Cells

Question 1

Nucleus

Answer 1

Largest organelle
Present in all plant and animal cells (not RBCs/Phloem sieve tubes)
Double membrane - nuclear envelope
Envelope has gaps - nuclear pores

Question 2

Mitochondria

Answer 2

Double membrane (outer and inner)
Site of aerobic respiration - makes ATP
Muscles and sperm cells have lots of mitochondria - require more energy
ATP made on inner membrane - Cristae

Question 3

Golgi

Answer 3

Stack of flattened , curved sacs
Sacs are made of membranes
Processes and packs proteins
- When proteins are ready the ‘bud’ off from the Golgi as Golgi Vesicles
Move to cell membrane and empty their contents out of the cell when they get there

Question 4

Lysosomes

Answer 4

Tiny bags of membrane of digestive enzymes

Question 5

Endoplasmic Recticulum

Answer 5

Network of membranes

Interconnected membranous sacs and tubules

Question 6

Rough endoplasmic recticulum

Answer 6

When ribosomes are attached
Site of protein synthesis
Proteins sent to Golgi for processing and packing

Question 7

Smooth endoplasmic reticulum

Answer 7

Has a different role depending on cell its in
Ovaries and Testes - makes steroid horemones
Liver cells - breaks down toxins into harmless substances

Question 8

Cell Wall

Answer 8

Always present in plant cells
Gives support
Made of cellulose (criss cross of cellulose fibres allows cell to swell not burst)

Question 9

Chloroplast

Answer 9

Plant cells only (only those that absorb light)

Sight of photosynthesis - makes ATP

Question 10

Vacuole

Answer 10

Permanent in plant cells - not in animal
Membrane bound organelle full of liquid
Forms in membrane called a Tonoplast
Contains water, sugars and enzymes

Question 11

Cytoskeleton

Answer 11

Network of microfilaments
Helps support the cell - keep its shape
Gives cell mechanical strength
Acts as a pulley - moves organelles through the cytoplasm

Question 12

Centrosomes and Centrioles

Answer 12

Animal cells only

Present in mitosis and meiosis

Question 13

Light microscope

Answer 13

Long wavelength of light rays - can only distinguish between 2 objects if they are 0.2um or further apart

Question 14

Strenghts of the light microscope

Answer 14

Specimens can be living or dead
Original colour can be viewed
Quite cheap to buy and operate

Question 15

Limitations of the light microscope

Answer 15

Low magnification

Low resolution

Question 16

Electron microscope

Answer 16

Light microscopes have a poor resolution as a result of a long wavelength
1930s - microscope developed that used a beam of electrons - not light

Question 17

Advantages to electron microscope

Answer 17

Short wavelength = higher resolution

Electrons are negatively charged so the beam can be focused using electromagnets

Question 18

Transmission electron microscope

Answer 18

Cosists of an electron gun that produces a beam of electrons that is focused onto the specimen by an electromagnet
Beam passes through thin section of specimen

Question 19

Advantages of TEM

Answer 19

Powerful magnification
Greater resolution
Short wavelength

Question 20

Limitations of TEM

Answer 20

Requires dead/dehydrated specimens - must be extremely thin
Does not show colour
Requires more time consuming preparations

Question 21

Advantages of Scanning electron microscope

Answer 21

High resolution

Very accurate measuring

Question 22

Limitations of SEM

Answer 22

Expensive

Requires skill

Question 23

Prokaryotic cell

Answer 23

Single
Smaller than eukaryotes
No nucleus or nuclear envelope + membrane bound organelles

Question 24

Ribosomes in a Prokaryotic cell

Answer 24

Site of protein synthesis
Not attached to membranes and smaller than eukaryotes
70s Ribosomes

Question 25

Cell walls in prokaryotes

Answer 25

Always have a clue wall | Made of Murein

Question 26

Flagella

Answer 26

Whip like structure Rotates - allowing bacterium to move Not all bacteria have a flagella - some have more than one

Question 27

Slime layer

Answer 27

Some bacteria have this outside cell wall | Used for protection and helps group of bacteria stick together

Question 28

DNA in prokaryotes

Answer 28

Plasmids | Separate tiny circles of DNA carrying only a few genes which occur throughout the cytoplasm

Question 29

Virus

Answer 29

Acellular - not made of or able to be divided into cells | Non living - unable to exist/ reproduce without a host cell

Question 29

Virus

Answer 29

Acellular - not made of or able to be divided into cells | Non living - unable to exist/ reproduce without a host cell

Question 30

Phagocytosis

Answer 30

1. Phagocyte detects the pathogen 2. Phagocyte moves towards it and engulfs the pathogen - forms a phagosome 3. Lysosomes within the phagocyte release digestive enzymes and break the pathogen down 4. The phagocyte places the antigens from the pathogen on its cell surface membrane - Antigen presenting cell

Question 31

Cellular immune response

Answer 31

T cells and cells in the immune system they react with eg. Phagocytes

Question 32

Humoral response

Answer 32

B cells , clonal selection and production of monoclonal antibodies

Question 33

T Cells

Answer 33

Type of WBC Activated by phagocytes Have receptor proteins which bind to antigens Helper T cell - release chemical signal to stimulate phagocytosis (and B cells) Cytotoxic T cell - kill abnormal and forgein cells

Question 34

B cells

Answer 34

1. When the antibody on the B cells finds a complementary antigen , it binds to it 2. This together with the substances released from helper T cells activates the B cell (clonal selection) 3. Activated B cell divides into plasma cells