Cell Theory

Question 1

Cell theory:

Answer 1

Cells are the fundamental unit of structure, function and organisation in all living organisms

Plant and animal tissues are composed of cells

Cells are the basic unit of life

Question 2

Microscopy:

Answer 2

Microscopic detail
High power microscopes - see and observe cell organelles
Used to magnify objects and to be able to see distinct cells that make up multicellular organisms
Allows us to see how structure affects function

Question 3

Light microscopy:

Answer 3

Developed in the 16th century
Uses visible light and magnifying lenses to observe small objects
Allows us to observe sub-cellular structures known as organelles eg nucleus

Limitations:
Low magnification and resolution making it hard to distinguish between close objects
Max mag: x1500
Max res: 200nm

Question 4

Electron microscopy:

Answer 4

Developed in 20th century
Uses beams of electrons in a vacuum with a wavelength of less than 1nm to visualise the specimen
Allows high detail of cell ultra structure
Produce images called micrograms
Mag: x500,000
Res: 0.1nm(high)

Question 5

Calculating magnification:

Answer 5

Magnification= size of image (ruler) (I) / actual size (A)

Question 6

Ultra structure & functions or organelles:

Prokaryotic:

Answer 6

Single celled organisms with simple structures that do not have a nucleus or any membrane bound organelles

Question 7

Eukaryotic:

Answer 7

Make up multi-cellular organisms such as plants and animals
Complex
Have a nucleus and membrane bound organelles
Approx 10-100ym
Can be seen using electron microscope

Question 8

Organelles & their functions

Plasma membrane:

Answer 8

Composed of a phospholipid bilayer with proteins embedded in the layers

Selectively permeable and regulates the transport of materials in and out
Separates trellis contents from the outside environment

Question 9

Cytoplasm:

Answer 9

Thick, gelatinous, semi transparent fluid

Maintains cell shape and stores chemicals needed by the cell for metasolic reactions

Question 10

Nucleus:

Answer 10

Largest organelle surrounded by nuclear envelope
Nuclear envelope has nuclear pores which allow movement of molecules through it
Nucleus contains chromatin

Controls and regulates cell activity
Houses genetic material - DNA and proteins

Question 11

Nucleolus:

Answer 11

dense spherical structure in the middle of the nucleus

Makes RNA and ribosomes

Question 12

Rough endoplasmic reticulum:

Answer 12

Network of membrane bound flattened sacs called cisternae studded with ribosomes

Protein synthesis takes place on ribosomes
Newly synthesised proteins are transported to the Golgi apparatus

Question 13

Smooth endoplasmic reticulum:

Answer 13

Network of membrane bound flattened sacs called cisternae
NO ribosomes

Responsible for synthesis and transport of lipids and carbohydrates

Question 14

Golgi apparatus:

Answer 14

A stack of membrane bound flattened sacs

Newly made proteins received here from rough ER
Modifies proteins &a packages them into vesicles to be transported to wherever needed

Question 15

Vesicles:

Answer 15

Small spherical membrane-bound sacs containing fluid

Transport materials inside the cell and secretory vesicles transport proteins that are released from the cell to the cell-surface

Question 16

Lysosomes:

Answer 16

Small spherical membrane-bound sacs containing hydrolytic enzymes

Breakdown waste material including old organelles

Question 17

Ribosomes:

Answer 17

Tiny organelles attached to rough ER or free floating in the cell.
They consist of two subunits and are not surrounded by a membrane

Protein synthesis occurs at the ribosomes

Question 18

Mitochondria:

Answer 18

Contain to membranes
Inner membrane is highly folded to form cristae
Central part called matrix

Sight of the final stages of cellular respiration

Question 19

Centrioles:

Answer 19

Small tubes of protein fibres

Form spindle fibres during cell division

Question 20

Function of animal cells:

Answer 20

Proteins synthesised and ribosomes on the rough endoplasmic reticulum
Newly synthesised proteins transported through cisternae of rough endoplasmic reticulum and all packaged into vesicles
Transported to Golgi apparatus & vesicles fuse with the surface of Golgi apparatus allowing proteins to enter
In Golgi apparatus proteins are modified and packaged into vesicles
Secretary vesicles Will transport proteins to be released from the cell meaning the cell-surface membrane to use it with a membrane and releases proteins by exocytosis

Question 21

Plant cell ultrastructure:

Answer 21

Plant cells have all cellular components that animal cells have except centrioles
Plant cells have additional structures and centrales as the main function is to produce carbohydrates during photosynthesis

Question 22

Plant cell structures and functions:

Cell wall:

Answer 22

Made of cellulose forming sieve like network

Protects and supports each cell and the whole plant

Question 23

Chloroplast:

Answer 23

Double membrane filled with fluid called stroma. Inner membrane is a continuous network of flattened sacs called thylakoids
A stack of thylakoids is called a granum
Grandma contain chlorophyll pigments

Site of photosynthesis. Light energy is trapped by chlorophyll and use to produce carbohydrate molecules from water and carbon dioxide

Question 24

Vacuole:

Answer 24

Membrane-bound sack in cytoplasm that contains cell sap

Maintains tugor to ensure a rigid framework in the cell

Question 25

Tonoplast:

Answer 25

Parsley permeable membrane of the vacuole

Selectively permeable to allow small molecules to pass through

Question 26

Amyoplast:

Answer 26

Double membrane bound sac containing
starch granules
Responsible for synthesis and storage of starch granules

Question 27

Plasmodesmata:

Answer 27

Microscopic channels which cross the cell walls of plant cells

Enable transport and communication between individual plant cells

Question 28

Pits:

Answer 28

Pores in the cell wall of the xylem

Allow water to enter and leave xylem vessels

Question 29

Structure and function of prokaryotic cell components (bacteria):

Cell wall:

Answer 29

Prokaryotic cells are surrounded by a cell wall made of peptidoglycan

Protects and supports each cell

Question 30

Capsule:

Answer 30

Slipperily outside cell wall

Protects the cell and prevents desiccation

Question 31

Ribosomes:

Answer 31

Smaller than ribosomes found in eukaryotic cells

Consist of two subunits and are not surrounded by a membrane

Protein synthesis occurs here

Ribosome size is determined by their ability to form sediment in the solution

Question 32

Nucleoide:

Answer 32

Meaning nucleus like

Irregularly shaped region that holds nuclear material without a nuclear membrane and where genetic material is localised
DNA forms one circular chromosome

Region where genetic information can be found and controls cellular activity

Question 33

Plasmid:

Answer 33

Small loops of DNA

Plasmids carry genes that may benefit the survival of the organism

Question 34

Function of bacterial cells:

Answer 34

Produce and secrete toxins that have an affect on other organisms.
DNA is free in the cytoplasm of a prokaryotic cell in the area called the nucleoid.
A section of DNA containing a genetic code for a metabolite unwinds and hydrogen bonds break.
RNA nucleotides lineup.
Messenger RNA is formed.
This process is known as transcription.
The next process is the production of the bacterial protein.
This is called translation which occurs at the ribosomes.
Transcription and translation can occur simultaneously as the genetic material is free in the nucleoide surrounded by ribosomes.
Newly made proteins/toxins are moved to the surface membrane ready to be secreted to cause infection.

Question 35

Gram staining:

Answer 35

To stains are added to the bacterial smear crystal violet and safranin.
If you see a purple stain it means that gram-positive bacteria are present
If the smear has retained a pink stain this indicates that gram negative bacteria are present
This is because the Finno cell walls and lipid membrane is allow ethanol to wash off the crystal violet purple staying and to then retain the pink safranin stain