Cells ( Core concepts )

Question 1

Structure and function of nucleus

Answer 1

Nucleus - contains the DNA which codes for protein synthesis, contains chromatin ( extended loosely coiled chromosomes of DNA and histoire protein )
Nucleolus - synthesis of rRNA and ribosomes
Nuclear pore - allowed transport of mRNA and nucleotide out of nucleus.
Nuclear envelope - separates the genetic material from the cytoplasm

Question 2

Function of cell membrane

Answer 2

Controls entry and exit of molecules into and out of the cell - it is selectively permeable

Question 3

Function of cytoplasm

Answer 3

site of cellular reactions

Question 4

Function of mitochondrion

Answer 4

site of aerobic respiration and synthesis of ATP.

Question 5

Structure of mitochondrion

Answer 5

rod shaped and has a double membrane, inner membrane folded
self replicating
Cristae increases SA on which part of the respiratory process takes place.
Matrix, DNA ( circular ) and ribosomes ( 70s )present

Question 6

Function of Rough endoplasmic reticulum ( RER )

Answer 6

transports proteins which are synthesised by the proteins attached

Question 7

Structure of Rough endoplasmic reticulum ( RER )

Answer 7

system of flattened sacs ( cisternae ) continuous with the nuclear membrane and has ribosomes attached

Question 8

Function of Smooth Endoplasmic reticulum ( SER )

Answer 8

synthesis and transport of lipids, no ribosomes attached

Question 9

Function of Golgi Body

Answer 9

Modifies and packages proteins for export
Synthesises glycoproteins
Production of liposomes

Question 10

Structure of Golgi Body

Answer 10

Planar stack of membrane bound flattened sacs
Cis face aligns with RER
Molecules are processed in cisternae
Modified proteins are packaged into vesicles to be transported around the cell or secretion out of the cell ( exocystosis )

Question 11

Function of centrioles

Answer 11

Used in spindle formation ( microtubes ) in cell division

Question 12

Structure of centrioles

Answer 12

consists of two hollow cylinders positioned at right angles to each other.

Question 13

Function of ribosomes

Answer 13

Protein synthesis, can be free or attached to RER

Question 14

Structure of ribosomes

Answer 14

made from rRNA and proteins
found free in the cytoplasm or attached to RER

Question 15

Function of lysosome

Answer 15

contain digestive enzymes used in phagocytosis

Question 16

Structure of lysosome

Answer 16

Fluid filled vesicles surrounded by a single membrane, containing enzymes

Question 17

Vesicles ( animal cells ) function

Answer 17

Act as a contractile vacuole to maintain osmotic pressure

Question 18

Vesicles ( animal cells ) structure

Answer 18

small membrane bound organelle

Question 19

Function of Large permanent vacuole

Answer 19

storage of ions and organic molecules eg proteins and maintaining osmotic pressure, maintains pH

Question 20

Structure of large permanent vacuole

Answer 20

large membrane bound organelle surrounded by a single membrane ( tonoplast )
contains cell sap ( mineral ions, water, enzymes, soluble pigments )

Question 21

Function of chloroplasts

Answer 21

site of photosynthesis

Question 22

Structure of chloroplasts

Answer 22

Disc shaped organelle
Contain double membrane which contains stroma with ribosomes, lipid, circular DNA and starch
Self replicating
Thylakoids - flattened discs stacked to form grana
Grana - contain photosystems with chlorophyll
Intergranal lamellae - tubes attach thylakoids in adjacent grana.

Question 23

Function of cell wall

Answer 23

Provides strength and support, freely permeable to water

Question 24

Structure of cell wall

Answer 24

made of cellulose microfibrils in a polysaccharide matrix

Question 25

Function of plasmodesmata ( found between two plant cells )

Answer 25

exchange of large organic materials via cytoplasmic streaming, allows communication between adjacent cells

Question 26

Structure of plasmodesmata

Answer 26

narrow threads of cytoplasm that pass through the cell walls of adjacent plant cells

Question 27

What is chromatin ?

Answer 27

A DNA - protein complex found in eukaryotic cells ( extended loosely coiled chromosomes of DNA and histoire protein )

Question 28

What 8 organelles do plant and animal cells have in common ?

Answer 28

plasma / cell surface membrane membrane bound nucleus nucleolus chromatin Mitochondria smooth and rough ER ribosomes Golgi body

Question 29

What 4 organelles are only found in plant cells ?

Answer 29

Chloroplasts Cell wall and plasmodesmata Large vacoule Tonoplast

Question 30

Roles of organelles in the synthesis and transport of biological molecules ( eg glycoproteins )

Answer 30

1) Nucleus contains DNA which codes for the amino acid sequence in a polypeptide chain 2) Inside the nucleus a mRNA copy of DNA is made by transcription. The mRNA leaves the nucleus via a nuclear pore and attaches to a ribosome on the RER in the cytoplasm. the nucleolus is the site of RNA synthesis which forms parts of ribosomes. 3) The ribosomes of the RER synthesise the polypeptide 4) The RER then transports the protein through the cell within its cisternae 5) At the end of the RER, protein is packaged into transport vesicle. Vesicle pinched off RER and moves towards and fuses with the Golgi Body 6) The Golgi Body chemically modifies the protein eg adding a carbohydrate to produce glycoproteins. 7) The modified protein is then packaged into a secretory vesicle which is pinched off by the Golgi Body, The secretory vesicle moves towards and fuses with the plasma membrane of the cell 8) The protein is secreted from the cell by exocytosis. This requires ATP which is synthesised by mitochondria during aerobic respiration 9) Alternatively, the secretory vesicle may stay within the cell - in which case it is called a lysosome and contains protease enzymes. Lysosomes fuse with worn out organelles and digest ( hydrolyse ) them. They may even burst and digest the entire cell .

Question 31

How are prokaryotic cells distinctive from eukaryotic cells ?

Answer 31

Prokaryotic cells lack a nucleus and membrane bound organelles ( eg nuclear membrane or ER )

Question 32

How is genetic information stored in prokaryotes ?

Answer 32

DNA is circular and lies free in the cytoplasm Plasmids are small rings of DNA

Question 33

How do ribosomes differ in prokaryotes compared to eukaryotes ?

Answer 33

70s ribsomes in prokaryotes ( smaller but contains murein ) , 80s ribsomes in eukaryotes

Question 34

Function and structure of plasma membrane in prokaryotes

Answer 34

Site of aerobic respiration Has infoldings of the cell membrane, called mesosomes, increasing its surface area, aiding cellular respiration

Question 35

Function of capsule in prokaryotes

Answer 35

A protective outer layer ( eg against phagocystosis by WBCs )

Question 36

Function of mesosomes in prokaryotes

Answer 36

infoldings of the cell membrane that increase the surface area available for aerobic respiration

Question 37

What could the circular DNA and plasmids in prokaryotes contain ?

Answer 37

Genes for antibiotic resistance

Question 38

Structure of a virus

Answer 38

Consist of a small piece of DNA or RNA surrounded by a protein coat Other viruses may have more than one protein coat and some may also have an outer lipoprotein envelope ( eg influenze virus and HIV )

Question 39

Where can similarities and differences in the cell structures of eukaryotes, prokaryotes and viruses be seen ?

Answer 39

Electron micrograph images

Question 40

What is meant by cell theory ?

Answer 40

New cells are formed from other existing cells The cell is a fundamental unit of structure, function and organisation in all living organisms

Question 41

In multicellular organisms, how are cells specialised ?

Answer 41

According to the function they perform leading to a division of labour.

Question 42

Define what is meant by a tissue

Answer 42

A group of similar cells working together to perform a function

Question 43

Epithelial tissue : function, examples

Answer 43

Lining tissue, covers the surface of organs, cavities and tubes Cells packed closely together No blood vessels but may have nerve endings Cells sit on basement membrane eg columnar epithelium of the mammalian small intestine Types of tissue include squamous, cuboidal, columnar, ciliated columnar and glandular

Question 44

Muscle tissue : function, examples

Answer 44

Contract to cause movement ( able to shorten their length ) ie striated ( skeletal and cardiac ) muscle tissue and smooth muscle tissue eg cardiac muscle tissue inside the cells are protein fibres made of actin and myosin, which slide past each other to shorten the cell

Question 45

Connective tissue : function, examples

Answer 45

Connects, supports and separates tissues and organs ( protect the body ) Contains cells and elastic and collagen fibres in an extracellular fluid ( matrix ) between the fibres are fat storing cells ( adipocytes ) and cells of the immune system eg blood, lymph, cartilage, bone, ligament, tendon, fibrous tissues etc eg areolar connective tissue

Question 46

Nerve tissue : function, examples

Answer 46

made of nerve cells ( nervous ) and gilal cells generates and transmits electrical impulses, sensory input, control muscles and glands, homeostasis etc

Question 47

What is meant by an organ ?

Answer 47

A group ( aggrevation ) of several ( different ) tissues working together to perform / carry out a particular function for the whole organism.

Question 48

How do you calculate magnification ?

Answer 48

Magnification = image size / actual size