cell structure and transport

Question 1

light microscopes…

Answer 1

-use a beam of light to form an image
-can magnify objects up to 2000 times
-can be used to view living objects
-are relatively cheap and easy to carry around

Question 2

electron microscopes…

Answer 2

-use a beam of electrons to form an image
-can magnify objects up to 2 000 000 times
-cannot be used for living objects
-are very expensive, need to be kept in special conditions

Question 3

what are the two types of electron microscope?

Answer 3

-the transmission electron microscope gives 2d images
-the scanning electron microscope gives 3d image (lower magnification)

Question 4

how to calculate magnification?

Answer 4

magnification = image size/ object size

Question 5

what is resolving power?

Answer 5

allows you to see dots … apart.
(light: 200nm, electron: 0.2nm)
.•. electron has higher magnification, but also a better resolving power

Question 6

all animal cells contain:

Answer 6

-nucleus

-cytoplasm (liquid in which the organelles are suspended, and where many chemical reactions take place)

-cell membrane (controls movement of substances such as glucose + mineral ions into cell, and movement of substances such as urea + hormones, out)

-mitochondria (where energy is transferred during aerobic respiration)

-ribosomes (where protein synthesis takes place)

Question 7

plant and algal cells, as well as the structures also in animal cells, have:

Answer 7

• a rigid cell wall, made of cellulose for support
  -chloroplasts (that contain chlorophyll for photosynthesis)
  -a permanent vacuole containing cell sap, which keeps the cell rigid and helps to support the plant.

Question 8

all eukaryotic cells:

Answer 8

eukaryotic cells all have a cell membrane, cytoplasm, and genetic material in a nucleus.

the nucleus contains chromosomes, which are made of the genetic material called DNA

Question 9

prokaryotic cells:

Answer 9

• consist of cytoplasm and cell membrane surrounded by a cell wall. the genetic material is not in a distinct nucleus. it forms a single DNA loop.
• prokaryotes may contain one or more extra small rings of DNA called plasmids.
• bacteria are all prokaryotes

Question 10

specialised features of nerve cells

Answer 10

• many dendrites to make connections to other nerve cells
• an axon to carry the impulse from one place to another, such as from your spine to your big toe
• nerve endings/ synapses, which pass impulses to other cells, by producing transmitter chemicals
• many mitochondria in the synapses to transfer the energy needed to make the transmitter chemicals

Question 11

two types of muscle cells

Answer 11

muscle cells can contract + relax. striated (striped)muscle cells are found in the muscles that enable your body to move.
Smooth muscle cells are found in the tissues of the digestive system and contract to move food along the gut.m

Question 12

specialised features of striated muscle cells:

Answer 12

-special proteins that slide over each other
-many mitochondria to transfer the energy to transfer the energy needed for chemical reactions
-a store of glycogen that can be broken down and used in respiration to transfer energy

Question 13

specialised features of sperm cells

Answer 13

• long tail, whips from side to side to move
• a middle section full of mitochondria to transfer the energy need by the tail to move.
• an acrosome to store digestive enzymes to break down the outer layers of the egg
• a large nucleus to contain the genetic information.

Question 14

specialised features of root hair cells

Answer 14

occur near the tips of roots. increase surface area of the root, so can absorb water + mineral ions efficiently. close to xylem tissue, that transports water and mineral ions through plant. root hair cells:
- greatly increase the surface area available for water to move into the cell
- have a large permanent vacuole - speeds up movement of water by osmosis from soil into cell
- have many mitochondria- transfer energy needed for the active transport of mineral ions into root hair cells.

Question 15

specialised features of photosynthetic cells

Answer 15

• have chloroplasts containing chlorophyll to trap the light need for photosynthesis.
• often found in continuous layers in the leaf and outer layers of stems
• have a large permanent vacuole that keeps cell rigid.

Question 16

specialised features of xylem cell:

Answer 16

two functions:
- transport water and mineral ions from roots to the stem and leaves
- supports the plant

• xylem cells are living when first formed.
• chemical called lignin builds up in spirals in cell walls.
• cells die, leaving king hollow tubes.
• water and mineral ions can move up tubes.
• the spirals and rings of lignin make the tubes of xylem very strong

Question 17

specialised features of phloem:

Answer 17

tissue that transports food made by photosynthesis to rest of the plant. phloem cells form tubes, but don’t become lignified like xylem.

-the cell walls between phloem cells break down to form sieve plates.
-phloem cells lose a lot of their structures but are kept alive by companion cells.
-their companion cells contain mitochondria that transfer energy to aid the movement of dissolved food in phloem.