Cell Organisation Flashcards by Oce F

Structure of prokaryotic cells

Contain no nucleus

No cell membrane

DNA/RNA is located in cytoplasm

Contains a cell wall

Divides through binary fission (rapid mitosis)

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Structure of eukaryotic cells

Contain a nucleus & membrane bound organelles

Only plants & fungi contain a cell wall

Division involves mitosis

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What is a cell membrane

A flexible, semi-permeable membrane (phospholipid bilayer) that separates the cells external & internal environment

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Transmembrane proteins (emdedded in cell membranes) help to perform

Movement of substances in/out of cells

Immunological identity (helps immune system to recognise our own cells)

Receptors (recognition site for
hormones)

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What is a cell junction

Contact/communication points between adjacent cell membranes of tightly packed cells

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Examples of tight junctions

Found in stomach, intestines & bladder

Where the transmembrane protein fuse cells together to reinforce the junctions & seal off passageways to prevent leaking

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Examples of gap junctions

Small fluid-filled tunnels between neighbouring cells

Nerves

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Which body cells do not have a nucleus

Red blood cells

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What does the nucleolus produce

RNA (Ribonucleic Acid)

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What are chromosomes

Thread-like structures of nucleic acids & proteins found in the nucleus of most living cells, carrying genetic information
Coiled up DNA

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How many chromosomes are in each cell in the body (apart from gametes)

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How many chromosomes are in gametes

23 pairs

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What are the two pairs of male & female gametes

Male - XY

Female - XX

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Why are males more likely to develop genetic diseases

If there is a disease on the single X chromosome, the Y cannot counteract it unlike female gametes

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What are histones

Proteins that DNA form a double helix around

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What is the meaning of epigenetics

Where enviornments can impact which genes are switched on

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What is the cytoskeleton

A network of protein filaments that extends through the cytosol

What do the protein filaments in the cytoskeleton assist

Help cells generate movement eg enables white blood cells to migrate to sites of injury

In muscle cells they are the organelle that enables muscle contraction

Physical support & shape

Assists in cell division

What is ATP

Adenosine Triphosphate - the energy currency of somatic cells

What processes do mitochondria undergo

Use oxygen & nutrients such as glucose to create ATP via aerobic respiration

What are ribosomes

The sites of protein synthesis containing high quantities of RNA
They are either free ‘mobile’ in cytoplasm or bound to rough endoplasmic reticulum

the difference between free ribosomes & stationary

Free ribosomes make protein for inside the cell whereas those on the rough endoplasmic reticulum make proteins for outside the cell

What is the Endoplasmic Reticulum (ER)

A network of membranes in the form of flattened sacs which extends from the nucleur envelope throughout the cytoplasm to the cell membrane

Endoplasmic- within plasma
Reticulum- network

Compare the two types of ER

Rough ER is continuous with the nucleur membrane & its outer surface is studded with ribosomes which synthesises & transports proteins
Smooth ER contains no ribosomes but instead unique enzymes which perform lipid & hormone synthesis, in the liver enzymes detoxify & in muscle it releases calcium for contraction

What is the function of the golgi apparatus

Modifies, sorts, packages & transports proteins received from the rough ER Enzymes modify the proteins & they bud off in transport vesicles It consists of flattened membranous sacs & most cells have several Golgi

What is the function of lysosomes

Vesicles that contain as many as 60 powerful enzymes which can breakdown a variety of molecules They recycle worn out organelles by engullfing, digesting & returning components to the cytosol for reuse Also used to digest foreign cells And release enzymes externally eg with sperm to assist egg entry Lyso- breakdown Soma-body

Process of mitosis

Full set of chromosomes is first duplicated & then evenly distributed into both daughter cells 1 division creating 2 identical diploid daughter cells Used for growth & repair But we are Born with a set number of brain & muscle cells & egg cells which cannot undergo mitosis

Process of meiosis

Gametes produce 4 haploid nucleus (half) cells through 2 divisions The 4 cells produced are non-identical

What is a zygote

Diploid cells which have 2 copies of chromosomes (23 pairs) | Zygote leads onto undergoing mitosis which develops into an embryo & eventually a foetus

The four amino acids in DNA sequences

Adenine Cytosine Thymine Guanine

The two phases of protein synthesis

1. Transcription - copy of one gene made into mRNA (messenger RNA) which travels out of the nucleus to a ribosome 2. Translation - ribosomes read the code & produces a chain of amino acids to form the required protein (If protein used within cell distributed by free ribsomones, if outside of cell by the Golgi)

Passive transport of molecules & examples

Movement of substances from an area of HIGH - low concentration (moving down the conc gradient) & requires no energy Eg Diffusion ie gases Osmosis Facilitated diffusion

Active transport of molecules & examples

Movement of substances from an area of LOW - high concentration (up the conc gradient) & requires ATP energy Egs Pumps (sodium potassium pump)- Endocytosis Exocytosis

What is pinocytosis

Specialised cells that drink fluids

What is diffusion

Movement of molecules down the conc gradient such as gases eg oxygen

What is osmosis

Movement of water down the conc gradient | Dilutes concentrated & concentrates diluted

What is facilitated diffusion

Movement down the conc gradient aided by transmembrane proteins For larger substances eg glucose & charged molecules

What are active transport pumps

Use protein pumps in the cell membrane to allow specific molecules up the conc gradient Sodium potassium pump important for nerves

What is endocytosis

Engulfing of particles into the cell through cell membrane extensions Either phagocytosis or pinocytosis

What is exocytosis

Removal of waste from the cell | Fuses with membrane before being expelled