Cell Structure (AQA A Level Biology): Flashcards

Cell theory underpins our understanding of structure, function and continuity in living organisms.

The cell-surface membrane is a phospholipid bilayer with embedded proteins that controls the entry and exit of substances from the cell.

The cell-surface membrane is composed of a phospholipid bilayer with embedded proteins.

The nucleus contains linear DNA (as chromosomes) and a nucleolus that produces ribosomes.

A mitochondrion is the site of aerobic respiration and ATP production.

Chloroplasts are the site of photosynthesis and contain chlorophyll for light absorption in plant cells.

The Golgi apparatus modifies and packages proteins and lipids, and forms vesicles such as lysosomes.

Lysosomes are vesicles that contain hydrolytic enzymes for digesting worn-out organelles or pathogens.

False.

The smooth endoplasmic reticulum synthesises and stores lipids and carbohydrates, while the rough endoplasmic reticulum is responsible for protein synthesis and transport.

Cell specialisation is the process by which eukaryotic cells become adapted to perform specific functions.

The structure of a cell is adapted to its role, so different cell types have features that help them perform their specific functions efficiently.

Red blood cells are biconcave and lack a nucleus, which creates more space for oxygen transport.

Protein-producing cells contain many ribosomes to support high levels of protein synthesis.

True.

The myelin sheath acts as an insulator and allows nerve impulses to travel faster along the axon.

Skeletal muscle fibres are multinucleated because individual muscle cells fuse during development.

The acrosome is a region at the head of a sperm cell that contains digestive enzymes to penetrate the egg during fertilisation.

Root hair cells have a long extension called a root hair that increases surface area to maximise absorption of water and mineral ions.

A specialised cell is a eukaryotic cell that has adapted to perform a specific function within a multicellular organism.

A group of specialised cells of the same type forms a tissue.

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

The heart contains muscle, connective and vascular tissues.

False.

Red blood cells are specialised to transport oxygen, whereas epithelial cells in the small intestine absorb nutrients.

A tissue is a group of similar specialised cells working together to carry out a specific function.

The heart is part of the circulatory system.

The biological levels of organisation are: cell → tissue → organ → organ system → organism.

A prokaryotic cell is a type of cell that lacks a nucleus and membrane-bound organelles. Examples include bacterial cells.

Prokaryotic cells are much smaller than eukaryotic cells.

The cytoplasm of prokaryotic cells lacks membrane-bound organelles, whereas eukaryotic cells have membrane-bound organelles in their cytoplasm.

A plasmid is a small, circular loop of DNA found in some prokaryotic cells that carries non-essential genes and can be transferred between bacteria.

The cell wall of prokaryotic cells contains murein, a type of glycoprotein.

False.

Only some prokaryotic cells have flagella and a capsule; these are additional structures not found in all prokaryotes.

70S ribosomes, which are smaller than the 80S ribosomes found in eukaryotic cells.

As a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins.

It is a protective outer layer that prevents desiccation and helps the cell evade immune system attack.

A flagellum is a long, rotating tail that provides motility; some bacteria have multiple flagella.

In prokaryotic cells, the circular DNA is free in the cytoplasm and is not associated with proteins.

A prokaryotic cell is a cell that lacks a true nucleus and membrane-bound organelles; its DNA is circular and found in the cytoplasm.

A eukaryotic cell is a cell that contains a nucleus and membrane-bound organelles, with its DNA associated with histone proteins, forming chromosomes.

In prokaryotic cells, DNA is circular and not associated with proteins, while in eukaryotic cells, DNA is linear and associated with histone proteins to form chromosomes.

The main component of the cell wall in prokaryotes is peptidoglycan (murein).

In prokaryotic cells, DNA is circular and not associated with proteins, while in eukaryotic cells, DNA is linear and associated with histone proteins to form chromosomes.

Cell division in prokaryotes occurs by binary fission, whereas in eukaryotes it occurs by mitosis or meiosis.

Prokaryotic cells have 70S ribosomes, while eukaryotic cells have 80S ribosomes.

The typical diameter of a prokaryotic cell is 0.5–5 µm, while a eukaryotic cell can be up to 100 µm.

A virus is a non-cellular, non-living infectious agent that contains genetic material (DNA or RNA) inside a protein coat called a capsid, cannot reproduce independently, and is always parasitic.

False.

Viruses cannot carry out protein synthesis themselves and must use the host cell's protein-building machinery.

Viruses are non-living because they do not have a cellular structure and cannot reproduce independently.

All viruses contain genetic material (DNA or RNA) and a protein coat called a capsid.

Viruses are parasitic because they depend entirely on a host cell to reproduce and carry out vital processes, often harming the host.

The protein coat that surrounds the genetic material of a virus is called a capsid.

They bind to receptors on host cells during invasion.

Either DNA or RNA, which can be single-stranded or double-stranded.

False.

Viruses are much smaller than both prokaryotic and eukaryotic cells.

Viruses have no metabolic activity, so they cannot carry out reactions themselves.

They do not grow or respond to stimuli.

They cannot reproduce independently and require a host.