Cell Structure & Organisation (Edexcel International A Level (IAL) Biology): Flashcards

A tissue is a group of cells of the same type that work together to perform a particular function.

Epithelial cells in the small intestine are specialised to absorb food efficiently.

False.

An organ is made up of several different tissues working together to perform a particular function.

An organ system is a group of organs working together to perform a particular function.

Xylem cells in plants are specialised to transport water around a plant.

The function of muscle tissue is to contract to move parts of the body.

The circulatory system is made up of the heart and blood vessels, and its function is to circulate blood around the body.

A leaf in plants is made up of palisade mesophyll, spongy mesophyll, and vascular tissue.

A specialised cell is a cell that has developed certain features to perform a specific function.

In multicellular organisms, specialised cells form tissues, tissues combine to form organs, and organs work together in organ systems.

The cell surface membrane is the partially permeable outer boundary of the cell that controls the exchange of materials between the cell's internal and external environments.

The nucleus contains genetic material (chromatin), is surrounded by the nuclear envelope, and controls the activities of the cell, including gene expression and ribosome production.

The nuclear envelope contains many nuclear pores that allow mRNA and ribosomes to exit the nucleus.

Mitochondria are the double-membraned organelles responsible for aerobic respiration and ATP production in eukaryotic cells.

Ribosomes are the sites of translation, where proteins are synthesised from mRNA using rRNA and proteins.

The rough endoplasmic reticulum is covered in ribosomes and involved in processing proteins.

The Golgi apparatus is a stack of flattened membrane sacs that modifies, packages, and transports proteins and lipids in vesicles.

Lysosomes contain hydrolytic enzymes that break down waste materials, worn-out organelles, and play a role in immune responses and apoptosis.

Centrioles are made from hollow fibres known as microtubules.

A eukaryotic cell is a type of cell with a membrane-bound nucleus and other organelles, found in animals, plants, fungi, and protists.

False.

Centrioles are found in animal cells but not in plant or fungal cells.

The cytoplasm of eukaryotic cells is divided into compartments called organelles.

The cytoplasm of eukaryotic cells is divided into compartments called organelles.

Eukaryotic cells are generally larger than prokaryotic cells.

Ultrastructure refers to the detailed internal structure of a cell, as seen under an electron microscope.

80S ribosomes are found in eukaryotic cells, while 70S ribosomes are found in prokaryotes, mitochondria, and chloroplasts.

An organelle is a specialised part of a cell that carries out a particular function.

The nucleus, ribosomes, rough endoplasmic reticulum (RER), Golgi apparatus and cell surface membrane are involved in the production and secretion of proteins.

Some organelles are membrane-bound, meaning that they are surrounded by membrane.

Transcription of the DNA code occurs in the nucleus.

Proteins formed within the cell are secreted at the cell surface membrane.

Ribosomes on the rough endoplasmic reticulum (RER) produce proteins that can be secreted out of the cell or become attached to the cell surface membrane.

Processed proteins from the RER are transported to the Golgi apparatus in vesicles.

True.

The Golgi apparatus modifies proteins and prepares them for secretion, such as in the case of extracellular enzymes.

A prokaryotic cell is a type of cell that lacks a membrane-bound nucleus and membrane-bound organelles, and has its genetic material as a single circular chromosome free in the cytoplasm.

A plasmid is a small, circular piece of DNA found in prokaryotic cells that is separate from the main bacterial chromosome and can replicate independently.

The capsule protects the cell from desiccation and phagocytosis, and helps bacteria adhere to surfaces.

In prokaryotic cells, the cell wall is made of murein, also known as peptidoglycan.

False.

Not all prokaryotic cells have plasmids; plasmids are only present in some prokaryotes.

A flagellum is a long, whip-like structure that enables movement of some prokaryotic cells.

Eukaryotic cells have 80S ribosomes, while prokaryotic cells have 70S ribosomes.

In prokaryotic cells, genetic material is in a single circular chromosome free in the cytoplasm, not enclosed in a nucleus and not associated with proteins. In eukaryotic cells, DNA is linear, associated with proteins, and contained within a nucleus.

Pili are short, hair-like structures on the surface of some prokaryotic cells used for attachment to surfaces and for transferring genetic material between cells.

Prokaryotic cells have a cytoplasm that lacks membrane-bound organelles.

False.

The cell wall of prokaryotes is made of murein, not cellulose.

All prokaryotic cells have ribosomes, but not all have capsules or plasmids.

A Transmission Electron Microscope (TEM) uses a beam of electrons transmitted through a thin specimen to produce a high-resolution 2D image, allowing internal structures within cells or organelles to be seen.

A Scanning Electron Microscope (SEM) produces 3D images by scanning a beam of electrons across the surface of a specimen, with the electrons bouncing off the surface and being detected.

TEMs produce high-resolution 2D images showing internal structures, while SEMs produce 3D images showing the surface of specimens.

TEMs use a beam of electrons that is transmitted through a thin specimen to create a 2D image.

SEMs can produce 3D images that show the surface of specimens.

True.

TEM (Transmission Electron Microscope) images have a higher resolution than SEM (Scanning Electron Microscope) images, allowing finer internal details to be observed.

You would use a Transmission Electron Microscope (TEM) to view the internal structure of an organelle in detail.

SEMs do not require the specimen to be thin, whereas TEMs do.

Magnification is how many times bigger the image of a specimen is compared to the actual size of the specimen.

Resolution, or resolving power, is the ability to distinguish between two separate points in an image.

Total magnification is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens.

The maximum resolution of a light microscope is 200 nm. Any points separated by less than this distance cannot be resolved.

False.

Electron microscopy requires the specimen to be dead.

Stains are used because the cytoplasm and cell structures are often transparent or difficult to distinguish without staining.

Differential staining is when multiple dyes are used so that different tissues within a specimen show up clearly.

Haematoxylin stains cell nuclei purple, brown, or blue, while methylene blue stains animal cell nuclei blue.

The phospholipid bilayer is about 10 nm thick, which is much smaller than the maximum resolution of a light microscope (200 nm).

Light microscopes use light to view specimens that are typically larger than 200 nm, while electron microscopes use a beam of electrons for higher resolution imaging.

Magnification is how many times bigger the image of a specimen is compared to its real-life size.

Total magnification = eyepiece lens magnification × objective lens magnification.

magnification = image size ÷ actual size

It is important because using different units would result in an incorrect value for magnification; both values must be in the same units for the calculation to be accurate.

An eyepiece graticule is a small disc with an engraved ruler placed in the microscope eyepiece to act as a ruler in the field of view.

The eyepiece graticule is calibrated using a stage micrometer, which has a known scale. The number of graticule divisions per micrometer unit is determined, so the size of each division can be calculated.

A stage micrometer is used to determine how many micrometre units each eyepiece graticule division represents.

The main function of an optical microscope is to allow scientists to see and study tissues, cells, and organelles that are too small to be seen with the naked eye.

When preparing a microscope slide with a liquid specimen, a coverslip is gently pressed on top to remove air bubbles.

Tissue samples must be thin so that light can pass through and the structures can be seen clearly under the microscope.

A biological drawing is a line drawing made to record the observations seen under the microscope, following specific rules for clarity and accuracy.

False.

In a plan diagram, only the arrangement of cells within a tissue or organ is shown; individual cell details are not drawn.