1.1 cell structure and 2.1 cell organisation

What is an oganelle?

A specialised subunit within a cell that has a specific function

What are the organelles within an animal cell?

Cell membrane

Cytoplasm

Mitochondria

Nucleus

Ribosomes

What are the organelles within a plant cell?

Cell membrane

Cellulose cell wall

Chloroplasts

Nucleus

Permanent vacuole

Cytoplasm

Mitochondria

Ribosomes

What is the function of the nucleus?

Contains the genes of the chromosomes

Controls the activities of the cell

What is the function of the cell membrane?

Controls the passage of substances in and out of the cell

What is the function of the cytoplasm?

A liquid gel in which the organelles are suspended and where most of the chemical reactions needed for life take place

What is the function of the mitochondria?

Where aerobic respiration takes place

What is the function of the ribosomes?

Where protein synthesis takes place

What is the function of the cell wall?

Strengthens and supports the cell

Made of cellulose in plant cells

What is the function of the chloroplasts?

Contain chlorophyll so they are green

Chlorophyll absorbs light so the plant can make food by photosynthesis

What is the function of the permanent vacuole?

A space in the cytoplasm filled with cell sap. This is important for keeping the cells rigid to support the plant

What is protein synthesis?

The process of making proteins

Define prokaryotes

Simple cell structure doesn’t have a nucleus, permanent vacuole or other large organelles

Define eukaryotes

More complex cell structure and does contain a nucleus and other large organelles

What are the organelles within a bacterial cell?

Genetic material-loose in cytoplasm

Ribosomes

Cytoplasm

Cell membrane

Cell wall

Plasmids

Piles, flagella, slime capsule-only in some bacteria

What is the function of the slime capsule?

A protective layer to help defend bacteria against toxins and from drying out

What is the function of the flagella?

Allows the bacteria to move

What is the function of the plasmids?

These are small circular DNA molecules that carry extra genes from their main DNA molecule-bacteria can transfer plasmids to othe bacteria e.g genes for antibiotic resistance are often on plasmids

What are the organelles within a yeast cell?

Cytoplasm

Mitochondria

Temporary vacuole

Cell wall-made of chitin

Cell membrane

Ribosomes

Nucleus

What is the magnification equation

I=AM

Image size = actual size × magnification

Define resolution

The smallest change in a quantity that gives a change in the reading that can be seen

Label the parts of a microscope

1 eyepiece

2 objective lense

3 stage

4 slide

5 diaphragm- not necessary to learn

6 light

7 fine focus dial

8 course focus dial

What is the method for required practical 1 - using a microscope, steps 1-5?

To prepare

Wear safety goggles as a precaution

1.Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers

2.Add a drop of water to the middle of a clean slide

3.Using the tweezers, place the epidermal tissue into the water on the slide

4.Add a drop of iodine solution to stain the onion (if not using a red onion)

5.Using a mounted needle, gently lower a cover slip on to the slide. Make sure there are no trapped air bubbles, which would obstruct the view of the specimen and make sure the slide covers the onion.

What is the method for required practical 1 - using a microscope, steps 5-12?

6.To use the light microscope

7.Clip the slide onto the stage

8.Select the lowest powered objective lens

9.Use the coarse adjustment dial to move the stage up to just below the objective lens

10.Look down the eyepiece and use the coarse adjustment dial to move the stage downwards until the image is roughly in focus

11.Adjust the focus with the fine adjustment dial, until you get a clear image of the onion cells

12.Repeat the processes with rhe higher magnification objectives to allow individual cells to be viewed

How are observations drawn?

1. Use a pencil with a sharp point

2. Make sure the drawing takes up at least half of the space available

3. Do not include colouring or shading

4. The subcellular structures should be drawn in proportion

5. Include a title and the magnification of the observation

6. Label the important features with a ruler

7. Use solid lines to draw

How to convert the different units?

Metres 10⁰ ×1000 Millimeters 10 -³ ×1000 Micrometers 10-⁶ ×1000 Nanometres 10-⁹

What is the maximum magnification of a light and electron microscope?

Light - ×1500 to ×2000

Electron - ×2 000 000

What is the resolution of a light and electron microscope?

Light - lower, resolving power of about 200 nanometres

Electron - higher, can view objects as small as 0.2 nanometres across

What are the advantages of a light microscope?

-Much cheaper

- Smaller/portable, can be used almost anywhere

-Can magnify live specimens

What are the disadvantages of a light microscope?

-Lower resolution of about 200nm

-Lower magnification- ×1500 ×2000

-Samples must be thin and transparent to view clearly

What are the advantages of an electron microscope?

-Higher resolution- can be as small as 0.2nm

-Higher magnification of around ×2 000 000

-More detail

-Can see in 3D

-Can see smaller things more clearly

What are the disadvantages of an electron microscope?

-Cannot view living specimens

-Very large

-Very expensive

-Have to be kept in a special temperature, pressure and humidity controlled rooms

-Can’t view in colour

-Harder to use

What is the role of disinfectant when using bacteria?

Kills bacteria on the desk

What is the role of a petri dish when using bacteria?

To grow bacteria

What is the role of agar jelly when using bacteria?

Food for the bacteria to grow on

What is the role of a bunsen burner when using bacteria?

Used to sterilise equipment and creates an updraft to stop airborne contamination

What is the role of an inoculation loop when using bacteria?

Transfer bacteria from the culture to the agar jelly

What is the role of a glass spreader when using bacteria?

Spread bacteria over the surface of the agar jelly

What is the role of an incubator when using bacteria?

To grow bacteria at <25⁰

Why are microorganisms not incubated above 25⁰ in schools?

Because it could make an infectious disease that could spread to humans

Define specialised

A cell that has features for a particular purpose

Define adaptations

Special features that enable a cell to carry out its function

What is the function of a sperm cell?

Sperms cells are usually released a long way from the egg they are going to fertilise. They contain the genetic information from the male parent. Depending on the type of animal, sperm cells need to move through water or the female reproductive system to reach an egg. They then have to break into the egg to fertilise it.

What are the adaptations of a sperm cell?

-A long tail whips from side to side to help move the sperm through water or to the female reproductive system

-The middle section is full of mitochondria which transfer the energy needed for the tail to work

-The acrosome stores digestive enzymes for breaking down the outer layers of the egg

-A large nucleus contains the genetic information to be passed on

What is the function of a muscle cell?

Specialised cells that can contract and relax. Stirated (striped) muscle cells work together in tissues called muscles. Muscles contract and relax in pairs to move the bones of the skeleton, so vertebrates can move on land and in water, and in some cases fly. Smooth muscle cells form one of the layers of tissue in the digestive system and they contract to squeeze food through the gut

What are the adaptations of muscle cells?

-They contain special proteins that slide over each other making the fibres contract

-Contain many mitochondria to transfer the energy needed for the chemical reactions that take place as the cells contract and relax

-They can store glycogen, a chemical that can be broken down and used in cellular respiration by the mitochondria to transfer the energy needed for the fibers to contract

What is the function of a nerve cell?

-They are specialised to carry electrical impulses around the body

-They provide a rapid communication system between the different parts of the body

What are the adaptations of nerve cells?

-Lots of dendrites to make connections to other cells

-An axon carries the nerve impulse from one place to another. They can be very long-longest in human runs from the base of spine to big toe

-Nerve endings/synapses are adapted to pass the impulses to another cell or between a nerve cell and a muscle using transmitter chemicals

-Contains lots of mitochondria to provide energy needed to make transmitter chemicals

What is the function of a red blood cell?

Pick up oxygen from the air in lungs and carry it to the cells where it is needed

What are the adaptations of a red blood cell?

-They are biconcave discs. Being concave (pushed in) on both sides, gives them an increased surface area to volume ratio for diffusion

-They are packed with a red pigment (haemoglobin) which binds to oxygen

-They have no nucleus, making more space for haemoglobin

What is the function of a root hair cell?

-Absorbes water and mineral ions from the soil

-Mineral ions are moved into the root hair cell by active transport

What are the adaptations of a root hair cell?

-Greatly increase the surface area available for water to move into the cell

-They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell

-Many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells

What is the function of a palisade cell?

Make food through photosynthesis

What are the adaptations of a palisade cell?

-Contains chloroplasts containing chlorophyll

-Positioned in continuous layers in the leaves and outer layers of the stem so they absorb as much light as possible

-Have a large permanent vacuole that helps to keep the cell rigid

What is the function of xylem?

The transport tissue that carries water and mineral ions throughout the plant. Also supports the plant

What are the adaptations of xylem?

-Are alive at first, then lignin builds up in the cell wall and the cells die and form long narrow tubes for the water and mineral ions to go through

-The spirals and rings of lignin in the cells are very strong to help withstand the pressure of water moving up the plant

What is the function of the phloem?

Carries the glucose made by photosynthesis around the plant

What are the adaptations of the phloem?

-The cell walls between the cells break down to form sieve plates, allows water carrying dissolved glucose to move along the tubes

-Supported by companion cells. The mitochondria of the companion cells transfer the energy needed to move dissolved sugars around the phloem

What is the function of a guard cell?

-Used to open and close the stomata

-Stomata allow carbon dioxide into the leaf

-Stomata allow oxygen and water vapour to leave

What are the adaptations of the guard cells?

-Arranged in pairs

-Cell wall closest to stomata is thicker and less flexible

-Cell wall on outermost edge is thinner and less flexible

-When water enters cells they swell up unevenly due to the difference in flexibility. This opens up the stomata

What is differentiation?

The process of becoming specialised

What are the levels of organisation?

Specialised cells →Tissues →Organs →Organ systems -Organism

What are tissues?

A group of specialised cells with similar structure working together to perform a common function e.g nervous, muscle

What are organs?

A group of tissues that work together to perform a common function e.g heart, brain, kidney

What are organ systems?

A group of organs that work together to perform an overall life process e.g circulatory, reproductive