Units 1 and 2 Cells and the Characteristics of Life

What you need to be able to do: 1 List and describe the characteristics of living organisms.

Starter How can you tell if something is alive?

Task Go to: http://www.exploratorium.edu/imaging- station/students/Characteristics_Student.doc and download the document. Follow the instructions and complete the sheet.

An action by an organism or part of an organism causing a change of position or place MOVEMENT

RESPIRATION The chemical reactions that break down nutrient molecules in living cells to release energy RESPIRATION

The ability to detect or sense changes in the environment (stimuli) and to make responses SENSITIVITY

A permanent increase in size and dry mass by an increase in cell number or cell size or both GROWTH

The processes that make more of the same kind of organism REPRODUCTION

The taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them NUTRITION

Characteristics of living things A mnemonic to help you remember: e Say what you see!

M R S G R E N ovement espiration ensitivity rowth eproduction xcretion utrition

Review and Homework Match up the pictures and descriptions of the life processes in your booklet. Complete the Living Things crossword.

2.1 Cell Structure and Organisation What you need to be able to do: 1 State that living organisms are made of cells. 2 Identify and describe the structure of a plant cell (palisade cell) and an animal cell (liver cell), as seen under a light microscope. 4 Describe the differences in structure between typical animal and plant cells.

Starter http://www.kscience.co.uk/animations/animal_c ell.htm Watch BrainPop video "Cells"

Cell Structure

Parts common to all cells Nucleus - contains genetic material which controls the activities of the cell Cytoplasm - chemical reactions take place here, controlled by enzymes Cell membrane - partially permeable, controls what comes in and out of the cell Mitochondria - aerobic respiration occurs here to release energy

Plant cells have these extra features Cell wall - strengthens the cell and provides support Chloroplasts - contain chlorophyll which absorbs light energy for photosynthesis Large permanent vacuole - contains cell sap to keep the cell turgid Note: animal cells may contain small, temporary food vacuoles

Looking at animal cells Preparing a temporary mount of cheek cells Try the echalk activity - preparing cheek cells

Looking at plant cells Preparation of onion skin temporary mount Look at the echalk activity - preparing onion cells

Tasks Review Make biological drawings of each of your slides. Remember the rules! Add a title and label the parts you can see. Answer past paper question 7. Review Cells Revision Video

2.1 Cell Structure and Organisation What you need to be able to do: 3 Relate the structures seen under the light microscope in the plant cell and in the animal cell to their functions. 5 Calculate magnification and size of biological specimens using millimetres as units.

Starter In Biology we study molecules to habitats. The size of these things varies enormously! Look here: http://www.cellsalive.com/howbig.htm and here: http://scaleofuniverse.com/ In the last lesson we used microscopes to look at cells. You used 10x and 40x lenses to magnify them.

Magnification How much an object is magnified under the microscope is calculated as follows: total magnification = eyepiece lens x objective lens So, if we use a 10x eyepiece lens and a 10x objective lens the total magnification is: 10 x 10 = 100x magnification

Calculating magnification of biological drawings The drawing you make of an object under a microscope is usually much larger than the object’s actual size You need to indicate how much bigger There are three things involved in magnification calculations; - the size of the drawing - the actual size of the object - the magnification of your drawing (how much bigger your drawing is compared to the real thing)

Magnification formula To find the magnification of your drawing, the formula is: magnification = size of drawing (mm) size of the real thing (mm) To find the size of your drawing is easy – just measure it with a ruler (in mm) The size of the real thing is usually given to you. BUT, you must convert to mm to use the formula

Estimating Cell Size We can use a clear plastic ruler to estimate the size of cells.

Appearance of ruler at 100x magnification

Appearance of onion cells at 100X magnification

Estimating the size of cells Average cell width 12 cells = 1mm so 1 cell = 0.083 mm Imagine the ruler lines! 12 Remember it is only an estimate! 5 Count the number of cells in 1 mm Average cell length 5 cells = 1 mm so 1 cell = 0.2 mm

2.2 Movement in and out of cells What you need to be able to do: 1 Define diffusion as the net movement of molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement. 2 Describe the importance of diffusion of gases and solutes and of water as a solvent.

What substances need to go in and out of a cell and why? Respiring animal cell: oxygen carbon dioxide glucose water

Photosynthesising plant cell: carbon dioxide glucose water oxygen Substances can move in and out of cells in 3 ways diffusion, osmosis and active transport

Diffusion Starter Watch BrainPops "Passive Transport" Add potassium permanganate to hot and cold water and observe

Tasks Can you describe what happens using the following words? particles, low, concentration, down, high, movement, random, concentration gradient. Describe and explain how temperature affects diffusion. Watch the echalk diffusion animation

The importance of diffusion Diffusion is the random movement of particles from a region of high concentration to a region of low concentration down a concentration gradient. Where in the human body is this important?

Watch this video and complete the table in your booklet:

Shorter distance = faster rate Review Apart from temperature, what other factors affect the rate of diffusion, how and why? Particle size Smaller size = faster rate Smaller particles move faster than larger ones (less energy needed) Diffusion distance Shorter distance = faster rate Less distance takes shorter time to travel Concentration gradient Bigger difference = faster rate Greater net movement down concentration gradient What other important feature is often seen in parts of the body where dffusion occurs? A LARGE SURFACE AREA