Lec 2 - Mam Phys

What are the six levels of structural organization in the human body?

Chemical, Cellular, Tissue, Organ, Organ System, Organismal.

What is the simplest level of structural organization?

Chemical level.

What makes up the chemical level?

Atoms combine to form molecules such as water and proteins.

What is the basic unit of life?

The cell.

What is the cellular level?

The level consisting of individual cells, the simplest living units.

What is a tissue?

A group of similar cells performing a common function.

What are the four basic tissue types?

Epithelial, connective, muscle, and nervous tissue.

What is an organ?

A structure composed of two or more tissue types that performs specific functions.

What is an organ system?

A group of organs working together to accomplish a common goal.

What is the organismal level?

All organ systems functioning together to sustain one organism.

Why are erythrocytes (red blood cells) shaped differently from most cells?

To maximize space for hemoglobin and oxygen transport.

Why are mature erythrocytes anucleate?

To provide more room for hemoglobin.

Why are sperm cells specialized?

To improve swimming ability for fertilization.

Why do neurons have long processes?

To communicate over long distances with other neurons or effector cells.

What are the two major categories of membrane transport?

Passive transport and active transport.

Does passive transport require ATP?

No.

What drives passive transport?

Existing concentration or electrochemical gradients.

What are the three forms of diffusion?

Simple diffusion, facilitated diffusion, and osmosis.

What is simple diffusion?

The movement of molecules directly through the membrane down their concentration gradient.

What substances commonly use simple diffusion?

Small nonpolar molecules such as O₂ and CO₂.

What is facilitated diffusion?

Movement down a concentration gradient through carrier proteins or ion channels.

Does facilitated diffusion require ATP?

No.

What limits the rate of facilitated diffusion?

The number of transport proteins available.

What is osmosis?

The diffusion of water across a selectively permeable membrane.

What drives filtration?

Hydrostatic pressure.

Where is filtration especially important?

The kidneys and capillary walls.

Does active transport require energy?

Yes, ATP either directly or indirectly.

What is primary active transport?

Transport driven directly by ATP hydrolysis.

What is secondary active transport?

Transport powered by an existing ion gradient established by primary active transport.

What is cotransport (symport)?

Movement of two substances in the same direction across the membrane.

What is countertransport (antiport)?

Movement of two substances in opposite directions across the membrane.

What is vesicular transport?

Bulk movement of materials into or out of the cell using vesicles.

What is exocytosis?

The release of substances from the cell by vesicle fusion with the plasma membrane.

What is endocytosis?

The uptake of substances into the cell by vesicle formation.

Does exocytosis move substances into or out of the cell?

Out of the cell.

Does endocytosis move substances into or out of the cell?

Into the cell.

What equation describes the rate of diffusion across a membrane?

Fick's Law.

According to Fick's Law, what increases the rate of diffusion?

Greater surface area, larger concentration gradient, and higher membrane permeability.

According to Fick's Law, what decreases the rate of diffusion?

Greater membrane thickness.

How does increasing membrane surface area affect diffusion?

It increases the diffusion rate.

How does increasing membrane thickness affect diffusion?

It decreases the diffusion rate.

How does increasing the concentration gradient affect diffusion?

It increases diffusion.

What happens to the rate of simple diffusion as the concentration gradient increases?

It continues to increase proportionally.

Why does facilitated diffusion eventually reach a maximum rate?

Transport proteins become saturated.

What are ion channels?

Transmembrane proteins that allow specific ions to cross the membrane.

What determines which ions pass through an ion channel?

Ion selectivity.

What are leak channels?

Channels that are normally open and allow continuous ion movement.

Which ion most commonly uses leak channels at rest?

Potassium (K⁺).

What are voltage-gated ion channels?

Channels that open or close in response to changes in membrane potential.

Which ions commonly use voltage-gated channels?

Na⁺, K⁺, and Ca²⁺.

What are ligand-gated channels?

Channels that open when a chemical messenger binds to them.

What is an example of a ligand-gated receptor?

The acetylcholine receptor.

What are intracellular calcium release channels?

Channels that release Ca²⁺ from intracellular stores such as the endoplasmic reticulum.

Name two intracellular calcium release channels.

Ryanodine receptors (RyR) and IP₃ receptors (IP₃R).

What are mechanosensitive ion channels?

Channels that respond to mechanical deformation such as stretch or pressure.

What is selective permeability?

The property of membranes that allows some substances to cross more easily than others.

Why is selective permeability important?

It allows cells to regulate ion movement and maintain homeostasis.

Which transport process is driven by hydrostatic pressure?

Filtration.

Which transport process is driven by ATP hydrolysis?

Primary active transport.

Which transport process is driven by existing ion gradients?

Secondary active transport.

Which transport process moves large particles using vesicles?

Vesicular transport.

Which transport mechanism is responsible for neurotransmitter release?

Exocytosis.

Which transport mechanism allows cells to engulf extracellular material?

Endocytosis.

Which transport mechanism is the fastest for small nonpolar molecules?

Simple diffusion.

Which transport mechanism becomes saturated?

Facilitated diffusion.

What is the main difference between passive and active transport?

Passive transport requires no energy and moves down a gradient, whereas active transport requires energy and can move against a gradient.