cell structure

• describe the structure and function of a cell-surface membrane

  cell-surface membranes contain embedded proteins. they enable control of the passage of substances across exchange surfaces by passive or active transport.
• describe the function of the nucleus and name the parts within it

  contains the hereditary material and controls the cell's activities. the nucleus is composed of the nuclear envelope, nuclear pores, nucleoplasm, chromosomes and the nucleolus
• function and structure of the nuclear envelope

  controls the exit and entry of materials in and out of the nucleus, and contains the reactions taking place within it.

  a double membrane that surrounds the nucleus.

  outer membrane continuous with endoplasmic reticulum and often has ribosomes on its surface.
• function and structure of nuclear pores

  allows the passage of large molecules out of the nucleus e.g., RNA.

  typically around 3000 pores in each nucleus, each 40-100nm in diameter
• function and structure of nucleoplasm

  granular, jelly-like material that makes up the bulk of the nucleus.
• function and structure of chromosomes

  consist of protein-bound, linear DNA.
• describe the function of mitochondria and name the structures within it

  mitochondria are the sites of the aerobic stages of respiration and are responsible for the production of ATP. the structures within are...

  • double membrane
  • cristae
  • matrix
• function and structure of double membrane in mitochondria

  surrounds the mitochondria and controls the entry and exit of material.

  inner of the two membranes is folded to form extensions - cristae.
• function and structure of cristae

  provide a large surface area for the attachment of enzymes and other proteins involved in respiration.

  are extensions of the inner membrane.
• function and structure of the matrix

  makes up the remainder of the nucleus.

  contains proteins, lipids, ribosomes and DNA which allows mitochondria to control the production of their own proteins.
• describe the function of chloroplasts and name the main structures within it

  chloroplasts are organelles that carry out photosynthesis. chloroplasts compose of...

  • the chloroplast envelope
  • grana
  • stroma
• function and structure of the chloroplast envelope

  high selective in what it allows to enter and leave the chloroplast.

  a double plasma membrane surrounding the organelle.
• function and structure of the grana

  where the first stage of photosynthesis takes place.

  grana are stacks of up to 100 disc like structures (thylakoids) which contain the photosynthetic pigment chlorophyll.
• function and structure of the stroma

  where the second stage of photosynthesis takes place.

  a fluid filled matrix. within the stroma are a number of other structures, such as starch grains
• describe the function of the golgi apparatus

  • process and package lipids and proteins - carried out by the cisternae
  • store and transport lipids and proteins - carried out by the vesicles
  • synthesise lysosomes - specialised vesicles
• describe the structure of the golgi apparatus

  • contain fluid-filled membrane bound sacs known as cisternae
  • contain smaller vesicles
• describe the function of lysosomes

  • digest invading cells - this process uses enzymes
  • break down waste material - this material includes old organelles
  • releases hydrolytic enzymes
• describe the structure of lysosomes

  • contain hydrolytic enzymes
  • surrounded by a membrane to keep enzymes separate from the cytoplasm of the cell
• what is the function of ribosomes

  site of protein synthesis - involved in the process of translation.

  80S found in eukaryotic cells and 70S in prokaryotic cells, mitochondria and chloroplasts.
• structure of ribosomes

  • made up of proteins and rRNA
  • consist of a large and small subunit
  • not surrounded by a membrane
• function of rough endoplasmic reticulum (RER)

  synthesis and transport of proteins
• structure of RER

  • covered with ribosomes (why its called rough)
  • contains a network of membranes enclosing the cisternae
  • the surface of the cisternae is covered with ribosomes
• function of smooth endoplasmic reticulum (SER)

  synthesis, storage and transport of lipids and carbohydrates
• structure of SER

  • same as RER but
  • lacks ribosomes
• function of cell wall

  provides strength to prevent the cell bursting under the pressure created by the osmotic entry of water

  gives mechanical strength to the plant
• structure of cell wall in plants

  • consists of microfibrils of the polysaccharide cellulose, embedded in a matrix.
  • a thin layer (middle lamella), which marks the boundary between adjacent cell walls and cements adjacent cells together.
• structure of cell wall in algae

  made up of either cellulose or glycoproteins, or a mixture of both
• cell wall structure in fungi

  do not contain cellulose

  comprise of chitin - a nitrogen containing polysaccharide, glycan and glycoproteins
• function of vacuole in plants

  helps to maintain pressure within the cell - keeps the cell rigid and stops the plant from wilting
• structure of vacuole in plants

  • contains cell sap
  • surrounded by a selectively permeable membrane known as tonoplast
• define specialised cells

  cells with certain features that allow them to carry out a particular function
• define tissue

  group of similar cells working together to carry out a particular function
• define organ

  a group of tissues working together to carry out a particular function
• define organ system


  a group of organs working together to carry out a particular function
• levels of organisations of cells in living organisms and give examples of each


  1. specialised cells - palisade cells
  2. tissues - epithelium, cartilage, and xylem
  3. organs - stomach, pancreas, and leaf
  4. organ systems - cardiovascular system, digestive system, and root system
• cell fractionation is a laboratory method used to isolate different components of the cell, specifically the organelles, so they can be studied in detail. it involves breaking the cell open and separating the organelles based on their size and density.
• the four main steps in cell fractionation are:

  1. sample preparation
  2. homogenisation
  3. filtration
  4. ultracentrifugation
• sample preparation - sample is placed in an ice-cold, isotonic buffered solution to protect the organelles during the fractionation process.

  ice-cold - slows down enzyme activity

  isotonic - ensures that water potential inside and outside organelles is the same

  buffered - keeping the pH constant is crucial to prevent denaturation
• homogenisation involves physically breaking open the cells. plasma membrane is disrupted, allowing organelles to be released into the solution.
• filtration - mixture is filtered to remove larger pieces of cell debris and any remaining tissue fragments.