Cell Biology: Introduction to Cells

Questions and Answers

What is the primary function of the cell membrane?

To store genetic information

To produce energy for the cell

To synthesize proteins for the cell

To regulate what enters and leaves the cell (correct)

Which of the following is NOT a characteristic of a cell?

Produces its own energy

Reproduces by division

Needs nutrition and oxygen

Can survive independently outside the body (correct)

What is the primary function of epithelial tissue?

To protect the body from external damage (correct)

To produce hormones and regulate metabolism

To transmit nerve impulses

To provide support and structure to the body

Which type of tissue is responsible for transmitting nerve impulses?

Nervous tissue Signup and view all the answers

What is the term for the group of cells with similar function?

Tissue Signup and view all the answers

What is the term for the structure formed by two or more primary types of tissues?

Organ Signup and view all the answers

Which of the following cells do not reproduce by division?

Nerve cells Signup and view all the answers

What is the term for the process by which cells respond to their environment?

Cell adaptation Signup and view all the answers

What is the function of cholesterol in the lipid layer of the cell membrane?

To provide structural integrity to the lipid layer Signup and view all the answers

What type of proteins pass through the entire thickness of the cell membrane?

Integral proteins Signup and view all the answers

Which of the following is NOT a function of integral proteins?

Helping in the diffusion of water-soluble substances Signup and view all the answers

What is the term for proteins that are partially embedded in the outer and inner surfaces of the cell membrane?

Peripheral proteins Signup and view all the answers

What is the purpose of the lipid layer in the cell membrane?

To allow only fat-soluble substances to pass through Signup and view all the answers

What is the term for carbohydrate molecules attached to proteins in the cell membrane?

Glycoproteins Signup and view all the answers

Which of the following is an example of an integral protein?

Cell adhesion proteins Signup and view all the answers

What is the function of peripheral proteins in the cell membrane?

To help in the diffusion of water-soluble substances Signup and view all the answers

What is the term for the arrangement of phospholipid molecules in the lipid layer of the cell membrane?

Bilayer Signup and view all the answers

What is the function of carrier proteins in the cell membrane?

To transport substances across the cell membrane Signup and view all the answers

What is the function of glycocalyx in cell membranes?

It helps in the tight fixation of cells with one another. Signup and view all the answers

How do carbohydrate molecules contribute to the selective permeability of the cell membrane?

They are negatively charged, preventing negatively charged substances from entering the cell. Signup and view all the answers

Which of the following is NOT a function of the cell membrane?

Synthesis of proteins. Signup and view all the answers

How does the cell membrane contribute to the exchange of gases?

It provides a surface area for gas exchange. Signup and view all the answers

Which of the following is NOT a function of carbohydrates in the cell membrane?

Facilitating the movement of water across the membrane. Signup and view all the answers

Which of these statements BEST describes the role of the cell membrane in maintaining the cell's shape and size?

The cell membrane provides a framework for the cytoskeleton, which supports the cell's shape. Signup and view all the answers

Which organ system is primarily responsible for digestion of food particles?

Digestive system Signup and view all the answers

What is the primary function of the respiratory system?

Supplying oxygen and removing carbon dioxide Signup and view all the answers

How are proteins, lipids, and carbohydrates proportionally composed in the cell membrane?

55% proteins, 40% lipids, 5% carbohydrates Signup and view all the answers

What structure of the cell membrane was first proposed by James F Danielli and Hugh Davson?

Danielli-Davson model Signup and view all the answers

Which model of the cell membrane proposed that proteins float in the lipid layer?

Fluid mosaic model Signup and view all the answers

What is the thickness range of the cell membrane mentioned in the content?

75 to 111Å Signup and view all the answers

What is the role of the endocrine system in the body?

Regulation and maintenance of normal life Signup and view all the answers

Which type of lipid is primarily found in the lipid layer of the cell membrane?

Phospholipids Signup and view all the answers

What distinguishes the fluid mosaic model from the Danielli-Davson model?

Fluid nature of the membrane Signup and view all the answers

What are the two parts of the cell body?

Nucleus and cytoplasm Signup and view all the answers

Study Notes

Introduction to Cells and Tissues

Cells are the fundamental units of life, essential for all living organisms.
Each cell requires nutrition and oxygen, produces energy, eliminates waste, maintains its environment, responds to invaders, and can reproduce, with exceptions like neurons.
Tissues consist of groups of similar cells and are classified into four primary types: muscle, nervous, epithelial, and connective tissues.

Organs and Organ Systems

Organs are structures formed from two or more primary tissue types that perform specific functions.
Types of organs include tubular (hollow) organs and compact (parenchymal) organs.
Organ systems are groups of interconnected organs that work together for specific bodily functions, such as:
- Digestive system: processes food.
- Excretory system: removes waste.
- Cardiovascular system: transports substances.
- Respiratory system: exchanges gases.
- Reproductive system: facilitates reproduction.
- Endocrine system: regulates growth and bodily functions.
- Musculoskeletal system: provides stability and movement.
- Nervous system: controls activities and intellectual functions.

Structure of the Cell

Every cell consists of a cell body, a nucleus, and surrounding cytoplasm, all encased by a cell membrane.

Cell Membrane

The cell membrane, or plasma membrane, is a protective and semi-permeable barrier between extracellular fluid (ECF) and intracellular fluid (ICF).
Thickness ranges between 75 to 111Å.
Composed of 55% proteins, 40% lipids, and 5% carbohydrates.

Models of Cell Membrane Structure

Danielli-Davson Model: Proposed a lipid "sandwich" covered with protein layers.
Unit Membrane Model: Replaced the previous model, indicating structured layers based on electron microscopy.
Fluid Mosaic Model: Current model recognizing a dynamic arrangement of proteins floating within a fluid lipid bilayer.

Lipid Layer and Phospholipids

The lipid layer is bilayered, consisting mainly of phospholipids which have hydrophilic heads and hydrophobic tails.
Cholesterol is interspersed among phospholipids, maintaining membrane integrity and fluidity.
The lipid layer's semi-permeability allows fat-soluble substances (e.g., oxygen, carbon dioxide) to pass, while being impermeable to water-soluble substances (e.g., glucose).

Protein Layers in the Cell Membrane

Composed of integral (transmembrane) proteins that span the membrane and peripheral proteins that are loosely associated.
Functions of proteins include:
- Structural integrity, transport, and as channels for molecules.
- Serving as receptors for hormones and neurotransmitters.
- Acting as enzymes for metabolic reactions.

Carbohydrates in the Cell Membrane

Carbohydrates form glycoproteins and glycolipids, contributing to the glycocalyx, a protective layer on the membrane.
Functions include:
- Restrictions on negatively charged substances.
- Facilitating cell adhesion and signaling through receptor functions.

Functions of the Cell Membrane

Protective barrier safeguarding the cytoplasm and organelles.
Selectively permeable to certain substances, enabling nutrient absorption and waste excretion.
Facilitates gas exchange (oxygen and carbon dioxide).
Maintains the cell's shape and size.

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Description

Learn about the characteristics of cells, the basic units of life. Discover how cells obtain nutrition, produce energy, and maintain their environment.