allow exchange with tissues)

Describe the heart

The heart is a succession of two types of chambers:

1. atrium: collects blood; is thin; primes the pump 

2. ventricle: pushes blood into vessels; thick wall; this is the pump 

How are closed circulatory and respiratory systems connected?

They coevolved as a united system. There is double circulation where there are two circuits of blood flow. 

Describe double circulation in mammals

There are two independent capillary circuits. For each cycle, 2 passages through the heart. The pulmonary vein and systemic arteries are rich in O2 and systemic veins and pulmonary artery are low in O2. The left heart controls the systemic circuit and the right heart controls pulmonary circuit. 

How is radius connected to the arborization (branching)?

Velocity/radius decreases with arborization

How are blood flow, resistance, pressure, and velocity related?

Blood is viscous and flows with no turbulence (laimnar: parallel). It depends on Poiseuille’s law: Flux = (change in Pressure)(0.4)(r⁴/nl). Flow rate = change in pressure/resistance; velocity = Q/cross sectional area ; P=QR

How is velocity and arborization related?

Diameter and velocity decrease when there is more arborization. Microcirculation is circulation in the smallest blood vessels (arterioles, capillaries, and venules). The net flow is unchanged but linear velocity is minimal in capillaries. Tissue perfusion occurs in the micro-capillary sector 

How is the flow in capillaries controlled?

Arterioles control the flow in capillaries. Distension of vessels due to blood pressure triggers smooth muscle contraction. This prevents a change in capillary diameter. Blood flow can then remain constant

What is vascular tone?

Increased vascular tone in a segment of blood vessel:

• decreases radius of arteriole, and thus flow

• increases resistance to blood flow

• alters blood volume distribution

• builds up pressure in the upstream compartment 

• arterioles are resistance vessels and control vascular tone allows to control blood flow locally

How is vascular tone/microcirculatory flow regulated?

It is under nervous control. If all arterioles open (sepsis and anaphylaxis) is distributive shock

What determines blood flow?

Blood flow from areas of higher pressure to areas of lower pressure. It is the pressure that blood exerts in all directions, including against the walls of blood vessels. 

Total fluid energy of blood = potential energy of pressure produced by the heart + kinetic energy + potential energy of position in Earth’s gravitational field (depends on height)

What is systole?

Ventricular contraction —> blood expulsed with high pressure in the aorta

What is diastole?

Refilling of blood following systole (pressure maintained by recoil, c auses lower pressure) 

How is blood presusre regulated along the circuit?

The recoil of elastix arterial walls plays a big role in maintaining blood pressure. Veins need valves to prevent backflow and muscle movements and breathing provide pressure and allow blood to return to the heart 

What is fluid exchange like in capillaries?

Capillaries have the highest cross-secitonal area so they have the lowest velocity. Ions, gases, organic molecules diffuse more or less freely. Hydrostatic pressure continuously decreases while progressing through capillaries. Capillaries are permeable to ions so osmotic pressure depends on plasma proteins (oncotic pressure) due to albumin mostly. Oncotic pressure is constant and becomes preeminent in the capillary bed. 

What are some human heart numbers?

90 cm³/sec is the cardiac output, left ventricle stroke volume is 70mL. thats 115,000 beats a day and 2,000 gallons of blood a day. Circuit time is about 1 min. 

What is blood flow in the left atrium/ventricle?

It pumps blood from the lungs into the systemic arteries (aorta) towards the body. It receives and ejects a blood rich in oxygen.

What is blood flow in the right atrium/ventricle?

It pumps blood from the body (vena cava) into the pulmonary artery towards the lung. It received and ejects a blood poor in oxygen. 

What are the role of valves?

They insure monodirectional flow. Backflow is an issue and valves allow blood flow in only one direction. 

• 2 atrioventricular valves (L: mitral/bicuspid, R: tricuspid)

• 2 semilunar valves (L: aortic, R: pulmonary)

What are the phases of the cardiac cycle?

1. atrial and ventricular diastole: blood flows in atria, then ventricles

2. atrial systole forces more blood in ventricles 

3. ventricular ejection (systole) of blood begins when the ventricular pressur exceeds arterial pressure and forces semilunar valves to oepn 

What are the heart sounds?

Lub = semilunar valves open

Dub = semilunar valves close 

the heart sounds by the turbulence when valves snap shut 

How is contraction timing mediated? 

It is mediated by the conduction system. Pacemakers are modified muscle cells that act more like neurons and can initiate the cardiac cycle. Electrical signals arise from the SA node and travels to AV node and budle of His. This stimulates purkinje fibers that trigger ventricular contraction 

What are cardiomyocytes?

They are striated muscle cells comparable to skeletal muscles but are mononucleated. They are deloparied and repolarized. They are connected by porous junctions (intercalated discs). Action potentials can travel through the tissue, inducing a wave of contraction 

depolarization: cell membrane becomes more positive (Na+ channels open)

repolarization: cell membrane returns to resting state (K+ channels open)

hyperpolarization: membrane potential becomes even more negative 

How can heart rate be modulated by the nervous system? 

Muscle generates the rhythym. If all innervaition is blocked, SA node still beats around 90-100 bpm. It is controlled by the autonomous nervous system (division of the peripheral nervous system that influences the function of internal organs)

How can heart rate be sped up or slowed down?

Sped up: fight or flight

Slow down: rest and digest

How do acetycholine and norepinephrine change the rhythm of SA node cells?

Acetylcholine froms vagus nerve allows K+ to flow out, hyperpolarizes cardiac myocyte —> leak takes longer to reach threshold. The heart rhythm is controlled by accelerating or slowing down the leak and thus modulating the frequency of Action potentials in the pacemaker 

Norepinephrine from sympathetic nerves binds beta 1 recepter —> increase Ca2+ depolarized cardiac myocyte —> Mb potential closer to threshold