AQA GCSE Biology (Triple Higher) – Topic 1: Cell Biology Flashcards

Comprehensive flashcards covering Grade 9 Atomised content for AQA GCSE Biology Topic 1: Cell Biology, including magnification, binary fission, cell cycle, and aseptic techniques.

What is the formula for magnification?

Magnification = $\text{Image size} \div \text{Actual size}$ ($I = A \times M$)

How do you calculate actual size?

$$\text{Actual size} = \text{Image size} \div \text{Magnification}$$

How many nanometres ($\text{nm}$) are in $1\,\mu\text{m}$?

$$1\,\mu\text{m} = 1000\,\text{nm}$$

How many micrometres are in $1\,\text{mm}$?

$$1\,\text{mm} = 1000\,\mu\text{m}$$

What is binary fission?

Asexual reproduction in bacteria producing two genetically identical cells.

What equation models bacterial growth by binary fission?

$$\text{Number of bacteria} = 2^n$$

What does $n$ represent in the equation $2^n$?

The number of divisions.

What is differentiation?

The process by which a cell becomes specialised for a specific function.

When do most animal cells lose the ability to differentiate?

At an early stage of development.

When can many plant cells differentiate?

Throughout life.

What are stem cells?

Undifferentiated cells that can divide and differentiate.

Where are embryonic stem cells found?

In the early embryo.

Where are adult stem cells found?

In tissues such as bone marrow.

What is the source of plant stem cells?

Meristems.

What is active transport?

Movement of substances against a concentration gradient.

Does active transport require energy?

Yes — energy from respiration ($ATP$).

What structure carries out active transport?

Carrier proteins in the cell membrane.

What is Stage 1 of the cell cycle?

Cell grows and DNA is replicated.

What happens during mitosis?

One set of chromosomes is pulled to each end of the cell.

What is Stage 3 of the cell cycle?

Cytoplasm and membrane divide, producing two identical cells.

What is mitosis?

Cell division producing two genetically identical daughter cells.

Why is the inoculating loop passed through a flame before use?

To sterilise it and kill microorganisms.

Why should the Petri dish lid be opened only slightly?

To reduce contamination from airborne microorganisms.

Why is adhesive tape used instead of fully sealing the lid?

Allows oxygen in while reducing contamination.

Why are agar plates incubated at a maximum of $25\,^{\circ}\text{C}$ in schools?

Reduces growth of harmful pathogens.

Why are Petri dishes stored upside down?

Prevents condensation dripping onto the agar.

What is an antibiotic's zone of inhibition?

The area where bacterial growth is prevented.

What equation calculates the area of a zone of inhibition?

$$\text{Area} = \pi r^2$$

What does a larger zone of inhibition indicate?

A more effective antibiotic/disinfectant.

What happens to a plant cell in a concentrated solution?

It becomes plasmolysed.

What is a plant cell called when full of water?

Turgid

What process forms a root hair cell from an unspecialised cell?

Differentiation

What term describes the folding in of the cell membrane during mitosis?

Invagination

What happens to chromosomes before mitosis?

DNA replication occurs.