Cellular division, cell diversity and cellular organisation

what is the cell cycle a process of?

the process that all body cells in multicellular organisms use to grow and divide

what does interphase involve?

cell growth and dna replication

what does m phase involve

• mitosis and cytokinesis

define mitosis?

• nuclear division, chromosomes separate into 2 nuclei

define cytokinesis?

• cytoplasmic division, cell divides into 2

what 3 separate growth stages is interphase separated into?

• G1, S and G2

what occurs in G1?

• the cell replicates organelles such as mitochondria

• high level of transcription and translation take place due to protein demand

what occurs in the s phase?

• all the chromosomes are replicated

• cell synthesises lots of dna

what occurs in the G2 phase?

• the cell replaces the energy stored used in the s phase

• continues carrying out transcription and translation

• repairs any damaged chromosomes

• cell continues to grow

what it called when a cell exits the cell cycle?

• G₀ phase

state the 3 reasons cells can enter the G₀ phase ?

• fully differentiated cells enter and stay there for the rest of their lives

• dna in cells can get damaged over time therefore the cell is no longer able to divide- senescent cells, the cell enter permenetaly

• cells can enter temporarily then triggered to enter the cell cycle during infection e.g. b memory cells

what is the cell cycle regulated by?

checkpoints

what do checkpoints help to ensure?

• to ensure that it is ok for the cell cycle to continue

How many checkpoints are there in the cell cycle?

3

what does the G1 checkpoint check for?

• G1 checkpoint where the cell checks that it has grown to the correct size, also checks for DNA damage

what does the G2 checkpoint check for?

• checks for DNA damage

• checks that the cell has grown to the correct size

what is the name of the final checkpoint in the cell cycle?

• the metaphase checkpoint

what does the metaphase checkpoint check for?

• checks that the chromosomes are assembled correctly on the spindle

what is mitosis necessary for?

• the growth of multicellular organisms and repairing damaged tissues

define diploid cells?

cells which contain chromosomes in pairs

what do scientists call the 2 identical molecules of DNA made after DNA relpication?

sister chromatids

what is the name of the point where the sister chromatids are joined?

• the centromere

is mitosis sexual or asexual reproduction?

asexual reproduction

what division stages make up mitosis?

• prophase

• metaphase

• anaphase

• telophase

what process comes before mitosis in the cell cycle?

interphase

what happens at interphase?

• the cell prepares to divide

• its dna is unravelled and it is replicated

• organelles also replicated so it has spare ones

• atp content increases

what happens at prophase?

• the chromosomes condense, get shorter and fatter

• centrioles move to opposite poles of the cell forming spindle fibres

• nuclear envelope breaks down and chromosomes lie free in the cytoplasm

what happens at the metaphase?

• the chromosomes become attached to the spindle by the centromere

• they line up along the centre of the cell

• at the metaphase checkpoint, the cell checks that all chromosomes are attached to the spindle before mitosis can continue

what happens at anaphase?

• the centromeres divide separating each pair of sister chromatids

• spindles contract pulling the sister chromatids to opposite ends of the cell

what happens at telophase?

• the chromatids reach the opposite ends of the cell

• they uncoil and become long and thin again

• they are called chromosomes again

• a nuclear envelope forms around each group of chromosomes ao there are now 2 nuclei

what happens in cytokinesis?

• the cytoplasm divides into 2

• clevage furrow forms to divide the cell membrane

• daughter cells which are genetically identical to the parent cell and each other

how to view chromosomes under a microscope?

• prepare a squash slide of plant root cells

• this then makes chromosomes easier to see after they have been stained

how is a zygote formed insexual reproduction?

• two gametes ( an egg and a sperm) join together at fertilisation to form a zygote

define meiosis?

• a type of cell division that happens in the reproductive organs to produce gametes

define haploid cells?

• cells with half the number or chromosomes

are gametes haploid or diploid?

• haploid

define homologous chromosomes ?

• chromosomes with exactly the same genes

what 2 divisions does meiosis invlovle?

meiosis I and meiosis II

what 4 stages is meiosis split into?

• prophase

• metaphase

• anaphase

• telaphase

what stage does meiosis begin with?

interphase

what happens in prophase I?

• the chromosomes condense then get shorter

• they arrange themselves into homologous pairs and cross over

• centrioles move to opposite ends of the cell forming spindle fibres

• nuclear envelope breaks down

explain crossing over?

• homologous pairs of chromosomes come together and pair up

• the chromatids twist around each other and bits of chromatids swap over

• the chromosomes still have the same genes but now have a different combination of alleles

state the name of the 2 main events which occur in meiosis which lead to genetic variation?

• crossing over

• independent assortment

what does the crossing over of chromatids in meiosis I mean?

• that each of the 4 daughter cells formed from meiosis contains chromatids with different alleles

explain independent assortment?

• it is completely random which chromosome from each pair ends up with in the daughter cell

what happens in metaphase 1?

• the homologous pairs atatch o the spindle fibres by their centromeres

• they line up across the centre of the cell

what happens in anaphase 1?

• the spindles contract separating the homologous pairs

• one chromosome goes to each end of the cell

what happens in telophase 1?

• a nuclear envelope forms around each group of chromosomes

define stem cells?

undifferentiated cells which can become specialised to carry out a particular function

how can stem cells in early embryos develop?

into any type of human cell

how can stem cells in adults develop?

into a limited range of human cells

what is the name of the process by which a stem cell becomes specialised for its job?

• differentiation

what can stem cells be used for in humans?

• to replace damaged cells

• make new skin cells

• make new blood cells

what can stem cells be used for in plants?

• needed to make new shoots and roots throughout their lives

• can differentiate into various tissue e.g phloem and xylem

what are erythrocytes also known as?

red blood cells

what are neutrophils also known as?

white blood cells

what can stem cells within bone marrow differentiate into?

blood cells

where are stem cells found in plants?

• the meristems

in what 3 ways can stem cells assist curing diseases?

• can be used to repair and replace damaged tissues

• can be used to treat neurological disorders

• can be used by scientists researching developmental biology

how are neutrophils specialised for their function?

• flexible shape allows them to engulf pathogens or foreign particles

• lysosomes within their cytoplasm contain digestive enzymes to break down engulfed particles

how are erythrocytes specialised for their function?

• biconcave disc shape provides a large surface area to volume ratio for gas exchange

• no nucleus so more room for haemoglobin

how are epithelial cells specialised for their function?

• cilliated epithelia in airways have cilia to beat particles away

• squamous epithelia in lungs are very thin for efficient diffusion for gases

how are sperm cells specialised for their function?

• flagellum to swim to egg

• lots of mitochondria to provide energy to swim

• acrosome contains digestive enzymes to enable sperm to penetrate surface of egg

how are palisade mesophyll cells specialised for their function?

• contain many chloroplasts therefore can absorb lots of sunlight

• thin walls so carbon dioxide can easily diffuse into the cell

how are root hair cells specialised for their function?

• large surface area for absorption

• thin permeable cell wall for entry of water and ions

• cytoplasm contains lots of mitochondria to provide energy for active transport

how are guard cells specialised for their function?

• help to open stomata to allow the leaf to exchange gases for photosynthesis

state the 4 types of animal tissue?

• squamous epithelium

• ciliated epithelium

• muscle tissue

• cartilage

what are squamous epithelium cells and where are they found?

• a single layer of flat cells lining a surface

• found on alveoli and lungs

what are ciliated epithelium and where are they found?

• a layer of cells covered in cilia

• found on surfaces where things need to be moved

• in trachea for instance where cilia waft mucus along

define muscle tissue?

• bundles of elongated cells called muscle fibres

state the 3 different types of muscle tissue?

• smooth muscle- found in lining of stomach wall

• cardiac muscle- found in heart

• skeletal muscle- you use to move

what is cartilage and where is it found?

• a type of connective tissue found in the joints

• also shapes and supports ears nose and windpipe

what are the 2 types of plant tissue?

• xylem tissue

• phloem tissue

function of the xylem?

• transports water and minerals up the stem

• supports the plant

function of phloem?

• transport sugars around the plant

• arranged into tubes

• made up of sieve tubes and companion cells

what do organs work together to form?

• organ systems

define organ?

• a group of tissues that work together to preform a particular function

define tissue?

• a group of cells that are specialised to work together to carry out a particular function