Week 11 / Cellular Process 1 & 2

Question 1

What are the 2 key types of body fluid pools, and how are they distributed?

(2,4)

Answer 1

Intracellular Fluid (ICF):
Located within cells
Makes up 2/3 of total body fluid

Extracellular Fluid (ECF):
Between cells = Interstitial fluid
In blood vessels = Plasma
In lymphatic vessels = Lymphatic fluid (Lymph)
Within brain and spinal cord = Cerebrospinal fluid

Question 2

Whats does solvent mean ?
Whats does solute mean?
What does concentration mean?
What does concentration gradient mean?

Answer 2

the liquid doing the dissolving
– Usually water

the dissolved material (particles or gas)

Amount of solute in a given amount of solvent

Difference in concentration between 2 areas of solution

Question 3

What is selective permeability?

Answer 3

allows a living cell to maintain different concentrations of certain
substances on either side of the plasma membrane.

Question 4

What are the 2 types of gradients across the plasma membrane and their functions?

Answer 4

Concentration gradient: Difference in the concentration of a chemical from one place to another (e.g., inside vs. outside of the plasma membrane).

Electrical gradient: Difference in electrical charges between two regions across the membrane.

Question 5

What constitutes an electrical gradient?

Answer 5

A difference in electrical charges between two regions constitutes an electrical gradient.

Question 6

What is the electrical gradient across the plasma membrane called?

Why are the concentration gradient and electrical gradient important for the plasma membrane?

What is the term for the combined influence of the concentration gradient and the electrical gradient on the movement of a particular ion?

Answer 6

The electrical gradient across the plasma membrane, which represents the difference in charge, is called the membrane potential.

The concentration gradient and electrical gradient are important because they help move substances across the plasma membrane, enabling the transport of ions and molecules essential for cell function.

The combined influence of the concentration gradient and the electrical gradient on the movement of a particular ion is referred to as its electrochemical gradient.

Question 7

What are the different mechanisms of molecule movement across membranes?

Answer 7

-Passive Transport

-Active Transport

-Endocytosis
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis

• Exocytosis

Question 8

What is active transport?

Answer 8

Active Transport :
Movement of substances against their concentration gradient, requiring energy.

Question 9

What is endocytosis? and the subtypes?

Answer 9

-Endocytosis: Process of taking substances into the cell, which includes:
- Phagocytosis: Cellular “eating” of large particles.
- Fluid Endocytosis (Pinocytosis): Cellular “drinking” of fluids and small particles.
- Receptor-Mediated Endocytosis: Selective uptake of molecules via specific receptors.

Question 10

What is exocytosis?

Answer 10

• Exocytosis: Process of expelling substances from the cell.

Question 11

What is phagocytosis?

Why is phagocytosis referred to as “cell eating”?

Which cells are able to perform phagocytosis?

Why is phagocytosis considered a vital defense mechanism?

Answer 11

Phagocytosis is the process by which cells engulf large, solid particles such as food or bacteria into vesicles.

It is called “cell eating” because the cell engulfs large particles or cells, similar to how an organism consumes food.

A few body cells, known as phagocytes, are able to carry out phagocytosis.

Phagocytosis is a vital defense mechanism because it helps protect the body from disease by engulfing harmful particles such as bacteria.

Question 12

What is passive transport?

Answer 12

-Passive Transport :
Movement of substances across the membrane without energy input.

Question 13

What are the types of passive transport? (3)

Answer 13

Simple Diffusion
Facilitated Diffusion
Osmosis

Question 14

What is the principle of diffusion?
(2)

Answer 14

• a passive process involving the random mixing of particles in a solution due to their kinetic energy
• Both the solutes (dissolved substances) and the solvent (liquid that does the dissolving) undergo diffusion.

Question 15

What factors influence the rate of diffusion? (5)

[Steepness of the Concentration Gradient,
Temperature,
Mass of the Diffusing Substance,
Surface Area,
Diffusion Distance
]

Answer 15

1. Steepness of the Concentration Gradient: Greater difference in concentration between two sides of the membrane increases the rate of diffusion.
2. Temperature: Higher temperatures result in faster diffusion rates.
3. Mass of the Diffusing Substance: Larger mass of diffusing particles leads to a slower diffusion rate.
4. Surface Area: Larger membrane surface area available for diffusion increases the diffusion rate.
5. Diffusion Distance: Greater distance over which diffusion must occur results in longer diffusion times.

Question 16

What are the key characteristics of simple diffusion?
[
Energy requirement ,
Movement [what makes it move] ,
Equalization [from what concentration to what does it move],
Lipid solubility
]

Answer 16

Energy Requirement:
No energy is required for simple diffusion.

Movement:
Molecules move due to gradients, which can include differences in concentration, pressure, or charge.
Equalization:
Molecules move from areas of high concentration to areas of low concentration to equalize the gradient.
Lipid Solubility:
The ability of molecules to diffuse also depends on their lipid solubility.

Question 17

What are the key characteristics of facilitated diffusion?
[
Definition ,
Energy requirement ,
Movement [ which gradient does it move] ,
Mechanisms [2],
]

Answer 17

Definition:
Facilitated diffusion allows solutes that are too polar or highly charged to move through the lipid bilayer by using a passive process.

Energy Requirement:
It requires a carrier protein in the membrane but does not require ATP.

Movement:
Solutes move down their concentration gradient.

Mechanisms:
Ion Channels: Specialized channels for ions to pass through the membrane.

Protein Transporters (Carriers): Proteins that help transport specific substances across the membrane.

Question 18

What are the key features of ion channels in facilitated diffusion?
[
Definition ,
function,
Ions Involved ,
What is Gated channel,
Types of Gated channel [3]
]

Answer 18

• Definition: Ion channels are integral transmembrane proteins

-FUNCTIONS: facilitate the passage of small, inorganic ions that cannot penetrate the nonpolar interior of the lipid bilayer due to their hydrophilic nature.

• Ions Involved:
  Ions such as Na⁺, K⁺, Cl⁻, and Ca²⁺ use specific protein channels to diffuse into and out of cells.
• Gated Channels:
  Ion channels can be gated, meaning part of the channel protein acts as a “plug” or “gate,” changing shape to open or close the pore.
• Types of Gated Channels:
  
  • Ligand-Gated:
    Open in response to the binding of a specific molecule (ligand).
  • Voltage-Gated:
    Open in response to changes in membrane potential.
  • Mechanically-Gated:
    Open in response to mechanical forces or changes in pressure.

Question 19

What is channel-mediated facilitated diffusion of potassium ions (K⁺)?

[
Definition [ what does it allow] ,
Process [which gradient do they move] ,
Gated Channel [ what i means in this context] ,
]

Answer 19

Definition:
Channel-mediated facilitated diffusion allows potassium ions (K⁺) to pass through a gated K⁺ channel in the plasma membrane.

Process:
K⁺ ions diffuse down their concentration gradient through the channel.

Gated Channel:
The K⁺ channel is gated, meaning it can open or close based on specific signals, allowing for regulated movement of potassium ions into or out of the cell.

Question 20

What are the key features of carrier-mediated facilitated diffusion?

[
Definition [ what is a carrier] ,
Binding (where does the solute bind more?),
Saturation,
Substances [ which substances are moved across the membrane] ,
]

Answer 20

• Definition:
  A carrier (or transporter) is used to move a solute down its concentration gradient across the plasma membrane.
• Binding:
  The solute binds more frequently to the carrier on the side of the membrane with a higher concentration of the solute.
• Saturation:
  When carriers are fully occupied, the transport maximum is reached, leading to saturation of the process.
• Substances:
  Common substances that move across the plasma membrane via carrier-mediated facilitated diffusion include glucose, fructose, galactose, and some vitamins.

Question 21

How does glucose enter body cells through facilitated diffusion?
[Binding [what does glucose bind to],
Shape change [ why does the transporter change shape],
Release [ where does glucose release]
]

Answer 21

1. Binding:
   Glucose binds to a specific carrier protein (glucose transporter) on the outside of the cell surface.
2. Shape Change:
   The transporter undergoes a change in shape, allowing glucose to pass through the membrane.
3. Release:
   The transporter releases glucose on the other side of the membrane, completing the process of facilitated diffusion.

Question 22

What is osmosis, and how does it occur?

[
Definition ,

What is the membrane permeable to ? ,

What 2 ways can the water pass through the plasma membrane?
]

Answer 22

• Definition:
  Osmosis is a special form of diffusion that involves the diffusion of water through a semi-permeable membrane.
• Membrane Properties:
  The membrane is permeable to the solvent (water) but impermeable to the solute.
• Movement of Water:
  Water molecules can pass through the plasma membrane in two ways:
  1. Simple Diffusion:
     By moving through the lipid bilayer via simple diffusion.
  2. Aquaporins:
     By moving through aquaporins, which are integral membrane proteins that function as water channels.

Question 23

check powerpoint for osmolarity

Answer 23

check powerpoint for osmolarity

Question 24

What is tonicity?

Answer 24

Tonicity is the ability of a solution to change the shape or tone of cells by altering their internal water volume

Question 25

What happens in isotonic solution?

Answer 25

cells retain there normal size and shape in isotonic solutions

Question 26

What happens in hypertonic solution?

Answer 26

cells lose water by osmosis and shrink in a hypertonic solution ,

Question 27

What happens in hypotonic solution?

Answer 27

cells take on water by osmosis until they become bloated and burst

Question 28

What is active transport?

What do we call transporters involved in active transport?

Can active transport pumps become saturated?

What are the two types of energy sources used in active transport?

How does primary active transport differ from secondary active transport?

Answer 28

Active transport is the movement of molecules against the concentration gradient, requiring energy.

Transporters involved in active transport are often called “pumps.”

Yes

(1) The direct use of ATP in primary active transport, and (2) The use of an electrochemical gradient in secondary active transport.

Primary active transport directly uses ATP as an energy source, while secondary active transport uses an electrochemical gradient to drive the process.

Question 29

What is the role of the Na+/K+-ATPase primary active transporter in cells?

What are the major primary active transport proteins found in most cells, besides Na+/K+-ATPase?

Answer 29

The Na+/K+-ATPase primary active transporter is found in every cell and helps

establish and maintain the membrane potential of the cell

The major primary active transport proteins are:
(1) Ca2+- ATPase
(2) H+- ATPase
(3) H+/K+ -ATPase

Question 30

Steps of primary transport? (6)

Answer 30

1.Cytoplasmic Na+ binds to
pump protein.

2.Binding of Na+ promotes
phosphorylation of the
protein by ATP.

3.Phosphorylation causes
the protein to change
shape, expelling Na+ to the
outside

4.Extracellular K+ binds to
pump protein.

5.K+ binding triggers
release of the phosphate.
Pump protein returns to
its original conformation.

6.K+ is released from the
pump protein and Na+ sites
are ready to bind Na+ again.
The cycle repeats.

Question 31

How does secondary active transport differ from primary active transport?

How many binding sites do transporters mediating secondary active transport have, and what do they bind?

What is the difference between co-transporters (symporters) and counter-transporters (antiporters)?

Answer 31

Secondary active transport uses an electrochemical gradient across a plasma membrane as its energy source, unlike primary active transport which uses ATP directly

Transporters mediating secondary active transport have two binding sites, one for an ion (e.g., Na+) and another for the cotransported molecule (e.g., Glucose).

Co-transporters (symporters) move molecules in the same direction, while counter-transporters (antiporters) move molecules in opposite directions.

Question 32

What is endocytosis?
What is exocytosis?

Answer 32

Endocytosis is the process of moving macromolecules into the cell by pinching the plasma membrane to form membrane-bound vesicles.

Exocytosis is the process of moving macromolecules out of the cell by the fusion of membrane-bound vesicles with the plasma membrane.

Question 33

What happens during endocytosis in vesicular transport (what does it involve)?
Does endocytosis require energy?
What are the three major types of endocytosis?

Answer 33

Endocytosis involves the packaging of extracellular materials into vesicles at the cell surface, allowing large volumes of extracellular material to enter the cell.

Yes, endocytosis requires energy in the form of ATP.

The three major types of endocytosis are:
1. Receptor-mediated endocytosis
2. Pinocytosis
3. Phagocytosis

Question 34

What is receptor-mediated endocytosis?

Can you give examples of substances taken up by cells through receptor-mediated endocytosis?

What type of vesicle is involved in receptor-mediated endocytosis?

Answer 34

Receptor-mediated endocytosis is a highly selective process where a vesicle forms after a receptor protein in the plasma membrane recognizes and binds to a specific particle in the extracellular fluid.

Examples include cholesterol-containing low-density lipoproteins (LDLs), transferrin (iron-transporting protein), some vitamins, antibodies, and certain hormones.

A clathrin-coated vesicle forms in the cytoplasm during receptor-mediated endocytosis.

Question 35

What are the steps in receptor-mediated endocytosis? (6)

Answer 35

1. Binding
2. Vesicle formation
3. Un-coating
4. Fusion with endosome
5. Recycling of receptors
   to plasma membrane
6. Degradation in
   lysosomes

Question 36

What happens during pinocytosis?

Why is pinocytosis referred to as “cell drinking”?

In which types of cells is pinocytosis most common?

What types of molecules are typically taken up by pinocytosis?

Answer 36

During pinocytosis, the plasma membrane forms an invagination, sinks inward, and pinches off to form a vesicle that brings dissolved materials into the cell.

It is called “cell drinking” because the process involves the uptake of materials dissolved in water.

Pinocytosis is most common in absorptive cells, particularly in the intestines and kidneys.

Most proteins and other large molecules are taken up by pinocytosis.