Topic 1 Core questions - Cell Biology Flashcards by Jasper Marcou

What are three common features of plant and animal cells (eukaryotes)?

1) Cell membrane
2) Cytoplasm
3) Genetic material in a nucleus.

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Which are bigger cells prokaryotes or eukaryotes?

Eukaryotes.

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True or false?

“Prokaryotic cells have a cell wall.”

True.

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True or false? “Prokaryotic cells have a nucleus.”

False.

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In what form is the genetic material in a prokaryotic cell?

A single DNA loop.

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What are the two types of cells?

Eukaryotic (plant and animal)

Prokaryotic (bacteria)

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What are the differences between prokaryotic and eukaryotic cells?

Prokaryotic cells are much smaller than eukaryotic cells.

Eukaryotic cells contain membrane bound organelles and a nucleus containing genetic materials, while prokaryotic cells do not.

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Name some common parts of eukaryotic cells.

Nucleus
Cytoplasm
Cell membrane 
Mitochondria 
Ribosomes
Chloroplasts 
Permanent vacuole (filled with cell sap).

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Describe the function of the nucleus.

Contains the genetic material of the cell.

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Describe the function of the cytoplasm.

The location of cellular reactions.

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Describe the function of the cell membrane.

To determine what is allowed into and out of the cell.

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Describe the function of the mitochondria.

Where aerobic respiration occurs to release energy.

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Describe the function of the ribosomes.

To bond amino acids together to form proteins (protein synthesis).

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Describe the function of the chloroplasts.

The location of photosynthesis.

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Describe the function of the permanent vacuole.

A storage area for ions and water, sometimes pigments.

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Which strong material is the cell wall of plant and algal cells made from?

Cellulose

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What is the definition of a cell?

The individual unit of an organism.

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What is the definition of a tissue?

Cells of the same type working together to perform a specific function.

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What is the definition of an organ?

A structure made from multiple tissue types to perform a specific function.

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What is the definition of an organ system?

Multiple organs working together to perform a specific function.

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Describe a specialisation of a sperm cell.

Mobile due to flagellum; many mitochondria to allow high energy release for movement; streamlined head; digestive enzymes in head to break down egg membrane.

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Describe a specialisation of a nerve cell.

Many mitochondria to provide lots of energy for active transport; many proteins embedded in cell membrane to allow ion movement.

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Describe a specialisation of a muscle cell.

Many mitochondria to provide lots of energy for contraction; many ribosomes to synthesise proteins.

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Describe a specialisation of a root hair cell.

Elongated shape to increase surface area for ion absorption; many mitochondria to provide lots of energy for active transport.

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Describe a specialisation of a xylem cell.

Little cell contents to allow easy movement of water and ions through each cell.

Describe a specialisation of a phloem cell.

Needs a companion cell to work optimally.

What is “cell differentiation”?

The process of a stem cell dividing and becoming a specialised cell.

When do most animal cells differentiate?

At an early stage of development.

What is different about plant cells’ differentiation?

They retain the ability to differentiate throughout life (e.g. a stem developing roots when planted in soil)

In mature animals, what is cell differentiation used for?

Repair and replacement of old/damaged cells.

What are the two advantages of electron microscopes over light microscopes?

1. Increased magnification | 2. Increased resolution.

What is the “resolution” or “resolving power” of a microscope?

The ability to determine two close objects as separate images.

What is the equation used to calculate magnification (M), the image size (I) or the actual size of an object (A)?

Magnifcation = image size / actual size of an objct

What is the difference between mm, µm and nm?

A factor of 1000.

If provided with enough nutrients and a suitable temperature, how often can bacterial cells divide?

Around every 20 minutes.

Describe the two ways bacteria can be grown in a laboratory.

1. In a nutrient broth solution, | 2. On an agar gel plate/petri dish.

What is a “contaminant”?

An unwanted species of microorganism growing in your culture.

What should you do with Petri dishes and culture media before use?

Sterilise it at high temperature to kill contaminants.

How do you sterilise inoculating loops?

Pass them through a Bunsen burner flame before use.

How should a Petri dish be stored in school?

Upside down, with tape securing the lid.

What is the maximum temperature cultures should be incubated at in schools or colleges?

25°C

Explain why the maximum incubation temperature for bacterial cultures in schools is 25°C.

To avoid growing potential pathogens.

If you were asked to calculate the cross-sectional area of a circular clear area around a disinfectant, what equation would you use?

πr²

What is a chromosome?

A coiled thread-like structure of nucleic acids (DNA) and protein found in the nucleus of eukaryotic cells.

What are genes?

Sections of DNA that contain the code for a particular protein.

In what arrangement are chromosomes found normally?

Pairs.

How many chromosomes does a human have?

23 pairs OR 46 in total.

What has to happen within the cell before it can divide? (2 steps)

1. Cell organelles (e.g. mitochondria and ribosomes) have to replicate, 2. DNA has to be replicated (copied).

How many chromosomes will be present in a cell after DNA replication?

92 OR 46 pairs.

To where do the chromosomes moves to during mitosis?

To opposite ends of the cell.

What occurs during cytokinesis?

The cytoplasm and cell membranes divide.

Mitosis is critical for….

…growth, replacement and development of an organism.

What is a stem cell?

An undifferentiated cell capable of giving rise to many more cells of the same type.

Describe the function of stem cells in embryos.

To develop into multiple cell types aiding in the development of the embryo into a mature organism.

Describe the function of stem cells in adult animals.

To be the source of cells used in growth and repair of the mature animal.

Describe the function of stem cells in plant meristems.

To allow a plant to keep growing throughout its life (animals stop growing when mature) by specialising into any type of cell.

What is a potential use of stem cells in medicine?

To treat conditions where cells have been damaged e.g. diabetes, paralysis.

What is the principle of therapeutic cloning?

An embryo is produced with the same genes as the patient.

Give an advantage of therapeutic cloning.

No rejection of the new cells by the patient (as they are the patitent’s own cells)

Give two potential problems with therapeutic cloning.

1. Risk of viral infection, | 2. Religious/ethical objections around the use of embryos.

How are plant stem cells used in horticulture (commercial plant growing)?

To create plant cuttings (clones of the original plant).

Give two advantages of the use of clones in horticulture.

1. Rare species can be cloned to prevent extinction, | 2. Crops with special adaptations (e.g. disease resistance) can be identically produced in large numbers.

Name the process whereby substances move in and out of a cell across the cell membrane.

Diffusion.

Define "diffusion".

The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient across a semi-permeable membrane.

Name three substances which move by diffusion within animal cells

1. Oxygen 2. carbon dioxide in gas exchange, 3. Urea out of cells to be excreted from the body.

Name three factors which affect the rate of diffusion.

1. The difference in concentrations (concentration gradient) 2. Temperature 3. Surface area of the membrane.

Does a single-celled organism have a high or low surface area:volume ratio?

High.

How do single-celled organisms get enough oxygen without having lungs?

Due to its small size, and therefore its high Surface area to volume ratio, diffusion across its membrane allows sufficient gas exchange

An organism has a surface area of 50m2 and a volume of 20m3. What is its surface area to volume ratio?

2.5:1

Why do multicellular organisms tend to need exchange surfaces and transport systems?

Low surface area to volume ratio, therefore cannot rely on diffusion across cell membranes.

Name two common features that aid the exchange of substances in animal small intestine & lungs; fish gills; plant roots and leaves.

1. Large surface area, | 2. Thin membrane to provide a short diffusion path.

Name two further features that aid the exchange of substances in animals but NOT plants.

1. An efficient blood supply, | 2. The ability to ventilate (to allow air to move in and out of the organism).

Define osmosis.

Osmosis is the diffusion of water molecules, from a region where the water molecules are in higher concentration, to a region where they are in lower concentration, through a partially permeable membrane

If an animal cell loses a lot of water, what happens?

It crenates (shrivels) and cellular reactions are slowed or stopped.

If an animal cell gains a lot of water, what happens?

It can lyse (burst) and die.

If a plant cell loses a lot of water, what happens?

It becomes plasmolysed (cell membrane shrinks away from the cell wall).

If a plant cell gains a lot of water, what happens?

It becomes turgid (cell membrane pushes up against the cell wall).

Define active transport.

The movement of substances from a low concentration to a high concentration (against a concentration gradient).

What two things does active transport require that diffusion doesn't?

1. A transport protein (found in the cell membrane), | 2. Energy.

From what reaction does the energy required for active transport come?

Respiration.

Where does active transport happen within a cell?

The mitochondria.

Give two examples of where active transport is used in Biology. (1 plant, 1 animal)

1. Plant root hair cells absorbing mineral ions from the soil, 2. Glucose absorption from the small intestine into the blood.