Cell biology and body chemistry

Question 1

Intro to cells

Answer 1

• Take nutrients
• Expel waste
• Grow and repair themselves
• Many different cells within the body but all have the same basic function
• Numerous chemical changes and processes within cells and tissues to maintain homeostasis

Question 2

Nucleus

Answer 2

• Contained within nuclear membrane
• Contains chromosomes
• Chromosomes contain DNA and this tells the cell how to function. It carries instructions on how to behave and info for protein synthesis

Question 3

Nucleolus

Answer 3

• Inside the nucleus - made up of RNA
• The nucleolus also produces ribosomes used in protein synthesis

Question 4

Cell membrane

Answer 4

• Covered with carbohydrates and these help the cell recognise other cells
• It is composed of phospholipid bilayer, this is a double layer of phospholipid molecules and has protein molecules embedded within it
• Cell membrane not only protects the cells but allows certain substances in and out of the cell (it is selectively permeable)

Question 5

Simple diffusion

Answer 5

• Oxygen and water enter the cell in this way. Molecules that are soluble in lipids will passively dissolve in the lipid part of the cell membrane and diffuse across it

Question 6

Facilitated diffusion

Answer 6

• A type of passive diffusion, this is where the substance attaches to a carrier protein to help it cross the cell membrane
• This occurs through pores in the cell membrane - these are pores along the membrane that allow small molecules to pass through

Question 7

Active transport mechanisms

Answer 7

• This form of transport requires a carrier and requires energy to enter the cell as it is moving against the concentration gradient (from low to high)
• The energy of the carrier ATP is used
• Sodium enters a cell this way

Question 8

Endocytosis and Exocytosis

Answer 8

• Cells can ingest materials by engulfing them
• Endocytosis - engulfed in membrane (vesicle)
• Phagocytosis - without membrane (a form of endocytosis)

Question 9

Cytoplasm

Answer 9

• Fluid that fills the inside of a cell - this provides the cell with support
• 40% of the body’s total weight is attributed to this intracellular fluid
• It contains glucose, proteins and ions

Question 10

Mitochondria

Answer 10

• Responsible for cellular respiration
• Energy extraction from food and energy is stored as ATP
• They have a folded membrane layer around them to increase the surface area

Question 11

Lysosomes

Answer 11

• Have a membrane lining and contain lysozymes
• They digest material taken in by the cell during phagocytosis/endocytosis
• They also destroy worn out organelles

Question 12

Ribosomes

Answer 12

• Site of protein synthesis
• Bind to mRNA
• Float freely in the cytoplasm or they can attach themselves to endoplasmic reticulum

Question 13

Rough endoplasmic reticulum

Answer 13

• A network of membrane lined interconnected tubes and cavities
• It has numerous ribosomes attached to its surface giving it its rough appearance
• Transports and adds structure to proteins that have been synthesised by ribosomes

Question 14

Golgi body

Answer 14

• These are stacks of flattened sacs and their function is the modification of proteins for their final destination
• Helps in the formation of lysosomes

Question 15

Smooth endoplasmic reticulum

Answer 15

• A network of membrane lined interconnected tubes and cavities, it has no ribosomes attached to it and therefore is smooth
• Its function is synthesis and transport of lipids and steroids

Question 16

Peroxisomes

Answer 16

• Bound by a single membrane and they contain enzymes (irate oxidase and catalase)
• Active process of detoxification (abundant in the liver and kidneys)

Question 17

Vacuoles

Answer 17

• They are filled with cell sap or food
• Its function is to maintain pressure within a plant cell
• Hold waste and other material

Question 18

Flagella

Answer 18

An extension of the cell membrane on certain cells to allow propelling moving for example sperm cells

Question 19

Cilia

Answer 19

• Similar to flagella, they are an extension of the cell membrane and allow similar wave-like movements over the cell surface to move debris and fluid

Question 20

Cell division terminology

Answer 20

• Chromosomes - thread-like structure of nucleic acids and proteins found in the nucleus, carrying genetic info in the form of genes
• Chromatid - each of the 2 thread-like strands into which a chromosome divides during cell division
• Centromere - the point on a chromosome by which it is attached
• Diploid - 2 sets of chromosomes (full set)
• Haploid - single set of unpaired chromosomes (half)
• Centrosomes - an organelle near the nucleus of the cell which contains the centrioles which form the spindle fibres for cell division
• Somatic cells - divide by mitosis these are the body cells apart from reproductive cells. These cells contain the diploid number of chromosomes. Almost all cells are somatic
• Germ cells - divide by meiosis - these cells are the sex cells, sperm and ova and these contain the haploid number of chromosomes

Question 21

Number of chromosomes

Answer 21

• Dog = 39 pairs, 78 total
• Cat = 19 pairs, 38 total

Question 22

Mitosis - Prophase

Answer 22

1) Prophase
- Chromosomes already replicated
- Nuclear membrane breaks down
- Chromosomes contract and shorten
- Centrioles are now at each end of cell
- Spindle fibres start to form

Question 23

Mitosis - Metaphase

Answer 23

2) Metaphase
- Chromosomes line up along the equator
- Chromatids draw apart at the centromere

Question 24

Mitosis - Anaphase

Answer 24

3) Anaphase
- Chromosomes attach themselves to spindle fibres
- Chromatids move apart to opposite poles of the cell

Question 25

Mitosis - Telophase

Answer 25

4) Telophase
- Chromatids will be the new chromosomes for the daughter cells
- Spindle fibres break down
- Nuclear membrane reforms itself
- Cell constricts in the middle until it divides into 2 (cytokinesis)

Question 26

Mitosis - Interphase

Answer 26

5) Interphase
- This phase is classed as rest phase (the phase in-between replication) - is often considered as the first, or the last phase
- But important stuff still happens here
- DNA makes a copy of itself ready for prophase

Question 27

Meiosis - overview

Answer 27

• Germ cells divide
• Resulting in the ova or sperm containing half of the number of chromosomes
• Meiosis occurs before fertilisation
• There are 8 stages
• Results in the production of 4 non-identical daughter cells

Question 28

Meiosis - Prophase 1

Answer 28

• Starts with a diploid number of chromosomes
• Identical chromosomes lie side by side and duplicate
• Crossing over occurs here resulting in new combination of genes
• This is why siblings are different from one another

Question 29

Meiosis - Metaphase 1

Answer 29

• Homologous pairs of chromosomes line at the equator of the cell
• Fibrous spindles start to form
• Chromosomes arrange in pairs

Question 30

Meiosis - Anaphase 1

Answer 30

• Pairs separate into chromatids and migrate along the spindle fibres towards the end of the cell

Question 31

Meiosis - Telophase 1

Answer 31

• Cytoplasm starts to divide
• The nuclear membrane doesn’t reform
• We now have 2 non-identical daughter cells

Question 32

Meiosis - Prophase 2

Answer 32

• Transitionary phase - no replication (as these need half-haploid number of chromosomes)

Question 33

Meiosis - Metaphase 2

Answer 33

• Chromosomes line up in the centre of the cell and attach to spindle fibres

Question 34

Meiosis - Anaphase 2

Answer 34

• Spindle fibres contract, pulling the chromatids apart at the centromere, so that they move to opposite ends of the cell

Question 35

Meiosis - Telophase 2

Answer 35

• The cytoplasm divides and the nuclear membrane reforms
• 4 cells have now been formed, each with half (haploid) the chromosome number of the original cell