Cells Flashcards
Give a brief description of cells
Cells are the basic unit of all living things and they contain many specialised organelles each of which carry out a particular function.
Nucleus
The nucleus contains the nucleolus and and is surrounded by the nuclear envelope which has nuclear pores in. It contains DNA which codes for protein synthesis
Nucleolus
Carries out the synthesis of r RNA and ribosomes
Nuclear pore
Allows transport of mrna out of the nucleus
Nuclear envelope
Separates the DNA from the cytoplasm
Cell membrane
Uses selective permeability to control substances entering and leaving the cell
Cytoplasm
Site of chemical reactions within the cell
Mitochondria purpose
Contains DNA and ribosomes, site of aerobic respiration ands the synthesis of ATP.
Mitochondria structure
Mitochondria have two membranes that are separated by a narrow fluid-filled intermembrane space. They are 1 to 10 micrometres in diameter. The inner membrane is is folded to create a greater surface area. The folds in the membrane are called cristae and this is where part of the respiratory process takes place. The interior matrix contains enzymes.
Rough endoplasmic reticulum RE r
Transport proteins synthesized by attached ribosomes. The re r is a system of flattened sacs (cisternae) continuous with the nuclear membrane and sometimes linking to the Golgi apparatus
Smooth endoplasmic reticulum s e r
The synthesis and transport of lipids. It forms a system of flattened sacs (cisternae) , is continuous with the nuclear membrane and is sometimes linked to the Golgi apparatus. It has no ribosomes unlike the rough endoplasmic reticulum
Golgi body / apparatus
It is similar to the endoplasmic reticulum but more compact and surrounded by vesicles. It chemically modified proteins, produces lysosomes, produces glycoproteins and packages proteins for secretion out of cell.
Centrioles
Used in spindle formation – microtubules - in Cell division. They are 2 hollow cylinders that are perpendicular to one another.
Ribosomes
Synthesise proteins. They are are two subunits made from r r n a ( ribosomal ) and protein. There is one large subunit and one small.
Lysosome
1 micrometer diameter. They are small vacuoles formed when small portions of Golgi body are pinched off. They contain and isolate digestive enzymes. They can release and destroy organelles. They manage the digestion full of material taken in to cell for example white blood cells engulf bacteria by phagocytosis and then lysosomes are used in the digestion of that bacterium
Vesicles in plants - large permanent vacuole
large membrane-bound organelles surrounded by a tonoplast (membrane). They store ions and organic molecules for example proteins and they maintain osmotic pressure
Vesicles in animals
They are small membrane bound organelles. They act as a contractile vacuole to maintain osmotic pressure.
Chloroplast structure
They are 2 to 10 micrometres in diameter and 1 micrometres thick. They have a double membrane. In chloroplasts there is a fluid called Stroma which contains ribosomes , lipids, circular DNA and starch granules . There are stacks called granum in chloroplasts. These stacks are of flattened sacs called thylakoids. They contain photosynthesis pigments such as chlorophyll. between the thylakoid form lamellae…?
Chloroplast function
They are the site of photosynthesis
Cell wall
Provides strength and support and is freely permeable to water . it is made of cellulose microfibrils in a polysaccharide Matrix
Plasmodesmata
These are seen between two plant cells. It is a narrow thread of cytoplasm that passes through cell walls of adjacent plant cells. They allow the exchange of large organic materials via cytoplasmic streaming. They allow communication between adjacent cells.
What organelles are present only in animal cells?
Lysosomes and centrioles
What organelles are present only in plant cells?
Large permanent vacuole, chloroplast, cell wall , plasmodesmata and smooth endoplasmic reticulum
What are prokaryotes
They include bacteria and were the first living thing on the planet.
What are the similarities of prokaryotes and eukaryotes?
They share ribosomes, cytoplasm, cell membrane and DNA
What are the differences of prokaryotes and eukaryotes?
Prokaryotes have 70s ribosomes and eukaryotes have 80s ribosomes. Prokaryotes have no membrane bound organelles. Prokaryotes don’t have a nucleus but eukaryotes do. The DNA in prokaryotes is circular, where is it is linear and bound to histo proteins in eukaryotes. The cell wall in prokaryotes is made of peptidoglycan but the cells are made from cellulose in plant cells, chitin in fungi and don’t exist in animal cells.
What do eukaryotes include?
Plant animal and fungus
What is magnification?
The number of times larger an image is compared with the real size of the object
magnification =
Size of image ÷ by actual size of specimen
magnification =
Size of image ÷ by actual size of specimen
What is a virus?
Genetic material encased in a protein capsid. It is non-cellular and cannot self replicate
What is a tissue
Groups or layers of similar cells working together to perform a specific function
Organ
A collection of different types of tissues working together to perform a specific function
What do plasma membranes do?
The control entry and exit of substances as they are selectively permeable. They have specialised roles depending on the location.
Where can one find plasma membranes?
On the external of a cell in both prokaryotes and eukaryotes. Within cells in eukaryotes for their membrane-bound organelles
What does it mean to be hydrophobic?
A substances nonpolar and nonionic, is soluble in organic solvents, likes other hydrophobic molecules, hate anything that is hydrophilic including water.
What does it mean to be hydrophilic ?
Something likes water, is water soluble, is polar or charged, likes other hydrophilic molecules and hates anything that is hydrophobic. Hydrophilic substances are attracted to water and polar, ionic or charged substances.
What are the 4 types of epithelium?
Ciliated columnar, cuboidal, squamous glandular
What are the three types of muscle?
Skeletal (striated), smooth , cardiac
How quickly do epithelial cells divide?
Quickly
Structure of squamous epithelium
cells are thin and smooth, cells are packed closely together and have a smooth lining to reduce friction. They have a basement membrane on the bottom
Function of squamous epithelium
Allow gas exchange to take place as thin cells mean a short diffusion distance. They are lining tissue and cover the surface of organs cavities and tubes
Locations of squamous epithelium
Alveoli and blood vessels
Location of cuboidal epithelium cells
Small intestine, kidney tubules and other tubes, glandular ducts
Location of of columnar epithelium tissue
Organs and tubers, small intestine ( microvilli)
Location of ciliated epithelial tissue
Organs and tubules, trachea and bronchi
Location of glandular epithelium tissue
Digestive system e.g. salivary glands
Function of glandular epithelium
To contain mucous secreting goblet cells, secrete enzymes, hormones,, mucus
Function of cuboidal epithelium cells
Involved in absorption or secretion
Function of ciliated epithelium cells
To support cilia function. The cilia waft to move dust and dirt out of air passages and the
Function of columnar without cilia epithelial cells
To support the microvilli as they increase surface area for absorption
What is the structure of cuboidal epithelial cells
They are cube like box shaped cells with a prominent nucleus. They sit on a basement membrane.
What is the structure of of columnar epithelial cells without cilia ?
They are column shaped and have microvilli and a basement membrane on the bottom
What is the structure of ciliated epithelial cells?
The column shaped and have a basement membrane on the bottom and have cilia on the top
What is the structure of glandular epithelial cells?
The secretory epithelial cells organised themselves into gland shapes. There are some columnar epithelial cells embedded amongst the epithelium tissue.
Describe epithelial tissue in general
They are lining tissue and cover the surface of organs, cavities and tubes . the cells are packed closely together and rest on and basement membrane
Describe muscle tissues in general
They can all contract to shorten their length, there are three types of muscle tissue , inside the cells are protein fibres made of actin and myosin which slide past each other to shorten the cell
What is connective tissue made out of
Collagenous fibres and elastic fibres
What is the structure of connective tissue
All the connective tissues except for blood contain the protein collagen in the extracellular material
What’s the function of connective tissue
Connects other tissues together and supports the body
where can connective tissue be found in the body
Everywhere for example blood bone cartilage. These are all forms of specialised connective tissue
What is the structure of skeletal muscle
Muscle cells are joined together to form fibres. The striations ( Stripes) are caused by overlapping protein molecules in the cells
What is the function of skeletal muscle
These muscles are used to move whole organisms or parts of them. For example skeletal movement, moving bones, maintaining posture and other body positions, supporting soft tissues.
Where are skeletal muscles located in the body
They are attached to bones by tendons
What is the structure of Smooth muscles
They are unclstriated, individual cells which can shorten in length
What is the function of Smooth muscle cells
They work automatically and are involved in many housekeeping functions of the body
Location of Smooth muscle tissues in the body
In the walls of the intestine and blood vessels, Iris, gastrointestinal tract, bladder, walls of hollow organs EG stomach
What is the structure of the cardiac muscle
Fibres are striated and branched. They are attached at the ends to adjoining fibres by thick plasma membranes called intercalated discs
Function of cardiac muscle
Rhythmic contraction pump blood through the heart
Location of cardiac muscle
Only in the heart
What does the term endosymbiotic mean
Two or more or organisms are in a mutually beneficial relationship….?
What prokaryotes came together to form cells as we know it
Engulfing bacteria, photosynthesising bacteria, respiring bacteria
How did chloroplasts come into existence
Engulfing bacteria engulf the photosynthesising bacteria
How did mitochondria come into existence
Engulfing bacteria engulfed respiring bacteria
What is the evidence of how chloroplasts and mitochondria came into existence?
The ribosomes are all 70s and genes in the DNA are similar in prokaryotes and mitochondria and chloroplasts. All three are self-replicating. The inner membrane of chloroplasts is similar to photosynthetic cells. The inner membrane of mitochondria is similar to respiring cells. The outer membrane is similar in structure between mitochondria, chloroplasts and the engulfing cell.
What is the structure of a glycoprotein?
Carbohydrate attached to a protein
What are intrinsic proteins
Proteins that are embedded in the phospholipid bilayer and are present the whole way through
What are extrinsic proteins
Proteins embedded in the phospholipid bilayer that are only in one layer of phospholipids
how wide is the phospholipid bilayer
7 nanometres
Are phosphate heads hydrophilic or hydrophobic?
Hydrophilic
What is the structure of a glycolipid
A polysaccharide attached to a phospholipid
What are the two types of intrinsic protein?
Channel protein and carrier protein
Describe the structure of cholesterol in the phospholipid bilayer
They are the smallest constituent and are embedded between fatty acid tails….?
Are fatty acid tails hydrophobic or hydrophilic?
Hydrophobic
What structure do intrinsic proteins have?
Tertiary structure 3D globular…..?
Describe chemically a hydrophilic head and hydrophobic tail
The hydrophilic head has a glycerol molecule which is bonded to to a phosphate group. The glycerol molecule is then bonded to one saturated fatty acid and one unsaturated fatty acids which make up the hydrophobic tails.
What are the roles of plasma membranes within cells
To separate cell components from cytoplasm in a process called compartmentalization. To hold components of metabolic pathways in place e.g. mitochondria
What are the roles of plasma membranes on the surface of cells?
Two separate cell contents from the outside environment, for cell recognition and signalling, to regulate transport of materials into or out of cells
What is the fluid mosaic model of a plasma membrane and why is it called that?
This model was suggested in 1972 to by singer and Nicolson. They stated that molecules are not bonded together so there is some movement but the membrane is relatively stable because of the nature of the phospholipid. It is called the fluid mosaic model because the phospholipids and proteins move around each other so they are fluid and and the arrangement of proteins within the phospholipid bilayer is like a mosaic.
How can the fluidity of the plasma membrane be proved?
Proteins can be marked, a photo taken and then another photo taken having left the marked proteins. By this time the proteins will have move proving membrane is fluid.
what is the function of the phosphate head?
To interact with the water external to the cell and in the cytoplasm.
What is the function of the hydrophobic tail
To allow the passing through of hydrophobic substances
What is the the purpose of intrinsic proteins?
To allow the passing through of hydrophilic substances.
What is the purpose of the phospholipid bilayer
To selectively enable substances to pass in and out of the cell by being a selectively permeable membrane
What does the term polar mean?
It means a molecule has inner charges resulting in a positive part and a negative part
How is diffusion affected by an increasing concentration difference across the membrane?
The rate of diffusion will increase
How is the rate of diffusion affected in facilitated diffusion as the concentration difference across the membrane is increased?
At first there is an increased rate of diffusion. It is faster than in simple diffusion because the proteins are specific to the molecules they are transporting. Then the rate of diffusion will no longer increase despite an increasing concentration gradient. This is because the channel carrier proteins act as limiting factors as they fully saturated at one time.
