cell structure and organisation Flashcards
what are the two equations for magnification?
magnification = eyepiece x objective lens
magnification = image size / actual size
what is the nucleus composed of?
nuclear envelope
nucleoplasm
chromatin
nucleolus
what is the function of the nucleus?
to retain the genetic information (DNA) which codes for protein synthesis
what is the nuclear envelope?
a double membrane with pores to allow the transport of mRNA and ribosomes out of the nucleus to the cytoplasm
what is the nucleoplasm?
cytoplasm-like material within the nucleus which contains chromatin
what is the chromatin?
made up of coils of DNA bound to histone protein.
during cell division, the chromatin condensed to form the visible chromosomes
what is the nucleolus?
within the nucleus are one or more small spherical bodies, each called nucleolus.
they synthesise ribosomal RNA
what is the function of mitochondria?
to release energy in the form of ATP during aerobic respiration
what is the mitochondria composed of?
double membrane and intermembrane
cristae
matrix
describe the intermembrane
mitochondria have a double membrane with a narrow, fluid-filled intermembrane space
what is the cristae?
the inner membrane is folded inwards to form extensions called cristae,
the cristae increase the surface are for ATP synthesis to occur
what is the matrix?
contains many chemical compounds including lipids proteins small ribosomes and a small circle of DNA to allow self replication in responds to the energy requirements of the cell.w
what is the function of ribosomes?
to assemble proteins in protein synthesis
describe the structure of ribosome
the small subunit and large subunit of a ribosome are made of RNA and protein
how does the structure of ribosomes help with protein synthesis?
protein synthesis (translation) occurs at ribosomes
mRNA from the nucleus fits into the groove between the two subunits and provides the code for a sequence of amino acids
where are ribosomes found?
they are found free in the cytoplasm
associated with rough endoplasmic reticulum
what is the cell membrane also known as?
- plasma membrane
- phospholipid bilayer
why is it important that the sample must be thin when preparing a microscope slide?
to ensure that all structures are 2D, visible and not overlapping
why is it important that the sample should be stained when preparing a microscope slide?
to be able to see clear structures visibly
why might staining sometimes be a disadvantages?
it can cause misconceptions and organelles are not actually coloured
describe the rough endoplasmic reticulum
the rough endoplasmic reticulum is an internal system of flattened membranous sacs, or cisternae, which are continuous within the nuclear membrane
what is the rough endoplasmic reticulum covered in?
- it is covered in ribosomes
- it gives a dotted appearance and gives it its name
describe the smooth endoplasmic reticulum
the smooth endoplasmic reticulum is similar in structure to the rough endoplasmic reticulum but has no ribosomes
what is the role of the smooth endoplasmic reticulum?
it is involved in the synthesis and transport of lipids
which type of cells have the smooth endoplasmic reticulum?
cells that store large quantities of carbohydrates, protein or fat
e.g liver and secondary cells
what is the golgi body made up of?
it is made up of interconnected flattened membranous sacs
define organelle
a specialised structure with a specific function inside a cell
define magnification
the number of times bigger an image is than the actual size of the object from which it is derived
define chromatin
coils of DNA bound to histone protein
define eukaryote
organisms made of cells that have membrane-bound organelles, with DNA within the nucleus in the form of chromosomes
define prokaryote
single celled organisms lacking membrane-bound organelles, such as nuclei, wit DNA free in the cytoplasm
define cristae
folds in the inner mitochondrial membrane
define tissue
an aggregation of specialised cells carrying out a specific function
define organ
an aggregation of several tissues that carry out a specific function for the whole organism
define organ system
two or more different organs working together to provide a common function
define organism
all the systems of the body working together, make an organism, which is a discrete individual
name 3 specialised plant cells
palisade cell
guard cell
root hair cell
name 5 plant tissues
xylem
phloem
palisade
spongy mesophyll
upper epidermis
what is the function of the xylem?
transport of water and dissolved minerals
what is the function of the phloem?
transport of sucrose and amino acids
what is the function of the palisade?
photosynthesis
what is the function of the spongy mesophyll?
some photosynthesis
provides air space for diffusion of gases in/out of the leaf
what is the function of the upper epidermis?
contains cells that are found on the top surface of a leaf ; protected by a waterproof waxy cuticle
name 3 plant organs
petal
leaves
stem
roots
what are the 4 primary tissue types in the human body?
- epithelial tissues
- muscle tissues
- connective tissue
- nerve tissue
define epithelial tissue
forms a continuous layer, covering or lining the internal and external surfaces of the body
how many types of epithelial tissue are there?
4
what are the names of the types of the epithelial tissue?
- squamous epithelium
- cuboidal epithelium
- columnar epithelium
- ciliated columnar epithelium
describe squamous epithelium
flattened cells found lining body cavities, such as the mouth and alveoli
describe cuboidal epithelium
cube-shaped cells found lining the kidney tubules and ducts of glands
describe columnar epithelium
elongated column-shaped cells that are found lining the stomach and intestines
describe ciliated columnar epithelium
column-shaped cells that have fine hair-lik projections (cilia) on the surfcde e.g in the trachea, oviduct
describe connective tissue
connects and anchors structures and gives strength and support to the body and its organs
give an example of a connective tissue
collagen
what is the function of collagen?
forms extracellular fibres that give strength to dense connective tissues such as the tendons and ligaments
where is collagen found?
tough outer layer of large blood vessels
describe muscle tissue
nerve impulses bring about muscle contraction, causing the muscle to shorten
as the contraction of the muscle ends, normal muscle length is once again attained
what are the 3 examples of muscle tissue?
cardiac muscle
skeletal muscle
smooth muscle
what is the major role of the skeletal system?
support
what is the major role of the muscular system?
movement
what is the major role of the circulatory system?
transport of gases and nutrients
what is the major role of the reproductive system?
reproduction
what is the major role of the endocrine system?
homeostatis
what is the major role of the excretory system?
removal of waste
what is the major role of the digestive system?
to breakdown food and absorb nutrients
what is the major role of the nervous system?
coordination and control
what is the major role of the respiratory system?
to exchange gases between blood and air
what is the major role of the immune system?
protection from pathogens
define organism
all the systems of the body working together to make and organism which is a discrete individual
define division of labour
the adaptation of different parts of an organism to carry out different functions
the more advanced the organism the greater the division of labour
define multicellular
organisms consisting of many specialised cells which form tissues and organs, which have various structures and organs
define unicellular
single celled organisms which carry out all life functions within one cell
define differentiation
the process by which a stem cell becomes specialised into a specific type of cell
name 5 specialised cells in the human body
- red blood cell
- egg cell (ovum)
- epithelial cell
- nerve cell
- sperm cell
what are viruses made up of?
made up of nucleic acid surrounded by a protein coat
some viruses have DNA while others contains RNA
what is the name of the virus that attack bacteria?
bacteriophages
why are viruses described as acellular?
they are not made of cells
why can viruses only reproduce inside a host cell?
- they do not have organelles, enzymes, chromosomes or cytoplasm
- without ribosomes, they cannot carry out protein synthesis
- without enzymes, they cannot replicate nucleic acid
how can viruses be transmitted?
- aerosol
- insect vectors
- exchange of bodily fluids
- bites by parasites
give 3 examples of viral infections
- small pox virus
- polio
- tobacco mosaic virus
how do viruses reproduce inside the host cell?
they hijack the host cell’s metabolism
they use the host cell’s organelles and enzymes
what structures do both plants and animals have?
- golgi
- nucleus
- ribosome
- mitochondria
- endoplasmic reticulum
- lysozyme
- cell membrane
what is a chloroplast made up of?
- stroma
- outer membrane
- granum
- thylakoid
- inner membrane
describe stroma
- a colourless, gelatinous matrix
- contains small ribosomes, circular DNA (for self replication), lipids and starch grains
what are thylakoids?
flattened sacs in the stroma
thylakoids are stacked to form ….
grana
grana connect to each other by …
lamellae
what is the function of chloroplast?
the site of photosynthesis
where is chlorophyll found?
within each thylakoid
what does the endosymbiotic theory state?
organelles such as chloroplast and mitochondria were originally free living prokaryotic cells
what are the main functions of the golgi body?
- modifying and packaging proteins into secretory vesicles
- secreting carbohydrates
- producing glycoprotein
- transporting and storing lipids
- forming lysosomes
describe lysosomes
single membrane bound vesicles that contain hydrolytic ezymes
how many functions of lysosomes?
2
what is the first function of the lysosome?
release hydrolytic enzymes when the cell needcs to break down worn-out organelles
what is the second function of the lysosome?
digest material that has been taken to a cell
e.g lysosomes fuse with the vesicle made when a white blood cell engulfs bacteria, and their enzymes digest the bacteria
how are phospholipid molecules arranged?
as a bilayer, with one sheet of phospholipid molecules opposite another
explain why the hydrophobic tails of both layers point towards the inside of the membrane
- the fatty acid tails are non-polar (hydrophobic) and repel water present in the cytoplasm and extracellular fluid
- the phosphate heads are polar/ hydrophilic and are attracted to the water
describe proteins in the membrane
- globular
- can be foujnd on surface
- partly embedded (extrinsic)
- extending completely across both phosophlipid layers (intrinsic)
where are carbohydrates found in the membrane?
only pointing of the outside of the cell
why is the model of the cell membrane called the fluid mosaic model specifically?
FLUID : the individual phospholipid molecules and proteins can move freely within a layer relative to one another, this makes the membrane fluid
MOSAIC : randomly distributed protein molecules that vary in shape and size forming a mosaic pattern
what is the main function of the cell membrane?
to aid transport of certain substances into/out of cell
e.g to obtain oxygen and remove carbon dioxide
what is the function of phospholipids?
forms a selective bilayer that allows non polar or uncharged molecules through but prevents the passage of polar or charged molecules
what is the function of extrinsic proteins?
associated with one layer only
may act as receptors for hormones
what is the function of intrinsic proteins?
acts as carriers or channels to allow the passage of charged or polar molecules such as glucose
what is the function of glycocalyx?
act as cell to cell recognition
e.g white blood cells in an immune response
also important in cell adhesion and acting as receptors
what is the function of cholesterol?
controls membrane fluidity
what is the tonoplast?
a single membrane which covers the vacuole
describe the cell sap in a vacuole
a solution which stores chemicals such as glucose, amino acids, minerals and vitamins
what is the role of the vacuole?
supporting soft plant tissues
describe centrioles
found in animal cells
found outside the nucleus
consists of two rings of microtubules arranged in hollow cylinders positioned at right angles to one another
during cell division, they migrate to opposite poles of the cell and form the spindle
describe plasmodesmata
narrow pores in the cell wall of plants
fine strands of cytoplasm pass through these
allows substance to move between connected cells
