chapter 1 cell Flashcards
whats the Protoplasm made of
- Slightly opaque, colorless, jelly-like
- 70% water
- Rest:
- Organic and inorganic salts
- Carbohydrates
- Lipids
- Nitrogenous substances – amino acids
- Compounds of the above
define Organelles
Internal, membrane-bound sacs/compartment that has a specific metabolic function within a cell and Allows compatible, interconnected reactions to proceed at different times
Organelles include
nucleus, mitochondria, ribosomes, endoplasmic reticulum (smooth & rough), Golgi apparatus/body, Lysosomes, vacuoles, centrioles, and centrosomes
functions of the Nucleus
- Helps control access to hereditary instructions contained in DNA
- Keeps DNA separated from all the substances and metabolic machinery in the cytoplasm
- Controls the cell’s processes of growth, repair and reproduction
where can you find the DNA
DNA is found in the nucleus
what is Nucleoplasm
specialized type of protoplasm found in the nucleus
what is a Nuclear envelope
it is Two membranes thick Each membrane is a lipid bilayer studded with various proteins Pores composed of proteins span both bilayers
define pores
Pores are passageways through which substances can move into and out of the nucleus in controlled ways
what is Nucleolus
Sites where the protein and RNA subunits of ribosomes are assembled.
what is Chromatin
Chromatin is loosely coiled strands of DNA
Prior to cell division, chromatin becomes _____________
Prior to cell division, chromatin becomes more tightly coiled (supercoiling) = chromosome
Chromosomes consist of
Chromosomes consist of 2 chromatids Held together by centromere
DNA organised into_____
DNA organized into genes
Genes control cell ______ and
__________
Genes control cell activities and
inheritance
how many chromosomes in human cells
48 Autosomes and sex chromosomes
functions of Mitochondria
Contain their own DNA (termed mDNA).
* They can divide on their own
* Function as the sites of energy release and ATP formation
* Double membrane
* Inner membrane contains folds called cristae
function of Ribosomes
- The sites of protein synthesis
- Not membrane-bound
- Consist of a small and larger subunit
- Free ribosomes – proteins inside the cell
- ER-bound ribosomes – proteins packaged in vesicles. It may be released outside the cell
define Endoplasmic reticulum
A network of membranes that forms the ‘circulatory system’ of a cell
what are the types of Endoplasmic reticulum and what is the difference between the two
- Rough endoplasmic reticulum (Rough ER) has numerous ribosomes Connected to the nuclear envelope
- Smooth endoplasmic reticulum (Smooth ER) lacks ribosomes Involved in lipid and steroid production
how does the Endoplasmic reticulum work
it is A transport system Protein molecules move from the rough ER into the smooth ER, which then sends them enclosed within the vesicles usually to the Golgi complex.
functions of the Golgi apparatus/body
- Flattened stacks of membrane-bound sacs
- Function as a packaging plant
- Formed at one end from vesicles budding off the ER
- Cis and trans faces
- Vesicles also used to make lysosomes
what is Lysosomes
*Relatively large vesicles formed by the Golgi
* Contain hydrolytic enzymes which destroy worn-out parts of a cell or
bacteria
* Break down food allowing them to be used for energy transfer in the cell
what is Vacuoles
Spaces within the cytoplasm
* Contain waste materials or secretions formed by the cytoplasm * Used for storage or digestion purposes
what are Centrioles
occur in pairs at right angles in the cytoplasm
* composed of a series of nine paired tubes arranged in a circular fashion
define Centrosomes
Dense area of cytoplasm containing the centrioles
define Cell membrane
Fine semi-permeable membrane composed of lipids and proteins
Cell membrane functions
*Separates the contents of cells from their external environments, controlling exchange between the two
* Enables separate compartments to be formed inside cells
* Acts as receptor sites for recognizing external stimuli
define Simple diffusion
Unassisted net movement of small nonpolar substances down their concentration gradient
what is Facilitated diffusion
it is a Concentration-dependent transport system that Involves the movement of larger hydrophilic molecules e.g. glucose
& amino acids
* May occur in either direction
* Process is strictly passive
* Requires protein carrier molecules
* Gated pores
what are Gated pores/Carriers
- Molecules bind specifically but reversibly
- Binding of the molecule causes the transmembrane protein to change shape
- Molecule is moved into the interior of the cell
- Molecule dissociates from the carrier
- Carrier returns to its original shape
what are the factors determining diffusion rates
1-The concentration gradient(The steeper the gradient, the faster the rate)
2-The surface area(The larger the surface area, the greater the rate of diffusion)
3-The size of the molecules( Small molecules diffuse faster than larger ones)
4-The distance that the molecules diffuse( If the distance is doubled, diffusion takes four times as long.)
5-The structure of the cell membranes(The larger the number and size of the pores in a membrane, the greater the diffusion)
what is Osmosis
The process of transferring water across the membrane by osmotic pressure
* Concentrations are unequal on the different sides of the membrane
* Water moves from dilute to concentrated solution
what is an Active transport
Transport across a membrane that relies on chemical energy * Molecules move against either an electrical or concentration
gradient. Can also include large molecules
what are the types of Active Transport proteins
*Uniporter – moves a single substance in 1 direction
* Symporter – moves 2 substance in the same direction
* Antiporter – moves 2 substances in opposite direction e.g. Na+/K+ pump
what are Active transport types
- Primary active transport(Uses energy directly E.g. Na+/K+ pump)
- Secondary active transport(Uses concentration created by primary active transport to move a molecule E.g. Na+/glucose)
how the Secondary active transport (Calcium) work
- Na-Ca exchanger transports Ca++ uphill from low intracellular to high extracellular.
- Na+ and Ca++ moves in the opposite directions across the cell membrane.
- The energy is derived from the downhill movement of Na.
if 2 daughter cells formed from mitosis which are identical to the parent cell the cells are called
diploid
if 4 daughter cells formed sexually through meiosis the cells are called
haploid
what is Mitosis
- Continuous process of making new cells for growth and repair
- Replace old worn out cells
Mitosis is divided into 4 main stages where the cell is actively dividing and one resting stage
interphase
prophase
metaphase
anaphase
telophase
what happens in Prophase
- Centrosome divides into 2 centrioles
- At the end of prophase (late prophase) chromatin shortens and
thickens forming chromosomes
what happens in Metaphase
- Nuclear membrane disappears
- Chromosomes align at the equator
what happens in anaphase
- Centrioles drawn further apart
- Chromatics divide and identical halves move to opposite poles
- Spindle threads of centrioles divide forming new centromeres
- Cell membrane constricts at centre
what happens in telophase
- New nuclear membrane reappears around each set of chromosomes
- Spindle fibers disintegrate
- Cell membrane continues to constrict.
- Daughter cells form by cytokinesis
what happens in Interphase
- The interval between two cell divisions
- Individual chromosomes cannot be distinguished
- DNA replication occurs
- Cell carries out normal metabolic activities
- Nuclear protein is synthesized
- Cell increases in size
what is Meiosis
- Two consecutive divisions: meiosis I and meiosis II
- No DNA synthesis (no S phase) between the two divisions
- Result: 4 cells with half the number of chromosomes of the starting cell, e.g., 2n -> n
- fusion of two such cells produces a 2n zygote
what is Synapsis
the fusion of chromosome pairs at the start of meiosis
what are Tetrads
four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids
what is Crossing over
exchange of genetic material between non- sister chromatids of homologous chromosomes
what happens in Meiosis I
- Prophase 1: Each chromosome dupicates and remains closely associated. These are called sister chromatids.
- Metaphase 1: Homologous chromosomes align at the equatorial plate. Crossing-over can occur during this stage.
- Anaphase 1: Homologous pairs separate with sister chromatids remaining together.
- Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.
Meiosis II
* Prophase 2: DNA does not replicate.
* Metaphase 2: Chromosomes align at the equatorial plate.
* Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole.
* Telophase 2: Cell division is complete. Four haploid daughter cells are obtained.
