Cell Transport Mechanisms

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Questions and Answers

What is the primary difference between diffusion and facilitated diffusion?

The primary difference is that diffusion involves the random movement of molecules, whereas facilitated diffusion involves the movement of large molecules with the assistance of transport proteins.

In which direction do molecules move during diffusion?

From an area of high concentration to an area of low concentration.

What is the function of transport proteins in facilitated diffusion?

To assist in the movement of large molecules across the cell membrane.

What is the definition of osmosis?

The movement of water across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration. Signup and view all the answers

What is the difference between passive and active transport?

Passive transport does not require energy, while active transport requires energy to move substances across the cell membrane. Signup and view all the answers

What is the concentration gradient?

The distribution of particles across space from high to low concentration. Signup and view all the answers

What is an example of diffusion in the human body?

Gas exchange at the alveoli (lungs) - oxygen from air to blood, carbon dioxide from blood to air. Signup and view all the answers

What is the purpose of active transport?

To move substances across the cell membrane against their concentration gradient. Signup and view all the answers

What is the primary source of energy for carrier proteins involved in active transport?

ATP Signup and view all the answers

What is the main difference between endocytosis and exocytosis?

Endocytosis involves the movement of substances into the cell, while exocytosis involves the movement of substances out of the cell. Signup and view all the answers

What is the function of phagocytosis in endocytosis?

To engulf solids Signup and view all the answers

What is the role of bacteria in our body's defense against pathogens?

They are the first line of defense against foreign invaders Signup and view all the answers

What is the approximate weight of bacteria in our body?

1.4 kg Signup and view all the answers

What is the difference between cellular and acellular organisms?

Cellular organisms are living, while acellular organisms are non-living Signup and view all the answers

What is the function of the Golgi body in exocytosis?

To package hormones into vesicles for removal from the cell Signup and view all the answers

What is the estimated number of bacteria living in the human intestines?

100 trillion Signup and view all the answers

Study Notes

Movement into and out of Cells

Molecules can cross the cell membrane through four ways: diffusion, osmosis, active transport, and cytosis.

Diffusion

Diffusion is the random movement of substances from a high concentration to a low concentration area until equilibrium is established.
It is a passive process, meaning it does not require energy.
Molecules that commonly diffuse across the cell membrane include oxygen and carbon dioxide during gas exchange in the lungs and during photosynthesis.
The concentration gradient is the distribution of particles from high to low concentration, and molecules always move down the concentration gradient to create an equilibrium.

Facilitated Diffusion

Facilitated diffusion is a form of passive transport that uses transport proteins to move large molecules across the cell membrane.
It occurs down the concentration gradient, hence it does not require energy.
Example: transport of large molecules like glucose across the cell membrane.

Osmosis

Osmosis is a special case of diffusion, involving water only.
It is the movement of water across a selectively permeable membrane from a region of low solute concentration to a region of high solute concentration.

Active Transport

Active transport is a process that uses membrane proteins to move substances across the membrane against the concentration gradient.
It requires energy, which is obtained from ATP.
Transport proteins involved in this process are called protein pumps/carrier proteins.

Cytosis

Cytosis is an energy-requiring process that involves the movement of substances into cells that are too large to cross the membrane.
There are two types of cytosis: endocytosis and exocytosis.

Endocytosis

Endocytosis involves the movement of large substances into the cell.
The cell membrane folds inward to form a vesicle that engulfs the substance to be transported.
Types of endocytosis include phagocytosis (engulfing solids) and pinocytosis (engulfing liquids).

Exocytosis

Exocytosis is the movement of a large substance out of the cell.
Vesicles from within the cell fuse with the membrane and release their contents into the extracellular environment.
Example: hormones are packaged into a vesicle by the Golgi body and removed from the cell by exocytosis.

Types of Microorganisms

Cellular (living) microorganisms include parasites, fungi, and bacteria.
Acellular (non-living) microorganisms include viruses and prions.

Bacteria

Bacteria are possibly the most numerous types of organisms on the planet.
They are very small, smaller than eukaryotic cells.
Bacteria can be harmful, but they are also needed to keep us healthy.
The bacteria on our skin, in our airways, and in our digestive system are the first line of defense against foreign pathogens that can cause infection and other problems.