Topic 1 Triple Organisation Cells and Microscopy

Question 1

Cells are

Answer 1

the basic building blocks of all living organisms

Question 2

A tissue is a

Answer 2

group of cells with a similar structure and function

Question 3

Organs are

Answer 3

aggregations of tissues performing specific functions

Question 4

Organs are organised into
which work together to form

Answer 4

organ systems
organisms

Question 5

Plant and animal cells are
they have a:

Answer 5

eukaryotic
cell membrane, cytoplasm and genetic material (DNA) enclosed in a nucleus

Question 6

nucleus function

Answer 6

which controls the activities of the cell

Question 7

cytoplasm function

Answer 7

in which most of the chemical reactions take place

Question 8

cell membrane function

Answer 8

which controls the passage of substances into and out of the cell. It also contains receptor molecules.

Question 9

mitochondria function

Answer 9

which is where aerobic respiration takes place

Question 10

ribosomes function

Answer 10

which are where protein synthesis occurs.

Question 11

In addition to the parts found in animal cells, plant cells often have:
chloroplasts which:
and

Answer 11

absorb light (using chlorophyll) to make food by photosynthesis
a permanent vacuole filled with cell sap, which supports the cell
Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.

Question 12

Bacterial cells are and :
they are made up of:

Answer 12

prokaryotic and are much smaller in comparison to eukaryotic cells
They have cytoplasm and a cell membrane surrounded by a cell wall.
The genetic material is not enclosed by a nucleus. It is a single DNA loop and there may be one or more small rings of DNA plasmids

Question 13

Sperm cell function and adaptations

Answer 13

Function: this is the male gamete (sex cell) . It carries genetic information from the father and fertilises the egg cell
Adaptations:-many mitochondria to provide energy for movement of the tail
-the head has a specialised sac of enzymes called acrosome that digests the outer lining of the egg cell
-long tail to help propel the sperm along to the nucleus
-nucleus contains half the number of chromosomes of an adult cell

Question 14

nerve cell function and adaptations

Answer 14

function; to transmit information(messages) as electrical impulses
adaptations: long- to carry impulses rapidly throughout the body with no gaps between neurones
-insulatory sheath made of fatty myelin- to speed up impulses (100m/s)
-branched endings(dendrites)-make connections with other neurones and allow several different pathways for the impulse

Question 15

Muscle cell function and adaptation :

Answer 15

function: contract and relax in order to move the skeleton, blood or substances in the body
adaptations: many mitochondria to provide energy for muscle contraction

Question 16

Root hair cell function and adaptation :

Answer 16

Function: Absorb water and mineral ions from the soil
Adaptations: - long ‘finger like’ villi which gives it a large surface area there is a thin wall to reduce the distance that molecules need to move to reach inside of the cell

Question 17

Xylem cell
function and adaptations

Answer 17

function: to transport water and mineral ions from the roots of the leaves of a plant and provides support for the plant
adaptations: -consist of dead hollow cells- maximising space for water and dissolved substances to be transported
-walls of the xylem vessels are lignified (coated with lignin) this strengthens the xylem

Question 18

Phloem cells
function and adaptations

Answer 18

Function: Phloem transports sucrose and amino acids up and down the plant.
Adaptations: Made of living cells (as opposed to xylem vessels, which are made of dead cells) that are supported by companion cells. Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)

Question 19

magnification =

Answer 19

size of image / size of real object

Question 20

milli

Answer 20

0.001

Question 21

centi

Answer 21

0.01

Question 22

micro

Answer 22

0.000001

Question 23

nano

Answer 23

Nano (symbol n) is a unit prefix meaning one billionth. Used primarily with the metric system, this prefix denotes a factor of 10−9 or 0.000000001.

Question 24

µm =

Answer 24

micro

Question 25

Understand how microscopy techniques have developed over time - explain how an electron microscope has increased understanding of sub-cellular structures:

Answer 25

light microscopes use light and lenses to form an image of a specimen and magnify it. They let us see individual cells and large subcellular structures like nuclei.

However electron microscopes use electrons instead of light to form an image. They have a much higher magnification than light microscopes. They also have a higher resolution. So they let use see much smaller things in more detail like the internal structures of mitochondria and chloroplasts. They even let us see tinier things like ribosomes and plasmids. This has enabled biologists to see and understand many more sub-cellular structures.

Question 26

Describe how to produce a slide.

Answer 26

Place specimen on a slide (the specimen should be very thin so light can pass through it)
Add a drop of water or dye (dyes like iodine solution make organelles easier to see)
Place a cover slip on top (lower on top at an angle to reduce the chance of trapping air bubbles)

Question 27

Describe how to use a microscope to focus on a specimen.

Answer 27

Place slide on stage (so specimen is above the hole in the stage)
Turn on light and adjust iris so you can see light coming through specimen
Select low power (x4) lens
Use the coarse focussing wheel to move the lens as close to the slide as possible (without them touching)
Look down the eyepiece lens
Focus by turning the coarse focussing wheel (in the opposite direction)To see at a higher magnification - change to medium/high power lens
Focus using the fine focussing wheel

To improve the image
To increase the magnification - change the objective lens to a higher power objective lens.
If the image is blurry - adjust the focussing wheels
If the image is too dark (or bright) - adjust the iris/diaphragm

Question 28

Produce a scientific drawing of a specimen.

Answer 28

Draw in pencil
Draw clear lines - not sketchy lines
Match the shape of the real cell - don’t just draw a blob
Draw the outline (of the cell/organelle) only - no shading
Label lines must touch what they are labelling (and should not have an arrow)
Label lines should be drawn with a ruler
Label lines should not cross