NEET Study Notes Cell Structure and Function: Cells are the structural and fundamental unit of all living organisms. In 1665, Robert Hooke discovered a cell from a thin section of cork under a microscope, which was self-made. Cells contain a dense membrane-bound structure which is called the nucleus. The nucleus contains chromosomes that contain DNA, the genetic material.

• Every year about 6-7 questions are asked from this topic which makes the weightage of this topic 15%. Check NEET Biology Syllabus
• In NEET Study Notes for Cell Structure and Function, important topics like Types of cells, parts of the cell, cell division, are explained that will help you to attempt questions from this unit in NEET 2022.

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Important Topics in NEET Cell Structure and Function

NEET Study Notes for Cell

Cell can be divided into prokaryotic cells and eukaryotic cells depending on the nature of the nucleus.

• Prokaryotic Cell- Cells that lack a membrane-bound nucleus are called prokaryotic. The nucleus in Prokaryotic cells are not well defined and called nucleoids. Prokaryotes have a cell wall that surrounds the cell membrane. The thick fluid that fills each cell is called cytoplasm.
• Eukaryotic cells- Cells that have well-defined membrane-bound nuclei are called eukaryotic cells. Eukaryotes include plants, animals, and fungi. Cell organelles such as plastids, mitochondria, Golgi bodies are present. Eukaryotes are mostly multi-cellular.

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Difference between Plant Cells and Animal Cells

Plants and animals are eukaryotes. However, there are certain distinctions between these cells.

Difference between Prokaryotic Cells and Eukaryotic Cells

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Cell Wall

• Cell Envelope consists of three-layered structure- outermost glycocalyx, cell wall and then plasma membrane.
• Cell wall is the outermost protective layer that is found in plant cells. These are not found in animal cells.
• Cell walls are composed of cellulose, hemicellulose, pectins, and proteins whereas the cell wall of algae is made up of cellulose,minerals like calcium carbonate.
• Plants can withstand wind, rain and high temperature due to the presence of these cell walls.

Plasma Membrane

• A thin permeable membrane, also known as cell membrane separates cells from one another and the internal contents of cells from the outside environment.
• Plasma Membrane provides a protective layer, Diffusion of gases and movement of other substances takes place through this plasma membrane.

Cytoplasm

• The substance that surrounds the nucleus and inside the cell membrane is cytoplasm.
• The cytoplasm also contains other organelles like flagella, mitochondria, centrosomes, plastids, etc.
• It exists in about half of the cell's volume.

Endomembrane System

The endomembrane system includes- endoplasmic reticulum, Golgi complex lysosomes, and vacuoles.

Endoplasmic Reticulum

• Endoplasmic Reticulum is the network of tiny tubular structures that are scattered in the cytoplasm.
• ER are present in most eukaryotic cells
• ER is made of three components- Cisternae, Vesicles and Tubules. These structures are bound by a single unit membrane.
• ER helps in the secretion and synthesis of proteins through golgi bodies.
• Based on the physical and functional properties- ER can be divided into Smooth and Rough ER.
• Rough ER synthesizes and secretes proteins in the cells. Smooth ER helps in synthesis of phospholipids and help metabolism.

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Golgi Apparatus

• Golgi Apparatus is a cell organelle that processes proteins so that these can be transported.
• It helps in the glycosidation of lipids and glycolisation of proteins.
• Golgi complex also aids in the formation of primary lysosomes.
• The Golgi body is made of four main types- Cisternae, Tubules, Secretory vesicles, and Golgian Vacuoles.

Vacuoles

• Vacuoles store water, minerals, and anthocyanin pigments.
• Vacuoles are larger in plant cells, in comparison to plant cells and also provide rigidity.
• Vacuole also maintains the osmotic relations of a cell, which help in water absorption.

Lysosomes

• Lysosomes are small vesicular structures that are bound by a membrane.
• Also known as suicide bags, these release digestive enzymes which break down the food.
• Lysosomes are absent in prokaryotes but absent in eukaryotes.
• Lysosomes are also responsible for removing dead organelles from the cell and protects the cell from damage.

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Mitochondria

• Mitochondria, also referred to as the powerhouse of the cell produce ATP
• Energy is produced during food molecule breakdown. These involve glycolysis, oxidative, decarboxylation, and oxidative phosphorylation.
• Products of cell respiration are used in the forming of steroids, cytochromes, chlorophyll, etc.

Plastids

• The largest organelles in plant cells are called plastids. These have DNA, RNA ribosomes, and double-membrane envelope.
• These contain pigments of various colors like orange, red, green, and colorless. Plastids carrying green-colored pigments are called chlorophyll.
• There are three types of plastids- Leucoplasts, Chromoplasts, and Chloroplasts.

Cilia and Flagella

• Cilia and Flagella are hair-like outgrowths of the cell membrane that help in locomotion, cleaning, circulation, feeding, etc.
• Cilia take part in the location as well as the attachment. These are small and cause the movement of cells or surrounding fluid.
• Flagella are slightly longer and involved only in locomotion.
• Cilia and Flagella are sensitive to changes in light, temperature, and contact.

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Ribosomes

• Ribosomes, also known as protein factories of the cell,
• It also serves as the site of protein synthesis of the cell.
• There are two types of Ribosomes- 70 S and 80 S. 70 S Ribosomes are found in prokaryotes, mitochondria, and eukaryotes plastids.
• 80 S Ribosomes are found in the cytoplasm of eukaryotes.

NEET Study Notes on Chemical Constituents of Living Cells

Biomolecules are organic compounds that contain carbon. Such molecules are present in living cells and help in the maintenance and metabolic processes of living organisms. The four main types of Biomolecules are:

• Amino Acids- Amino acids are called structural units or digestive end products of the nutrients. These are carbon-containing compounds. Each amino acid comprises of one central carbon enclosed by four substituents groups. These are hydrogen, carboxyl, amino, and a variable group designated as the R group.
• Lipids- Water-insoluble compounds like glycerol, fats, steroids, etc are called lipoids. Lipids provide more energy as compared to carbohydrates. The three types of lipids are simple lipids, Compound Lipids, and Derived Lipids. Lipoproteins is the substance by which the membrane system of a cell is formed.
• Nucleic Acids-Nucleic Acids are a combination of carbon, hydrogen, oxygen, nitrogen, phosphorous. These are the genetic material that is present in an organism that includes DNA and RNA.

NEET Study Notes on Cell Cycle and Cell Division

Cell Cycle

Cell Growth, DNA Replication, and cell division are the stages of the cell cycle. While this cell cycle is simple in prokaryotes, it is a complex process in eukaryotes.

• Cell Cycle is divided into interphase and M.Phase (Mitosis)

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Interphase

• Interphase is that phase which constituents around 95% of the cell cycle.
• It is the time period between the end of a cell division and the commencement of the next cell division.
• Interphase is divided into three phases- G1, S, and G2
• Gap 1 is the duration between previous mitosis and next cell cycle DNA replication.
• S phase- S phase or Synthesis is the phase in which DNA replication occurs. While the chromosomes remain the same, DNA content and centriole are duplicates.
• Gap 2- In this phase, the cells, continue to grow and prepare for mitosis.

M.Phase

• During the phase cell division actually occurs.
• This phase is divided into karyokinesis (a division of the nucleus) and cytokinesis (a division of the cytoplasm)
• Mitosis is also known as equation division as the number of chromosomes in a parent cell is equal to the number of chromosomes in the daughter cell.

NEET Sample Questions for Cell Structure and Function

Question: What are Ribosomes sites for?

1. Protein Synthesis
2. Fat Synthesis
3. Respiration
4. Photosynthesis

Answer: Protein Synthesis

Ribosomes, also known as the protein factory of the cell are the sites for protein synthesis Ribosomes are composed of ribonucleic acid and proteins. There are two types of Ribosomes - 70 S and 80 S.

Question: What is the cell wall of a plant composed are of?

1. Carbohydrates
2. Lipids
3. Cellulose
4. Lipoprotein

Answer: Cellulose

Cellulose fibers are long linear most abundant macromolecules that are comprised of glucose molecules. These fibers compound in bundles of 40, these are known as microfibrils.

Question: Organelle that serves as an area from where molecules are distributed across the cell is called as?

1. Mitochondria
2. Golgi Apparatus
3. Plastids
4. Vacuole

Answer: Golgi Apparatus

Question: What is Mitoplast?

1. Name for Mitochondria
2. Mitochondria without outer membrane
3. Mitochondria without Membranes
4. Mitochondria without inner membrane

Answer: Mitochondria without outer membrane

Question: Which cell organelle stores energy in the form of ATP and is responsible for cellular respiration?

1. Mitochondria
2. Lysosomes
3. Ribosomes
4. Centrosomes

Answer: Mitochondria

Mitochondria is known as the powerhouse of the cell as it stores energy in the form of ATP and is also responsible for cellular respiration. Chloroplast and Mitochondria are double membrane-bound organelles and present only in eukaryotes.

Question: What is a Plasma membrane?

1. Flexible
2. Selectively permeable
3. Lipoprotein membrane
4. All of these

Answer: All of this

Plasma membrane is found in cells that help in the separation of the interior components from the cell with the external environment.

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