Anatomy and physiology Unit 3 Content

Everything covered in unit 3 of EXSC 223.

The 4 essential concepts in physiology

1. Physiology uses gradients.

2. Negative feedback regulation is essential to homeostasis.

3. Regulate protein function by regulating its shape.

4. principle of complementarity of structure and function.

Physiology uses gradients

gradients are a difference in amounts of something that drive physiology. gradients tend to move from a high to low concentration, enabling processes like diffusion and osmosis. gradients cause movements which produce a physiological affect. an example of this is the movement of oxygen from the lungs into the bloodstream. there is a high concentration of oxygen in the lungs, so the oxygen will move down the gradient into less concentrated blood, facilitating gas exchange.

Negative feedback regulation is essential to homeostasis.

mechanisms in the body perform negative feedback when homeostasis is disturbed. The negative response opposes the original change to restore balance in the body, keeping the environment stable. For example, when you eat food, your blood sugar rises, triggering insulin release (negative feedback) to lower glucose levels (homeostasis). Not restoring homeostasis can lead to disease.

regulate protein function by regulating its shape

Proteins fold into specific shapes to interact with other things, like a lock and ley. you can turn a protein on and off by altering its shape. For example, enzymes have a specific active site that substrates fit into. This shape can be changed by factors such as temperature or pH, which can activate or deactivate the protein's function.

Principle of complementarity of structure and function

states that the structure of a body part reflects its function. This means that the way a body part is shaped or arranged is suitable for the job it performs, emphasizing that anatomy and physiology are closely related. For example, a red blood cell has a large surface are but is also a flat disk, creating a short distance for oxygen to travel in to it.

Cell theory

1*. Cells are the basic structural and functional unit of living organisms.

2*. All living things are made up of 1 or more cells.

3*. Continuity of life has a cellular basis.

4. organism activity depends on individual and collective activities of cells.

5. Energy flow occurs within cells.

6. Cells contain DNA in chromatin/chromesomes.

7. Within a species, cells have the same chemical composition (DNA)

3 Major parts of eukaryotic cells

1. nucleus (with the exception of red blood cells)

2. cytoplasm (cytosol +organelles)

3. plasma membrane (separates internal from external)

Diversity of cells within the human body

1. Cells that connect body parts, form linings or transport gases (ex. epithelial cells)

2. Cells thar move organs and body parts (ex. skeletal muscle cells)

3. Cells that store nutrients (ex. fat cells)

4. cells that fight diseases (ex. macrophages)

5. Cells that gather information and control body functions (ex. neurons)

What do cells do all day while you are working?

• Segregate

• communicate

• hold hands

• Identify alien invaders

• internal support

• transport and digest

• clone

• build/remodel/demolish

Why is the cell membrane a fluid mosaic model?

because it is incredibly fluid and flexible, almost like cooking oil, as well as dynamic, because the face of the mosaic is always changing and shifting by the proteins within. It is made up of 2 layers of phospholipids, with cholesterol, proteins, and carbohydrates embedded and connected to the membrane.

What is the structure and characteristics of a phospholipid molecule, like the ones that make up the cell membrane?

Phospholipids are ampipathic molecules that contain a hydrophillic, polar, phosphorus containing head, a glycerol backbone, and a hydrophobic, nonpolar tail made of 2 fatty acids. The membrane is an auto-assembling structure which determines what can and cant cross it.

describe the role of cholesterol in the plasma membrane.

Cholesterol makes up about 20% of the plasma membrane. Cholesterol molecules are ampipathic, allowing molecules to embed in between phospholipids to maintain the stability of the membrane. It also lowers the freezing point of the membrane, making it more flexible at lower temperatures. Human steroids are derived from cholesterol. Context matters when it comes to cholesterol, as it can be seen as a bad thing because it can promote CVD, when in reality it plays a crucial role in maintaining fluidity and integrity of cell membranes. It can be harmful or helpful in certain conditions.

glycocalyx

The glycocalyx is the “sugar coat” on the extracellular side of the plasma membrane. It consists of glycoproteins attached to integral and peripheral proteins, as well as glycolipids attached to phospholipid molecules with the function of acting as identifiers to help with cell to cell recognition.

Integral proteins

Transmembrane proteins with both hydrophillic and hydrophobic regions wedged between the phospholipid bilayer. They span the entire membrane and are involved in a variety of functions, including transport, acting as channels or carriers for substances to cross the membrane, and serving as receptors for signal transduction.

Peripheral membrane proteins

Peripheral membrane proteins are not embedded within the lipid bilayer but are loosely attached to the surface of the membrane. They play roles in signal transduction, serve as enzymes, and help maintain the cell's shape and structure.

passive transport (diffusion)

Passive transport (diffusion) is the movement of molecules across a cellular membrane without the use of energy, driven by the concentration gradient, allowing substances to move from areas of higher concentration to lower concentration. consists of simple diffusion, facilitated diffusion, and osmosis.

Simple diffusion

unassisted cross-membrane diffusion of small particles that are nonpolar or lipid soluble straight through the lipid bilayer. This happens with molecules such as fatty acids, steroids, and gases like O2 and CO2.

Facilitated diffusion

transporting molecules across a membrane from high to low concentration through specific transmembrane proteins, allowing molecules to cross the lipid bilayer without energy input. The first type is channel transport which are water filled protein channels that allow ions and small polar molecules to pass, while the second type is carrier proteins that bind to specific substances and change shape to transport them across the membrane in order to bypass nonpolar regions (ex. Glucose)

Osmosis

The movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration, typically facilitated by specialized channel proteins called aquaporins.

Rate of diffusion is affected by:

Gradient: as the concentration difference increases, the rate of diffusion also increases. Temperature: higher temperatures increase kinetic energy, enhancing diffusion. Distance: A longer distance to travel will decrease the rate. Size of particles: smaller particles diffuse more easily.

effect of membrane permeability

diffusion: solute moves through a semipermeable membrane from high to low solute concentration: volume remains unchanged. osmosis: solute cannot cross the membrane, so instead, the water moves from low solute concentration to high concentration, resulting in a volume change. An example of this is when you take in too much sodium, water moves into your cells and swells you.

effect of solutions of varying tonicity

isotonic: a solution where the concentration of solutes is equal inside and outside the cell, resulting in no net movement of water. hypertonic: a solution with a higher solute concentration than inside the cell, causing water to move out and the cell to shrink. hypotonic: a solution with a lower solute concentration than inside the cell, leading to water moving in and the cell swelling. (real life ex. saline in a medical settingis often isotonic to prevent cell damage.)

Active transport

the process whenever a cell uses energy to move solute across a membrane. the substance may be too large to pass through the channels, incapable of dissolving in the lipid bilayer, or moving against its concentration gradient. There is primary and secondary active transport.

primary active transport

calcium, hydrogen, and most importantly, sodium potassium pumps, are energized by the transfer of a phosphate group from ATP. The protein will then chage its shape in order to move a specific solute according to it’s electrochemical gradient and concentration gradient.

Sodium potassium pump activity

The protein the pump is made of is called Na+/K+ ATPase. The process starts when 3 cytoplasmic Na+ ions are bound to the pump, triggering ATP hydrolysis where the pump is phosphorylated. This phosphorylation changes the pump's shape and releases Na+ outside the cell. Then, it takes in 2 K+ ions from the extracellular fluid, which triggers the release of the phosphate. The protein returns to its normal shaoe and releases K+ into the cytoplasm, rebonding ATP.

What does it mean when the cell is polarized when it is at homeostasis?

The cell is said to be polarized when there is a difference in electric charge across its membrane, resulting in a negative interior relative to the outside. This is because along with positive Na+ ions on the outside of the cell, there are also some negative Cl- , whereas on the inside there is not only K+ but also an abundance of negatively charged proteins from the cytoskeleton and phosphates from phosphorylation. In this state, the unequal distribution of ions creates a resting membrane potential (homeostasis) which the sodium potassium pump is active in maintaining.