CELLS Flashcards
TOPIC 2
STRUCTURE OF NUCLEUS
- Nuclear envelope: double membrane surrounding nucleus, outer membrane continuous with the RER of cell
- Nuclear pores: allow passage of larger molecules, such as mRNA, out of nucleus
- Nucleoplasm: granular, jelly-like material making up the bulk of nucleus
- Chromosomes: protein-bound, linear DNA
- Nucleolus: small spherical region in nucleoplasm-Manufactures ribosomal RNA and assembles ribosomes
FUNCTION OF NUCLEUS
- Controls cell’s activities - produces mRNA and tRNA - protein synthesis-controls entry and exit of materials, and contains nuclear reactions
- Retains genetic material in form of DNA and chromosomes
- Manufactures ribosomal RNA and ribosomes
STRUCTURE OF MITOCHONDRIA
- Double membrane surrounding organelle - controls entry and exit of material.
- Cristae - extensions of the inner membrane, providing a large surface area for attachment of enzymes and other proteins during respiration
- Matrix - makes up remainder - contains proteins, lipids, ribosomes and DNA and some respiratory enzymes
FUNCTION OF MITOCHONDRIA
responsible for ATP production
STRUCTURE OF CHLOROPLAST
- Chloroplast envelope - double plasma membrane, highly selective, surrounds organelle
- Grana - stacks of disc-shaped thylakoid membrane
- Thylakoids - contain chlorophyll used in photosynthesis, can be linked by lamellae to other grana
- Stroma - fluid-filled matrix + contains starch grains
FUNCTION OF CHLOROPLAST
Site of Photosynthesis:
Granal membranes provide a large SA for photosystems, enzymes
Chloroplasts contain DNA and ribosomes - can quickly and easily manufacture some of proteins needed for photosynthesis
STRUCTURE OF ENDOPLASMIC RETICULUM
- 3D system of sheet-like membranes - continuous w/outer membrane of nuclear double membrane
- Membrane contains a network of tubules and flattened sacs called cisternae
- RER - ribosomes on outer surface of membranes
- SER - lacks ribosomes on its surface and is often more tubular in its appearance
FUNCTION OF ENDOPLASMIC RETICULUM
RER
1. Large SA for protein/glycoprotein synthesis
2. Provides a pathway for material transport throughout cell, especially for proteins
SER
1. Synthesises, stores and transports lipids and carbohydrates
STRUCTURE OF GOGLI BODY
- Compact system of flattened sacs and stacked membranes-cisternae
- Vesicles - modified proteins and lipids transported to cell membrane where they fuse with it, and then egest contents to outside
FUNCTION OF GOLGI BODY
- Form glycoproteins by adding carbs to proteins
- Produce secretory enzymes, such as those secreted by pancreas - apparatus is developed in secretory cells, especially those in small intestine
- Secrete carbs, such as cellulose for plant cell walls
- Transports, modifies and stores lipids
- Forms lysosomes
STRUCTURE OF LYSOSOMES
spherical membrane bound sacs containing lysozymes
FUNCTION OF LYSOSOMES
- Hydrolyse foreign material ingested by phagocytes
- Exocytosis of enzymes to destroy extra-cellular material
- Apoptosis - programmed cell death.
Autolysis - breaking down cells after death - Digest worn out organelles - can recycle chemicals
STRUCTURE OF RIBOSOMES
- Small cytoplasmic granules found in all cells, free-floating or associated w/RER
- 80S - found in eukaryotic cells, slightly larger
- 70S - in prokaryotic cells, slightly smaller
- 2 Subunits - large and small - contain ribosomal RNA and proteins
FUNCTIONS OF RIBOSOMES
Carry out translation stage of protein synthesis to produce polypeptides
STRUCTURE OF CELL WALL
Found in plants, algae and fungi
- Cellulose microfibrils embedded in a matrix - contribute to overall cell wall strength are considerably strong.
and other polysaccharides - Middle lamella - marks the boundary between adjacent cell walls and cements adjacent cells together
FUNCTION OF CELL WALL
- Cellulose to provide mechanical strength to prevent cell wall bursting under pressure created by osmotic entry of water
- To provide mechanical strength to cell as a whole
- Allows water to pass along it - contributes to the movement of water through the plant
STRUCTURE OF VACUOLES
- Fluid-filled sac bounded by a single membrane
- Single membrane around it called tonoplast
- Solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
FUNCTION OF VACUOLES
- Support herbaceous plants and herbaceous parts of woody plants by making cells turgid
- The sugars and amino acids can act as temporary food source
- Pigments - may attract pollinating insects due to colour
OUTLINE THE ROLE OF ORGANELLES IN PRODUCTION, TRANSPORT + PROTEINS FROM EUKARYOTIC CELLS (4)
DNA in the nucleus
ribosomes produces proteins
mitochondria produce ATP
Golgi body package
vesicles fuse with cell membrane
RER transport
ALL FEATURES PROKARYOTES HAVE
70s ribosome
murine cell wall
no membrane bound organelles-no nucleus
SOME FEATURES PROKARYOTES HAVE
capsid
flagella
EUKARYOTES VS PROKARYOTES
DNA enclosed in nucleus VS DNA floating free in cytoplasm
DNA is long + linear VS DNA is circular
contains histones VS contains no histones
has membrane organelles VS has no membrane organelles
cell wall is cellulose + chitin VS cell walls contain murien
ribosomes 80s VS ribosomes 70s
no slime capsule VS sometimes have slime capsule
VIRUSES
Viruses are acellular as they have no cell surface membrane, are not made of cells, have no organelles, cannot respire and no metabolic reactions
Viruses are extremely small and cannot be seen w/light microscope-enter living cells and multiply w/assistance of the host cells, causing diseases
FEATURES ALL VIRUSES HAVE
genetic material-codes for viral proteins
capsid-protects genetic material
attachment proteins-complementary to + bind to receptors on its specific host cell
ATTACHMENT PROTEINS
specific for each virus-so different viruses will attach to different receptors that are complementary to their attachment proteins-viruses are specific and can only infect one type of cell e.g. HIV viruses only infect T helper cells + replicate inside them
MAGNIFICATION EQUATION
M= I/A
MAGNIFICATION
how much bigger image is compared to real structure
RESOLUTION
ability to see two points as two points, rather than merged into one
LIGHT MICROSCOPE
.Use lenses to focus a beam of light through specimen
.Lower resolution than electron microscopes
.Can view live specimens
.Simple staining and slide preparation
.Can see colours
ELECTRON MICROSCOPES: TEM + SEM
.Use electromagnets to focus beam of electrons through or onto specimen
.Denser parts absorb more electrons and appear darker
.Higher resolution than light, due to smaller wavelength of electrons
.Specimen must be placed in a vacuum and so must be dead
.Longer preparation time, w/more complex staining procedure, which can produce artefacts
TEM
.Can see internal structure of organelles
.Specimen must be extremely thin
.Image is only in 2D
.Black and white image only
.highest magnification and resolution
SEM
.Resolution not as high as TEM
.3D image produced of the surface
.Black & white only
USING A LIGHT MICROSCOPE
1.add drop of water
2.add a single layer of cells
3.add a drop of stain to cells
4. add a cover slip and push down gently
CELL FRACTIONATION
cell homogenisation to break open cell
filter to remove large debris
use isotonic to prevent organelles from bursting
cold reduce enzyme activity
buffered prevent enzyme denaturing
centrifuge to sperate nuclei
respin at supernatant to different speeds in the pallet
HOMOGLOUS CHROMOSOMES
pairs of chromosomes that are same size w/same genes-One chromosome is inherited from each biological parent
G1 INTERPHASE
involving growth of cell and replication of its DNA
G1 IN CANCER
chemotherapy prevent synthesis of enzymes needed for DNA replication-If these aren’t produced cell is unable to enter synthesis phase disrupting cell cycle and forcing cell to kill itself
S PHASE INTERPHASE
cells DNA is replicated
S PHASE IN CANCER
radiation and some drugs damage DNA several points in cycle-DNA is checked for damage- if severe is detected cell would kill itself – preventing further tumour growth Some drugs can stop DNA unwinding prior to replication
G2 INTERPHASE
synthesises proteins needed for cell division