B1 - Cell Structure And Transport

Question 1

What are the main 5 units of measurement
> What are their sizes in comparison to each other
> What are their units

Answer 1

1 kilometre (km) = 1000 metres (m)
1 m = 100 centimetres (cm)
1cm = 10 millimetres (mm)
1mm = 1000 micrometres (μm)
1 μm = 1000 nanometres (nm)

Question 2

When were light microscopes first develoepd

Answer 2

Mid - 17th century

Question 3

How do light microscopes work and how much can they magnify

Answer 3

> they use a beam of light to form an image of an object
the best ones magnify up to x2000

Question 4

When was the electron microscope invented

Answer 4

in the 1930s

Question 5

How do electron microscopes work and how much can they magnify

Answer 5

> They use a beam of electrons to form an image of an object
the best ones magnify up to x2 000 000

Question 6

What are the two types of electron microscopes and what are their major differences

Answer 6

> Transmission electron microscopes - 2D images with high magnification and resolution
Scanning electron microscopes - 3D images but lower magnifications

Question 7

What are the disadvantages of electron microscopes

Answer 7

> very expensive
have to be kept in special temperature, pressure and humidity controlled rooms

Question 8

What are the two formulas for calculating magnification

Answer 8

> magnification = mag. eyepiece lens x mag. objective lens
magnification = image size / real size of object

Question 9

What is resolution

Answer 9

the ability to distinguish between two different points

Question 10

What is resolving power and what is the resolving power of light and electron microscopes

Answer 10

> resolving power affects how much detail a microscope can show
a light microscope has a resolving power of around 200nm
an electron microscope has a resolving power of around 0.2nm

Question 11

How big are animal cells

Answer 11

around 10-30 μm

Question 12

How big are plant cells

Answer 12

around 10-100 μm

Question 13

What are the main structures within an animal cell (5)
> What are their main functions

Answer 13

> nucleus - (controls activities of the cell)
cytoplasm - (liquid gel-like substance where organelles are suspended, where most chemical reactions happen)
cell membrane - (controls the passage of substances into and out of the cell)
mitochondria (Structures where aerobic respiration occurs)
ribosome (Where protein-synthesis takes place)

Question 14

What are the main structures in a plant cell (8)
> What are their main functions

Answer 14

> chloroplasts - (where photosynthesis occurs in green areas of plants)
Permanent vacuole - (filled with cell sap to keep the cell rigid)
cell wall - (gives the cell structural strength)
nucleus - (controls activities of the cell)
cytoplasm - (liquid gel-like substance where organelles are suspended, where most chemical reactions happen)
cell membrane - (controls the passage of substances into and out of the cell)
mitochondria (Structures where aerobic respiration occurs)
ribosome (Where protein-synthesis takes place)

Question 15

What are eukaryotic cells

Answer 15

cells that contain a cell membrane, cytoplasm and genetic material within a nucleus

Question 16

What are prokaryotic cells and how big are they

Answer 16

cells which do not have their genetic material enclosed within a nucleus. They are around 0.2 - 20μm

Question 17

What are plasmids

Answer 17

extra small rings of DNA in prokaryotes that code for very specific features such as antibiotic resistance

Question 18

Are bacteria eukaryotes or prokaryotes

Answer 18

prokaryotes

Question 19

What are orders of magnitude

Answer 19

comparisons between sizes of objects in powers of 10

Question 20

> What do nerve cells do
How are nerve cells specialised to do this (3)

Answer 20

> they carry electrical impulses around the body - provide rapid communication around the body
lots of dendrites to make connections with other cells
axons that carry nerve impulses from one place to
another
synapses that are adapted to pass impulses to other cells or to a muscle using transmitter chemicals

Question 21

> What do muscle cells do
How are muscle cells specialised to do this (3)

Answer 21

> cells that can contract and relax to move bones in the body or do other bodily functions
special proteins that slide over each other, making the muscle contract
contain many mitochondria to transfer the energy needed for cells to contract and relax
they can store glycogen which can be broken down and used in cellular respiration

Question 22

> What do sperm cells do
How are sperm cells specialised to do this (4)

Answer 22

> contain genetic information from the male parent which fertilises the egg for reproduction
long tails that help it swim faster
lots of mitochondria which provide energy for the tail
they store digestive enzymes for breaking down the outer layer of the egg
a large nucleus contains genetic information to be passed on

Question 23

> What do root hair cells do
How are root hair cells specialised to do this (3)

Answer 23

> they help the plant to take in water from the ground
they increase surface area which speeds up osmosis
they have a large vacuole that speeds up movement of water
they have many mitochondria to provide energy for active transport

Question 24

> What do photosynthetic cells do
How are photosynthetic cells specialised to do this (3)

Answer 24

> they photosynthesise to provide food for the plant
contain chlorophyll that trap light needed for photosynthesis
positioned in layers in the leaves to absorb as much light as possible
large permanent vacuole that helps keep the cell rigid to be as large as possible

Question 25

> What do xylem cells do
How are xylem cells specialised to do this (2)

Answer 25

> they are the transport tissues in plants that carry water and minerals up the plant
lignin builds up in the tubes - the xylem cells then die, producing long, hollow tubes that allow water and mineral ions to pass
the rings of lignin makes the tube strong and helps withstand the pressure

Question 26

> What do phloem cells do
How are phloem cells specialised to do this (2)

Answer 26

> the transport tissue that carries food made by photosynthesis around the body of the plant
cell walls between cells break down to form sieve plates that allow food to travel through them
they lose internal cells but are supported by companion cells. The mitochondria form these cells provide energy

Question 27

What is diffusion

Answer 27

the spreading out of particles of any substance in a solution or gas, resulting in a net movement from an area of high concentration to an area of lower concentration down a concentration gradient

Question 28

What are three factors that affect the rate of diffusion

Answer 28

the difference in concentration, temperature and available surface area

Question 29

What is osmosis

Answer 29

the diffusion of water though a partially permeable membrane

Question 30

What do isotonic, hypertonic and hypotonic mean

Answer 30

isotonic - the concentration of solutes is the same inside and outside the cell
hypertonic - the concentration of solutes is higher outside than inside the cell
hypotonic - the concentration of solutes is lower outside than outside the cell

Question 31

What is turgor

Answer 31

the pressure formed when no more water can physically enter the plant cell, making it rigid

Question 32

What does active transport do

Answer 32

it moves substances from a more dilute solution to a more concentrated solution against the concentration gradient

Question 33

Do active transport, osmosis or diffusion require energy

Answer 33

active transport - yes
osmosis - no
diffusion - no

Question 34

what is the relationship between SA:V ratio and size

Answer 34

the larger an object, the smaller the value

Question 35

What are some adaptations to make exchanging materials more efficient (3)

Answer 35

• a large surface area
• a thin membrane
• efficient blood supply to keep the concentration gradient steep