Biology Unit 1 (B1 Cell structure and function)

What is the cell theory?

The Cell theory states that all living organisms are composed of one or more cells, that the cell is the basic unit of life, and that all cells arise from pre-existing cells.

What does Eukaryotic Cell mean?

A cell that has a nucleus and membrane bound-organelles- ( eg: mitochondria)

What is the function of a plasma membrane? PLANT AND ANIMAL CELL

Separates the internal environment of the cell from the external environment and controls what goes in and out of the cell.

What is the function of the cytoplasm?  PLANT AND ANIMAL CELL

Contains membrane bound organelles and where a lot of chemical reactions take place

What is the function of the nucleus including the nucleolus in plant and animal cells

Contains DNA

Nucleolus makes ribosomes and RNA

What is the function of the rough endoplasmic reticulum

Carries our protein synthesis and transports proteins

What is the function of the smooth endoplasmic reticulum in animal and plant cells

Carries out lipid synthesis and transports lipids

What is the function of the Golgi apparatus in plant and animal cells

Modifies and processes proteins

Packages them into vesicles

What is the function of the Golgi vesicle in animal and plant cells

Transports materials inside cells and transports materials to plasma membrane

What is the function of lysosomes

Contains hydrolytic enzymes to break down waste and old organelles

What is the function of ribosomes in plant and animal cells

Where protein synthesis takes place

What is the function of mitochondria in plant and animal cells

Site of aerobic respiration and ATP is produced

What is the function of a centriole in the animal cell

Makes spindle fibres for chromosomes to attach to during cell division

What is the function of the cell wall in plant cells

Made of cellulose so offers structural support and allows most substances to enter the cell wall

What is the function of the chloroplasts in the plant cell

Where photosynthesis takes place

What is the function of the vacuole in plant cells

Stores water and minerals in plant cells and helps maintain turgor pressure

What is the function of the tonoplast in plant cells

Partially permeable membrane around the vacuole that controls movement of molecules in and out of vacuole

What is the function of amyloplasts in plant cells

Stores starch made from glucose produced during photosynthesis

What is the function of plasmodesmata and pits in plant cells

Allows transport of water and mineral ions from cell to cell

What is the definition of a prokaryotic cell?

Smaller cell with no nucleus or membrane bound organelles

What is the function of a nucleoid in a prokaryotic cell?

DNA one circular chromosome connected end to end

What is the definition of plasmids in prokaryotic cells

Contains extra beneficial genes like antibiotics resistance and allows extra beneficial genes to be transferred

What is the function of the 70s ribosomes in prokaryotes

Where protein synthesis takes place

What is the function of the capsule in prokaryotic cells

Prevents phagocytosis and prevents bacterium from drying out

What is the function of the cell wall in prokaryotic cells

Offers structural support as it’s made of cellulose. Allows substances to enter in and out of the cell. Peptidoglycan prevents cells from bursting and protects it

What is the function of the flagellum in prokaryotes

Provides movement

What is the function of the pili in prokaryotic cells

Helps attach to surfaces and other bacteria

Define a gram stain

A method where you identify the two types of bacteria using dyes to show the difference in their cell wall structure

What is the thickness and presence of an outer lipid membrane for gram positive bacteria?

Thickness: Thicker

Presence: Absent

What is the thickness and presence of an outer lipid membrane for gram negative bacteria?

Thickness: thinner

Presence: present

What are each stages of the gram staining technique and what do they do?

Crystal Violet: stains bacteria purple

Iodine: Helps fix the purple stain more strongly

Ethanol: removes the crystal violet iodine complex from gram negative bacteria

Safranin: stains the now colourless gram negative bacteria red or pink allowing it to be seen

Why do gram positive bacteria turn purple?

They have a thicker cell wall with lots of peptidoglycan and have no outer membrane

Why do gram negative bacteria turn pink?

They have a thinner cell wall with not a lot of peptidoglycan and have an outer membrane

Explain the link between gram result and choice of antibiotics

Knowing whether bacterium is gram positive or gram negative helps doctors choose effective antibiotics. Since gram negative bacteria has an outer membrane, it prevents antibiotics like penicillin from entering so a diff antibiotics should be used. Since gram positive bacteria lacks this membrane, it is more effective for penicillins to work.

Define the term magnification

How many times larger the image is than the object

Define resolution

Shortest distance between 2 points that can still be distinguished as two separate entities.

Optical microscopes have a lower resolution compared to electron microscopes. What does this mean?

This means microscopes can’t see two separate points clearly like electron microscopes can, which makes it harder to identify organelles

Why do electron microscopes have a higher resolution than light microscopes?

Electron microscopes have higher resolution than optical microscopes because electron beams have shorter wavelengths than visible light.

What are advantages and disadvantages of a light microscope

Advantages: specimens are in colour, can view live specimens and low technical skills required

Disadvantages: can only see largest organelles such a nucleus due to low resolution, light has a longer wavelength so a lower resolution.

What are advantages and disadvantages of electron microscopes

Advantages: can be used to see smallest organelles such as ribosomes, greater magnification.

Disadvantages: expensive and specimens are in black and white

How do you go from cm-mm, mm-um and um-nm

Cm-mm = x10

Mm-um = x1000

Um-nm = x1000

Rank the following in order from smallest to largest and define them.

Organ, organ system, tissue, cell and organelle

1. organelle- small part inside of cell that does a job such as a nucleus

2. Cell- smallest living part of an organism, like a prokaryotic cell

3. Tissue- a group of specialised cells working together to carry out a specific function like the epithelial tissue

4. Organ- a group of specialised tissues working together to carry out a specific function, such as a stomach

5. Organ system- a group of specialised organs working together to carry out a specific function