Cells as the Basis of Life

investigate different cellular structures.

prokaryotic and eukaryotic

Prokaryotic

Prokaryotic organisms do not have membrane bound organelles, i.e. they do not have a nucleus, mitochondria or chloroplasts. The prokaryotic genome is in a circular DNA/protein single chromosome called the nucleoid. Many prokaryotes have fimbriae which are short hair-like structures on the surface that help the prokaryote stick to other cells or to a substrate. Flagella are used by motile bacteria for movement to move either towards or away from stimuli.

Eukaryotic

A eukaryote has membrane organelles, e.g. nucleus, mitochondria. Eukaryotes include single-celled organisms, e.g. some protista and some fungi and multicellular organisms, e.g. plants, animals, some protists and some fungi.The endomembrane system of eukaryotic cells includes the cell membrane, the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes and other vesicles and vacuoles found within the cell.

technologies that are used to determine a cell’s structure and function

Light microscope

Energy Source

The energy is generated by a light bulb.

Focus

Specimen
Preparation

Magnification

Resolution

Can live specimen be viewed?

Image: Colour /
Black & White

Condenser Lens - This lens system is located immediately under the stage and focuses the light on the specimen.

  1.  Place a drop of fluid in the centre of the slide.
    
  1. Position sample on liquid, using tweezers.
    
  1. At an angle, place one side of the cover slip against the slide contacting outer edge of the liquid drop.
    
  1. Lower the cover slowly, avoiding air bubbles.
    
  1. Remove excess water with the paper towel.
    

400-1000 times

Resolution in an ideal light microscope is limited to around 200 nm

yes

Colour

Electron microscope

Energy Source

Electron microscopy uses a beam of electrons as an energy source.

Focus

This beam is focused onto the sample using a magnetic lens.

Specimen
Preparation

Samples must be cut into very thin cross-sections. This is to allow electrons to pass right through the sample. After being fixed and dehydrated they are examined.

Magnification

Between 1 and 50 million times

Resolution

0.05 nm

Can live specimen be viewed?

no

Image: Colour /
Black & White

B and W

Prokaryotic and eukaryotic cell structures

comparing and contrasting different cell organelles and arrangements

Similarities

Golgi apparatus

Ribosomes

Cytoplasm

Differences

Nucleus

Chloroplasts

Mitochondria

Vacuole

Nucleolus

Endoplasmic reticulum

Lysosome

Functions of organelles:

Nucleus: The nucleus controls and regulates the activities of the cell.

Chloroplast: structure within the cells of plants and green algae that is the site of photosynthesis, the process by which light energy is converted to energy.

Mitochondria: Generates most of the chemical energy needed to power the cell's biochemical reactions.

Golgi apparatus: Helps process and package proteins.

Ribosomes: Site for protein synthesis in the cell.

Vacuole: Remove and stores waste and nutrients produced during autophagy (when part of the cell is broken down due to age or damage).

Cytoplasm: It provides a platform upon which other organelles can operate within the cell.

Endoplasmic reticulum: Its function is to produce proteins for the rest of the cell to function.

Lysosome: They break down excess or worn-out cell parts.

How materials can move into and out of cells

Diffusion and ossmosis

Diffusion

Passive movvement of a substance from an area of high solute concentration or low concentration.

Osmosis

Passive movemnet of water to an area of higher concentration

Cell membrane

Phospholipid

peripheral protein

Channel protein

Carrier protein

Cholesterol

Glycoprotein

Cholesterol functions to immobilise the outer surface of the membrane, reducing fluidity. It makes the membrane less permeable to very small water-soluble molecules that would otherwise freely cross. It functions to separate phospholipid tails and so prevent crystallisation of the membrane.

A channel protein, a type of transport protein, acts like a pore in the membrane that lets water molecules or small ions through quickly.

Phospholipids provide barriers in cellular membranes to protect the cell, and they make barriers for the organelles within those cells.

Peripheral proteins form temporary bonds with the cell membrane, allowing them to detach and reattach at specific times, with specific signals.

Carrier protein is a type of cell membrane protein involved in facilitated diffusion and active transport of substances out of or into the cell.

Glycoproteins are found on the surface of the lipid bilayer of cell membranes. Their hydrophilic nature allows them to function in the aqueous environment, where they act in cell-cell recognition and binding of other molecules.

Endocytosis and exocytosis

Endocytosis

Endocytosis is a general term describing a process by which cells absorb external material by engulfing it with the cell membrane. Endocytosis is usually subdivided into pinocytosis and phagocytosis.

Exocytosis

Exocytosis is the fusion of secretory vesicles with the plasma membrane and results in the discharge of vesicle content into the extracellular space and the incorporation of new proteins and lipids into the plasma membrane.

Ezymes

Whta are they?

Enzymes are proteins that help speed up metabolism, or the chemical reactions in our bodies. They build some substances and break others down. All living things have enzymes. Our bodies naturally produce enzymes. But enzymes are also in manufactured products and food

Made of

Enzymes are protein molecules which are made up of long chains of amino acids.

Activation energy

Enzymes provide an alternative pathway for a chemical reaction. They lower the activation energy, allowing reactants to reach the lower activation energy values more quickly and thereby increase the rate of reaction.

Models

Induced fit

The induced-fit model is a model for enzyme–substrate interaction to describe that the substrate is capable of inducing the proper alignment of the active site of the enzyme, causing the latter to subsequently perform its catalytic function.

Lock and key

Lock-and-key model is a model for enzyme-substrate interaction suggesting that the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.