01 Cell structure and Function Premium Version

In cytosol, small molecules and ions may form true solutions, and some large molecules form colloidal solutions.

The correct arrangement of layers in a plant cell wall from inside to outside is secondary wall, primary wall, and middle lamella

Under the electron microscope, mitochondria appear to be vesicles, rods or filaments and also show complex morphology.

Carbohydrates extend out from the outer surface of the membrane and are attached either to membrane lipids as glycolipids or to proteins as glycoproteins.

Which one of the following organelle is found in both prokaryotic and eukaryotic cells Ribosome

Prokaryotic cells do not have a membrane-bound nucleus, whereas eukaryotic cells have a distinct nucleus

SER

the mammalian spermatozoon has a single flagellum, the unicellular green alga Chlamydomonas has two flagella, and the unicellular protozoan Paramecium is covered with a few thousand cilia.

The Golgi complex, or Golgi apparatus, is responsible for modifying, sorting, and packaging proteins and lipids into vesicles for transport to various cellular locations, including the synthesis of plant cell wall components.

Microtubules

In the fluid mosaic model, the phospholipid bilayer of the cell membrane has hydrophobic (water-fearing) tails that face inward, away from water, and hydrophilic (water-loving) heads that face outward towards the water on both sides of the membrane. Proteins and other molecules float within or on this bilayer, contributing to the “mosaic” aspect.

Smooth → lipid Rough → protein

Nucleoli contain DNA that direct the synthesis of rRNA, components of ribosomes which are essential in protein synthesis.

Plastids are the unique organelles found only in plant cells. Glyoxysomes are present only in plant cells It contains a number of enzymes including glycolic acid, oxidase and catalase

The lipid bilayer of cell membranes is hydrophobic, allowing the passive transport of non-polar, lipophilic substances, while polar or charged substances require specific transport mechanisms.

The nucleolar organizer in a region of one or more chromosomes in the nucleolus which contains DNA copies that direct rRNA synthesis.

Ribosomes are tiny organisms, which are involved in the synthesis of Protein

Cyclosis (cytoplasmic streaming) actively moves organelles like mitochondria through the cell. This process is driven by the cytoskeleton (particularly actin filaments) and facilitates nutrient distribution and cellular communication.

In cytosol, small molecules and ions may form true solutions, and some large molecules form colloidal solutions. A colloidal solution may be a sol (non viscous) or a gel (jelly like or viscous).

Microtubules are cylindrical structures made of tubulin proteins and are the most cylindrical in shape among the cytoskeletal elements. They play key roles in maintaining cell shape, cell division, and intracellular transport.

Prokaryote has no true nucleus. It has single circular DNA and there is a lack of histones.

Glyoxysomes are specialized peroxisomes found in plants that contain enzymes for the glyoxylate cycle, which converts fatty acids into carbohydrates, especially during seed germination.

Each dictyosome is formed of bundles of curved and flattened cisternae, associated tubules and secretory vesicles.

Middle lamella cements together the walls of the neighboring cells. It is usually thin and about 1 um in thickness. In woody tissues the middle lamella is commonly lignified.

Mitochondrial DNA is located in the matrix or sometimes attach to the inner mitochondrial membrane. The DNA encodes a similar set of rRNAs, tRNAs and essential mitochondrial proteins.

The 70S ribosomes are found in prokaryotes while slightly larger 80S in eukaryotes.

Single, circular, double stranded molecule not bound by membrane

The finger-like infoldings of the inner membrane of mitochondria are known as cristae. These structures are important for the mitochondrial function in energy production.

Both the tonoplast and lysosome are organelles which are bound by a single membrane each, whilst the nucleus and chloroplast have 2 enveloping membranes.

The 70S ribosomes are found in prokaryotes while slightly larger 80S in eukaryotes.In mitochondira it is 70S.

Some proteins extend completely through the double layer of lipids from one side to the other and are called intrinsic proteins. Some other proteins are smaller and are placed among the phospholipids molecules. These are on one side of the membrane and are called extrinsic proteins.

The cell membrane contains protein channels and pores that facilitate the movement of ions and molecules across the membrane through both active transport (requiring energy) and passive transport (not requiring energy).

Ribosomes are the cellular machinery where protein synthesis occurs. They read mRNA and assemble amino acids into proteins. While the nucleus (a) contains DNA instructions for proteins, ribosomes carry out the actual synthesis.

Ribosomes can be found floating freely within the cytosol and bound to the rough endoplasmic reticulum (RER). Both sets are involved in protein synthesis, but those attached to the RER specifically synthesize proteins destined for secretion or for use in membranes.

In the cytosol mitochondria move about in cytoplasm due to cytoplasmic streaming movements. This is an active mass movement of cytoplasm which is called cyclosis.

Processing og glycoprotein is function of golgiapparatus.

Lysosomes contain hydrolytic enzymes for digesting cellular waste and foreign particles, play a role in autophagy (self-digestion of cellular components), and can cause destruction of cells in certain conditions, like programmed cell death (apoptosis).

Endoplasmic reticulum membranes vary widely in appearance from cell to cell. These channels are separated from the cytoplasmic materials by the spherical or tubular membranes one above the other, called cisternae (singular: cisterna).

The inner membrane of mitochondria forms extensive infoldings called cristae, which increase the surface area for the electron transport chain involved in ATP production

ATP synthase is located in the inner membrane of the mitochondria. It plays a critical role in the production of ATP during oxidative phosphorylation by utilizing the proton gradient established by the electron transport chain.

The rough endoplasmic reliculum is involved in the synthesis of Proteins

Peroxisomes contain enzymes like catalase and oxidases that break down fatty acids (via β-oxidation) and detoxify alcohol. Lysosomes (b) digest cellular waste, while the Golgi apparatus (d) modifies and packages proteins.

Pinocytosis (“cell drinking”) is the uptake of liquids/small dissolved molecules via vesicle formation.

Site of aerobic respiration (Krebs cycle, ETC).

Mitochondria were first observed as granules in muscle cells by Richard Altmann in 1894. Muscle cells have a high demand for ATP (produced by mitochondria), which correlates with a high density of mitochondria within these cells.

In animals, peroxisomes are found in both liver and kidney cells, where they detoxify harmful substances and break down fatty acids.

Mature red blood cells (RBCs) do not have a nucleus, as they lose it during their development to make space for hemoglobin.

The smooth endoplasmic reticulum is the primary site of steroid hormone synthesis. It contains enzymes for lipid metabolism and steroid production. Other organelles like Golgi apparatus are involved in processing but not synthesis of steroids.

Nucleus stands out as slightly darker than the surrounding cytoplasm. They are typically about 10 um in diameter.

The cell wall is fully permeable, allowing the movement of substances like water, ions, and some molecules through it. Its primary function is to provide structure, support, and protection to the cell.

Magnesium is a central component of the chlorophyll molecule, which plants use to capture light energy for photosynthesis.

Virtually all eukaryotic cilia and flagella are remarkably similar in their organization, possessing a central bundle of microtubules, called the axoneme, in which nine outer doublet microtubules surround a central pair of singlet microtubules.

The ribsosome has a diameter of about 20 nm and has two parts: a small sub-unit and large sub-unit. The nucleus is about 7 mm, the mitochondrion is about 2 mm and smaller organelles like the Golgi apparatus and lysosome are somaller than 0.2 mm since they cannot be seen under the light microscope.

mRNA (messenger RNA) is synthesized in the nucleus through the process of transcription, where a gene’s DNA sequence is copied to make an RNA molecule.

70S ribosomes are characteristic of prokaryotes, including bacteria. Eukaryotic cells typically contain 80S ribosomes, although 70S ribosomes can also be found within the organelles of eukaryotes, such as mitochondria and chloroplasts.

Microtubules are long, unbranched slender tubulin protein structures

Lysosomes are bounded by single membrane and contain numerous hydrolytic and acid phosphatase enzymes. These enzymes are synthesized on RER and are further processed in the Golgi apparatus. The processed enzymes are budded off as Golgi vesicles and are called primary lysosomes. These contain those. enzymes which can digest the phagocytosed food particles.

The secondary wall follows the order of primary wall in development. It is laid down inside the primary wall. Its thickness is about 5-10 um, more or less rigid, crystalline, and strongly optically active.

The nucleus was discovered by Robert Brown in 1831.

The phospholipids of cell membranes align with one another, such that their hydrophobic tails are buried inside the two hydropholic layers formed by the phosphate groups. This produces s sheet composed of two parallel molecular layers called a phospholipid bilayer that forms the fundamental structure of membranes.

Double-membraned: Mitochondria, nucleus, chloroplasts. Single-membraned: ER, Golgi, lysosomes, glyoxysomes.

The vacuole is surrounded by a single membrane in plant cells, whereas other organelles like the nucleus and mitochondria are surrounded by double membranes.

The smooth endoplasmic reticulum (ER) is primarily involved in the synthesis of lipids, including oils, phospholipids, and steroids. The rough ER is associated with protein synthesis.

The Golgi body, also known as the Golgi apparatus, is responsible for modifying, sorting, and packaging proteins and lipids for secretion outside the cell.

Ribosomes are synthesized in nucleolus of the nucleus. An example of protein synthesized by free ribosomes is Haemoglobin in young RBCs.

The presence of ribosomes and DNA inside mitochondria indicate that some proteins are synthesized in it, so it is a self replicating organelle.

A tissue is defined as a group of similar cells that work together to perform a specific function in an organism. For instance, muscle tissue is made up of muscle cells that enable movement, while epithelial tissue consists of cells that form protective layers. Organelles refer to structures within a cell, and a system refers to a group of organs working together, thus making “tissue” the correct choice here.

Plant → cellulose Animal → cell wall absent Fungi → chitin

Chromoplasts impart colour to the plant parts other than green. They are present in the petals of the flower and in the ripened fruits. They help in pollination and dispersal of seeds.

Leucoplasts are colorless. They are triangular, tubular or of some other shape.

Prokaryotic cells include bacteria, and lack membrane-bound organelles, e.g. nuclear membrane, instead, the nucleus is known as a nucleoid.

A network of microtubules, microfilaments, and intermediate filaments provides structural support. Animal cells lack cell walls (a); membranes (b) are flexible, and cytoplasm (c) is fluid.

This describes the “9+2” microtubule arrangement characteristic of eukaryotic cilia and flagella

Intermediate filaments is made of Fibrous units.

Chloroplasts are the organelles in plant cells where sunlight energy is captured for photosynthesis. They contain chlorophyll, which allows the plant to convert light energy into chemical energy, producing glucose and oxygen.

Ribssosomes contain ribosomal RNAs (ribonucleic acids). Chloroplasts and mitochondria contain circular DNA (deoxyribonucleic acid), similar to those found in prokaryotic cells; this supports the theory of endosymbiosis. The golgi apparatus does not contain nucleic acids.

Prokaryotic cell walls, such as those found in bacteria, are primarily composed of murein, also known as peptidoglycan. Murein provides structural support and protection to the bacterial cell.

Hooke discovered cell walls in cork (1665), while protoplast (living cell content) was described later.

Plastids (e.g., chloroplasts) are found only in plant cells.

the mammalian spermatozoon has a single flagellum, the unicellular green alga Chlamydomonas has two flagella, and the unicellular protozoan Paramecium is covered with a few thousand cilia.