Cell Biology, Microscopy, the Cell Cycle, and Stem Cells

Flashcards covering cell structures, specialized animal and plant cells, light and electron microscopy, the cell cycle and mitosis, stem cell biology, and blood donation versus laboratory stem cell therapies.

What is the function of the nucleus in animal and plant cells?

It contains genetic material and controls the activities of the cell.

What role does the cytoplasm play in a cell?

It is the site where chemical reactions take place.

What is the function of the cell membrane?

It controls the passage of chemicals into and out of the cell.

What process occurs in the mitochondria, and what is its role?

Energy is released here through respiration.

What is the function of ribosomes?

They are the site where proteins are synthesised (made).

What is the role of the cell wall in plant cells?

It strengthens the cell and keeps it rigid.

What is the function of chloroplasts?

They contain chlorophyll and absorb light to make glucose by photosynthesis.

What is the function and content of the permanent vacuole in plant cells?

It supports the cell and is filled with sap (stores water and sap).

How do bacterial cells differ from animal cells regarding cell type, nucleus, and DNA structure?

Bacterial cells are prokaryotic, have no nucleus, and have a single circular DNA loop loose in the cytoplasm; animal cells are eukaryotic, have a nucleus, and keep their DNA inside the nucleus.

How do bacterial cells compare to animal cells regarding plasmids, ribosomes, cell walls, and mitochondria?

Bacterial cells contain plasmids, smaller ribosomes, and a cell wall, but lack mitochondria. Animal cells do not have plasmids or a cell wall, have larger ribosomes, and contain mitochondria.

What adaptations allow a sperm cell to fertilise an egg cell?

A tail for movement, enzymes in the head to penetrate the cell, a nucleus containing genetic information, and lots of mitochondria to provide the energy required to reach the egg cell.

What adaptations enable nerve cells to carry information from one part of the body to another?

Dendrites extend to connect to other neurones, and a long axon (nerve fibre) carries electrical impulses.

What adaptation allows muscle cells to produce movement?

They contain lots of mitochondria to provide the energy required for contracting.

What adaptations enable root hair cells to absorb water and minerals from the soil?

A long "finger-like" shape that increases surface area, a thin cell wall, and no chloroplasts.

How are xylem cells adapted to carry water from the roots to the leaves?

They are strengthened by lignin spirals, arranged end-to-end, and have broken down end walls to form hollow tubes.

How are phloem cells adapted to transport glucose within a plant?

They have fewer sub-cellular structures, are arranged end-to-end, and have end walls that act like a "sieve" to allow sugar through.

How do electron and light microscopes compare in maximum magnification and resolution?

Electron microscopes achieve over $\times 500\,000$ magnification with a resolution of $0.5\,\text{nm}$, whereas light microscopes reach up to $\times 2\,000$ magnification with a resolution of $200\,\text{nm}$.

How do electron and light microscopes differ in sample preparation, mobility, vacuum requirements, and specimen state?

Electron microscopes require complicated sample preparation, a vacuum, dead specimens, and are large and immoveable; light microscopes have easy preparation, require no vacuum, can view living or dead specimens, and are small and easy to carry.

What are the two formulas used to calculate magnification?

$\text{Magnification} = \text{Objective lens} \times \text{Eyepiece lens}$ and $\text{magnification} = \frac{\text{size of image}}{\text{size of real object}}$.

What are the key steps to focus a slide and achieve a magnification of $\times 50$ using a light microscope?

Place slide on stage; use lowest power ($\times 4$) objective; adjust mirror/light; move stage as close to lens as possible without touching; turn focussing knob so stage moves away until in focus; use fine focus for a clear image; change to $\times 10$ objective with $\times 5$ eyepiece (giving $\times 50$ total magnification) and refocus.

What events take place during Stage 1 (Interphase) of the cell cycle?

The cell enlarges, DNA is duplicated (copied) so there are two identical sets of chromosomes, and extra copies of mitochondria and ribosomes are made.

What events occur during Stage 2 (Mitosis) of the cell cycle?

One set of chromosomes is pulled to each side (chromosomes separate or move to opposite poles/ends of cell), the nucleus divides, and two nuclei are formed.

What happens during Stage 3 (Cytokinesis) of the cell cycle?

The cytoplasm and cell membrane divide, splitting the cell into two genetically identical cells.

What is the biological definition of differentiation?

The process by which a cell changes and acquires different sub-cellular structures to become specialised for its function.

What is the primary role of cell division in mature (older) animals?

It is mainly restricted to repair and replacement.

What is a stem cell?

An undifferentiated / unspecialised cell capable of giving rise to many more cells of the same type, and from which certain other cells can arise through differentiation.

What is the differentiating capability of human embryonic stem cells?

They can be cloned and made to differentiate into most different types of human cells.

What types of cells can adult bone marrow stem cells form?

They can form many types of cells, including blood cells.

What characterizes plant meristem tissue throughout the life of a plant?

It can differentiate into any type of plant cell throughout the plant's entire life.

What are two practical applications of cloning plants using meristem stem cells?

Rare species can be cloned to protect them from extinction, and crop plants with special features (such as disease resistance) can be cloned to produce large numbers of identical plants for farmers.

Which two medical conditions may potentially be helped by stem cell treatment?

Diabetes and paralysis.

What is therapeutic cloning and what is its primary advantage?

An embryo is produced with the same genes as the patient, meaning the stem cells obtained from the embryo are not rejected by the patient's body.

What are the potential risks and objections associated with stem cell usage?

Potential risks include the transfer of viral infections, and some people hold ethical or religious objections.

How do blood donation and laboratory stem cell production compare in the time required to obtain red blood cells?

Blood collection from a vein takes $10\,\text{minutes}$, whereas producing red blood cells from stem cells in a laboratory takes $28\,\text{days}$.

How long can donated blood be stored, and how often can a person donate?

Donated blood can be stored for $35\,\text{days}$, and a person can donate blood every $12\,\text{weeks}$.

What are the main advantages of using volunteer blood donation over laboratory-grown stem cells?

It is an easier and quicker process, has a regular supply available immediately for emergencies, can be stored longer ($35\,\text{days}$) than it takes to make stem cells ($28\,\text{days}$), can be separated into components to treat multiple people/conditions, is a tested treatment, and is free/inexpensive.

What are the disadvantages of relying on blood donations compared to stem cell production?

It relies on volunteers, causes donor inconvenience/discomfort, risks supply shortages or mismatched components, carries risk of viral/blood infection, may be wasted, and risks rejection because the blood does not come from the patient's own cells.