The structure and function of cellular organelles

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Organisation of the Body




How they work..

Light microscopes use compound lenses and light to magnify living or dead specimens.

Both transmission and scanning electron microscopes use electrons to magnify objects (only dead specimens).

Their use..

The lenses on a light microscope bend (or refract) the light, making objects appear closer.

An electron microscope is used to view things too small to be seen using a light microscope.

Their clarity..

LM’s have a lower clarity of a specimen, therefore cannot view in as much detail.

EM’s have a higher clarity because of the use of electrons, not light.


A resolution of 20 nm, creating images to see the details of cells but not of cells organelles.

A high resolution, creating a higher magnification of up to 2 million times.


Light microscopes can magnify an object using light up to 2000 times.

Whereas electron microscopes use their electrons to magnify an object over 500,000 times.

Q2: a)Attached file containing Appendix 1 Organisation of the Body.

b)Table shown on following page.




Ribosomes function is to read the code and link amino acids together represented by messenger RNA which is formed from the cell’s main DNA. Proteins are synthesised from this code meaning that the synthesis of all new proteins occurs from the ribosomes. They are to assemble the proteins of the cell and may in some situations, number in millions depending on the protein production level.


Chromatins function is to package DNA into a smaller volume so it is able to fit in a cell. This helps to strengthen DNA, allow mitosis and meiosis, control gene expression and DNA replication. It is a composition made up of DNA and protein, found inside the nucleus of cells. Histone proteins are the major proteins that are found in chromatin.

Endoplasmic reticulum

(both rough and smooth)

Endoplasmic reticulum’s (ER) function as a manufacturing and packaging system. Rough ER’s are important in the synthesis and packaging of proteins. Smooth ER’s are the storage organelle of creation and storage of lipids and steroids.

Golgi apparatus

Golgi apparatus function is to modify, sort and package proteins for secretion, and packing proteins and lipids. Golgi apparatus transport lipid molecules around the cell and is the creation of lysosomes (specialised vesicles).


Flagella are found in bacteria, archaea and eukaryote (protists, plants, animals & fungi). Flagella’s function is to move liquid past the surface of the cell.


Mitochondria’s function is to act like a digestive system and take in nutrients and breaking them down. They convert energy usable by the cell, are the sites of cellular respiration (generating fuel for cell’s activity), cell division, cell growth and cell death.


The nucleus’ function is to be the control center of the cell; maintaining integrity of genes, protein synthesis, cell division and growth, controls the activities of the cell by regulating gene expression and the characteristics of an organism. It is the most prominent organelle of the cell.


Lysosomes are also known as being the stomach of the cell. Their function is the digest any excess organelles, food particles, or engulfed viruses/bacteria.

c)The structure of red blood cells (erythrocytes) help it function by using its flexible disc shape; increasing the surface area and enhancing the rate of diffusion of oxygen across their plasma membranes. They contain hundreds of haemoglobin molecules that transport the oxygen to the lungs. The hairs that are above the cell nucleus are known as the ciliated epithelial, and their function is to remove any bacteria, mucus or dust from the interior of the lungs. With their structure they help the function of the cell by lining the respiratory tract with cilia in order to catch any daily intake of particles (i.e. Dust) and moving them out by causing sneezes to occur. Spermatozoa’s structure helps to complete their function by using their flagellums (tails) to move fast in order to reach and fertilise a woman’s egg in the fallopian tube. The sperm help to penetrate the egg to start meiosis and create unique genes. The head of a spermatozoon contains hydrolytic enzymes that help to digest their way through the woman’s oocyte. Also helping the function of spermatozoa within the structure is the use of mitochondria; providing energy for the tail to ‘swim’ faster to the oocyte.


‘The cell membrane is a fluid mosaic model made up of lipids and protein molecules.’

The composition of the cell membrane is a mix of proteins and lipids, which are both imperative to the structure and function of the cell. Lipids help to give membranes their flexibility and are mainly for insulation, whereas the proteins monitor and maintain chemical climate and assist in transferring molecules across the membrane. Surrounding the cell membranes is a bilayer of phospholipids (fats). The main role of the cell membrane is to protect the cell from its surroundings. It is selectively permeable to ions and organic molecules and is able to control the movement of particles that enter and exit the cells. Another function of the cell membrane is that it controls the information that travels between cells and the environment, by using its receptors to generate signals.


  • Active transport – a cell that requires energy to transport and is the movement of individual ions or molecules across the cell membrane into a higher concentration.
  • Passive transport (diffusion) – occurs when molecular substances are spread across cell membranes and are free to move. The substances move from high concentration to low concentration and do not need any input of energy.
  • Osmosis – the movement of water from high water concentration to low water concentration through a partially permeable membrane (allows small particles through, but not larger molecules).





  1. Use of energy

Does not require the use of energy, as it is an exergonic.

Energy is renewable but has little impact on the environment.

Uses energy to overcome concentration and electrochemical gradient.

  1. Concentration gradient

Particles move from a high area of concentration to a low area of concentration.

Particles move from a high water concentration to a low water concentration.

Particles move from a low concentration to a high concentration.

  1. Occur

Stomata of leaves during photosynthesis.

Plant cells.

Small intestine.

  1. How do they leave a cell..

Diffusion is a form of gas.

Osmosis is a liquid (water).

Glucose, amino acids, salts.

  1. Rate

Concentration, temperature and size of molecules.

Temperature, concentration and distance.

Temperature, concentration of oxygen and concentration of glucose.


Type of tissue

Describe how the structure of the tissue is linked to function

Nerve tissue

The major structural and functional unit of nervous tissue is the nerve cell (neuron). Nerve tissue is made up of 3 types of neurons: motor, sensory and interneurons. The cell body contains a nucleus and has dendrites branched off to bring impulses towards the body. The axon (unbranched fibre) carries information away from the cell body.

Muscle tissue

There are 3 different types of muscle tissue: skeletal (striated muscle that is attached to the bones by tendons that associate and help with the movement of the body), cardiac (a branched muscle where the cells are joined together by discs that allow the synchronization of the heart beat to happen) and smooth (found in the various parts of the body i.e. arteries, and contract slower than the skeletal muscle but are able to sustain for a longer time).

Connective tissue

Like others, there are different types of connective tissue but all of those contain the same; cells, fibres and intercellular substance. The connective tissues support, anchor and connect various parts of the human body.

Epithelial tissue

There are various different types and shapes of epithelial tissue; columnar, cuboidal and squamous. The functions of these are to protect, secretion, transcellular transport, selective absorption and detection of sensation. Having tightly packed layers within the cells of epithelial tissue helps with the way they work.


a)The heart contains muscle tissue that pumps the blood around, fibrous tissue that make up the heart valves, and cells that help to maintain the rhythm and rate of the heart beats. Cardiac tissue makes up the heart as it never tires or pauses. The liver contains hepatic cells which make up 60% of the liver tissue.

b)The function of the heart is to take blood low in oxygen from the body, through the right hand side of the heart and to the lungs. Then from the lungs, oxygenated blood flows through the other side of the heart and provides fuel for the body. The function of the liver is to regulate the blood sugar levels, get rid of any toxins and to produce bile. Being the second largest organ in the body, it also has functions of digestion, immunity and the storage of nutrients within the human body.

c)The stomach is a part of the digestive system and its main function is to store food, break it down and digest it in order to extract the necessary nutrients needed that have been consumed. It also produces carious enzymes i.e. acid and pepsin. Ovaries are a vital part of the reproductive system. They have two main functions in the body – they are the organs that produce oocytes in order for fertilisation to occur, and they also produce reproductive hormones, oestrogen and progesterone.

d)The heart and liver of the human body interact by working as a team ensuring that blood circulates throughout the body. The heart pumps the blood around whilst at the same time the liver is cleaning it, both partnering up to ensure a smooth cycle of circulation and filtration. The livers function to produce bile is vital in keeping the blood circulating the human body and its organs, for example the heart. Without saying, both blood and bile are linked together through health and great pair.


ABPI Resources for School, 2014. ‘Diffusion, Osmosis and Active Transport’. [online] Available at: <>

BBC, 2014. ‘Science: Human Body and Mind’. [online]. Available at: <>

Liver Support, 2014. ‘The Link Between Liver and Heart Health’. [online]. Available at: <>

Merck Manuals, 2009. ‘Tissues and Organs’. [online]. Available at: <>


ABPI Resources for School, 2014. ‘Diffusion, Osmosis and Active Transport’. [online] Available at: <>

A Level Notes, 2014. ‘The Fluid Mosaic Model’. [online] Available at: <>

BBC, 2014. ‘Science: Human Body and Mind’. [online]. Available at: <>

Liver Support, 2014. ‘The Link Between Liver and Heart Health’. [online]. Available at: <>

Merck Manuals, 2009. ‘Tissues and Organs’. [online]. Available at: <>

MS Nucleus, 2014. ‘Life Cycle: Human Biology’. [online] Available at: <>