Cell membrane structure diagram with labels for lipid bilayer, protein channel, and carbohydrate chains.
Diagram of a cell membrane showing the lipid bilayer, embedded proteins, and carbohydrate chains, illustrating the structure and function of the cell membrane.
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Show Answer Key & Explanations
Step-by-step solution for: Biology Cell Worksheets
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Show Answer Key & Explanations
Step-by-step solution for: Biology Cell Worksheets
Let’s go through each question one by one and fill in the correct answers based on biology concepts about cell membranes, walls, diffusion, osmosis, and facilitated diffusion.
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1. Name two functions of the cell membrane:
- Controls what enters and leaves the cell (selective permeability)
- Protects the cell and gives it shape
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2. The cell membrane contains _protein_ molecules that are embedded in the lipid bilayer.
*(Proteins help with transport, signaling, and structure.)*
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3. Why do scientists call the membrane a “mosaic”?
Because it’s made of many different parts (like proteins, lipids, carbohydrates) arranged like tiles in a mosaic — not uniform, but patchy and varied.
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4. On the image, label the:
*(Since we can’t draw here, I’ll describe where each part is usually located in a standard fluid mosaic model diagram.)*
a. lipid bilayer → The double layer of phospholipids forming the main structure (the “background” of the membrane).
b. protein channel → A protein spanning across the membrane, often shown as a tunnel or pore for molecules to pass through.
c. carbohydrate chains → Attached to proteins or lipids on the *outside* surface of the membrane; look like little branched trees sticking out.
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5. What three types of organisms have cell walls?
- Plants
- Fungi
- Bacteria
*(Note: Animal cells do NOT have cell walls.)*
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6. What is the main function of the cell wall?
To provide structural support and protection — helps the cell keep its shape and prevents bursting under pressure.
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7. What are plant cell walls composed of?
Cellulose (a strong carbohydrate fiber)
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8. One of the most important functions of the cell membrane is to _regulate_ the movement of dissolved _substances_ from the liquid on one side of the membrane to the liquid on the other.
*(It controls what goes in and out — selective permeability.)*
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9. A solution is a _mixture_ of two or more substances.
*(Specifically, a homogeneous mixture where one substance dissolves in another.)*
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10. Define diffusion:
The movement of particles from an area of higher concentration to an area of lower concentration until evenly spread out.
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11. When the particles are the same throughout, the system has reached _equilibrium_.
*(No net movement anymore — balanced.)*
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12. Diffusion depends on _random_ particle movements, therefore it [does] does not require energy.
→ Circle: does not
*(Diffusion is passive — no ATP needed.)*
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13. If a substance is able to diffuse across a membrane, the membrane is said to be _permeable_ to that substance.
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14. Define osmosis:
The diffusion of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
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15.
- Isotonic means → Equal solute concentration inside and outside the cell → no net water movement.
- Hypertonic means → Higher solute concentration outside the cell → water moves OUT of cell.
- Hypotonic means → Lower solute concentration outside the cell → water moves INTO cell.
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16. Because cells are hypertonic in relation to fresh water, _osmosis_ produces a net movement of water into the cell. If that happens, the cell will become _swollen_ and can even burst.
*(Animal cells can burst; plant cells don’t because of their cell wall.)*
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17. In plant and bacteria cells, what keeps them from bursting due to osmotic pressure?
Their rigid cell wall provides strength and prevents bursting.
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18. Cell membranes have _transport proteins_ that make it easy for certain molecules to cross the membrane.
*(Like channels or carriers that help specific molecules move without energy.)*
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19. When proteins help molecules move across the membrane, it is called _facilitated diffusion_.
*(Still passive — no energy used — just helped by proteins.)*
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Final Answer:
1. Controls what enters/leaves the cell; protects and shapes the cell
2. protein
3. It’s made of many different parts arranged like a mosaic
4. a. lipid bilayer = double layer of phospholipids; b. protein channel = tunnel-like protein across membrane; c. carbohydrate chains = sugar branches on outer surface
5. Plants, fungi, bacteria
6. Provides support and protection; maintains shape
7. Cellulose
8. regulate; substances
9. mixture
10. Movement of particles from high to low concentration until evenly distributed
11. equilibrium
12. random; does not
13. permeable
14. Diffusion of water across a membrane from high to low water concentration
15. Isotonic = equal solute concentration; Hypertonic = higher solute outside; Hypotonic = lower solute outside
16. osmosis; swollen
17. Cell wall
18. transport proteins
19. facilitated diffusion
---
1. Name two functions of the cell membrane:
- Controls what enters and leaves the cell (selective permeability)
- Protects the cell and gives it shape
---
2. The cell membrane contains _protein_ molecules that are embedded in the lipid bilayer.
*(Proteins help with transport, signaling, and structure.)*
---
3. Why do scientists call the membrane a “mosaic”?
Because it’s made of many different parts (like proteins, lipids, carbohydrates) arranged like tiles in a mosaic — not uniform, but patchy and varied.
---
4. On the image, label the:
*(Since we can’t draw here, I’ll describe where each part is usually located in a standard fluid mosaic model diagram.)*
a. lipid bilayer → The double layer of phospholipids forming the main structure (the “background” of the membrane).
b. protein channel → A protein spanning across the membrane, often shown as a tunnel or pore for molecules to pass through.
c. carbohydrate chains → Attached to proteins or lipids on the *outside* surface of the membrane; look like little branched trees sticking out.
---
5. What three types of organisms have cell walls?
- Plants
- Fungi
- Bacteria
*(Note: Animal cells do NOT have cell walls.)*
---
6. What is the main function of the cell wall?
To provide structural support and protection — helps the cell keep its shape and prevents bursting under pressure.
---
7. What are plant cell walls composed of?
Cellulose (a strong carbohydrate fiber)
---
8. One of the most important functions of the cell membrane is to _regulate_ the movement of dissolved _substances_ from the liquid on one side of the membrane to the liquid on the other.
*(It controls what goes in and out — selective permeability.)*
---
9. A solution is a _mixture_ of two or more substances.
*(Specifically, a homogeneous mixture where one substance dissolves in another.)*
---
10. Define diffusion:
The movement of particles from an area of higher concentration to an area of lower concentration until evenly spread out.
---
11. When the particles are the same throughout, the system has reached _equilibrium_.
*(No net movement anymore — balanced.)*
---
12. Diffusion depends on _random_ particle movements, therefore it [does] does not require energy.
→ Circle: does not
*(Diffusion is passive — no ATP needed.)*
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OSMOSIS
13. If a substance is able to diffuse across a membrane, the membrane is said to be _permeable_ to that substance.
---
14. Define osmosis:
The diffusion of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.
---
15.
- Isotonic means → Equal solute concentration inside and outside the cell → no net water movement.
- Hypertonic means → Higher solute concentration outside the cell → water moves OUT of cell.
- Hypotonic means → Lower solute concentration outside the cell → water moves INTO cell.
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16. Because cells are hypertonic in relation to fresh water, _osmosis_ produces a net movement of water into the cell. If that happens, the cell will become _swollen_ and can even burst.
*(Animal cells can burst; plant cells don’t because of their cell wall.)*
---
17. In plant and bacteria cells, what keeps them from bursting due to osmotic pressure?
Their rigid cell wall provides strength and prevents bursting.
---
FACILITATED DIFFUSION
18. Cell membranes have _transport proteins_ that make it easy for certain molecules to cross the membrane.
*(Like channels or carriers that help specific molecules move without energy.)*
---
19. When proteins help molecules move across the membrane, it is called _facilitated diffusion_.
*(Still passive — no energy used — just helped by proteins.)*
---
Final Answer:
1. Controls what enters/leaves the cell; protects and shapes the cell
2. protein
3. It’s made of many different parts arranged like a mosaic
4. a. lipid bilayer = double layer of phospholipids; b. protein channel = tunnel-like protein across membrane; c. carbohydrate chains = sugar branches on outer surface
5. Plants, fungi, bacteria
6. Provides support and protection; maintains shape
7. Cellulose
8. regulate; substances
9. mixture
10. Movement of particles from high to low concentration until evenly distributed
11. equilibrium
12. random; does not
13. permeable
14. Diffusion of water across a membrane from high to low water concentration
15. Isotonic = equal solute concentration; Hypertonic = higher solute outside; Hypotonic = lower solute outside
16. osmosis; swollen
17. Cell wall
18. transport proteins
19. facilitated diffusion
Parent Tip: Review the logic above to help your child master the concept of cell biology worksheet.
