Cell membrane

Question 1

phospholipid

Answer 1

each phospholipid is represented by a hydrollic head (absorbs water or dissolves in water)

a hydrophobic tail (water avoiding or unable to dissolve in water)

Heads are attracted to water and tails are repelled

Question 2

Fluid mosaic model

Answer 2

in the fluid mosaic model there is a bilayer of phospholipids (fats) which are arranged with their hydrophobic tails (fatty acids) facing inwards and their hydrollic heads (phosphate) facing outwards

Question 3

The role of the membranes

Answer 3

the cell membrane regulates the passage of materials into and out of the cell
based on what is considered the OPTIMUM CONCENTRATION LEVEL for a material the membrane determines whether it will be allowed passage
works most often specifically on the concentration of water and different types of ions

Question 4

the role of the membranes

Answer 4

the cell membrane maintains a relatively stable internal conditions via the passive movement of some substances along a concentration gradient via diffusion and osmosis

Question 5

how do you calculate total magnification?

Answer 5

total magnification =ocular magnification x objective magnification

Question 6

What is field of view (FOV)

Answer 6

the field of view is the diameter of the circle seen through a microscope
the smaller the FOV, the greater the magnification
1mm = 1000 micrometeres

Question 7

how to calculate an objects actual diameter

Answer 7

FOV diameter/ estimated number of cells across FOV

Question 8

calculating for High power (hp)

Answer 8

HP FOV= LP FOV x LP magnification/HP magnification

Question 9

Cell membrane

Answer 9

the membrane surrounding a cell, plasma membrane, forms a boundry seperating the living cell from non-living surroundings

Question 10

what does the plasma membrane do

Answer 10

selectively controls the movement of materials into and out of the cell
responsible for cell to cell recognition (eg. when cells aggregate into tissues)
is a dynamic stucture with distinct inside and outside faces

a plasma membrane is common to all cells. It forms their outer limit
However, bacteria, fungi, plant cells also have a cell wall but that is structurally distinct and lies outside the plasma membrane

Question 11

what is the selectively permeable membrane

Answer 11

the cell wall is permeable, allowing hte passage of almost a;l materials, the plasma membrane is selectively permeable, controlling the movement of substances into/out of cells

cell membranes are represented according to a fluid mosaic model due to they are:
fluid- the phospholipid bilayer is viscous and individual phospholipids can move position
mosaic the phospholipid bilayer is embedded with proteins, resulting in a mosaic of components

Question 12

passive/active transport

Answer 12

substances must move in/out of the cell either with or without energy
they are moved across the plasma membrane either by:
passive transport (not requiring energy)
- diffusion (simple and dacillitated)
- osmosis
active transport (energy requiring)

Question 13

Passive transport

Answer 13

passive transport involves the movement of materials along a concentration gradient
high concentration —> low concentration

as materials are moving down a concentration gradient, the expenditure of energy (ATP) is NOT required
simple diffusion- movement of small molecules (oxygen, carbon dioxide ect)
osmosis - movement of water molecules

Question 14

diffusion

Answer 14

diffusion describes the movement of molecules from high to low concentration along a concentration gradient
in biological systems, diffusion often occurs partially permeable membranes
| molecules in solutions tend to slowly spread apart (diffuse) over time

Question 15

concentration gradient

Answer 15

the concentration gradient is the process of particles, moving through a solution/gas from an area with a higher number of particles to lower number
these areas are typically seperated by a membrane. This membrane can be permeable, semi permeable or non-permeable

direction of net movement from area of greatest concentration to lowest concentration is ——>

Question 16

Facilitated diffusion

Answer 16

charged particles (such as chloride and sodium ions ) and relatively large molecules (eg. glucose and amino acids) do not readily pass through the phospholipid bilayer 
facilitated diffusion provides a way to help them enter the cell, through the action of carrier proteins and channel proteins

Question 17

Facillitated diffusion

Answer 17

particles move from one side of the membrane down the concentration gradient meditated by specific membrane carriers or channel proteins

carrier proteins: change shape and release substances on the other side (restored back to their original shape)
channel proteins: allow certain size and shape particles through. These are specific for a substance and don’t bind with molecules being transported
diffusion will continue until equilibrium is reached, this means there will be an equal distribution of molecules throughout the space

Question 18

Osmosis

Answer 18

Osmosis is the movement of water across a semipermeable membrane from a region of low to high solute concentration (until equilibrium is reached)
as solutes cannot cross a cell membrane unaided, water will move to equalise the two solutions
osmosis does not require energy so it is known as passive transport

Question 19

Isotonic

Answer 19

if the fluids inside and outside the cell are of equal solute concentration, the external solution is said to be isotonic- the same

Question 20

What is hypotonic?

look at binder

Answer 20

a solution with a lower solute concentration than another
in animal cells in a hypotonic solution (water movement) eg. fresh water the cell swells and burts

in plant cells in a hypotonic solution it swells but cell wall prevents cell from bursting (vacuole containing water flushes outwards) shrinks

Question 21

What is hypertonic?

Answer 21

a soultion with a higher solute concentration than another
in animal cells hypertonic solutions eg. salt water the cells shrinks and crinkles
in plant cells the cell shrinks

Question 22

osmosis in plants and animals

Answer 22

water continues to enter plants cells by osmosis until the cell contents are swollen and pressing the cell membrane against the cell wall.

Question 23

in osmosis what happens when the cell is turgid or flaccid

Answer 23

the cell is turgid (swelling) giving strength to cells and maintaining the stem’s erect structure

cells are flaccid (shrinking) if they lost their turgidity due to excess water loss from cells—> plant is seen to wilt

Question 24

What is active transport

Answer 24

active transport uses energy to transport particles across membranes and because it uses energy can move substances against a concentration gradient from a low to high gradient

Question 25

active transport

Answer 25

enables a cell to maintain internal concentrations of small solutes that differ from concentration in its environment and is performed by specific carrier proteins in the membrane

Question 26

active transport

Answer 26

transport proteins use ATP energy to move molecules from a low concentration to a high concentration (the reverse of diffusion) these proteins only work in one direction acting as one way valves these pumps are important as ppl with cystic fibrosis cannot produce them in adequate amounts

Question 27

simple diffusion (passive transport)

Answer 27

hydrophobic small molecules (water, oxygen, carbon dioxide no membrane protein required down concentration gradient is the direction of the movement of molecules no energy requirement

Question 28

osmosis (passive transport)

Answer 28

water no membrane protein required down concentration gradient is the direction of the movement of molecules no energy requirement

Question 29

facilitated diffusion (passive transport)

Answer 29

``` hydrophilic molecules (calcium ions glucose amino acids and sodium ions) type of membrane protein required is channel protein /carrier protein ``` down concentration gradient is the direction of the movement of molecules no energy requirement

Question 30

active transport

Answer 30

hydrophillic molecules (gluecose, amino acids, sodium ions, potassium ions) type of membrane protein required is carrier protein against the concentration gradient is the direction of the movement of molecules requires energy

Question 31

types of active transport

Answer 31

endocytosis exocytosis (the membrane is mobile) these processes involve the formation of membrane bound vesicles or vacuoles

Question 32

endocytosis

Answer 32

active transport that usually moves large polar molecules that cant pass through the hydrophobic cell membrane into the cell as cells use endocytosis to transport large molecules that proteins can't transport they require vesicles and energy during endocytosis the plasma membrane invaginates (folds in) around the molecules to be transported into the cell

Question 33

phagocytosis

Answer 33

phagocytosis is a form of endocytosis, phagocytosis (literally cell eating) describes the engulfment and transport of solid particles into the cell for example, a macrophage engulfs a Staphylococcus bacterium `

Question 34

exocytosis

Answer 34

exocytosis releases substances from the inside of the cell to the outside of the cell in multicellular organisms various types of cells are specialized to manufacture and export products from the cell to everywhere else in the body or outside it

Question 35

Direction of movement of materials across cell membranes are based on factors such as:

Answer 35

- concentration | - physical and chemical nature of materials