Biology AQA

• What is a cell's ultrastructure?

  The organelles that make up the cell.
• What are the main structures of eukaryotic cells?

  Nucleus cell-surface membrane; mitochondria; Golgi apparatus and golgi sacs; smooth endoplasmic reticulum; rough endoplasmic reticulum; ribosomes. Chloroplasts (in plants and algae); cell wall (plants, algae and fungi); cell vacuole (plants).
• What is the structure of the nucleus?

  Surrounded by a double membrane (the nuclear envelope). Contains chromosomes (Protein bound linear DNA); nucleoplasm; an 1 or more nucleoli.
• What is the function of the nucleus?

  Stores the human genome, controls the cell by providing instructions for protein synthesis.
• What is the structure and function of the nucleolus?

  Spherical region of the nucleus, produces ribosomes. May be multiple in one nucleus
• What is the structure of the nuclear envelope?

  A double membrane embeded with channel proteins forming pores. Continuous with endoplasmic reticulum.
• what is th e function of the nuclear envelope?

  Separates the nucleus from the rest of the cell. Pores allow ribosomes and mRNA to leave the nucleus.
• What is the structure of the rough endoplasmic reticulum (RER)?

  A system of fluid filled membranes studded with ribosomes. Continuous with the nuclear membrane. Large surface area formed by folding.
• What is the function of the rough endoplasmic reticulum (RER)?

  Synthesis of proteins and glycoproteins. Provides a pathway to transport materials, especially proteins.
• What is the structure of the smooth endoplasmic reticulum (SER)?

  A system of fluid filled membranes. No ribosomes.
• What is the structure the Golgi apparatus?

  A stack of flattened membrane bound sacs called cisternae.
• What is the function of the Golgi apparatus?

  Vesicles from the ER join, bringing their products. Here they are modified, by adding sugar to make glycoproteins, adding lipids to form glycolipids. It makes secretory enzymes; secretes carbohydrates; transports and modifies lipids; creates lysosomes.
• What is the structure of the ribosomes?

  2 subunits, large and small. Made of rRNA . 2 types 80s found in eukaryotes, 70s found in prokaryotes.
• What is the function of the ribosomes?

  Proteins synthesised here.
• What is the structure of the mitochondria?

  Double membrane bound. Inner membrane folded into cristae within a fluid filled matrix. Contain own DNA and 70s ribosomes.
• What is the structure of the lysosomes?

  Membrane bound sacs containing hydrolytic (digestive) enzymes and lysozymes.
• What is the function of the lysosomes?

  Break down old organelles and foreign matter for reuse. Hydrolyse ingested material. Release enzymes to destroy other substances. Break down the cell after cell death (autolysis).
• What is the structure of the chloroplasts?

  Double membrane bound. Inner membrane forms flat discs filled with chlorophyll called thylakoids, in stacks called granum. These are surrounded by a fluid matrix called the stroma. Contain own DNA and 70s ribosomes.
• What is the function of the chloroplasts?

  Site of photosynthesis.
• What is the structure the cell wall?

  Present in plants, algae and fungi only.Made of polysaccherides, bundles of cellulose fibres in plants, chitin in fungi.
• What is the function of the cell wall?

  Provides support and strength, maintaining the cell's shape. prevents the cell from bursting when turgid. Permeable to allow solutions through.
• Which structures are involved in the production of proteins?

  Nucleus; RER; transport vesicle; Golgi apparatus
• What is the structure of the vacuole?

  Fluid filled membrane sac. In a plant the membrane is called the tonoplast.
• What is the structure and function of the vacuole?

  It contains salts, sugars, amino acids, waste and sometimes pigments.
• what is the function of a plant's vacuole?

  Provides structure to plants by making cells turgid. Temporary food store. Provides colour to plants attracting insects.
• What is the structure and function of the plasma membrane?

  Phospholipid bilayer, cholesterol, proteins, glycoproteins, glycolipids. Separates cell contents from external environment. Controls what enters and leaves the cell. Identifies cell as self. Acts as a receptor for various chemicals. site of chemical reactions.
• What kind of organisms have specialised cells?

  Multicellular organisms
• Why are the cells of an organism grouped into tissues, organs, etc?

  For increased efficiency.
• Describe epithelial tissue.

  A sheet of cells that typically line organs. They are protective and/or secretory (release substances). E.g. thin flat cells of the alveoli aid diffusion. Cilliated epithelial tissue of trachea moves mucus.
• What are the five main components of the nucleus?

  Nucleolus, nuclear pores, nuclear envelope, nucleoplasm, and chromatin
• What is the function of the nucleolus?

  It makes rRNA and assembles ribosomes
• What is the diameter of nuclear pores?

  50-70 nm
• What is the structure of the nuclear envelope?

  It is a double-layered structure with two adjacent membranes
• What is nucleoplasm?

  Granular jelly-like material that makes up the bulk of the nucleus
• What is chromatin?

  Granular appearance of hereditary material in non-dividing cells
• What are the main functions of the nucleus?

  Acts as the control center of the cell, keeps genetic material, and makes ribosomal RNA and mRNA
• What is the typical shape and size of mitochondria?

  Usually rod-shaped and 1-10 micrometers in length
• What are the three main components of mitochondria?

  Double membrane, cristae, and matrix
• What is the function of cristae in mitochondria?


  They provide a larger surface area for the attachment of enzymes involved in respiration
• What is the role of the matrix in mitochondria?


  It contains proteins, lipids, ribosomes, and DNA for protein production