Animal Cell: Important Notes For NEET 2023 Biology

The NEET 2022 exams are quickly approaching. Brace yourself up for these as early as possible! Most students say that NEET 2022 Biology is the easiest section to understand. It is the simplest subject to score. Particularly interesting is the “Animal Cell” topic. It is a fundamental topic that students study in their upper secondary classrooms. Students should grasp these key concepts while studying for the NEET 2022 Biology exams by Learning Biology Concepts – Topics and Definitions. Here are some important notes on animal cells that can assist students in effective preparation for the NEET 2022 Biology exams.

Students must have read the term “animal cells” thousands of times in their NCERT Biology textbooks. Now the question arises what it is? And how many cell organelles are present in it? So let’s get into it!

Define Animal Cell

As you can learn from Biology Concepts – Topics and Definitions, animal cells are categorised as eukaryotic cells. These cells do not have a cell wall and are only surrounded by the plasma membrane. The plasma membrane helps hold all the cell organelles, including the nucleus, in their right place. Plant cells have an additional outer layering, cell wall, giving them external protection.

Animals account for about three-quarters of all species. They are the most diversified collection of living organisms on the planet. These systems in the body are improved by their core elements’ capacity to move, respond to sensory input, adjust to climate conditions, and respond to diverse feeding, defence, and reproduction strategies. Unlike plants, animals cannot produce their foods. Thus, they rely on plants in some way.

Animal Cell Structure

Many structural organelles are present in an animal cell encased in the plasma membrane, allowing it to function effectively, activating functions that assist the host (animal). The cells in the animal’s body help them move, reproduce, react to stimuli, and digest and absorb food. Thus, the cells allow the host (animal) to operate normally.

List of Animal Cell Organelles

Plasma Membrane (Cell Membrane)

• A plasma membrane, also known as a cell membrane, can be defined as a thin semi-permeable protein-enriched membrane layer that envelops an animal cell.
• It comprises lipids, which form a barrier between the cell and its outer environment.
• It surrounds and safeguards the cell’s content.

Nucleus

• The nucleus is known as the information hub of the cell.
• It is a spherical-shaped organelle protected by a double-layered nuclear membrane that separates it from the cytoplasm, mostly found in the centre of a cell.
• The major function of the nucleus is to maintain and regulate cell development activities and sustain cell metabolic activity.
• The nucleus stores all genetic information inside itself.
• The nucleoplasm, often known as the house of chromosomal DNA and genetic materials, contains the nucleus and its constituent organelles.

Cytoplasm

• It is a gel-like fluid that houses all cell organelles and is surrounded by the cell membrane.
• Mitochondria, Endoplasmic reticulum, Ribosomes, Lysosomes, Golgi apparatus, intermediate filaments, microfilaments, microtubules, and vesicles are examples of these organelles.

Mitochondria

• They are known as the powerhouse of the cells, i.e. they are the power stations that produce energy in the form of AdenosinTri-Phosphate ( (ATP) by transforming nutrients and oxygen into energy, allowing the cell to function and release excess power.
• It is a double membrane-bound organelle found in all eukaryotic cells’ cytoplasm.
• The total number of mitochondria present in each cell depends significantly on the functioning of the cell.

Ribosomes

Ribosomes are found in all living cells. They are tiny organelles composed primarily of RNA cytoplasmic granules and 40 per cent proteins. They can be found freely floating in the cytoplasm, with some connected to the endoplasmic reticulum. It is the location of protein production.

Endoplasmic Reticulum (ER)

• ER is a repeated folded membranous organelle composed of a thin network of flattened linked compartments (sacs) that joins the cytoplasm to the cell’s nucleus.
• There are membranous spaces within its membranes known as cristae, and membrane folding is called cristae.
• Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER) are the two forms of ER differentiated based on their structure and function.

Golgi apparatus (Golgi bodies/Golgi complex)

• Its main role is to move, alter, and bind proteins and lipids into golgi vesicles to be delivered to their intended places. Only one or more golgi bodies are present in animal cells, whereas plant cells have hundreds of these.
• These membrane-bound cell organelles are located near the nucleus and the endoplasmic reticulum in the cytoplasm of eukaryotic cells. 

Lysosomes

• Lysosomes are highly acidic organelles containing digesting enzymes; thus, each lysosome is covered by a membrane to safeguard it from the outside environment. It is where cell nutrients are digested and excreted, and cells are renewed.
• They are spherical subcellular organelles that are found in nearly all eukaryotic cells.

Cytoskeleton

• The cytoskeleton’s main role is to establish a network that organises the cell’s components while also maintaining the cell’s structure.
• These are fibrous networks created from diverse proteins present in the cytoplasm of eukaryotic cells consisting of long chains of amino acids.
• These networks are made up of 3 types of filaments: actin filaments (Microfilaments), microtubules, and intermediate filaments.

Microtubules

• These are straight, long, hollow cylinder filaments of 13-15 sub-filaments (protofilaments) of tubulin, a globular protein present primarily in eukaryotic cells.
• These filaments can be seen all around the cytoplasm of an animal cell.
• They help in transporting cell organelles, such as mitochondria and vesicles. For example, carrying vesicles from the neuron cell body to the axon terminals and back to the cell body.

Centrioles

These organelles can reproduce or make duplicates on their own. It comprises nine microtubule bundles, helping organise the cell division process.

Peroxisomes

• These are the most widespread micro-bodies present throughout the cell cytoplasm. 
• They are spherically shaped, membrane-bound cell organelles. 
• Their main purpose is to aid in chemical detoxification by transferring hydrogen atoms from different oxygen molecules to form hydrogen peroxide, which neutralises bodily toxins such as alcohol.

Cilia and Flagella

• They are locomotive projections located on the cell’s surface.
• They are formed of filament strands. These filaments contain both partial and complete microtubules, which help to expand the projections.
• Sperm cells have flagella, enabling them to move to the ova for fertilisation.
• Cilia aid in the movement of surface particles, particularly on the epithelial layer of the nostrils and the movement of mucus over the cell’s surface.

Endosome

• Its primary purpose is to fold the plasma membrane in. The folding permits chemicals to enter the cell via the extracellular fluids.
• Their major function is to eliminate waste from the cell through endocytic processes like exocytosis and phagocytosis.

Vacuoles

• The main role of vacuoles is to store food, water, and sugary carbohydrates and remove waste products.
• They can also vary their functionality to supply vital responsibilities that suit the cell by changing form and size.

Microvilli

Microvilli are the surface protrusions located in the intestinal lining, on the surfaces of egg cells, and white blood cells. They offer an increased surface area to absorb digested food and water effectively.

Summary

In simple words, a cell is a structural and functional unit of life. These cells perform their specialized jobs. They vary in shape, size, and structure. Both plants and animals are composed of eukaryotic cells. They share some common characteristics. However, they possess certain differentiation, too, because animals have a more active lifestyle. Furthermore, animals are dependent on plants for their nourishment. They lack specialized cell organelles such as chloroplasts.

Animal Cell is a fundamental topic. Students appearing for the NEET 2022 Biology examination Syllabus of Biology for NEET 2022 must thoroughly understand these topics to perform well on the NEET 2022 exams.