Cell Physiology and Structure

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Questions and Answers

What percentage of total body weight does the plasma account for?

15%

20%

5% (correct)

10%

Which factor contributes to lower total body water percentage in females compared to males?

Higher fat content in females (correct)

Increased metabolic rate in females

Higher muscle mass in females

Lower body weight in females

Which fluid compartment constitutes the highest percentage of total body water?

Extracellular fluid

Transcellular fluid

Intracellular fluid (correct)

Interstitial fluid

What physiological condition could lead to a lesser total body water percentage?

Obesity Signup and view all the answers

Which of the following fluids is considered transcellular fluid?

Cerebrospinal fluid Signup and view all the answers

At what developmental stage does total body water percentage typically reach adult levels?

Puberty Signup and view all the answers

What is the primary role of water in digestion?

As a solvent for digestive enzymes Signup and view all the answers

What role does osmolarity play in the body?

Regulates fluid movement between compartments Signup and view all the answers

What is the primary energy source for primary active transport mechanisms?

Hydrolysis of ATP Signup and view all the answers

In which type of transport do Na+ ions typically assist in the movement of glucose into the cell?

Secondary active transport Signup and view all the answers

Which of the following correctly describes the function of the Na+/K+ pump?

Transports 3 Na+ out and 2 K+ into the cell Signup and view all the answers

Which type of transport protein is characterized by transporting two different substances in opposite directions?

Antiporter Signup and view all the answers

What type of active transport mechanism primarily uses energy stored in an electrochemical gradient?

Secondary active transport Signup and view all the answers

Which of the following is an example of exocytosis in cells?

Releasing hormones and enzymes Signup and view all the answers

What does the Ca²+ pump primarily function to regulate within the cardiac and skeletal muscles?

Calcium concentrations Signup and view all the answers

The breakdown of which molecule is essential for the functioning of ATPase enzymes?

ATP Signup and view all the answers

What is the primary role of the cell membrane?

Controls the movement of substances in and out of the cell Signup and view all the answers

Which type of lipid primarily makes up the cell membrane?

Phospholipids Signup and view all the answers

How does the presence of cholesterol affect the cell membrane?

Reduces fluidity and increases stability of the membrane Signup and view all the answers

What characterizes transmembrane proteins in the cell membrane?

They span the entire thickness of the membrane Signup and view all the answers

Which of the following correctly describes the arrangement of phospholipids in the cell membrane?

Hydrophilic heads are on the inner and outer surfaces with hydrophobic tails in between Signup and view all the answers

What is a function of the receptors found in the cell membrane?

To stimulate or inhibit cell functions upon binding with chemicals Signup and view all the answers

Which type of protein is associated with the inner or outer surface of the cell membrane?

Peripheral proteins Signup and view all the answers

Which of the following describes the permeability of the cell membrane?

Selectively permeable to ions and organic molecules Signup and view all the answers

What role does interstitial fluid play during periods of hemorrhage?

It provides a reservoir for vascular volume. Signup and view all the answers

Which system is responsible for rapid control of homeostasis through nerve impulses?

Nervous System Signup and view all the answers

What is the primary function of hemoglobin in relation to oxygen concentration in extracellular fluid?

It buffers oxygen concentration. Signup and view all the answers

How is blood glucose level regulated in the body?

Through hormone secretion from endocrine glands. Signup and view all the answers

What characteristic facilitates rapid exchange of water and solutes in the body?

Proximity of cells to blood vessels. Signup and view all the answers

What happens to the affinity of hemoglobin for oxygen when it reaches the lungs?

It increases due to high oxygen tension. Signup and view all the answers

What is the role of water in maintaining pH levels in body fluids?

It dissociates into H⁺ and OH⁻ ions. Signup and view all the answers

Which sensation does not require water for its function?

Tactile sensation Signup and view all the answers

What physiological response occurs when arterial blood pressure increases?

Inhibition of vasomotor center. Signup and view all the answers

What is the primary function of the endocrine system in homeostasis?

It secretes hormones for slow regulation. Signup and view all the answers

At what percentage of total body weight loss does thirst sensation typically occur?

1% Signup and view all the answers

Which ions primarily compose the intracellular fluid (ICF)?

Potassium and Phosphate Signup and view all the answers

What characterizes sensible water loss?

It can be measured directly. Signup and view all the answers

What primarily drives the difference in ion composition between intracellular fluid (ICF) and extracellular fluid (ECF)?

Cell membrane integrity and energy supply. Signup and view all the answers

How does the high specific heat of water benefit the body?

It prevents rapid changes in body temperature. Signup and view all the answers

What happens to cardiac output and blood pressure during severe dehydration if not compensated?

They decrease due to reduced blood volume. Signup and view all the answers

What effect does negative feedback control have on homeostatic functions?

It inhibits the function to restore balance. Signup and view all the answers

Which of the following is true about positive feedback control?

It results in an increase of the initiating stimulus. Signup and view all the answers

Which mechanism is involved in the regulation of arterial blood pressure during a rise in blood pressure?

Inhibition of the vasomotor center. Signup and view all the answers

What initiates the positive feedback mechanism during parturition?

Stretch of the uterine cervix. Signup and view all the answers

In the context of blood glucose regulation, what triggers the secretion of insulin?

Elevated blood glucose levels above normal. Signup and view all the answers

What is a characteristic outcome of positive feedback mechanisms in abnormal conditions?

They can lead to life-threatening situations. Signup and view all the answers

How does increased CO2 concentration affect pulmonary ventilation?

It induces an increase in ventilatory response. Signup and view all the answers

What is the overall impact of negative feedback mechanisms on homeostasis?

They lead to a stable and balanced internal environment. Signup and view all the answers

Study Notes

Physiology of the Cell

The human body is comprised of systems (e.g., cardiovascular, respiratory, digestive).
Systems are composed of organs with complementary functions.
Organs are made of tissues, which are made of cells.
Cells are the fundamental structural units in the body.
Functions of the body's parts work together to maintain health.

Structure of the Cell

A mass of protoplasm, consisting of cytoplasm, cell organelles, and the nucleus.
A cell membrane surrounds the cell.

Cell Membrane Structure and Function

A double layer of lipids and proteins, separating the cytoplasm from its surroundings.
Function:
- Protects the cell from its environment.
- Controls movement of substances in and out of cells and organelles (selectively permeable).
- Contains receptors to stimulate or inhibit cell functions.
Structure:
- Lipids: Primarily phospholipids (polar heads and non-polar tails) and cholesterol (affects membrane fluidity). Arranged in a bilayer.
- Proteins: Embedded in the lipid bilayer, some combined with lipids (lipoproteins) or carbohydrates (glycoproteins).
  - Peripheral proteins: on the membrane surface.
  - Integral proteins: span the entire membrane.
  - Functions: Membrane receptors relay signals between the cell and external environment.
- Carbohydrates: Small amount, combined with lipids (glycolipids) or proteins (glycoproteins), on the outer surface of the membrane.
- Functions Include: cell attachment, receptor sites, and charge regulation.

Transport Across Cell Membranes

Passive Transport:
- Movement of substances down a concentration gradient (no energy required).
- Types: Simple diffusion, Facilitated diffusion.
- Simple Diffusion: Movement of molecules from high to low concentration. Factors affecting rate: concentration gradient, molecular weight, and medium solubility.
- Facilitated diffusion: Movement of substances with the aid of carrier proteins, across the membrane
- Factors affecting rate: Distance, temperature, membrane thickness.
- Routes: through lipid bilayer (small molecules), or protein channels (large molecules).
- Types of protein channels: Non-gated (always open), Gated (open/close based on stimuli).
  - Types of gated channels: Voltage-gated(respond to membrane voltage changes) and Ligand-gated (respond to chemical signaling).
Active Transport:
- Movement of substances against a concentration gradient (requires energy—ATP).
- Types:
  - Primary active transport: energy directly from ATP breakdown (e.g., Na+/K+ pump).
  - Secondary active transport: uses electrochemical gradient created by primary active transport. (e.g., Na+/glucose cotransporter)

Endocytosis & Exocytosis

Endocytosis: Cell taking in large molecules or particles.
- Types: Receptor-mediated (particles bind to receptors) and non-receptor-mediated (Phagocytosis, Pinocytosis).
Exocytosis: Release of large molecules and particles from the cell—through vesicles.

General Physiology

Composition of the human body: ~60% water, ~18% protein, ~15% fat, ~7% minerals.
Body Fluids: Total body water (TBW): Intracellular fluid (ICF) (40%), Extracellular fluid (ECF) (20%).
Water importance: Solvent, nutrition, digestion, absorption, excretion, maintaining body osmolarity, cell membrane function, body temp regulation.
Homeostasis: Process of maintaining internal conditions constant
- Control mechanisms: Nervous, Endocrine, and Chemical
- Feedback Mechanisms: Negative (response opposes the initial stimulus) or Positive (response amplifies the initial stimulus). Examples provided in the text.

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Description

Explore the intricacies of cell physiology, including how cells function within various systems of the human body. This quiz delves into the structure and function of cell membranes, illustrating the critical role cells play in maintaining health and homeostasis.