Cell cycle ALL

Neutrophil (structure)

White blood cell

• multi-lobed nucleus

• granular cytoplasm

• many lysosomes

Neutrophil (structure relates to function)

• Can squeeze through small gaps and get to site of infections 

• Contain enzymes which attack pathogens  

Erythrocyte (structure)

• Biconcave shape 

• No nucleus  

• Flexible 

Erythrocyte (structure relates to function)

• Increased SA:Vol 

• Increased space for haemoglobin  

• Squeeze through narrow capillaries 

Sperm cell (structure)

• Tail or flagellum 

• Contain many mitochondria 

• Acrosome contains digestive enzymes 

Sperm cell (structure relates to function)

• Flagella = capable of movement  

• Many mitochondria = supply energy needed to swim  

• Enzymes on acrosome = digest protective layers around ovum  

Cambium cell (structure)

• Thin walls  

• Small vacuoles  

• Dense cytoplasm 

Cambium cell (structure relates to function)

• Thin cell wall = divide easily and differentiate into xylem or phloem 

• Small vacuole = more space for cytoplasm and nucleus which allows for rapid mitosis  

• Dense cytoplasm = supports high metabolic activity needed for cell division 

Root hair cell (structure)

Many root hairs on surface of cell

Root hair cell (structure relates to function)

Many hairs on surface =

• Increases surface area  

• Maximises uptake of water and minerals 

Palisade cells (structure)

• Thin cell walls  

• Large vacuole  

• Many chloroplasts  

• Chloroplasts can move 

Palisade cells (structure relates to function)

• Thin cell walls = increased rate of diffusion of carbon dioxide 

• Large vacuole = maintain turgor pressure  

• Many chloroplasts which can move = absorb lots of light  

Guard cell (structure)

• Thick inner wall  

• Thin outer wall  

Guard cell (structure relates to function)

• Lose water = less swollen and stomata closes  

• Gain water = outer wall bends outwards and stomata open  

What is the definition of a tissue?

A collection of differentiated cells that have a specialised function or functions 

What is the definition of an organ?

A collection of tissues that are adapted to perform a particular function of an organism  

What is the definition of an organ system?

A number of organs working together to carry out a major function in the body

What is the epidermal tissue in plants + function?

Outer layer on top and bottom of leaf  

• Waxy cuticle:  prevents water loss 

• Stomata and guard cells: open/close to regulate gas exchange and transpiration 

What is the mesophyll tissue in plants + its function?

Where photosynthesis occurs 

• Palisade mesophyll: contain many chloroplast - absorb light for photosynthesis  

• Spongy mesophyll: layer below, large air spaces for gas exchange  

What is the vascular tissue in plants + its function?

Vascular bundle within the mesophyll 

• Xylem tissue: transports water and minerals from the roots to the leaves  

• Phloem tissue: transports assimilates from source cells to sink cells 

What is the epithelium in animals?

• Tissue that is adapted to cover body surfaces, both internal and external  

• Made up of thin, continuous sheets of tightly packed cells  

What is the basement membrane in animals?

• Found beneath epithelium  

• Thin and strong sheet-like form of extracellular matrix  

• Line the basal side of epithelial tissues  

• Provides foundational support, 

• Separates tissues into compartments  

• Anchors cells to underlying connective tissue 

• Acts as a selective filter 

Squamous epithelium (structure)

• Very thin  

• One cell thick  

Squamous epithelium (structure relates to function)

Short diffusion distance = faster diffusion  

Ciliated epithelium (structure)

• Cilia on surface  

• Goblet cells  

Ciliated epithelium (structure relates to function)

• Waft mucus away from the lungs  

• Produce mucus which traps bacteria and pathogens - preventing them from reaching the lungs  

Cartilage (structure)

• Contains elastin and collagen  

• Firm, flexible  

• Composed of chondrocyte cells in extracellular matrix 

Cartilage (structure relates to function)

• Prevents the ends of bones rubbing  

• Can be stretched  

• Softens impact  

Muscle cells (structure)

Skeletal fibres = contain myofibrils + contractile proteins  

Muscle cells (structure relates to function)

Can shorten in length in  order to move bones  

Epidermis (in plants) structure

• Waxy, waterproof cuticle  

• Contain stomata  

Epidermis (structure relates to function)

• Reduce water loss  

• Allow for diffusion of gases in/out of leaf  

Xylem tissue (structure)

• Elongated dead cells  

• Lignin in cell walls 

Xylem tissue (structure relates to function)

• Hollow, water and minerals can be transported throughout  

• Provide structural support  

Phloem tissue (structure)

• Columns of sieve tube cells 

• Sieve plates 

Phloem tissue (structure relates to function)

Transports assimilates  

What is a stem cell?

An unspecialised cell that has the potential to either divide and self renew or to divide and differentiate

Two types of stem cells

1. Embryonic stem cells

2. Tissue stem cells

What is an embryonic stem cell?

Come from the blastocyst

• a very early embryo

What is a tissue stem cell?

Come from adult cells

• skin

• bone marrow

What are the three types of stem cell?

1. Totipotent

2. Pluripotent

3. Multipotent

What is a totipotent stem cell?

• Have capacity to self-renew by dividing

• Can develop into any type of cell

• Including extra-embryonic tissues

Extra-embryonic tissues = placenta, umbilical cord and amniotic fluid

What is a pluripotent stem cell?

• Capacity to self-renew by dividing

• Can develop into all cells of the adult body

• NOT extra-embryonic tissues

What is a multipotent stem cell?

• Capacity to self-renew into different types of cells present in a specific tissue or organ

• Most adult stem cells are multipotent

What is the role of embryonic stem cells in the blastocyst?

• Pluripotent

• Have capacity to repeatedly divide

• Provide a renewing source of stem cells

• Can develop into any type of body cell

What is the role of tissue stem cells?

• Self renew

• Replace specialised cells

• Differentiate into limited type of cells (multipotent)

When embryonic stem cells are extracted what type of stem cell are they?

Pluripotent

How could embryonic stem cells be useful in drug testing?

• In pre-clinical trials

• Identify potential side effects

• Efficacy of drug

What is somatic cell nuclear transfer (therapeutic cloning )?

• Nucleus is removed from donor egg cell

• Nucleus is removed from the patients somatic cell and introduced into egg cell

• Resultant cell is allowed to divide and produce several cells

• Some of these cells can be used to create cultures of stem cells

Advantages of therapeutic cloning

• Resultant cells are pluripotent

• Cells can potentially produce many different types of cells

• Would have same antigens as patient = will not be rejected by immune system

What are induced pluripotent stem cells?

• Cell taken from patients body

• Genetic reprogramming used to add certain genes to the cell

• iPS cell behaves like an embryonic stem cell

Advantage of iPS cells

No need for embryos

Example of treatment using stem cells to repair damaged tissues

Bone marrow transplant

• Treats blood/immune system disorders

• By replacing stem cells that differentiate into blood cells

• Patients own faulty stem cells are destroyed using chemo

• Bone marrow from healthy tissue matched donor is injected

• Healthy stem cells from donor self renew and differentiate into healthy blood cells

What are the reasons for mitosis?

1. Growth

2. Repair

3. Asexual reproduction

Stages of mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telephase

What are the two parts of prophase?

1. Early prophase

2. Late prophase

Early prophase

• Centrioles move towards opposite poles

• DNA starts to condense into chromosomes

• Nuclear membrane starts to disintegrate

• Nucleolus disappears

Late prophase

• Chromosomes continue to condense

• Each one is visible as two chromatids, held together at the centromere

• Spindle fibres begin to form

Metaphase

• Spindle fibres attach to the centromeres

• Chromosomes are moved by the spindle fibres to the equator of the cell

Anaphase

• Centromeres divide and spindle fibres attached to the chromatids shorten

• Chromatids are pulled to opposite poles of the cell

• Chromatids have characteristic V shape as they are dragged

Telephase

• Chromatids have reached the poles and are now chromosomes

• Detach from the centromeres and start to uncoil

• Nucleolus reforms

• Nuclear membrane reforms

In plants = cell plate begins to form down the centre of the cell

What is cytokinesis?

Division of the cytoplasm to separate the cells

Cytokinesis in plant cells

• Cell plate is constructed in the middle of the cell

• Cell wall materials are delivered by vesicles

• Vesicles are derived from the golgi

• Vesicles join together to become the plasma membranes

Cytokinesis in animal cells

• Contractile ring - made of micro tubular elements

• Constricts plasma membrane to form a cleavage furrow

• Moves inward to separate the cells using energy

What is interphase?

• Period of growth and normal working

• When the cell is not dividing

• Cell spends majority of time in this phase

Three stages of interphase

1. First growth phase (G1)

2. Synthesis phase (S)

3. Second growth phase (G2)

What happens in G1?

• Cells increase in size

• Cytoplasm volume increases

• Organelles duplicate

• RNA synthesised

• Protein synthesis

What happens in S?

• DNA replication

• each chromosome consists of two sister chromatids

What happens in G2?

• Organelles continue to replicate

• Energy stores increase

• Protein / enzymes continue to be synthesised and activated

Three parts of the cell cycle

1. Interphase

2. Mitosis

3. Cytokinesis

Two stages of cell division

1. Mitosis

2. Cytokinesis

What is mitosis?

The division of the nucleus

What is cytokinesis?

The division of the cytoplasm and membranes

What is G0?

• Cell moves out of the cell cycle

• Can be permanent or temporary

• Cell can undergo apoptosis or differentiation

What is apoptosis?

Genetically programmed cell death

Reasons for G0

1. Differentiation

2. Damaged DNA

What is a cell cycle checkpoint?

Points at which cell division can be halted

• if mutations are discovered

• damage to DNA can be repaired

What are the two main checkpoints?

1. G1/S checkpoint

2. G2/M checkpoint

What does the G1 checkpoint check for?

• Cell size

• Nutrients

• Growth factors

• DNA damage

What does the G2 checkpoint check for?

• Cell size

• DNA replication

• DNA damage