51 short questions of 9th Class Biology Chapter 3, The Cell, with exam-ready answers in the book's words: the textbook exercise questions plus SLO-based questions asked in board papers. Punjab Board new syllabus.
Exam-ready answers. Learn the meaning, then write them in your own words.
The short questions at the end of the chapter in your book.
It modifies proteins coming from rough ER and packs them into Golgi vesicles, which are kept in the cell (e.g. lysosomes bud off from it) or sent out as secretions.
Their digestive enzymes break down food in food vacuoles, cellular wastes and damaged organelles, recycling materials; they can also store molecules for later use.
Smooth endoplasmic reticulum (SER). (In liver cells, peroxisomes also neutralise toxic substances.)
Lipid metabolism, transport of materials from one part of the cell to another, and detoxifying harmful chemicals; in muscle cells it helps in contraction.
| Plant cells | Animal cells |
|---|---|
| one large central vacuole | many small, temporary vacuoles |
| membrane: tonoplast; cell sap inside | water and food; contractile or food vacuoles |
| gives turgor pressure | no turgor role |
Wastes, worn-out organelles and undigested molecules would pile up in the cell; food in food vacuoles would not be digested, and the cell would be damaged or die. (Lysosomal storage diseases in humans are due to this.)
Cristae are folds of the inner mitochondrial membrane that increase the surface area for respiration, so more reactions can occur and more ATP is made.
Chromatin is the fine thread-like material of DNA and proteins in the nucleus. When a cell starts dividing, its chromatin condenses and takes the shape of thick chromosomes. They are the same material in two forms.
Neurons: they transmit nerve impulses; dendrites receive and the axon carries impulses away from the cell body.
They are green cells specialized for photosynthesis, with many chloroplasts; their shape and arrangement allow maximum absorption of light.
An unspecialized cell that has the ability to make a variety of specialized cell types, e.g. the zygote; bone marrow stem cells make blood cells.
| Structure | Made of |
|---|---|
| Cell membrane | lipids and proteins, small amounts of carbohydrates |
| Fungal cell wall | chitin |
| Plant cell wall | cellulose (also hemicellulose, pectin, lignin) |
| Bacterial cell wall | peptidoglycan |
| Ribosomes | rRNA and proteins |
| Chromosomes | DNA and proteins |
The book's in-text exercises first, then short questions on every topic of the chapter (SLO-based), as asked in board papers.
Vacuoles store waste products as well as water and nutrients; contractile vacuoles collect and pump out extra water and wastes.
The liquid part of the cytoplasm, including molecules and small particles like ribosomes, but not membrane-bound organelles.
It oversees cellular activities by directing the production of proteins; its DNA carries the genes that control all activities.
Prokaryotic cells are simple and do not have membrane-bound organelles; eukaryotic cells are more complex and have membrane-bound organelles and a nucleus.
Cilia are short and numerous; flagella are longer and fewer. Both (in eukaryotes) have a 9 + 2 arrangement of microtubules and help in movement.
Robert Hooke discovered cells in cork; Robert Brown observed the nucleus in 1831.
It provides shape, strength, protection and support to the protoplasm.
Middle lamella, primary wall and secondary wall.
Cellulose, hemicellulose and pectin; cellulose fibres crisscross to form a strong wall.
A membrane that allows some molecules to pass through it while it blocks many others.
Carbohydrates joined with proteins (glycoproteins) or with lipids (glycolipids) on the cell membrane.
Pores in plant cell walls connecting the cytoplasm of neighbouring cells, for communication and transport.
Medium for organelles; transport of materials; site of metabolic reactions like glycolysis; also stores food and wastes.
A double membrane around the nucleus; semi-permeable with many nuclear pores.
It contains genes which control all cell activities and is responsible for transmitting characteristics to the next generation.
It is made of DNA only and floats in the cytoplasm; there is no nuclear envelope.
Microtubules (tubulin), microfilaments (actin) and intermediate filaments (keratin, vimentin).
Ribosomes are not bounded by membranes, so prokaryotes, which lack membrane-bound organelles, still have them.
RER has ribosomes and makes proteins; SER lacks ribosomes and works in lipid metabolism, transport and detoxification.
Camillo Golgi (1898). Cisternae are the flattened sacs stacked to make the Golgi apparatus.
Christian René de Duve. Lysosomes bud off from the Golgi apparatus.
They produce energy (ATP) by aerobic respiration, breaking glucose with oxygen.
Thylakoids are sac-like structures carrying the pigments; a stack of thylakoids is a granum (plural grana), inside the chloroplast.
Their bright carotenoid pigments colour petals and fruits, helping in pollination and in the dispersal of fruits and seeds.
A barrel-shaped organelle of 9 triplets of microtubules. A pair at right angles makes the centrosome.
Centrioles located near the cell membrane of cells having cilia or flagella; they form cilia and flagella.
The outward pressure of the central vacuole on the cytoplasm and cell wall, which makes plant cells turgid and maintains their shape.
Rigid cellulose wall for support; chloroplasts for making food (also a large vacuole for turgor, plasmodesmata for transport).
No rigid wall, so they change shape (white blood cells); lysosomes for cleanup (also centrioles for spindles, flagella for movement).
The process after cell division in which cells get different sizes, structures and metabolic features and become specialized for a function.
Guard cells (leaf epidermis) regulate the opening and closing of stomata; root hair cells (root epidermis) increase surface area to absorb water and minerals.
Skeletal: long, striated, voluntary, attached to bones. Smooth: spindle-shaped, non-striated, involuntary, in walls of internal organs.
Dendrites are short extensions that receive impulses and carry them to the cell body; the axon is a long extension carrying impulses away from it.
The biconcave disc shape provides more surface area to absorb and release oxygen.
Storage of glycogen, iron and some vitamins; detoxification; making clotting proteins; recycling old red blood cells; secreting bile.
The specialization of different parts of a system to perform specific tasks more efficiently, within cells (organelles) and across cells (tissues).
In the skin (wound healing), liver (repair), bone marrow (blood and immune cells) and gut.
