Unit 1.2 Flashcards
What are all cells made up of?
phospholipids and proteins
Biological membranes?
so thin their structure cannot be distinguished in their light microscope and their electron microscope appear as a single line
Eukaryotic cells?
contain membrane-bound organelles which are enclosed enzymes in the cytoplasm
What is the advantage?
potentially harmful chemicals such as enzymes are isolated and molecules with particular functions such as chlorophyll can be concentrated in one area.
Membranes?
provide a large surface area for the attachment of enzymes involved in metabolic processes and they provide a transport system inside the cell.
Standard unit of measurement?
m
Organelle?
a specialised structure with a specific function inside a cell
SI units for length
kilometre?
km
0.001 per m
10 ^3 m
measured ecosystems
metre?
m
1 per m
1 number of metres
used in larger organisms
milimetre?
mm
1000 per metre
10 to the power of -3 number of m
used in tissues
micrometre?
meumetres
1,000,000 number per metre
10 to the power of -6
used to measure cells and organisms
nanometer?
nm
1,000,0000,000 number per metre
10 to the power of -9
used to measure molecules
What does the Nucleus look like ?
most prominent feature in the cell
usually spherical and 10 - 20 nanometres in diameter
contains DNA which with protein comprises the chromosomes
Chromosomes direct protein synthesis because they are the site of transcription
DNA also provides a site for DNA replication
Components of nucleus?
bounded by 2 membranes called the nuclear envelope with pores which allow the passage of large molecules, such as mRNA and ribosomes out of the nucleus
Outer membrane is continuous with endoplasmic reticulum
Granular material in nucleus = nucleoplasm. Contains chromatin which is made of coils of DNA bound to protein
During cell division, chromatin condenses into chromosomes
Within the nucleus, one or more small spherical bodies each called a nucleolus
Sites of formation of rRNA - constituent of ribosomes
Mitochondria?
often cylindrical and 1-10 nanometres in length
compromise
2 membranes, separated by a narrow fluid-filled inter-membrane space. The inner membrane = is folded inwards to form a Cristae
An organic matrix, which is a solution containing many compounds including lipids and proteins
A small circle of DNA so mitochondrion can replicate many compounds, including lipids + proteins
A small circle of DNA , so a mitochondrion can replicate and code for some of its proteins and DNA
70 s ribosomes which allow protein syngthesis
Function of Mitochondria?
to produce ATP in aerobic respiration
Some of the reactions occur in the matrix and others on the inner membrane
Cristae provides a large surface area for the attachment of enzymes involved in respiration
Why fo they need a plentiful supply of ATP?
they are metabolically active cells such as muscle cells need a lot of ATP as they contain many mitochondria reflecting the high metabolic activity taking place
Why do mitochondria have a larger surface area cylindrical than being sphere?
being cylindrical reduces the diffusion distance between the edge and centre making aerobic respiration more efficient
Chloroplasts?
occur in the cells of photosynthesising tissue
in many plants, highest conc is in the palisade mesophyll cells, just below the upper surface of the cells
Structure of Chloroplast?
Each chloroplast is surrounded by 2 membranes - comprising of the nuclear envelope
Stroma - fluid-filled and contains some of the products of photosynthesis, including liquid droplets and starch grains which can take up to a large part of the stroma
they contain 70s ribosomes and circular DNA which enable them to make some of their own proteins and self-replicate
Within the stroma?
many closed, flattened sacs called thylakoids
A stack of thylakoids = a granum
Each granum comprises between 2 and 300 parallel sacs
Chlorophyll = found in the thyalokoids
arrangement produces a large surface area, efficient for trapping light energy
Endosymbiotic theory?
theory that describes the origin of chloroplasts and mitochondria
As far back as 1883, the division of chloroplasts was seen to closely to resemble that of free cyanobacteria
In the 1920s, the idea that mitochondria was once independent bacteria = also suggested
Endoplasmic reticulum?
an elaborate system of parallel double membranes forming flattened sacs with interconnected, fluid-filled spaces between them called cisternae
ER is connected to the nuclear envelope
System allows the transport of materials through the cells
There are 2 types of ER.
Rough ER?
has ribosomes on the outer surface and transports the proteins made there
RER = present in large amounts in cells that make a lot of protein, such as cells making amylase in the salivary glands
Smooth ER?
Comprises membranes that lack ribosomes. It is associated with the synthesis and transport of lipids
Ribosomes?
smaller in prokaryotic than eukaryotic cells
PRO = 70s whereas
EU = 80s where they occur singly or attached to membranes on the RER
ribosomes = one large and one small subunit
important in protein synthesis
Golgi Body?
resembles the structure of ER but is more compact
Vesicles containing polypeptides pinch off from RER and fuse with the stack of membranes which constitute the Golgi Body
Proteins = packaged and modified
Lysosomes?
small temporary vacuoles surrounding a single membrane formed by being pinched off from the Golgi body
contain and isolate potentially harmful digestive enzymes from the remainder of the cell.
Enzymes in lysosomes can also digest material that has been taken into the cell
Centrioles?
occur in all animal cells and most protoctistans but not in the cells of higher plants
Located just outside the nucleus
Centrioles = 2 rings of microtubules, making hollow cyclinders positioned at right angles to one another
Together, sometimes called centrosome
during cell division, centrioles organise the microtubules that make the spindle
Vacuoles?
Most plant cells have a large permanent vacuole which consists of a fluid-filled sac bounded by a single membrane, the tonoplast
they contain cell sap, a solution which stores chemicals such as glucose, amino acids and minerals + may store vitamins and pigments as in oranges
major role in supporting soft plant tissues
Cell wall?
largely consists of cellulose
held together in microfibrils which = aggregated into fibres
Functions
Transport - gaps between the cellulose fibres make the cell wall fully permeable to water and dissolved molecules + ions
Mechanical strength - the structure of cellulose microfibrils = very strong
Communication between cells - cells have pores called pits through which strands of cytoplasm pass
Plasmodesmata?
fine strands of cytoplasm that extend through pores in plant cell walls connecting the cytoplasm of one cell with that of another
Differences between animal cells and plant cells ?
Animal cells dont have a cell wall whereas plant cells do
Animal cells dont have chloroplasts but plant cells do
Animals cells dont have plasmodesmata but plant cells dp
Animal cells have a temporary vacuole whereas plant cells have a permanent one
centrioles are present whereas in plant cells they are absent from higher plant cells
Energy store is glycogen in animal cells whereas its starch in plant cells
Organelles are interrelated?
functions within the cell are related
Nucleus contains chromosomes in which DNA encodes proteins
Nuclear pores in the nuclear envelope allow mRNA molecules, transcribed off the DNA to leave the nucleus and attach to the ribosomes in the cytoplasm or on the rough ER
ribosomes contain rRNA transcribed from DNA located at the nucleolus
Protein synthesis occurs on ribosomes, producing proteins in their primary structure
Polypeptides = made on the ribosomes are moved through the RER and are packaged into vesicles. The vesicles bud off the RER and carry the polypeptides to the golgi body where they are chemically modified and packaged
Golgi body produces vesicles containing newly synthesised proteins. May be lysosymes - containing digestive enzymes used within the cell. May be secretory vesicles which carry proteins to the cell membrane for exocytosis
Phospholipids and triglycerides move through the smooth endoplasmic reticulum to various destinations in the cell
Prokaryote?
simple celled organism, lacking membrane - bound organelles such as a nucleus with its DNA free in the cytoplasm
Eukaryote?
An organism containing cells that have membrane bound organelles with DNA in chromosomes within the nucleus
Viruses?
not made of cells and are not classified with living organisms. seem to exist at interface between living and non living systems
Example of Prokaryotic cells ?
bacteria and Archaea
Distinguishing features of prokaryotes?
have no nucleus
internal membranes so unlike eukaryotic cells have no membrane bound organelles
DNA loose in cytoplasm
Peptidoglycan (murein cell wall)
70S ribosomes
Cytoplasm
Cell membrane
Differences between prokaryotes and eukaryotes?
PRO
small ( 1- 10 nanometres)
no organelles
DNA = free in cytoplasm
no nuclear envelope
Plasmids may be present
Murein cell wall
No chloroplasts
No mitochondria
present meosomes
70 S ribosomes
Eukaryotes
Larger ( 10 -100 nanometres)
Membrane bound organelles
DNA = combined with protein in chromosomes
double membrane- nuclear envelope
no plasmids
cellulose cell wall
chloroplast
present mitochondria
absent mesosome
80s ribosome
Viruses?
not made of cells and so are described as acellular
no organelles no chromosomes or cytoplasm
Diseases caused by viruses?
Humans
flu, chicken pox, cold HIV, mumps, rubella, Ebola
Plants
tobacco mosaic virus, cauliflower mosaic virus
Birds
Avian flu
Other mammals
swine flu, cow pox feline leukaeima virus
Differentiation?
the development of a cell into a specific type
Stem cells?
undifferentiated cell with the potential to become any cell type
Tissue?
A group of cells working together wit a common function structure and origin in the embryo
Epithelial tissue?
forms a continuous layer, covering or lining the internal and external surfaces of the body
Epithelia have no blood vessels but may have nerve endings.
The cells sit on a basement membrane, made of collagen and protein and vary in shape and complexity. Often have a protective or secretory function
Simplest form?
simple cuboidal epithelium, in which cells have a cube shape and the tissue is just one cell thick.
Occurs in proximal convoluted tubule of the kidney nephron and ducts of salivary glands.
Columnar epithelium?
have elongated cells
Those lining tubes that substances more through such as oviduct and trachea have cilia
Squamous epithelium?
consists of flattened cells on a basement membrane
form walls of the alveoli and line the bowmans capsule of nephron
Skeletal muscle?
attached to bones and generates locomotion in mammals
has bands of long cells or fibres which give powerful contraction but muscle tires easily
Voluntary muscles so you can choose whether to contract them or not
Smooth muscle?
has individual spindle shaped cells which contract rhythmically but contract less powerfully than skeletal muscle. They occur in the skin, in the walls
of blood vessels and in the digestive and respiratory tracts.
You cannot control these muscles so are involuntary
do not have stripes either and are called unstriped muscle
Cardiac muscle?
only occur in the heart
structure and properties are somewhat between skeletal and smooth muscle
have stripes but lack long fibres of skeletal muscle
contract rhythmically without any stimulation from nerves and hormones although these can modify their contraction
cardiac muscle do not tire
connective tissue?
connects supports or separates tissue and organs
contains elastic and collagen fibres in an extracellular fluid or matrix
Organ?
group of tissues working in a structural unit, working together and performing a specific function
Examples of organs?
e.g in the eye contains nervous, connective, muscle and epithelial tissues
in plants - leaf contains epidermal tissue, vascular tissue and ground tissue between vascular bundles
Organ systems?
group of organs working together with a particular role
all systems of body work together, making an organism
Examples of organ systems?
Digestive
Stomach and ileum
Excretory
Kidney and bladder
Skeletal
cranium and femur
Circulatory
heart and aorta
Reproductive
ovary and testis
Respiratory
trachea and lung
nervous
brain and spinal cord
magnfication?
the number of times an image is bigger than the object from which it dervived
resolution?
the smallest distance that can be distinguished as 2 separate points in a microscope
