WEEK TWELVE - Nutrition and metabolism 2 Flashcards
(30 cards)
Carbohydrate metabolism; explain the processes in which glucose is catabolised to produce ATP
glycolysis
- occurs rapidly in cell cytoplasm –> yields **2 ATP **
- anaerobic
- series of conversions splits glucose molecule –> 2 pyruvic acid molecules
1. phosphorylation
2. priming
3. cleavage
4. oxidation
5. dephosphorylation
**aerobic respiration
**- yields ~ 36 ATP
- completely oxidises pyruvic acid –> CO2 + H2o
- ATP generates in mitochondria + requires o2 as final electron acceptor
- eg krebs cycle, ETC and oxidative phosphorylation
principal steps
1. matrix reactions [Krebs cycle] controlling enz = in mitochondrial matrix
- Pyruvic acid converted → acetyl-CoA → enters citric acid cycle
- 2 NAD+ → converted to NADH per/cycle
- 1 ATP produced/per cycle
- membrane reaction whose enzyme are bound to mitochondrial membrane [ECT]
- Electrons transferred along transport chain –> Protons [H+] pumped → into intermembrane space
- Movement of H+ ions through enzyme SPINS it
= creates energy needed to form ATP from ADP + Pi [inorganic phosphate]
- Oxygen = final electron acceptor [water molecule]
anaerobic fermentation
- occurs in absence of o2 and reduces pyruvic acid to lactic acid
- NADH donates pair of electrons –> pyruvic acid = reducing it to lactic acid and degenerating NAD+
- the lactic acid leaves cell and travels to liver [stored as glycogen or released as glucose]
- when O2 available again, the liver oxidizes lactic acid back to pyruvic acid and it undergoes aerobic respiration
- fermentation = inefficient = not favoured by brain/heart
Glycogen metabolism; describe the synthesis and breakdown of glycogen within the body
ATP = used quickly after it is formed –> extra glucose will be stored as glycogen
glycogenesis
- glucose –> glycogen
- stim by insulin [avg adult contains 450g]
glycogenolysis
- glycogen –> glucose
- Stimulated by glucagon, cortisol, and epinephrine
- only liver cells can release glucose back to blood
gluconeogenesis
- glycerol and AAs –> glucose
- When carbohydrates stores = LOW = the body needs to use non-carbohydrate sources
Describe the processes of lipid catabolism and anabolism
Triglycerides = STORED in adipocytes
- Constant turnover of molecules every 3 weeks
- Released → blood then transported and either oxidised or redeposited in other fat cells
Lipogenesis
- Synthesising fat from other sources
- AAs + sugars used to make fatty acids + glycerol
Lipolysis
- Breaking down fat for fuel
- Glycerol enters glycolysis and fatty acids broken down = acetyl-CoA
Ketogenesis
- Fatty acids catabolised → acetyl groups
Describe the processes of protein catabolism and anabolism
catabolism
- from AA pool –> dietary AAs + 100g of tissue protein broken down/day –> free AAs
- may be used to synth new proteins or can be converted –>** fat/glucose** to be used as fuel for energy production
anabolism
- AAs undergo deamination of NH2 group = keto acid –> then converted to pyruvci acid, acetyl-CoA, or other citric acid cycle intermediates
- NH2 becomes NH3 [converted to urea by liver - ornithine cycle]
Define the absorptive state of metabolism and explain what happens to the macronutrients in this state
- abs state occurs with the arrival of food to the stomach/intestines where the abs of nutrients will occur
- lasts ~4 hrs after meals [time of nutrient abs + use for energy needs]
- in the abs state, glucose is readily available as ATP fuel, preventing the body from drawing on stored fuel eg glycogen
-in the abs state incoming nutrients are used for short-term metabolism and the excess is used for the anabolism of energy stores. - excess glucose is converted into its storage form - glycogen which is then stored in the liver or musc. [facilitated by insulin sec by pancreas]
- AAs are used for protein synthesis, supporting tissue growth and repair
- **fatty acids **are converted into triglycerides and stored in adipose tissue as long term energy storage.
Define the post-absorptive state of metabolism and explain what happens to the macronutrients in this state
- func = homeostatically regulated blood glucose conc between 90-100 mg/dL which is critical for proper brain function
- reg mainly by symp.NS and glucagon but also insulin and cortisol
- when stomach/intest are empty, body uses stored fuels to ensure glucose supply
carbs
- glucose is drawn from glycogen reserves for up to 4 hrs then synthesised from other compounts
fat
- adipocytes and hepatocutes convert glycerol –> glucose in gluconeogenesis
- FFAs are oxidised by liver = ketone bodies [used as alternate energy source, leaving more glucose for the brain]
protein
- if glycogen and fat reserves are depleted, protein is used as fuel eg musc protein
Describe the hormonal and nervous regulation of each state
Define basal metabolic rate and state factors that alter it
Amount of calories burnt whilst doing NO activity
- measured 12 hrs after a meal in thermoneutral environment
Affected by
Gender - M ^ than F
Prolonged dieting - decreases BMR
Thyroid hormone lvls - decreased lvls = LOWER BMR
Exercise - elevated following exercise
Age - decreases w/ age due to decreased muscle mass
Increased muscle mass from exercise = increased metabolic rate
Describe how sex is determined by chromosomes
Each zygote inherits 23 chromosome from mother // 23 from father
- 22 pairs of homologous autosomal chromosomes
- 23rd pair = sex chromosomes [x and y]
- every egg contains an X chromosome but half of sperm carry X and other carry Y chromosome
- if fertilsation w/ XX = F
- XY = M
> > sex determined by sperm which penetrate egg at fertilisation
Describe how sexual phenotype is determined
in 5-6 week old embryo - an undifferentiated gonadal ridge develops = homologous tissue of gonad EITHER develops into testes or ovaries
M
- testies-determining factors [TDF] [product of SRY gene on Y chromosome] = conversion to testes, developement of seminiferous tubules and Leydig cells
leydig cells sec testosterone
- begins 8th week and peaks at 12-14th wk
- Masculinises embryonic structures then T declines to very low levels until puberty
F
In 5-6 wk old embryo → Absence of Y chromosome and TDF = female ovaries
- Ovarian follicles do not appear until 2nd trimester
Describe how the accessory sex organs & external genitalia develop
Presence/absence of testes determines the accessory sex organs/external genitalia
M accessory organs derived from Wollfian/mesonephric ducts
- under the influence of TESTOSTERONE [stims wolffian duct]
- sertoli cells sec Mullerian Inhib Factor [MIF]
- genital tubercle enlarges –> forms penis
- urethral groove elongates and closes completely
- Urethral folds give rise to the penile urethra
- Labioscrotal swellings develop into the scrotum
F accessory organs derived from Mullerian/paramesonephric ducts
- develops in absence of testosterone
- absence of MIF = development of mullerian ducts
- in absence of testosterone = wolffian ducts regress
- genital tubercle –> forms clitoris
- Urethral groove remains OPEN as the vestibule
- Urethral folds → labia minora
- Labioscrotal swellings become labia majora
State which male and female reproductive organs are homologues of each other
M and F organs that develop from the same embryonic structure are said to be homologous or homologues of each other
Penis [glans] x clitoris
Male urethra x labia minora
Scrotum and x majora
Describe the anatomical features of the scrotum and testes
scrotum
Pouch of skin, muscle and CT that contains testes
Keeps the testes 3 degrees LOWER then core body temperature [needed for sperm production] [cremaster reflex]
Testes = male gonad
Functions
- Hormone production [testosterone and inhibin]
- Gamete production by spermatogenesis [spermatozoa]
- each teste surrounded by two tunics
1. inner tunica albuginea
- fibrous capsule
- outer tunica vaginalis
- derived from peritoneum
CT septa divide testes into 250-300 lobules, each containing 1-3 seminiferous tubules
- surrounding the lobules are Leydig/interstitial cells which sec testosterone
Explain how the testes are kept 3°C lower than core temperature
THREE MECH
1. dartos
- smoo.musc that wrinkles/relaxes scrotal skin
- wrinkling = thickens scrotal skin to minimise heat loss
- relaxing - thins skin = promotes heat loss
- cremaster reflex
- bands of skel.musc originating from external oblique which elevate that testes - pampiniform plexus ‘
- Counter-Current Heat Exchange
- warm arterial blood passes the plexus and transfers heat to venous blood = cooling effect
Describe the anatomical features of the epididymis, vas deferens & urethra
epididymis
- func = storage and maturation of sperm
- long, coiled tube which transports sperm from testes –> vas deferens [ductus deferens]
- 3 regions - head, body, tail
vas deferens
- runs from epididymis –> through inguinal canal –> pelvic cavity
- terminus expands to form ampulla then joines the duct of seminal vesicle forming the **ejaculatory duct **
- propels sperm from epididymis to urethra via peristalsis
- vasectomy includes the cutting/ligating of the vas deferens
urethra
- converys both urine and semen [at dif times]
- THREE regions
1. prostatic urethra
- portion surrounding prostate
- carries urine/sperm –> out of body
- membranous urethra
- from prostate gland –> perineum - spongy / penile
- runs through penis, opens to outside at external urethral orifice
List the accessory reproductive glands and state their contribution to the composition of semen
Prostate gland
contributes ⅓ of fluid to the total semen volume
Seminal vesicle
~ 60% of semen
Bulbourethral Gland /Cowper’s Gland
Most alkaline mucus, trace amounts
- precum
- neutralises acidity of vagina for sperm transport
Describe the anatomical features of the penis
copulatory organ used for insemination of sperm into the vagina
erection - erectile tissue fills w blood during excitement = causing penis enlargment and rigidity
- Corpus spongiosum = surrounds urethra and expands to form the glans and bulb of penis
- Corpora cavernosa - paired dorsal erectile bodies
Detail the pathway of sperm from formation to ejaculation
> seminiferous tubules > rete testis > efferent ductules > epididymis > vas deferens > inguinal canal > ejaculatory duct > urethra
Define puberty, state what causes it and when it occur in males
physical change - child’s body matures → adult body capable of sexual reproduction + enable fertilisation
- Between onset of gonadotrophin secretion until first menstrual period [~ 12 yo] OR first ejaculation of viable sperm [~ 14yo]
Reproductive system remains dormant for years after birth
- Surge of pituitary gonadotrophins begins development
- **10-12 in M **
- 8-10 in F
List the hormones of the hypothalamo-pituitary-testicular axis and state their actions on the axis
- GnRH → ant.pit. → LH + FSH
- FSH → sertoli/sustentacular cells → androgen binding protein [ABP]
- LH → leydig/interstitial cells → testosterone
- ABP + testosterone = spermatogenesis
- Testosterone → stims libido + development of secondary sex organs + characteristics
- Testosterne = - feedback of GnRH secretion + v pit. sens. To GnRH
- sertoli/sustentacular cells → inhibin → selectively inhibits FSH sec = reduce spermatogenesis
List the actions of testosterone
- embryonic development of reproductive structures
- development of secondary sex characteristisc during puberty
- maintenance of spermetogenesis
- proper functioning of accessory reproductive glands
- regulation of gonadotrophin secretion
- maintains sex drive
- may enhance aggressive behaviour
- stims hair growth
- hypertrophy of larynx → deepening of voice + adams apple
State how older age affects the reproductive system in men
Decline in testosterone secretion w age
- Peak sec at **7mg/day at age 20 **
- Declines to 20% of that by 80yo
andropause = gradual reduction of testosterone with increasing age
= ^ in FSH and LH after ~ 50yo produces male climacteric [andropause]
Reduced negative feedback of testosterone causes :
- Mood changes, hot flashes, insomnia, weight gain, memory/musc/bone loss
Briefly describe meiosis
Cell division only to produce gametes
- Meiosis = chromosomes are halved from 2n → n = gamete formation
Name the stages in meiosis and state what happens to chromosome number after each division
