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32 Cards in this Set

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How are extracellular enzymes made? (6 marks)

DNA is transcribed at the nucleus

1)*protein is synthesised at the ribosome (translation)

2) protein from ribosome on RER

3) travels through RER

+ is processed (adding carbohydrate) & folded (change to 3D shape)

4) protein travels in a vesicle to the GA

5) then through the GA

is processed (carbohydrate chains added) & packaged

6) released as a vesicle

7) move to the cell surface (fuses with cell surface membrane) & is secreted as an extracellular enzymes

Tissue (& example)

Similar cells that work together to perform a function

E.g. Cardiac muscle tissue

Organ (&example)

Made of various tissues grouped together + work together to perform the a function

E.g. heart > muscular, nervous, connective tissue

Organ system (&example)

Many different organs that work together to perform the a function

E.g. Circulatory system > heart, arteries, veins, capillaries

Mitosis > interphase

- G1 & G2 = synthesis of organelles & proteins

- S = multiplication of chromosomes

- organelles replicates so there are spare ones

- ATP content is increased > needed for cell division (at the end of the cycle)

Mitosis (prophase)

- DNA condenses

- nuclear envelope breaks down

- centrioles move to opposite ends of the cells and begin to form spindles

- Chromosomes are free floating in the cytoplasm

Mitosis (metaphase)

- chromosomes meet at the Middle of the cell (equator)

- attached to the spindles by their centromeres

Mitosis (Anaphase)

- spindles contract & pull chromatids towards opposite poles of the cell

- centromere is divided into 2 when sister chromatids split

Mitosis (Telophase)

- chromatids uncoil & becomes long & thin again > become chromosomes

- cytokinesis: the cytoplasm splits into 2

- 2 separate nuclei form in 2 separate cells (nuclear envelope forms around each)

- daughter cells are genetically identical to the original cell

Cortical reaction

- sperm head (cell membrane) fuses with the egg cell membrane

- corticle granules releases when sperm head (cell membrane) touches egg cell membrane

- corticle granules thicken the zona pellucida to ensure its impenetrable to other sperm (prevent polyspermy)

(ONLY sperm nucleus enters egg cell as flagellum is discarded)

Acrosome reaction

- when the sperm head touches the egg cell (zona pellucida/follicle cells) the acrosome swells (bursts)

- digestive enzymes are released which break down the zona pellucida (allowing the sperm to penetrate/ move towards the egg cell membrane)

Why is it important that meiosis occurs

- produces haploid nuclei

- combine to create a diploid nuclei

Prokaryotes (general points)

- unicellular organisms/ smaller & simpler

- e.g. bacteria

- organelles/ ultrastructure is similar

Eukaryotes (general points)

- multicellular/ complex and large

- e.g. all animal and plant cells

- similar organelles/ ultrastructure

What is the role of the acrosome?

To allow the sperm to penetrate the egg cell

What is the purpose of the zona pellucida?

To protect the egg cell from damage

To prevent polyspermy

What is fertilisation (definition)

The fusion of gametes (egg & sperm cell) to form a zygote

What does locus mean (in this module)?

The location of genes on a chromosome

Sex Linked genes

- more likely on males due to one X chromosome

- if a female has a faulty/recessive allele for the characteristic on one sex chromosome the other X chromosome is likely to contain a dominant allele to over ride this

- sex linked because the alleles for these disorders are on the sex chromosomes

How does meiosis ensure genetic variation?

1)Independent assortment: random combination of chromosomes (so alleles) from both parents > gametes have a possibility of MANY unique combinations

2)Crossing over: some sections of chromosomes are swapped (twist around each other & combine to new chromosome) > unique gene (allele) combinations that are not present in either parent

What is the role of mitosis

- growth (producing new identical cells)

- repair (replacing old cells with new identical cells)


- can differentiate into most cell types

- not extra embryonic stem cells e.g. placental cells & umbilical cord cells

- some genes inactivated > X turn into these types of cells


- can differentiate into all cell types

- including extra embryonic cells e.g. placental & umbilical cord cells

- no genes are inactivated

How does society influence the use of stem cells

1. Monitoring (deciding the maximum age of an embryo)

2. Info (giving public& government info)

3. Licensing (checking the source of stem cells)

4. Allowing research (deciding whether research is allowed)

5. Guidlines (laws in stem cell use)

How does crossing over happen

- Homologous pairs line up

- exchange of chromosome segments between non-sister chromatids

- meiosis > contain combinations of genes dif from their parents

-some sections of chromosomes twist around each other, are swapped & combine to new chromosome

How does independent assortment happen

random combination of chromosomes in meiosis

How do features of the sperm aid reproduction? (All except acrosome)

- ATP > energy used for movement of the flagellum

- flagellum > ability if sperm to swim (move)

Features of the egg cell

- big lipid droplets > for energy > nutrition for the egg cell

- follicle cells > protective coat

- zona pellucida > protective layer > stops penetration/ damage

- corticle granules > prevent polyspermy

What makes extracellular proteins

Ribosomes on RER

Observing mitosis

• cut off garlic root tip

• leave in acetic alcohol, then water, then HCL

• macerate the root tip with mounted needle/ mount under a coverslip

• stain garlic root tip (orcein ethanoic)

• observe mitosis > count no. of visible chromosomes > calculate mitotic index

• control - temperature of solution (place in incubator at 25 degrees), source of garlic (same plant)

What is the mitotic index

The proportion of cells undergoing mitosis

Mitotic index = no. of cells with visible chromosomes/ total no. of cells

What is the difference between an embryo and a zygote

Zygote is firmed from the fusion of the gametes > embryo formed from zygote (so at a later stage)