Cell Biology Flashcards
Discuss possible exceptions to cell theory.
4 marks
- skeletal muscle fibers are larger/have many nuclei/are not typical cells
- fungal hyphae are (sometimes) not divided up into individual cells
- unicellular organisms can be considered acellular
because they are larger than a typical cell/carry out all functions of life - some tissues/organs contain large amounts of extracellular material
- e.g. vitreous humor of eye/ mineral deposits in bone/ xylem in trees/other example
- statement of cell theory/all living things/most tissues are composed entirely of true cells
Eukaryotic cells have intracellular and extracellular components. State the functions of one named extracellular component.
4 marks
name of component: 1 max
- plant cell wall/cellulose
functions: 3 max
- (plant cell wall) strengthens/supports the cell/plant (against gravity);
- prevents the entry of pathogens;
- maintains the shape of plant cells;
- allows turgor pressure/high pressure to develop inside the cell;
- prevents excessive entry of water to the cell;
Explain how the surface are to volume ratio influences cell sizes.
3 marks
- small cells have larger ratio (than larger cells)/ratio decreases as size increases
- surface area/membrane must be large enough to absorb nutrients/oxygen/substances needed
- surface area/membrane must be large enough to excrete/pass out waste products
- need for materials is determined by (cell) volume
- cell size is limited (by SA/Volume ratio)/cells divide when they reach a certain size
- reference to diffusion across/through membrane/surface area
Outline differentiation of cells in a multicellular organism.
4 marks
- differentiation is development in different/specific ways
- cells carry out specialized functions/become specialized
- example of a differentiated cell in a multicelluar organism
- cells have all genes/could develop in any way
- some genes are switched on/expressed but not others
- position/hormones/cell-to-cell signals/chemicals determine how a cell develops
- a group of differentiated cells is a tissue
Describe the importance of stem cells in differentiation.
3 marks
- stem cells are undifferentiated cells;
- embryo cells are stem cells;
- stem cells can differentiate in many/all ways / are pluripotent/totipotent;
- differentiation involves expressing some genes but not others;
- stem cells can be used to repair/replace tissues/heal wounds;
Totipotent – Can form any cell type, as well as extra-embryonic (placental) tissue (e.g. zygote)
Pluripotent – Can form any cell type (e.g. embryonic stem cells)
Multipotent – Can differentiate into a number of closely related cell types (e.g. haematopoeitic adult stem cells)
Unipotent – Can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)
Draw a labelled diagram to show the ultrastructure of Escherichia coli.
6 marks
- cell wall – with some thickness;
- plasma membrane – shown as single line or very thin;
cytoplasm; - pilus/pili – shown as single lines;
- flagellum/flagella – shown as thicker and longer structures than pili and embedded in cell wall;
- 70S ribosomes;
- nucleoid / naked DNA;
approximate width 0.5 μm / approximate length 2.0 μm;
Draw a labelled diagram to show the organelles which are found in the cytoplasm of plant cells.
6 marks
- rough endoplasmic reticulum
- free ribosomes
- Golgi apparatus
- mitochondrion
- chloroplast
- vacuole
- nucleus
- lysosome
- smooth endoplasmic reticulum
State one function of each of the following organelles: lysosome, Golgi apparatus, rough endoplasmic reticulum, nucleus, mitochondrion.
5 marks
- lysosome: hydrolysis/digestion/break down of materials (macromolecules)
- Golgi apparatus: synthesis/sorting/transporting/secretion of cell products
- rough endoplasmic reticulum: site of synthesis of proteins (to be secreted)/ intracellular transport of polypeptides to Golgi apparatus
- nucleus: controls cells activities/mitosis/replication of DNA/transcription of DNA (to RNA)/directs protein synthesis
- mitochondrion: (aerobic) respiration/generates ATP
Draw a labelled diagram showing the ultra-structure of a liver cell.
4 marks
- (plasma) membrane – single line surrounding cytoplasm;
- nucleus – with a double membrane and pore(s) shown;
- mitochondria(ion) – with a double membrane, the inner one folded into internal
projections, shown no larger than half the nucleus; - rough endoplasmic reticulum – multi-folded membrane with dots/small circles on surface;
- Golgi apparatus – shown as a series of enclosed sacs with evidence of vesicle formation;
- ribosomes – dots/small circles in cytoplasm/ribosomes on rER;
- lysosome;
Distinguish between the structure of plant and animal cells.
6 marks
- plant cells have cell walls, animals do not
- plant cells have plastids/ chloroplasts, animals do not
- plant cells have a large central vacuole, animals do not
- plant cells store starch, animal cells store glycogen
- plant cells have plasmodesmata, animal cells do not
animal cells - animal cells have centrioles, plant cells do not
- animal cells have cholesterol in the cell membrane, plant cells do not
plant cells are generally have a fixed shape/ more regular whereas animal cells are more rounded
Using a table, compare the structures of prokaryotic and eukaryotic cells.
5 marks
P: prokaryotic cells; E: eukaryotic cells
- DNA: P: naked/loop of DNA; E: associated with protein/histones/nucleosomes/DNA in chromosomes
- location of DNA: P: in cytoplasm/nuceloid/no nucleus; E: within a nucleus/nuclear membrane
membrane bound organelles: P: none; E: present
ribosomes: P: 70S ; E: 80S - plasma membrane: P & E: same structure within both groups
- cell wall: P: peptidoglycan/not cellulose/not chitin; E: cellusose/chitin/not peptidoglycan
- respiratory structures: P: no mitochondria; E: mitochondria
- pili: P: pili present E: pili absent;
- plasmids: P: plasmids (sometimes) present E:plasmids absent;
- flagella: P: flagella solid E: flagella flexible/membrane-bound;
Draw a diagram to show the structure of a cell membrane.
5 marks
- phospholipids labelled with hydrophillic (heads) and hydrophobic (tails)
- phospholipid bilayer clearly shown and labelled
proteins shown in the bilayer and labelled - transmembrane and peripheral/extrinsic proteins shown and labelled
- glycoproteins shown and labelled
- cholesterol shown and labelled
- glycolipids shown and labelled
- thickness shown as 10 nm/ + or - 2 nm
Explain how the structure and properties of phospholipids help to maintain the structure of cell membranes.
9 marks
- hydrophobic tail/hydrophilic head
(head made from glycerol and phosphate
tail made from two fatty acids) - saturated/ unsaturated fatty acid (in tail)
- arrangement in membrane
- phospholipids form a bilayer
(heads face outside the membrane/ tails face inside the membrane/ hydrophic interior/ hydrophilic exterior of membrane)
A suitable annotated diagram may incorporate all or many of the above points. Award 5 marks maximum for a suitable diagram that is labelled correctly.
- phospholipids held together by hydrophobic interactions
- phospholipid layers are stabilized by interaction of hydrophilic heads and surrounding water
- phospholipids allow for membrane fluidity/ flexibility
fluidity/ flexibility helps membranes to be (functionally) stable
- phospholipids with short fatty acids/ unsaturated fatty acids are more fluid
- fluidity is important in breaking and remaking membranes (e.g. endocytosis/ exocytosis)
- phospholipids can move about/ move horizontally/ “flip flop” to increase fluidity
- hydrophilic/ hydrophobic layers restrict entry/ exit of substances
Explain the role of vesicles in transportation of materials within cells.
8 marks
- vesicles are membrane bound packages/droplets
- formed by pinching off/budding off a piece from a membrane
- can carry proteins
- rough ER synthesizes proteins
- proteins enter/accumulate inside the ER
- transported to Golgi apparatus for processing
targeted to/transported to specific cellular organelles - fuse with membrane of organelle so contents of vesicle join the organelle
- transported to the plasma membrane
- fuses with plsma membrane releases/secretes contents
- exocytosis
Describe the process of active transport.
4 marks
- uses/ requires energy/ ATP
- goes against concentration gradient/ lower to higher concentration
- requires a protein in the cell membrane/ pump/ carrier protein (reject channel)
- hydrolysis of ATP/ ATP –> ADP + phosphate
- involves a conformational change in the pump/ protein/ diagram to show this
