Cell Biology

Using a Microscope: Step 1

Clip slide onto the stage

Using a Microscope: Step 2

Ensure the lowest powered objective lens is over the slide

Using a Microscope: Step 3

Use the coarse adjustment knob to bring the stage up just below the lens

Using a Microscope: Step 4

Look down the eye piece and gradually move the stage downwards using the coarse adjustment knob

Stop when the image is roughly in focus

Using a Microscope: Step 5

To bring the image into focus adjust the fine adjustment knob until you get a clear image

Using a Microscope: Step 6

To observe the image with a higher magnification, change the objective lens to a higher power and readjust the stage using the coarse and fine adjustment knobs

Microscopy Step 1

Use the lowest objective lens to find the biggest field of view

Microscopy Step 2

Use the coarse focus to move the stage

Microscopy Stage 3

Use the fine focus to get a clear image

Microscopy Stage 4

Eyepiece Lens x Objective Lens = Magnification

Microscopy Stage 5

Use the equation Magnification = Image Size/Actual Size

Electron Microscopes

• Have a higher magnification

• Have a higher resolution

Total Magnification Equation

Total Magnification=Eye Piece Magnification x Objective Lens Magnification

Magnification Equation

Magnification=Image/Actual

Actual Size Equation

Actual Size=Image Size/Magnification

Image Size Equation

Image Size=Actual Size x Magnification

Blurry Image

Use the focus dials to make an image clearer

Step 1

Peel off the epidermal tissue of the onion using tweezers

Step 2

Add a drop of water to a clean slide

Step 3

Place the epidermal tissue into the water on the slide

Step 4

Add a drop of iodine to stain the cell so structures within the cell can be observed

Step 5

Place a cover slip on top of the specimen

Animal and Plant Cell: Cytoplasm

Where chemical reactions occur

Animal and Plant Cells: Nucleus

Stores genetic information/controls the cell

Animal and Plant Cells: Mitochondria

Release energy from respiration

Animal and Plant Cells: Ribosomes

Makes protein

Animal and Plant Cell: Cell Membrane

Controls what enters and exits the cell

Plant Cell Only: Chloroplast

Contains chlorophyll to absorb sunlight for photosynthesis

Plant Cell Only: Vacuole

Stores sap

Plant Cell Only: Cell Wall

For structure8

Animal Cells

• Cell membrane

• Nucleus

• Mitochondria

• Ribosomes

• Cytoplasm

Plant Cell

• Permanent vacuole

• Chloroplasts

• Cell wall

• Cell membrane

• Nucleus

• Mitochondria

• Ribosomes

• Cytoplasm

Eukaryotes

• Have a nucleus

• Bigger than prokaryotes

Prokaryotes (bacteria)

Have loose chromosomal DNA/plasmid DNA

Animal and Plant Cells

Eukaryotic cells which have genetic material (DNA) that forms chromosomes and is contained within a nucleus

Stem Cells

Unspecialised cells that can become specialised from embryos and bone marrow

Light Microscope

• Uses light to form images

• Living samples can be views

• Relatively cheap

• Low magnification

• Low resolution

Electron Microscope

• Uses a beam of electrons to form images

• Samples cannot be living

• Expensive

• High magnification

• High resolution

Bacterial Cells

• Single celled

• No nucleus just a single loop of DNA

• Have small rings of DNA called plasmids

• Smaller than eukaryotic cells

Sperm Cell Function

Fertilises an ovum (egg)

Sperm Cell Adaptations

• Tail to swim to the ovum and fertilise it

• Lots of mitochondria to release energy from respiration, enabling the sperm to swim to the ovum

Red Blood Cell Function

Transport oxygen around the body

Red Blood Cell Adaptations

• No nucleus so more room to carry oxygen

• Contain a red pigment called haemoglobin that binds to oxygen molecules

• Flat bi-concave disc shale to increase surface area to volume ratio

Muscle Cell Function

Contract and relax to allow movement

Muscle Cell Adaptations

• Contains protein fibres which contact to make the cells shorter

• Contains lots of mitochondria to release energy from respiration allowing the muscles to contract

Nerve Cell Function

Carry electrical impulses around the body

Nerve Cell Adaptations

• Branched endings called dendrites to make connections with other neurones or effectors

• Myelin sheath insulates the axon to increase the transmission speed of the electrical impulses

Root Hair Cell Function

Absorb mineral ions and water from the soil

Root Hair Cell Adaptations

• Long projection speeds up the absorption of water and mineral ions by increasing the surface area of the cell

• Lots of mitochondria to release energy for the active transport of mineral ions from the soil

Palisade Cell Function

Enable photosynthesis in the leaf

Palisade Cell Adaptations

• Lots of chloroplasts contain chlorophyll to absorb light energy

• Located at the top surface of the leaf where it can absorb the most light energy

Diffusion Definition

Spreading out if particles resulting in a net movement from an area of a higher concentration to an area of a lower concentration

Diffusion Movement of Particles

Particles move down the concentration gradient from an area of high concentration to an area of low concentration

Is energy required for Diffusion?

No it is a passive process

Diffusion Examples: Humans

• Nutrients in the small intestine diffuse into the blood in the capillaries through the villi

• Oxygen diffuses from the air in the alveoli into the blood in the capillaries

• Carbon dioxide diffuses from the blood in the capillaries into the air in the alveoli

• Urea diffuses from cells into the blood for excretion by the kidney

Diffusion Examples: Plants

• Carbon dioxide used for photosynthesis diffuses into leaves through the stomata

• Oxygen produced during photosynthesis diffuses out of the leaves through the stomata

Diffusion Examples: Fish

• Oxygen from water passing over the gulls diffuses into the blood in the gill filaments

• Carbon dioxide diffuses from the blood in the gill filaments into the water

Osmosis Definition

The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

Osmosis Movement of Particles

Water moves from an area of lower solute concentration to an area of higher solute concentration

Is energy required for Osmosis?

No it is a passive process

Osmosis Examples: Plants

• Water moves osmosis from a dilute solution in the soil to a concentrated solution in the root hair cell

Active Transport Definition

Movement of particles from a low concentration to a high concentration requiring energy from respiration

Active Transport Movement of Particles

Particles move against the concentration gradient from an area of low concentration to an area of high concentration

Is energy required for Active Transport?

Yes it is using energy released during respiration

Active Transport Examples: Humans

HUMANS

• Active transport allows sugar molecules to to be absorbed from the small intestine when the sugar concentration is higher in the blood than in the small intestine

Active Transport Examples: Plants

• Active transport is used to absorb mineral ions into the root hair cells from more dilute solutions in the soil

Factors that Affects the Rate of Diffusion

1) Difference in concentration - the steeper the concentration gradient the faster the rate of diffusion

2) Temperature - the higher the temperature the faster the rate of diffusion

3) Surface Area of the Membrane - the larger the membrane surface area the faster the rate of diffusion

Adaptations for Exchanging Substances: Single Celled Organisms

• Single celled organisms have a large surface area to volume ratio

  • Allows enough molecules to move across their cell membranes to meet their needs

Adaptations for Exchanging Substances: Multicellular Organisms

• Multicellular organisms have a small surface area to volume ratio

  • They need specialized organ systems and cells to be transported into and out of their cells

Exchanging Substances

Works most efficiently when they have a large surface area, a thin membrane and good blood supply

Villi in the Small Intestine

• For absorbing nutrients

• Network of capillaries

• Large surface area

• Thin wall - 1 cell thick

• Good blood supply

Alveoli in the Lungs

• For gas exchange

• Network of capillaries to provide a good blood supply

• Rate of diffusion is increased because the membrane has

  • Large surface area

  • Moist

  • Only one cell thick (short diffusion pathway)

Fish Gills

• For gas exchange

• Made up in stacks of thin filaments with

  • Large surface area to increase diffusion

  • Network of capillaries for a good blood supply

Root Hair Cells

• For uptake of water and minerals

• Lots of mitochondria to take in mineral ions by active transport

• Large surface area to help efficient absorption of water and minerals ions

Cell Cycle Stage 1

Chromosomes duplicate and the number of sub cellular structures (ribosomes/mitochondria) increase

Cell Cycle Stage 2

Mitosis - One set of each chromosome pulled to opposite ends of the cell and the nucleus divides

Cell Cycle Stage 3

Cell membrane and cytoplasm split to produce 2 genetically identical daughter cells

Osmosis Step 1

Cut equal lengths of potato using a cork borer

Osmosis Step 2

Use a paper towel to dab off excess water

Osmosis Step 3

Weigh each piece of potato using a mass balance

Osmosis Step 4

Place each piece of potato in a different concentration of solution and leave for a set amount of time

Osmosis Step 5

Use paper towel to dab off excess water and re-weigh each piece of potato

Independent Variable

Concentration of Solution

Dependent Variable

Change in Mass of Potato

Control Variables

• Variety of potato

• Length and diameter of potato

• Volume of solution

• Temperature

Possible Source of Error

Zero error on scales