B4

Question 1

What does the efficiency of transport of substances by diffusion depend on?

Answer 1

The size of the organism, specifically the surface area to volume ratio.

A higher surface area to volume ratio leads to more efficient diffusion.

Question 2

What is the relationship between size and surface area to volume ratio in small organisms?

Answer 2

Small organisms have a larger surface area to volume ratio.

This allows them to efficiently obtain nutrients and remove wastes by diffusion.

Question 3

Calculate the volume (V) and surface area (SA) of a cube with a side length of 1 cm.

Answer 3

V = 1 cm³, SA = 6 cm².

The ratio of SA to V for this cube is 6.

Question 4

Calculate the volume (V) and surface area (SA) of a cube with a side length of 4 cm.

Answer 4

V = 64 cm³, SA = 96 cm².

The ratio of SA to V for this cube is 1.5.

Question 5

Why can small organisms rely on diffusion for gas exchange?

Answer 5

Due to short diffusion distances, high surface area to volume ratio, and low metabolic demands.

These factors enhance the efficiency of diffusion.

Question 6

What limitations do large organisms face regarding diffusion?

Answer 6

Large organisms have a low surface area to volume ratio, making diffusion inadequate for supplying needs and removing waste.

The large distances involved slow down the transport of materials.

Question 7

What adaptations have large organisms evolved for gas exchange?

Answer 7

Specialized organs for gas exchange, such as tracheae in insects.

These adaptations help in efficient gas exchange despite lower SA to V ratios.

Question 8

What three factors affect the rate of diffusion?

Answer 8

• Area of diffusion
• Difference in concentration
• Thickness of diffusion surface

Larger areas and thinner surfaces speed up diffusion.

Question 9

True or False: Diffusion is faster when surfaces are thick.

Answer 9

False.

Thinner surfaces facilitate faster diffusion.

Question 10

What systems have large organisms evolved to transport gases and nutrients?

Answer 10

Transport systems for carrying O2, CO2, and food molecules quickly around the body.

These systems are necessary due to the inefficiency of diffusion over larger distances.

Question 11

Fill in the blank: The surface area to volume ratio is given by _______.

Answer 11

SA/V

Question 12

What is the primary function of the cell surface membrane?

Answer 12

Maintains osmotic balance and allows cell recognition by hormones

The cell surface membrane controls movements of substances in and out of the cell.

Question 13

What are the main components of the cell surface membrane?

Answer 13

• Lipids (phospholipids and cholesterol)
• Proteins
• Carbohydrates (glycoproteins and glycolipids)

These components contribute to the structure and function of the membrane.

Question 14

List three properties of cell membranes.

Answer 14

• Flexible
• Fluid
• Selectively permeable

These properties are essential for the functioning of the cell membrane.

Question 15

What advancements were necessary to understand the arrangement of cell membrane components?

Answer 15

Development of techniques such as electron microscopy and use of radioactive isotopes

This research led to the creation of models explaining the structure of cell membranes.

Question 16

What is the fluid mosaic model?

Answer 16

A model describing the cell membrane as a fluid lipid bilayer with a mosaic of proteins, glycoproteins, and glycolipids

This model provides a scientific explanation for the structure and properties of cell membranes.

Question 17

What are the characteristics of phospholipids in the fluid mosaic model?

Answer 17

• Hydrophilic (water-loving) head
• Hydrophobic (water-hating) tail

This dual nature allows phospholipids to form bilayers in an aqueous environment.

Question 18

What substances pass easily through cell membranes according to the fluid mosaic model?

Answer 18

Lipid-soluble substances

Ionic and polar molecules do not pass easily through membranes.

Question 19

What is the Davson-Danielli model?

Answer 19

A model proposed in 1935 that accounts for protein and lipid but fails to explain many membrane facts

It suggests a protein layer on the outside of the membrane.

Question 20

What are the similarities between the fluid mosaic model and the Davson-Danielli model?

Answer 20

• Both have a phospholipid bilayer with protein

However, they differ in the arrangement of proteins within the membrane.

Question 21

In which model are glycolipids, glycoproteins, and cholesterol present?

Answer 21

Fluid mosaic model

These components are not included in the Davson-Danielli model.

Question 22

Fill in the blank: The fluid mosaic model has a _____ lipid bilayer.

Answer 22

fluid

This refers to the dynamic nature of the lipid bilayer in the model.

Question 23

What are the two types of transport across membranes?

Answer 23

Passive transport and active transport

Passive transport does not require energy, while active transport does.

Question 24

What are the three kinds of passive movement?

Answer 24

Diffusion, facilitated diffusion, and osmosis

These processes allow substances to move across membranes without the use of energy.

Question 25

What is diffusion?

Answer 25

Movement of particles from high concentration to low concentration ## Footnote This occurs until equilibrium is reached.

Question 26

What conditions must be met for diffusion to occur?

Answer 26

* The membrane is permeable * The particle and/or pore is not charged * The particle is soluble ## Footnote Charged or too large particles cannot diffuse easily.

Question 27

What happens at equilibrium in terms of particle movement?

Answer 27

Net movement is zero, but particles still move across in both directions ## Footnote Concentration is the same on both sides of the membrane.

Question 28

What is facilitated diffusion?

Answer 28

The process where larger or charged molecules pass through a membrane via channel proteins ## Footnote Examples include glucose and sodium ions.

Question 29

What are the two types of membrane proteins involved in facilitated diffusion?

Answer 29

* Channel protein * Carrier protein ## Footnote Channel proteins allow molecules through a pore, while carrier proteins change shape to transport molecules.

Question 30

What is osmosis?

Answer 30

Diffusion of free water molecules through a partially permeable membrane ## Footnote It occurs from high water potential to low water potential.

Question 31

What is the net movement of water in osmosis?

Answer 31

From a solution with high water potential (low solute concentration) to low water potential (high solute concentration) ## Footnote This movement helps to balance solute concentrations.

Question 32

What is a simple demonstration of osmosis?

Answer 32

Water rises in a sucrose solution after a period of time ## Footnote This shows the movement of water molecules towards higher solute concentration.

Question 33

Fill in the blank: Osmosis is the diffusion of _______.

Answer 33

free water molecules ## Footnote It specifically involves water movement across membranes.

Question 34

How could drugs be designed to enter a cell rapidly?

Answer 34

By utilizing osmosis and facilitating rapid movement through membranes ## Footnote This involves understanding the principles of passive transport.

Question 35

What is active transport?

Answer 35

Movement against a concentration gradient using energy from ATP ## Footnote Active transport is essential for moving substances into or out of cells when they are in lower concentrations outside than inside the cell.

Question 36

What is the structure of an ATP molecule?

Answer 36

ATP is made of ribose, an adenine base, and three phosphate groups ## Footnote ATP stands for adenosine triphosphate, which serves as the energy currency of the cell.

Question 37

What happens when the bond between the second and third phosphate in ATP is broken?

Answer 37

Energy is released ## Footnote This energy can be used for energy-requiring processes within the cell.

Question 38

What is required to regenerate ATP from ADP?

Answer 38

Energy is required to add a third phosphate bond ## Footnote The process is known as phosphorylation, which converts ADP back to ATP.

Question 39

What processes do vesicles facilitate?

Answer 39

Endocytosis and exocytosis ## Footnote These processes transport large molecules into and out of cells, respectively.

Question 40

Define endocytosis

Answer 40

Movement into the cell ## Footnote This process involves the engulfing of substances by the cell membrane.

Question 41

Define exocytosis

Answer 41

Movement out of the cell ## Footnote This process involves the fusion of vesicles with the cell membrane to release contents outside.

Question 42

What is phagocytosis?

Answer 42

A type of endocytosis also known as 'cell-eating' ## Footnote It involves engulfing large structures like bacterial cells.

Question 43

What is pinocytosis?

Answer 43

A type of endocytosis also known as 'cell-drinking' ## Footnote It involves engulfing liquid substances.

Question 44

What is the role of ATP in endocytosis and exocytosis?

Answer 44

ATP provides the energy required for both processes ## Footnote Without ATP, these processes cannot occur effectively.

Question 45

What is the fluid nature of the cell membrane important for?

Answer 45

It allows for endocytosis and exocytosis to occur ## Footnote The fluidity of the membrane is crucial for the movement of vesicles.

Question 46

How does insulin move out of the cell?

Answer 46

Insulin is packaged in vesicles and transported to the pancreatic duct ## Footnote This process involves exocytosis, where vesicles fuse with the cell membrane to release insulin.