Cell Structure And Size Of Specimens

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Cell Structure: Animal Cells

Animal cells have a cell membrane that separates them from surroundings.
They contain cytoplasm, a gel-like liquid where chemical reactions occur.
The nucleus contains the genetic material (DNA).
Mitochondria are the site of aerobic respiration, releasing energy.
Ribosomes are the site of protein synthesis.

A typical animal cell

Cell Structure: Plant Cells

Plant cells have all animal cell structures: cell membrane, cytoplasm, nucleus, mitochondria, ribosomes.
Additionally, they have a cellulose cell wall for structural support.
Chloroplasts contain chlorophyll and absorb light energy for photosynthesis.
A permanent vacuole stores cell sap and provides support.

A typical plant cell

Bacterial Cells (Prokaryotes)

Bacteria have a cell wall made of peptidoglycan (not cellulose).
They have a cell membrane, cytoplasm, and ribosomes.
DNA is circular and not enclosed in a nucleus; some have plasmids.
Bacteria lack internal membranes: no nucleus, mitochondria, or chloroplasts.

A typical bacterial cell

Functions of Cellular Structures

Cell membrane: controls passage of substances into/out of the cell.
Nucleus: contains DNA, controls cell activities (animal/plant only).
Mitochondria: site of aerobic respiration (animal/plant).
Ribosomes: protein synthesis (all cell types).
Chloroplasts: photosynthesis (plant only).
Cell wall: provides support and shape (cellulose in plants, peptidoglycan in bacteria).
Permanent vacuole: storage and support (plant only).
Plasmids: small DNA loops carrying extra genes (bacteria).

Specialised Cells

Cells differentiate (become specialised) to carry out specific functions in the body.
Root hair cell: has a long extension (root hair) that increases surface area for absorption of water and mineral ions; thin walls let water move through quickly; no chloroplasts (underground, no light).
Xylem vessel: dead cells with no top/bottom walls, forming a continuous tube for water transport; walls thickened with lignin for support.
Palisade mesophyll cell: column-shaped to pack many cells under the leaf's upper surface and contains many chloroplasts for maximum photosynthesis.

Root hair cell

Organisation of Cells

Cells divide to produce new cells for growth and repair.
Cells can become specialised to carry out specific functions.
Levels of organisation: cells → tissues → organs → organ systems → organism.
Examples: palisade mesophyll cells form leaf tissue; leaf is an organ.

Levels of organisation

Magnification Formula

Formula: magnification = image size ÷ actual size.
Equation triangle: M = I / A; I = M × A; A = I / M.
Units must be the same (e.g., both in mm or both in μm).
Magnification has no units (e.g., ×10, ×3000).

Magnification equation triangle

Converting Between Units

1 mm = 1000 μm (micrometres).
To convert μm to mm, divide by 1000; to convert mm to μm, multiply by 1000.
Common error: forgetting to convert units before using magnification formula.

Converting mm to μm

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练习题

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1.Which of the following structures is found in both animal and plant cells?
Easy
- ACell wall
- BChloroplast
- CNucleus
- DPermanent vacuole
2.Bacterial cells contain a nucleus.
Easy
True or false?
3.State one function of the cell membrane.
Easy
4.Match each cell structure to its function.
Medium
- Nucleus
- Chloroplast
- Ribosome
- Contains genetic material
- Site of photosynthesis
- Site of protein synthesis
5.Arrange the following levels of biological organisation from smallest to largest:
Easy
- Tissue
- Organ
- Cell
- Organ system
6.Which of the following is present in a bacterial cell but not in an animal cell?
Medium
- AMitochondrion
- BCell wall made of peptidoglycan
- CNucleus
- DRibosome
7.A student measures the length of a bacterium as 2 μm. She draws it with a length of 50 mm. What is the magnification of her drawing?
Medium
- A27500
- B25000
- C30000
- D22500
8.Name the structure that contains chlorophyll in a plant cell.
Easy

更多题目

9.Which of the following statements about the cell wall is correct?
Medium
- APlant cell walls are made of peptidoglycan.
- BBacterial cell walls are made of cellulose.
- CPlant cell walls are made of cellulose.
- DAnimal cell walls are made of cellulose.
10.The inner membrane of mitochondria are visible under a light microscope.
Easy
True or false?
11.Which of the following is found in plant cells but not in animal cells?
Easy
- ACell membrane
- BMitochondrion
- CChloroplast
- DRibosome
12.Bacterial cells have a nucleus.
Easy
True or false?
13.Which of the following are found in both plant and animal cells? (Select all that apply)
Medium
- ACell wall
- BMitochondria
- CChloroplasts
- DRibosomes
- ENucleus
14.Arrange the following levels of biological organisation from smallest to largest.
Easy
- Tissue
- Organ
- Cell
- Organ system
15.A student observes a cell under a light microscope and sees a nucleus, chloroplasts, and a cell wall. Which type of cell is most likely being observed?
Easy
- AAnimal cell
- BBacterial cell
- CPlant cell
- DFungal cell
16.Match each cell structure to its correct function.
Medium
- Cell membrane
- Nucleus
- Mitochondrion
- Ribosome
- Controls passage of substances into and out of the cell
- Contains genetic material (DNA)
- Site of aerobic respiration
- Site of protein synthesis
17.Which of the following structures are found in both plant and animal cells? Select all that apply.
Medium
- ACell wall
- BCell membrane
- CChloroplast
- DMitochondrion
- EPermanent vacuole
18.Which of the following is a correct conversion?
Easy
- A1 mm = 100 μm
- B1 mm = 1000 μm
- C1000 mm = 1 μm
- D1 μm = 1000 mm
19.Place the following structures in order of size from smallest to largest: a) ribosome, b) nucleus, c) mitochondrion, d) cell.
Medium
- Ribosome
- Mitochondrion
- Nucleus
- Cell
20.A student sees a cell under a light microscope with a nucleus, cell wall, and chloroplasts. Which type of cell is it?
Easy
- AAnimal cell
- BPlant cell
- CBacterial cell
- DFungal cell
21.A student observes a cell under a light microscope and identifies a cell wall, a large permanent vacuole, and chloroplasts. Which of the following could the cell NOT be?
Hard
- APalisade mesophyll cell
- BRoot hair cell
- CSpongy mesophyll cell
- DGuard cell
22.A cell has the following features: circular DNA, cell wall made of peptidoglycan, no mitochondria, and plasmids. Which type of cell is it?
Medium
- AAnimal cell
- BPlant cell
- CBacterial cell
- DFungal cell
23.Which of the following are visible using a light microscope? (Select all that apply)
Medium
- ANucleus
- BRibosome
- CChloroplast
- DMitochondrion
- ECell wall
24.A student draws a diagram of a cell that is 80 mm wide. The actual width of the cell is 0.02 mm. What is the magnification of the drawing?
Medium
- Ax0.00025
- Bx40
- Cx400
- Dx4000
25.Which of the following structures are found in both animal and plant cells? (Select all that apply)
Easy
- ACell membrane
- BCell wall
- CMitochondria
- DChloroplasts
- ERibosomes
26.A student observes a cell using a light microscope and identifies a cell wall, a large permanent vacuole, and chloroplasts. Which of the following could the cell be?
Medium
- Aa liver cell
- Ba palisade mesophyll cell
- Ca red blood cell
- Da bacterial cell
27.A student measures the length of a bacterium in a micrograph as 25 mm. The magnification of the micrograph is ×5000. What is the actual length of the bacterium in micrometres (μm)?
Medium
- A5 μm
- B50 μm
- C500 μm
- D0.5 μm
28.Which of the following structures are visible using a light microscope? (Select all that apply)
Medium
- Anucleus
- Bribosome
- Cchloroplast
- Dmitochondrion
- Ecell wall
29.A student uses a light microscope to view a specimen. She sees a cell with a cell wall but no chloroplasts. The cell is most likely a:
Medium
- Apalisade mesophyll cell
- Bbacterial cell
- Croot hair cell
- Dliver cell
30.Which of the following structures is found in plant cells but not in animal cells?
Easy
- ACell membrane
- BMitochondria
- CChloroplasts
- DRibosomes
31.Which of the following structures are found in both plant and animal cells? (Select all that apply)
Easy
- ANucleus
- BCell wall
- CMitochondria
- DChloroplasts
- ERibosomes
32.A student observes a cell under a light microscope and sees a cell wall, a large permanent vacuole, and chloroplasts. Which of the following could the cell be?
Medium
- AA palisade mesophyll cell from a leaf
- BA root hair cell from a root
- CA red blood cell from a human
- DA bacterial cell
33.Arrange the following levels of biological organisation from smallest to largest: tissue, cell, organ, organ system.
Easy
- tissue
- cell
- organ
- organ system
34.A student uses a light microscope to view a plant cell. Which of the following structures would be visible under the light microscope?
Medium
- ARibosomes
- BMitochondria
- CNucleus
- DCell membrane detail
35.Which of the following structures are found in both plant and bacterial cells? (Select all that apply)
Medium
- ACell membrane
- BCellulose cell wall
- CRibosomes
- DMitochondria
- ECytoplasm
36.A student measures the length of a plant cell in a micrograph as 40 mm. The actual length of the cell is 0.02 mm. What is the magnification?
Medium
- Ax0.0005
- Bx2000
- Cx0.8
- Dx800
37.Which of the following is a specialised cell adapted for absorption of water and minerals from the soil?
Easy
- APalisade mesophyll cell
- BRoot hair cell
- CCiliated epithelial cell
- DRed blood cell
38.Chloroplasts are found in both plant and animal cells.
Easy
True or false?
39.Which of the following is the site of protein synthesis in a cell?
Easy
- ANucleus
- BRibosome
- CMitochondrion
- DChloroplast
40.Mitochondria are the site of aerobic respiration in cells.
Easy
True or false?
41.Which of the following structures is present in bacterial cells but not in plant cells?
Easy
- ACell wall
- BRibosomes
- CPlasmids
- DCytoplasm
42.Complete the sentence.
Easy
The organelle that is the site of aerobic respiration is the ____.
43.Complete the sentences about converting units.
Easy
1 mm = ____ μm. To convert μm to mm, divide by ____.
44.A plant cell is 0.05 mm in actual length. Under a microscope, its image measures 25 mm. What is the magnification?
Medium
45.A student measures the image of a mitochondrion as 15 mm in a textbook diagram. The actual length of the mitochondrion is 0.005 mm. What is the magnification of the diagram?
Medium
46.State the function of mitochondria in a cell.
Easy
47.Convert the following units:
Easy
A bacterial cell is 2 μm long. This is equal to ____ mm.
48.State the function of the cell wall in a plant cell.
Easy
49.Explain how the structure of a root hair cell is adapted to its function of absorbing water and minerals from the soil.
Medium
50.Explain how the structure of a palisade mesophyll cell is adapted for photosynthesis.
Medium
51.A plant cell is 0.05 mm in actual length. Under a microscope, its image measures 25 mm. What is the magnification?
Medium
- A550
- B450
- C600
- D500
52.A student measures the image of a mitochondrion as 15 mm in a textbook diagram. The actual length of the mitochondrion is 0.005 mm. What is the magnification of the diagram?
Medium
- A3000
- B3300
- C2700
- D3600

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