AQA GCSE Biology - Cell Structure

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What are the main characteristics of a eukaryotic organism?

A eukaryotic organism is an organism whose cells contain membrane-bound organelles

True or False? Prokaryotic organisms contain a nucleus.

False. Prokaryotic organisms do not contain a nucleus.

What is a prokaryotic organism?

A prokaryotic organism is an organism whose cells lack a nucleus and other membrane-bound organelles.

True or False? All prokaryotic organisms are single-celled.

True. Prokaryotic organisms are always single-celled.

Define the term plasmid.

A plasmid is a small circular loop of DNA found in prokaryotic cells.

True or False? Eukaryotic cells are larger than prokaryotic cells.

True. Eukaryotic cells are larger than prokaryotic cells.

How many micrometres (µm) are in a millimetre (mm)?

There are 1000 µm in 1 mm. There are 1

What is 1

000

True or False? To convert a measurement from nanometres to micrometres you must multiply by 1000.

False. You must divide by 1000.

If a eukaryotic cell is 100µm wide and a prokaryotic cell is 1µm wide

how much bigger is the eukaryotic cell in terms of orders of magnitude?

What separates cells from their surrounding environment?

The cell membrane.

Name the largest organelle present within animal cells.

The nucleus.

Name the structures present in plant cells that are not present in animal cells.

Cell wall

True or False? Ribosomes are present in both plant and animal cells.

True. They are the site of protein synthesis.

Name three organelles found within animal cells.

Nucleus

What is the smallest organelle present in both plant and animal cells?

Ribosomes.

True or False? The gel-like fluid present inside both plant and animal cells is the chloroplast.

False. It is the cytoplasm.

True or False? The role of the nucleus is to release energy for the cell.

False. The nucleus stores genetic information; mitochondria release energy.

What is the function of chloroplasts within plant cells?

Chloroplasts absorb light energy during photosynthesis.

True or False? Plant cell walls control the passage of substances in and out of cells.

False. The membrane regulates this; the cell wall provides structural support.

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

It stores cell sap and provides structural support.

True or False? Mitochondria are the site of aerobic respiration.

True.

Define the term specialised cell.

A cell that has developed specific characteristics to perform a particular function.

Give an example of a specialised plant cell.

Root hair cell

Give an example of a specialised animal cell.

Sperm cell

True or False? Root hair cells have an increased surface area.

True. This helps absorb more water and mineral ions.

What is the function of a nerve cell?

To conduct electrical impulses and transmit signals.

True or False? An adaptation of a muscle cell is that they contain a lot of mitochondria.

True. To provide energy for contraction.

True or False? Sperm cells contain a full set of chromosomes (46) from the father.

False. Sperm cells contain half the amount of DNA found in normal body cells.

Why are root hair cells adapted to contain a large number of mitochondria?

To provide energy for active transport of mineral ions from soil into the cell.

What is the function of a phloem cell?

Phloem cells form a long vessel to allow the plant to transport dissolved sugars and amino acids.

True or False? Phloem vessels are strengthened and supported by a substance called lignin.

False. Xylem vessels are supported by lignin.

What is cell differentiation?

The process by which a cell changes to become specialised.

True or False? Almost all cells in a multicellular organism contain different genetic information.

False. Almost all cells contain the same genetic information.

What determines the features of specialised cells?

The expression of genes in the nucleus.

True or False? All plant cells differentiate early in development.

False. Many plant cells retain the ability to differentiate throughout life.

When does most cell differentiation occur in animals?

During early stages of development

What is a light microscope?

An instrument that uses light and lenses to magnify specimens

What does resolution mean in microscopy?

The ability to distinguish between two closely spaced objects as separate entities.

What is an electron microscope?

An instrument that uses electron beams instead of light to provide higher resolution and magnification.

True or False? Electron microscopes use light beams for imaging.

False. They use electron beams.

True or False? Upon the invention of the light microscope in the 17th century

scientists were able to view cell structure in detail.

What is the formula for calculating magnification?

The formula for calculating magnification is: magnification = image size ÷ actual size.

True or False? Magnification has units.

False. Magnification does not have any units and is just written as

What is the equation for calculating the actual size of a specimen?

The equation for calculating the actual size of a specimen is: actual size = image size ÷ magnification.

What is the purpose of a magnification scale in microscope drawings?

A magnification scale is included to show the actual size of the observed specimen.

What is a microscope slide?

A microscope slide is a thin

What stain is used for cheek cells?

Methylene blue is used to stain cheek cells.

True or False? Iodine is used to stain onion cells.

True. Iodine is used to stain onion cells.

What should be avoided when preparing a microscope slide?

Smudging the glass slide and trapping air bubbles under the coverslip should be avoided when preparing a microscope slide.

What is an objective lens?

An objective lens is the lens on a microscope that is closest to the specimen. Most light microscopes have several objective lenses at different powers for viewing specimens at different levels of magnification.

True or False? The highest-powered objective lens should always be used first when viewing a specimen under a light microscope.

False. The low-power lens should always be used first.

What are the key characteristics of biological drawings?

Biological drawings should follow specific rules

How large should biological drawings be?

Biological drawings should take up at least half of the space available on the page.

Define the term binary fission.

Binary fission is a type of simple cell division by which bacteria multiply.

What happens to the number of bacterial cells after a binary fission event?

The number of bacterial cells increases by a power of 2 (doubles) each time binary fission occurs.

What is aseptic technique?

Aseptic technique is a method used to prevent contamination by unwanted microorganisms when working with cultures.

True or False? Lifting the lid of a petri dish only slightly when transferring bacterial cultures is primarily to prevent air from entering.

False. Lifting the lid slightly primarily reduces the risk of contamination by other microorganisms.

Why should the inoculating loop be passed through a hot flame before it is used to transfer bacteria to a culture medium?

The inoculating loop should be passed through a hot flame to kill any microorganisms present on the loop; this prevents contamination.

Why should the lid of the petri dish be secured with tape at intervals around the dish

rather than all the way around?

What is the highest incubation temperature for growing bacteria in a school lab and why?

The maximum allowed temperature for growing bacteria in a school lab is 25°C

What is an inhibition zone in the context of culturing microorganisms?

An inhibition zone is an area around a disc of antibiotic

What is the equation for calculating the area of an inhibition zone?

The equation for calculating the area of an inhibition zone is: Area = πr²

What is the mean division time of bacteria?

Mean division time is the average length of time it takes for a bacterial cell in a population to divide.

True or False? A large zone of inhibition indicates that the antibiotic is effective at killing the bacteria.

True. The bigger the zone of inhibition

What is indicated by the absence of a zone of inhibition around an antibiotic disc?

If there is no zone of inhibition

When investigating the effect of antibiotics on bacterial growth using agar plates and zones of inhibition

what should be used as an experimental control?

How can microorganisms be cultured for use in an investigation?

Bacteria can be cultured in a nutrient broth solution or as colonies on an agar gel plate.