Cell Structure & Diversity

Question 1

What must a cell do?

Answer 1

Manufacture cellular materials, Obtain raw materials, Remove waste, Generate the Required Energy, Control all of the above.

Question 2

What does the plasma membrane at the boundary of each cell do?

Answer 2

Provides special conditions within the cell, acts as a semi-permeable barrier

Question 3

How does the plasma membrane provide the ideal conditions and act as a semipermeable barrier?

Answer 3

Allows passage of oxygen, nutrients and waste. Controls movement of substances in and out of the cell. This interaction with the environment limits the maximum size of the cell.

Question 4

How does the size of a cell dictate the surface area to volume ratio?

Answer 4

A small cell has a larger surface area to volume ratio.

Question 5

What forms the plasma membrane?

Answer 5

A double layer of phospholipids with various embedded or attached proteins. The hydrophilic heads face outwards with the hydrophobic tails facing inwards. They move!

Question 6

What affects the membrane fluidity?

Answer 6

The composition of fatty acids

Question 7

What does saturation of the phospholipids in the membrane look like?

Answer 7

Packed tightly together, less fluidity. VISCOSE! (like honey, a bit slower to move)

Question 8

What does unsaturatedness of phospholipids in the membrane look like?

Answer 8

Tails prevent tight packing, more fluidity.

Question 9

How does temperature affect the fluidity of the membrane?

Answer 9

High temps = more fluidity (think melted, becomes liquid)
Low temps = More viscose (think colder temps, makes it harder)

Question 10

What does cholesterol do in the membrane?

Answer 10

Stabilises the fluidity. Helps the cells work properly.

Question 11

What do plasma membrane proteins do?

Answer 11

Determine the function of the membrane. They have multiple different functions and are found in different types of cells. The function is often specific to the cell type but cells can have multiple diff proteins.

Question 12

What functions are membrane proteins involved in?

Answer 12

Signal transduction, Cell recognition, Intercellular joining, Linking cytoskeleton and extracellular matrix, membrane transport.

Question 13

The protein function signal transduction is what?

Answer 13

Relay messages from the body (or outside environment) into the cell.

Question 14

The protein function cell recognition is what?

Answer 14

The cells ability to distinguish one type of neibouring cell from another. It often involves glycoproteins (proteins with added sugars).

Question 15

The protein function intercellular joining is what?

Answer 15

Some proteins form long lasting connections between cells

Question 16

The protein function linking cytoskeleton and extracellular matrix does what?

Answer 16

This allows the cells to physically connect with proteins structures outside of the cell

Question 17

The protein function membrane transport is what?

Answer 17

Allows small amounts of molecules to move across the membranes. This can be passive (no energy required) or active (energy required)

Question 18

What are the defining factors for whether membrane transport or bulk transport needs to be used for things to get over the cell membrane?

Answer 18

Size. It depends what the molecules are, how big they are and how much of it is being moved at a time.

Question 19

What is passive transport?

Answer 19

When the molecules move down (with) the concentration gradient, so no energy is needed to get them across.

Question 20

What is active transport?

Answer 20

When the molecules move against the concentration gradient, so energy is required to get them across.

Question 21

Diffusion: What are membranes permeable to?

Answer 21

Lipid soluble (hydrophobic) molecules. Eg. gasses/steroid hormones

Question 22

Diffusion: What are membranes NOT permeable to?

Answer 22

Charged molecules such as glucose ions and water

Question 23

What is facilitated diffusion used for?

Answer 23

For hydrophilic molecules. It requires membrane proteins called carriers and channels

Question 24

How are carriers different to channels?

Answer 24

Carriers undergo a shape change to help guide the molecule

Question 25

Facilitated diffusion for water requires what?

Answer 25

Aquaporins. These are channel proteins. And this is a process called osmosis.

Question 26

What is osmosis?

Answer 26

The process of water moving from an area of high water (low solute) to an area of low water (high solute) through a semipermeable membrane.

Question 27

Active transport requires what type of proteins?

Answer 27

Transport proteins. They require ATP (energy)

Question 28

Active transport allows for a cell to have what?

Answer 28

An internal concentration of a substance that is different from its surroundings. For example something inside the cell could be higher than outside the cell.

Question 29

Can active transport go both ways (is it bidirectional)?

Answer 29

Yes

Question 30

Co-tansport is what?

Answer 30

Indirect active transport (so it requires energy). One substance is powered across the membrane and its concentration gradient is used to power the movement of a second substance against its concentration gradient.

Question 31

How do different parts of the cells do different things?

Answer 31

Organelles

Question 32

What do organelles do?

Answer 32

Provide special conditions for specific processes, keep incompatible processes apart, allows specific substances to be concentrated, from concentration gradients, package substances for export/transport.

Question 33

What are organelles like? (way to remember how organelles work)

Answer 33

A house. The different rooms in a house have different functions. The organelles are the different rooms (the walls being the membrane around the organelles), they separate the function inside the cell.

Question 34

List the key organelles in an animal cell

Answer 34

Endoplasmic reticulum, Nucleus, Mitochondrium, Golgi apparatus, Lysosome

Question 35

List the key organelles in a plant cell

Answer 35

Endoplasmic reticulum, Nucleus, Golgi apparatus, Mitochondrium, Central Vacoule, Chloroplast.